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. 2023 Oct 26;18(10):e0293314. doi: 10.1371/journal.pone.0293314

Comorbidity clusters and in-hospital outcomes in patients admitted with acute myocardial infarction in the USA: A national population-based study

Salwa S Zghebi 1,2,*, Martin K Rutter 3,4, Louise Y Sun 5, Waqas Ullah 6, Muhammad Rashid 7,8, Darren M Ashcroft 9,10, Douglas T Steinke 9, Stephen Weng 11, Evangelos Kontopantelis 1,12, Mamas A Mamas 7,8
Editor: Amirmohammad Khalaji13
PMCID: PMC10602297  PMID: 37883354

Abstract

Background

The prevalence of multimorbidity in patients with acute myocardial infarction (AMI) is increasing. It is unclear whether comorbidities cluster into distinct phenogroups and whether are associated with clinical trajectories.

Methods

Survey-weighted analysis of the United States Nationwide Inpatient Sample (NIS) for patients admitted with a primary diagnosis of AMI in 2018. In-hospital outcomes included mortality, stroke, bleeding, and coronary revascularisation. Latent class analysis of 21 chronic conditions was used to identify comorbidity classes. Multivariable logistic and linear regressions were fitted for associations between comorbidity classes and outcomes.

Results

Among 416,655 AMI admissions included in the analysis, mean (±SD) age was 67 (±13) years, 38% were females, and 76% White ethnicity. Overall, hypertension, coronary heart disease (CHD), dyslipidaemia, and diabetes were common comorbidities, but each of the identified five classes (C) included ≥1 predominant comorbidities defining distinct phenogroups: cancer/coagulopathy/liver disease class (C1); least burdened (C2); CHD/dyslipidaemia (largest/referent group, (C3)); pulmonary/valvular/peripheral vascular disease (C4); diabetes/kidney disease/heart failure class (C5). Odds ratio (95% confidence interval [CI]) for mortality ranged between 2.11 (1.89–2.37) in C2 to 5.57 (4.99–6.21) in C1. For major bleeding, OR for C1 was 4.48 (3.78; 5.31); for acute stroke, ORs ranged between 0.75 (0.60; 0.94) in C2 to 2.76 (2.27; 3.35) in C1; for coronary revascularization, ORs ranged between 0.34 (0.32; 0.36) in C1 to 1.41 (1.30; 1.53) in C4.

Conclusions

We identified distinct comorbidity phenogroups that predicted in-hospital outcomes in patients admitted with AMI. Some conditions overlapped across classes, driven by the high comorbidity burden. Our findings demonstrate the predictive value and potential clinical utility of identifying patients with AMI with specific comorbidity clustering.

Introduction

Coronary heart disease (CHD) is the leading cause of mortality worldwide [1, 2], with over 800,000 patients sustaining an acute myocardial infarction (AMI) each year in the US [1]. Multimorbidity (or comorbidity) is defined as the co-existence of two or more comorbidities in the same individual [3]. The number of people living with multiple long-term conditions has increased in recent years driven by increased life expectancy and improved healthcare [3]. In the US, the prevalence of multimorbidity and affects more than one quarter of adults [4, 5]. Among patients with incident cardiovascular disease (CVD), 81.1% have at least one comorbidity and the proportion of patients who develop multiple comorbidities is increasing over time [6]. Studying multimorbidity patterns informs clinical guidelines, healthcare policy developers and healthcare professionals to better understand the holistic care needs of patients. Multimorbidity is multifaceted with links to polypharmacy, low medication adherence, adverse clinical outcomes including readmissions, poor quality of life and life satisfaction [7, 8].

Despite the current increasing prevalence of multimorbidity in people with CVD and the potential impact of associated outcomes, identifying multimorbidity patterns/clustering is limited. Latent class analysis (LCA) can be used to identify such clusters, identifying classes of ‘similar’ individuals grouped based on a set of observed variables, such as comorbidities [911], and it performs better than other clustering methods [12]. Some past studies on US cardiovascular admissions examined comorbidities but not their detailed patterns or in terms of multimorbidity burden or looked at latent subgroups in the prediction adverse outcomes in people admitted with AMI [1316].

In this study, we used US nationwide data to identify patients with AMI as the primary cause of hospitalization. We aimed to 1) examine comorbidity burden and how it may cluster in different groups using data on 21 chronic conditions; 2) describe the socio-demographic characteristics of the identified latent comorbidity groups; and 3) examine associations between the comorbidity classes and in-hospital outcomes.

Methods

Data source

Data were derived from the US Nationwide Inpatient Sample (NIS) which is the largest all-payer data on inpatient stays from all US hospitals participating in the Healthcare Cost and Utilization Project (HCUP). Sponsored by the US Agency for Healthcare Research and Quality (AHRQ), the NIS data is the largest available all-payer data on inpatient stays from US states participating in the Healthcare Cost and Utilization Project (HCUP), covering over 97% of the US population [17]. The design of NIS approximates a 20% stratified sample of all admissions from long-term acute care hospitals and community hospitals, except rehabilitation [17]. The NIS provides anonymized data on primary and secondary hospitalization diagnoses from over 7 million annual inpatient stays between 2004 and 2018, recorded in discharge abstracts [17, 18]. AHRQ sampling weights were applied for each admission for national level estimates. We used modified weights in all analyses to take the NIS sampling design change in 2012 into account. Further database documentation is available online [19].

Study design and study population

This was a retrospective cohort study including data for all individuals aged ≥35 years with acute myocardial infarction (AMI) (International Classification of Diseases (ICD)-Tenth Revision (ICD-10) codes I21*, I22*) as the primary discharge diagnosis between January and December 2018.

Data variables and outcomes

Variables included were age, sex, race (White, Black, Hispanic, Asian or Pacific Islander, Native American, Other, unknown), median household income quartiles for patient’s ZIP Code, weekend admission, total hospital charges, length of hospital stay (LOS), and hospital region. Admission records with missing age, sex, LOS, total costs, elective, weekend admissions, or death status were excluded (N = 685, 0.8%). Other missing variables, such as race were assigned to a separate ’unknown’ category.

We extracted data on 21 comorbidities recorded in the admission records using the HCUP Elixhauser comorbidity software ICD-10 codes [20]; diabetes (with or without complications) (DM), peripheral vascular disease (PVD), heart failure (HF), valvular disease (VD) (including stenosis, insufficiency, congenital, prosthetic, or rheumatic disorders of heart and pulmonary valves), hypertension (HTN) (including gestational HTN), dyslipidaemia, coronary heart disease (CHD), anaemias, atrial fibrillation or flutter (AF), coagulopathy, depression, obesity, chronic kidney disease (CKD), hypothyroidism, transient ischemic attack (TIA)/ stroke, rheumatoid arthritis (RA)/collagen vascular diseases, liver disease, cancer, weight loss, psychoses, and chronic obstructive pulmonary disease (COPD).

In-hospital outcomes of interest were all-cause mortality, acute ischemic stroke, major bleeding (including haemorrhagic stroke), procedure-related bleeding, cardiac tamponade, use of assist device or intra-aortic balloon pump (IABP), coronary artery bypass graft (CABG), and percutaneous coronary intervention (PCI), LOS (days), and total hospital costs (S1 Table).

Statistical analysis

Categorical variables, described as frequencies with percentages, were compared using Pearson’s Chi-squared test. Continuous variables, described as mean and standard deviation (SD) or median and interquartile range (IQR) (as appropriate as per the normal distribution of the variable), were compared using the Mann-Whitney U test for differences across 2 groups (such as gender), or using the Kruskal-Wallis test (non-normally distributed variables) or one-way ANOVA (normally distributed variables) for differences across >2 groups (such as latent classes). Nominal (exploratory) P-values were estimated and reported.

Generalized structural equation modelling (gsem) was used to identify categorical unobserved (latent) classes [21]. Latent class analysis relates a set of observed categorical variables (in this case the 21 comorbidities) to a set of latent variables, thus assigning the population to subgroups of ‘similar’ individuals referred to as ’latent classes’ [911]. LCA is a common approach to identify comorbidity clusters and is reportedly superior to existing methods [12]. As suggested previously, the number of latent classes can be decided by comparing the values of Akaike’s information criterion (AIC) and Schwarz’s Bayesian information criterion (BIC) of models based on different numbers of classes, where smaller AIC and BIC values are better and indicate the optimal number of classes [9, 22, 23]. Following assessment of models with 2–8 classes, AIC and BIC values decreased marginally with increasing number of classes from two to six (S2 Table). Given the trivial differences of AIC/BIC values (0.11%/0.10%) between the 5-class/6-class models, the 5-class model was chosen as a reasonable compromise, showing informative separation of the examined 21 comorbidities with a smaller number of classes. Latent class marginal probabilities (95% CI) were estimated.

Multivariable logistic regression models estimated odds ratios (OR) and 95% confidence intervals (CI) for likelihood of all binary outcomes, such as mortality and PCI. Negative binomial regression (selected over Poisson regression given the dispersion of LOS data) estimated incidence rate ratios (IRR) and 95%CIs for predictors of count outcome (LOS). Multivariable linear regression estimated regression coefficients and 95%CIs for predictors of total hospital charges. The largest (most common) class was used as the reference group in all regression models to assess the risk of outcomes in comparison to AMI patients with the most common comorbidity burden profile. Analyses were survey-weighted using the provided sampling weights to produce a nationally representative estimate of the entire US population of hospitalized patients.

Results

Comorbidity latent classes

Overall, mean (±SD) age was 67 (±13) years, 38% were females, and 76% were White and 12% were Black (Table 1). Patients in Class 2 were the youngest (62 ± 13 years) and had the highest male proportion (66%, 66–67%) and the highest proportion on Medicaid as the primary expected payer (10%, 10–11%), and the lowest hospital costs ($59,855 (IQR 57,402) compared to patients in other classes (Table 1 and S1 Fig). On the other hand, the COPD/VD/PVD group (Class 4) included the oldest patients (75 ± 11 years) and fewest Hispanic individuals among all patients hospitalized with AMI, while the diabetes/CKD/HF group (Class 5) had the lowest proportion of White patients (70%) and highest of Black patients (17%). By both age and sex, 64% of females vs. 51% of males in Class 4 were aged 75+years (S1 Fig). Results of significance testing for differences across the latent classes are summarized in S3 Table.

Table 1. Baseline characteristics of the emerged comorbidity latent classes.

Overall Class 1 (Cancer/ coagulopathy/ liver) Class 2 (Least burdened) Class 3 (CHD/ dyslipidaemia) Class 4 (COPD/VD/PVD) Class 5 (DM/CKD/HF)
Weighted admissions, N (%) 416,655 39,640 (9.5%) 85,455 (20.5%) 173,825 (42%) 47,525 (11%) 70,210 (17%)
Admissions per 100,000 population 127.4 12.1 26.1 53.1 14.5 21.5
Age (years), mean ±SD 67±13 71±14 62±13 65±12 75±11 72±11
Age categories, % (95% CI)
 35-44y 4.3 (4.11; 4.4) 3.4 (3.0; 3.8) 8.3 (7.9; 8.8) 4.5 (4.3; 4.8) 0.9 (0.7; 1.1) 1.3 (1.1; 1.5)
 45-54y 13.9 (13.6; 14.1) 10.1 (9.5; 10.8) 22.3 (21.7; 23.0) 16.1 (15.7; 16.5) 4.0 (3.7; 4.4) 6.8 (6.4; 7.2)
 55-64y 24.8 (24.5; 25.1) 20.2 (19.3; 21.1) 30.1 (29.5; 30.8) 28.9 (28.4; 29.4) 13.4 (12.8; 14.1) 18.3 (17.7; 19.0)
 65-74y 26.5 (26.2; 26.8) 23.9 (23.0; 24.8) 21.6 (22.0; 22.2) 28.0 (27.5; 28.4) 25.3 (24.4; 26.2) 31.4 (30.6; 32.2)
 75+ y 30.6 (30.3; 30.9) 42.5 (41.4; 43.6) 17.6 (17.1; 18.2) 22.5 (22.0; 22.9) 56.3 (55.3; 57.3) 42.2 (41.4; 43.0)
Sex, % (95% CI)
 Male 62.4 (62.0; 62.7) 55 (54.3; 56.5) 66 (65.5; 66.9) 65 (64.9; 65.9) 57 (55.6; 57.6) 58 (57.3; 59.0)
 Female 37.6 (37.3; 38.0) 45 (43.5; 45.7) 34 (33.1; 34.5) 35 (34.2; 35.2) 43 (42.4; 44.4) 42 (41.0; 42.7)
Race, % (95% CI)
 White 75.6 (75.3; 75.9) 72.9 (71.9; 73.9) 77.9 (77.3; 78.5) 75.8 (75.3; 76.2) 82.0 (81.2; 82.8) 69.6 (68.8; 70.4)
 Black 12.1 (11.9; 12.4) 15.2 (14.4; 16.0) 9.6 (9.2; 10.0) 11.4 (11.0; 11.7) 9.4 (8.8; 10.0) 17.2 (16.6; 17.9)
 Hispanic 4.9 (4.7; 5.0) 4.7 (4.27; 5.21) 4.7 (4.4; 5.0) 5.2 (5.0; 5.4) 2.9 (2.6; 3.2) 5.8 (5.4; 6.2)
 Asian/Pacific Islander 1.4 (1.3; 1.5) 1.2 (0.96; 1.4) 1.5 (1.3; 1.7) 1.4 (1.3; 1.5) 1.1 (0.9; 1.3) 1.7 (1.5; 2.0)
 Native American 0.4 (0.3; 0.4) 0.3 (0.2; 0.5) 0.3 (0.3; 0.4) 0.4 (0.3; 0.4) 0.3 (0.2; 0.4) 0.5 (0.4; 0.6)
 Other 2.5 (2.4; 2.7) 2.7 (2.3; 3.0) 2.5 (2.3; 2.8) 2.8 (2.6; 2.9) 1.74 (1.5; 2.0) 2.5 (2.2; 2.8)
 Unknown 3.1 (3.0; 3.2) 3.0 (2.7; 3.4) 3.5 (3.3; 3.8) 3.2 (3.0; 3.3) 2.7 (2.4; 3.0) 2.7 (2.4; 2.9)
STEMI, % (95% CI) 27.0 (26.7; 27.3) 24.36 (23.4; 25.3) 41.19 (40.5; 41.9) 28.93 (28.5; 29.4) 18.4 (17.7; 19.2) 12.43 (11.9; 13.0)
Median household income quartiles, % (95% CI)
 $1-$43,999 30.3 (30.0; 30.6) 32.9 (31.9; 34.0) 27.5 (26.8; 28.1) 29.8 (29.3; 30.3) 29.9 (29.0; 30.9) 34.0 (33.2; 34.8)
 $44,000-$55,999 28.9 (28.6; 29.2) 29.3 (28.4; 30.4) 28.4 (27.7; 29.0) 29.0 (28.5; 29.4) 29.3 (28.4; 30.3) 29.0 (28.1; 29.6)
 $56,000-$73,999 22.9 (22.6; 23.2) 20.6 (19.7; 21.5) 24.1 (23.5; 24.8) 23.4 (22.9; 23.8) 22.5 (28.4; 30.3) 21.6 (21.0; 22.3)
 ≥ $74,000 16.5 (16.2; 16.8) 15.7 (14.9; 16.5) 18.5 (17.9; 19.1) 16.5 (16.1; 16.9) 16.9 (16.2; 17.7) 14.3 (13.8; 14.9)
 Unknown 1.4 (1.4; 1.5) 1.5 (1.2; 1.8) 1.6 (1.4; 1.8) 1.4 (1.3; 1.6) 1.4 (1.2; 1.6) 1.2 (1.0; 1.4)
Primary Payer, % (95% CI)
 Medicare 57.9 (57.6; 58.2) 67.0 (66.0; 68.1) 38.1 (37.4; 38.9) 51.4 (50.9; 51.9) 79.8 (79.0; 80.6) 78.0 (77.3; 78.7)
 Medicaid 8.6 (8.4; 8.7) 9.2 (8.6; 9.8) 10.3 (9.8; 10.7) 9.2 (8.9; 9.5) 5.1 (4.7; 5.6) 6.9 (6.5; 7.3)
 Private 25.6 (25.3; 25.9) 16.5 (15.7; 17.4) 39.1 (38.4; 39.8) 30.7 (30.3; 31.2) 11.3 (10.7; 11.9) 11.4 (10.9; 12.0)
Weekend admission, % 26.3 (26.0; 26.6) 26.9 (25.9; 27.9) 27.6 (27.0; 28.3) 26.2 (25.8; 26.7) 25.3 (24.5; 26.2) 25.2 (24.5; 25.9)
Length of stay LOS (days), median (IQR) 3 (3) 4 (6) 2 (2) 2 (2) 4 (5) 5 (5)
Total hospital charges ($), median (IQR) 64,758 (74,632) 60,427 (102,851) 59,855 (57,402) 66,270 (66,567) 65,168 (94,639) 69,939 (100,440)
Region of hospital, % (95% CI)
 Northeast 25.2 (25.0; 25.5) 28.9 (27.9; 29.9) 27.0 (26.4; 27.7) 24.2 (23.7; 24.6) 25.3 (24.5; 26.2) 23.5 (22.8; 24.2)
 Midwest 32.1 (31.8; 32.4) 28.2 (27.2; 29.2) 30.8 (30.1; 31.5) 32.8 (32.3; 33.3) 33.2 (32.2; 34.1) 33.3 (32.5; 34.1)
 South 42.7 (42.4; 43.0) 42.9 (41.8; 44.0) 42.2 (41.5; 42.9) 43.0 (42.5; 43.5) 41.5 (40.5; 42.5) 43.2 (42.4; 44.0)

Significance testing: Nominal (exploratory) P-values across the five latent classes were all significant (p<0.001).

CHD: coronary heart disease; CI: confidence interval; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; DM: diabetes; HF: heart failure; IQR: interquartile range; PVD: peripheral vascular disease; SD: standard deviation; STEMI: ST segment elevation myocardial infarction; VD: valvular disease.

A total of 416,655 weighted AMI admissions (N = 83,331 unweighted), corresponding to 127.4 admissions per 100,000 population, were included. More than 99% of patients had ≥1 comorbidity; mean (±SD) of 4.7 (±2.1) comorbidities. Out of the five latent classes that emerged, latent Class 3 was the largest (42%) with highest probability of patient membership (36%), while Class 1 was the smallest (9.5%) with lowest probability of membership (10.8%). The comorbidity profile for the full cohort, across the five latent classes and by sex is described in Table 2, Fig 1 and S2 Fig. The most prevalent comorbidities across all classes were HTN, CHD, dyslipidaemia, and diabetes. However, each class included the highest prevalence of ≥1 unique comorbidity defining five distinct phenogroups: patients in Class 1 had the highest prevalence of cancer, coagulopathy, and liver disease; Class 2 included the youngest and least burdened patients but with highest proportion of ST segment elevation myocardial infarction (STEMI) (41%); CHD and dyslipidaemia in Class 3; COPD, VD, PVD in Class 4; and diabetes, CKD, HF in Class 5. Patients in Class 5 had overall the highest comorbidity burden compared to patients in other classes. Heat maps for comorbidity profile per class are presented in Fig 2.

Table 2. Comorbidity classes emerging from latent class analysis of comorbidity profile of patients admitted with AMI in 2018.

Overall Class 1 (Cancer/coagulopathy/ liver) Class 2 (Least burdened) Class 3 (CHD/ dyslipidaemia) Class 4 (COPD/VD/PVD) Class 5 (DM/CKD/HF)
Weighted No. of admissions, N (%) 416,655 39,640 (9.5%) 85,455 (20.5%) 173,825 (42%) 47,525 (11%) 70,210 (17%)
Patient membership, %probability (95% CI) NA 10.8 (10.0–11.6) 22.7 (20.9–24.6) 35.6 (33.8–37.5) 13.4 (12.4–14.4) 17.5 (16.4–18.7)
Comorbidities, % proportion (95% CI)
 HTN (incl. gestational HTN) 81.8 (81.5; 82.1) 66.5 (65.5; 67.5) 40.4 (39.7; 41.2) 95.0 (94.8; 95.2) 94.4 (93.9; 94.8) 99.6 (99.5; 99.7)
 Coronary heart disease (CHD) 80.8 (80.5; 81.1) 46.6 (45.5; 47.7) 67.2 (66.5; 67.9) 90.6 (90.3; 90.9) 88.5 (87.8; 89.1) 87.3 (86.8; 87.9)
 Dyslipidaemia 68.5 (68.1; 68.8) 5.6 (5.1; 6.1) 35.2 (34.5; 35.9) 92.6 (92.3; 92.9) 83.1 (82.4; 83.9) 74.7 (74.0; 75.4)
 Diabetes (DM) 40.9 (40.5; 41.2) 23.8 (22.8; 24.7) 5.8 (5.5; 6.2) 51.2 (50.6; 51.7) 7.1 (6.6; 7.7) 90.7 (90.2; 91.1)
 Heart failure (HF) 34.2 (33.9; 34.5) 61.7 (60.6; 62.7) 5.5 (5.1; 5.8) 18.1 (17.7; 18.5) 63.4 (62.5; 64.4) 73.7 (72.9; 74.4)
 Chronic obstructive pulmonary disease (COPD) 22.5 (22.2; 22.8) 32.7 (31.7; 33.8) 11.3 (10.8; 11.8) 16.9 (16.5; 17.3) 40.7 (39.7; 41.7) 32.0 (31.2; 32.8)
 Chronic kidney disease (CKD) 22.1 (21.8; 22.4) 25.0 (24.0; 25.9) 0 5.9 (5.7; 6.2) 35.1 (34.2; 36.1) 78.6 (77.9; 79.3)
 Obesity 20.9 (20.7; 21.2) 10.2 (9.5; 10.9) 10.2 (9.7; 10.7) 29.2 (28.7; 29.6) 3.4 (3.1; 3.8) 31.5 (30.7; 32.3)
Anaemias 16.0 (15.7; 16.2) 24.9; (24.0; 25.9) 2.7 (2.5; 3.0) 3.6 (3.4; 3.8) 26.6 (25.7; 27.5) 50.6 (49.8; 51.5)
 Valvular disease (VD) 15.3 (15.0; 15.5) 16.8 (16.0; 17.7) 5.5 (5.2; 5.8) 7.0 (6.7; 7.2) 45.7 (44.7; 46.7) 26.4 (25.7; 27.1)
 Hypothyroidism 12.4 (12.1; 12.6) 11.1 (10.4; 11.8) 7.2 (6.8; 7.6) 11.0 (10.6; 11.3) 18.9 (18.1; 19.7) 18.5 (17.8; 19.1)
 Atrial fibrillation (AF)/flutter 11.2 (11.0; 11.4) 22.6 (21.7; 23.5) 3.3 (3.0; 3.5) 5.1 (4.9; 5.3) 27.8 (26.9; 28.7) 18.3 (17.7; 19.0)
 Peripheral vascular disease (PVD) 9.5 (9.3; 9.74) 6.2 (5.7; 6.8) 3.2 (2.9; 3.4) 4.5 (4.3; 4.7) 40.4 (39.5; 41.4) 10.8 (10.3; 11.4)
 Depression 9.4 (9.2; 9.6) 8.0 (7.4; 8.6) 5.0 (4.7; 5.4) 9.9 (9.6; 10.2) 12.2 (11.5; 12.9) 12.4 (11.9; 13.0)
 TIA/Stroke 7.9 (7.8; 8.1) 4.1 (3.67; 4.55) 1.7 (1.5; 1.9) 6.6 (6.31; 6.8) 18.4 (17.7; 19.2) 14.0 (13.5; 14.6)
 Coagulopathy 5.9 (5.8; 6.1) 15.0 (14.3; 15.8) 1.1 (1.0; 1.3) 3.1 (2.90; 3.3) 11.1 (10.5; 11.7) 10.3 (9.8; 10.8)
 Weight loss 3.0 (2.9; 3.1) 14.2 (13.4; 15.0) 0.4 (0.4; 0.6) 0.2 (0.2; 0.23) 7.4 (6.9; 7.9) 3.8 (3.5; 4.1)
 Cancer 2.8 (2.7; 3.0) 9.7 (9.1; 10.4) 1.0 (0.8; 1.1) 1.2 (1.1; 1.3) 5.8 (5.4; 6.3) 3.4 (3.1; 3.7)
 RA & collagen vascular diseases 2.6 (2.5; 2.7) 3.7 (3.3; 4.1) 1.9 (1.7; 2.1) 1.9 (1.7; 2.0) 5.6 (5.1; 6.1) 2.9 (2.6; 3.2)
 Liver disease 2.2 (2.1; 2.3) 6.5 (6.0; 7.1) 0.5 (0.4; 0.6) 1.8 (1.7; 2.0) 1.7 (1.4; 1.9) 3.5 (3.2; 3.8)
 Psychoses 2.1 (2.0; 2.2) 4.5 (4.0; 4.9) 1.3 (1.2; 1.5) 2.2 (2.0; 2.3) 0.8 (0.6; 1.0) 2.2 (2.0; 2.4)

Significance testing: Nominal (exploratory) P-values across the five latent classes were all significant (p<0.001).

Top and bottom prevalence per comorbidity presented in bold.

HTN: hypertension; RA: rheumatoid arthritis; TIA: transient ischemic attack.

Fig 1. Radar charts for percentage prevalence of comorbidities per latent class, overall and by sex.

Fig 1

Radar charts present the percentage prevalence of comorbidities per latent class ranging from 0% (chart centre) to 100%.

Fig 2. Heat maps for percentage prevalence of comorbidities per latent class.

Fig 2

Based on cut-off value of 25% to resemble the reported prevalence of multimorbidity in US adults. HTN: hypertension; PVD: peripheral vascular disease; HF: heart failure; AF: atrial fibrillation; CHD: coronary heart disease; COPD: chronic obstructive pulmonary disease; TIA: transient ischemic attack; RA/collag vas dis: rheumatoid arthritis/collagen vascular disease; CKD: chronic kidney disease.

Associations between latent classes and in-hospital outcomes

In-hospital mortality

Overall, 4.4% of the cohort died in hospital (S4 Table). There was large variation in mortality rate; from 11% of patients in Class 1 to 1.8% in Class 3 (S3 Fig). Patients from all classes, including the youngest/least burdened phenogroup (Class 2), were between 2- and 5-fold higher odds of in-hospital mortality than patients in Class 3 (Table 3 and S5 Table, Fig 3).

Table 3. Odds ratios (95% CI) for risks of in-hospital outcomes in patients admitted with AMI in 2018.
Class 1 (Cancer/ coagulopathy/ liver) Class 2 (Least burdened) Class 3^ (CHD/dyslipidaemia) Class 4 (COPD/VD/PVD) Class 5 (DM/CKD/HF)
In-hospital death 5.57 (4.99; 6.21) 2.11 (1.89; 2.37) Ref 2.85 (2.54; 3.21) 2.89 (2.60; 3.22)
Major bleeding * 4.48 (3.78; 5.31) 1.04 (0.85; 1.27) Ref 3.14 (2.63; 3.74) 3.20 (2.73; 3.75)
Acute ischemic stroke 2.76 (2.27; 3.35) 0.75 (0.60; 0.94) Ref 2.00 (1.63; 2.46) 1.71 (1.42; 2.06)
Procedure-related bleeding 2.09 (1.33; 3.28) 1.09 (0.71; 1.65) Ref 2.25 (1.48; 3.44) 0.94 (0.58; 1.53)
Cardiac tamponade 4.28 (2.64; 6.94) 1.18 (0.70; 2.01) Ref 3.70 (2.27; 6.02) 1.58 (0.93; 2.70)
Use of assist device/IABP 4.33 (3.67; 5.09) 1.08 (0.90; 1.28) Ref 2.95 (2.47; 3.52) 2.63 (2.24; 3.08)
CABG 0.83 (0.75; 0.91) 0.38 (0.34; 0.41) Ref 1.41 (1.30; 1.53) 1.26 (1.17; 1.35)
PCI 0.34 (0.32; 0.36) 1.06 (1.02; 1.10) Ref 0.53 (0.50; 0.55) 0.45 (0.43; 0.47)

All models adjusted for age, sex, race, and latent classes.

* Includes haemorrhagic stroke.

^Class 3 is the largest class and was selected as the reference group.

CABG: coronary artery bypass graft; CHD: coronary heart disease; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; DM: diabetes; HF: heart failure; IABP: intra-aortic balloon pump; PCI: percutaneous coronary intervention; PVD: peripheral vascular disease; VD: valvular disease.

Fig 3. Forest plot of ORs or regression coefficients (95%CI) for in-hospital outcomes.

Fig 3

CABG: coronary artery bypass graft; IABP: intra-aortic balloon pump; PCI: percutaneous coronary intervention.

Major bleeding

Overall, 1.7% had major bleeding with rates ranging between 0.8% in Classes 2 and 3 to 4% in Class 1 (S4 Table, S3 Fig). The ORs (95% CI) for major bleeding were 3.14 (95%CI: 2.63–3.74) in the COPD/PVD/VD (Class 4), and 4.48 (3.78–5.31) in the cancer/coagulopathy/liver group (Class 1), when compared to Class 3.

Acute ischemic stroke

Overall, 1.1% had stroke with rates ranging between 0.6% in Class 2 and 2.4% in Class 1 (S4 Table). Patients in classes 1, 4 and 5 were at higher risks (ORs ranging between 1.71 (1.42; 2.06) to 2.76 (2.27; 3.35)), whereas patients in Class 2 were less likely to experience stroke (OR = 0.75, 0.60–0.94), than Class 3.

Other outcomes

Overall, 51% and 8.1% received PCI and CABG, respectively (S4 Table). Approximately, 30% of patients in the Class 1 vs. 63% of Class 2 underwent PCI (S3 Fig). All patients, except Class 2, had lower odds for receipt of PCI and 1-day longer stays, in comparison to Class 3. Estimates for the other outcomes are described in Table 3, S5S7 Tables. S4 Fig summarizes the predictive margins of probabilities of binary outcomes.

Discussion

Main findings

Using a representative cohort of 416,655 AMI admissions from a national US inpatient database, we identified distinct phenogroups defined by varying comorbidity profiles via latent classes. While a few comorbidities were dominant across all classes, such as HTN and CHD, each class had the highest prevalence of ≥1 specific comorbidity, resulting in five unique phenogroups. The youngest/least burdened phenogroup (Class 2) comprised primarily males and had the highest proportion of STEMI admissions. By contrast, the oldest class (Class 4) had the lowest proportion of Hispanic patients and lowest prevalence of obesity. The phenogroups identified have very different clinical outcomes, with those in the cancer/coagulopathy/liver disease class (Class 1) having the greatest risk of in-hospital mortality with 5-fold higher odds compared to patients in Class 3 characterised by CHD/dyslipidaemia. We also report differences in other relevant outcomes including major bleeding (between 0.8%-4%) and in-hospital stroke (0.6%-2%). Finally, we observe that there is heterogeneity in revascularisation, with PCI rates varying from 30% to 63%.

Findings in relation to literature

Comorbidity burden in patients with AMI

The number of people living with comorbidities is increasing worldwide. In the US, the prevalence of multimorbidity is growing and affects >25% of adults [4, 5], and it increases with age among patients with CVD [24]. We found that the most common comorbidities were HTN, CHD, dyslipidaemia, diabetes, HF, chronic pulmonary disease, and CKD. This is in agreement with previous US studies [5, 2528], Whilst previous work has described the prevalence of comorbidities in patients with CVD, there are only a few studies around how these comorbidities cluster, and whether patient groups with particular clusters of comorbidities have different clinical trajectories/outcomes [26, 28]. To our knowledge, no prior studies have created latent subgroups in the prediction of adverse outcomes in US people admitted with AMI. Our analysis showed good phenogroup separation of a large cohort of patients hospitalized for AMI into five novel latent classes. We used LCA as it is reportedly superior to other clustering approaches [12], and it has shown to improve the prediction of adverse in outcomes in distinct phenogroups with CVD [2931]. A large LCA of multimorbidity burden in 693,388 patients admitted with AMI between 2003 and 2013 in England and Wales was based on seven conditions: HTN, diabetes, HF, renal failure, cerebrovascular disease, PVD, and COPD or asthma [32]. Their analysis revealed a high (dominated by CHD and PVD), medium (dominated by PVD and HTN), and low (low prevalence of comorbidities but with PVD) multimorbidity classes. These three classes are not directly comparable to ours given the different included conditions as we examined 21 comorbidities, including mental illness, which further highlights the inclusivity and potential clinical applicability of our findings. However, both studies agree that HTN and diabetes were among the most common comorbidities in AMI admissions. Their study also reports that 59.5% of patients (N = 412,809) had ≥1 comorbidity in comparison to >99% of patients in our study which indicates the different multimorbidity burden between both populations, the more limited number of comorbid conditions that were considered in that analysis, as well as the rapidly increasing prevalence of multimorbidity over time as our later data shows. In China, 75.7% of 49,453 patients with CHD admitted between 2018 and 2020 had ≥1 comorbidity, which is closer to our estimates than UK data [33]. The investigators conducted LCA of 13 comorbidities (CVD, diabetes and Parkinson’s disease) which resulted in three comorbidity classes: severe (dominated by HF), moderate (dominated by HTN and diabetes), and mild (fewest comorbidities) which differ from our phenotypes [33].

Examining the clinical and socio-demographic profiles of patients in the emerged classes may inform clinical practice on class membership and why some comorbidities were grouped together. For example, we found that CKD prevalence ranged between 0–35% in Classes 1–4, but was 79% in Class 5, alongside diabetes and HF. One in three adults with diabetes has CKD [34] and type 2 diabetes increases risk of HF development two-fold [35]. Furthermore, approximately 50% of patients with HF have CKD [36], where HF is a risk factor for CKD and vice versa [3739]. Additionally, other possible determinant of this clustering is that Class 5 have the highest proportion of Black people (17%) who are evidently disproportionally affected by higher burden of diabetes [40, 41], CKD [42], and HF [43] compared to other ethnic groups in the US.

Class 1 includes a higher proportion of females (45%) than Classes 2–5 which is possibly explained by the combination of higher prevalence of comorbidities known to be more common in females, e.g., liver disease [44] (5% in C1 vs. 0.4–2.9% in C2-C5), and hypercoagulation (coagulopathy) [45] (11% vs. 0.7%-8.2% in C2-C5). Class 1 also has the lowest burden of dyslipidaemia (5.7% vs. 33–91% in C2-C5) that is known to be less common in females, possibly due to the reported high prevalence of diagnostic inertia of dyslipidaemia in women [46].

Our findings show that no comorbidity was exclusive per a latent class, especially for the most common comorbidities in AMI population e.g., HF that is most prevalent at 74% in the DM/CKD/HF group (Class 5) while it is also diagnosed in 62% of people in Class 1. Reportedly, HF leads to activation of coagulation (increased levels of thrombin formation and activation of fibrinolysis) [47, 48] and also due to possible cardiohepatic interactions related to the commonly co-existing liver disease and HF [49]. Collectively, these may explain the rates of HF in this Cancer/Coagulopathy/Liver disease dominant group (Class 1).

Patients in Class 4 were the oldest and had the highest prevalence of COPD, VD, and PVD compared to other classes. VD prevalence is significantly higher with increasing age [50], and COPD is prevalent in patients referred to heart valve surgeries [51], whereas PVD is commonly encountered in patients with COPD due to shared risk factors such as smoking [52]. Our findings are consistent with these epidemiological data, as while COPD, VD, and PVD are also prevalent in classes 1–3, and 5, the clustering analysis determined that patients with AMI and ≥1 of these comorbidities (e.g. COPD) are more similar to patients with the other two comorbidities (VD/PVD) than to patients with COPD, VD, or PVD in classes 1–3, and 5. Hence, Class 4 separated patients with the highest prevalence of these inter-related comorbidities into a distinct phenogroup. In addition, the high prevalence of AF/flutter in Class 4 is likely attributed to the highest prevalence of baseline stroke that often co-exists with AF. AF is an important risk factor for ischaemic stroke [53] as people with AF are up to five times more likely of having stroke [54], which is also shown in S4 Table. Furthermore, ~50% of patients with HF have CKD [36], where HF is a risk factor for CKD and vice versa [3739]. This may also explain the relatively high prevalence of CKD in Class 4 (35%) that has the second highest proportion of HF. The later observation may also be linked to the fact that CKD is more common in US people aged 65+ years than in younger people [55], where people in Class 4 are the oldest across all classes.

In summary, our findings suggest that the grouping of some comorbidities in specific classes is likely driven by shared pathophysiology or due to health disparities, such as age and race.

Association between comorbidity classes and in-hospital outcomes

The presence of ≥1 comorbidity has been associated with adverse outcomes among patients with AMI [25, 26, 56, 57]. However, to the best of our knowledge, no prior US study has assessed whether different clusters of comorbidities impact outcomes differentially. We found that the five comorbidity classes identified had very different outcomes.

In-hospital mortality. Patients in Class 1 had the highest odds of in hospital mortality compared to patients in the common Class 3. This observation is likely attributed to that almost a tenth of patients (9.7%) had cancer and that these individuals have poor outcomes [58]. Class 5 included the oldest patients with the highest prevalence of COPD which partially explains their increased odds for in-hospital mortality compared to Class 3. We also observed that the youngest/least burdened Class 2 had higher odds of mortality than Class 3 which likely may be due to that a high proportion of patients in Class 2 present with STEMI 41% or were burdened by other comorbidities (beyond the 21 we studied). A study reported that people in the high (dominated by CHD and PVD) and medium (PVD and HTN) comorbidity classes in UK AMI admissions between 2003 and 2013 were at 2.4-fold (95%CI: 2.3–2.5) and 1.5-fold (95% CI 1.4±1.5) higher risk of all-cause death compared to the low class, respectively [32]. Similarly, people with CHD in the severe (dominated by HF) and moderate (HTN and DM) comorbidity classes in China were associated with greater risks of mortality and rehospitalization than those in the mild class [33]. In comparison, we found higher mortality risk in the least burdened class as explained above, but we included far more comorbidities and investigated more outcomes besides mortality.

Major bleeding and stroke. In comparison to patients in the ’common’ group (Class 3), all classes were at higher risk for bleeding and acute stroke outcomes except the youngest/least burdened patients (Class 2). Patients in the cancer/coagulopathy/liver disease group had the worse outcomes and had 4.5-fold higher odds of having a major bleeding episode (which includes haemorrhagic stroke events) and 2.8-fold higher odds for ischemic stroke. Reportedly, coagulopathies, anemia, and thrombocytopenia associated with cancers increases the risk of major bleeding complications in AMI [58]. Our finding is also in line with several studies reporting that liver disease increases the risk for overall, ischemic/haemorrhagic stroke and that most people with liver cirrhosis have coagulopathy, dyslipidaemia, and heart disease, which are associated with developing stroke [59, 60].

PCI. Members of the highest comorbidity burden group (diabetes/CKD/HF, Class 5) were less likely to be treated with PCI than members of the ’common’ group (Class 3). Reportedly, patients admitted with AMI with higher comorbidity burden are less likely to have cardiac catheterisation [25, 27].

Potential clinical and research implications

In current clinical practice, patients with CVD without comorbidities are increasingly an exception. Based on contemporary US data, our detailed mapping of comorbidity profile by patient characteristics and association with outcomes improves the understanding of AMI multimorbidity burden which has possible implications in supporting clinicians, wider healthcare professionals (HCPs), and policy makers towards developing timely and tailored screening, prevention, and care programmes of these comorbidities in people with AMI. These implications include helping clinicians to identify higher-risk patients with AMI with specific multimorbidity phenotypes as a starting point to assess personalized interventions to reduce premature mortality and possibly prioritising interventions for those at greatest risk of poor outcomes, and defining multidisciplinary therapeutic pathways and novel technologies tailored to the multimorbidity burden in these specific groups. In addition, our findings on the associations of some comorbidity classes with worse outcomes, and our hypotheses as to why certain comorbidities are grouped together (e.g. the clustering of diabetes, CKD, and HF in the Black-dominant Class 5), highlight that prevention and timely screening programmes of some conditions may help in early detection and better management of these comorbidities, in people with AMI. Our identification of higher risk phenotypes may be useful in highlighting patients that may have greatest benefit from early outpatient follow up, and involvement of multi-speciality teams for inpatient or follow-up care. Furthermore, our defined phenotypes can also inform developers of clinical guidelines to consider multimorbidity in their decision-making algorithms [5], primarily in relation to the use of invasive treatments (e.g. NSTEMI), where there may be equipoise, particularly in elderly comorbid patients, thus moving away from current classic individual-condition guidelines.

Areas for future work include the external validation of our findings in a distinct and independent cohort, developing more inclusive research study designs to accommodate people with multimorbidity, examining longitudinal multimorbidity patterns, investigating why comorbidities cluster and how non-cardiovascular comorbidities possibly interact with outcomes in AMI.

Strengths and limitations

Our analysis is based on mapping the comorbidity burden of a cohort of nearly half-million AMI US admissions using 21 physical and mental health conditions from a nationally representative sample of the US population. To our best knowledge, this is the first study to examine the comorbidity burden of US AMI hospitalizations by patient factors using LCA and assess its association with outcomes. LCA is reportedly an optimum multimorbidity clustering algorithm and superior when compared to other existing clustering methods with many advantages e.g., accommodating different types of data, having a high within-method repeatability, and uniquely identifying small comorbidity clusters possibly not identified by most other clustering methods [12]. In addition, applying sampling weights produced estimates that are generalizable to a larger population than the studied sample size, but not necessarily to all patients with AMI. Therefore, our findings are likely broadly generalizable given the size and the ethnic diversity of the patient cohort and may have possible implications for care for wider population of multimorbid patients with AMI who are often excluded from clinical trials. Our study has the following limitations. The diagnoses are based on recorded codes, where there is a possibility of inaccurate coding. The dataset lack information on timing of events or in-hospital outcomes and on the underlying cause of death. The analysed data may include recurrent admissions, which cannot be identified, driven by the NIS design based on admission record as the unit of analysis. We have not externally validated the results, but this has been highlighted as a priority for future work. Finally, we may have missed other comorbidities, but we aimed to include AMI-related and AHRQ/ELIXHAUSER-verified comorbidities [20] to minimise misclassification.

Conclusions

Patients admitted with AMI have a high comorbidity burden, including non-cardiometabolic comorbidities, which we defined into five distinct phenogroups that are highly predictive of specific adverse outcomes. The grouping of some comorbidities in specific classes is likely driven by shared pathophysiology or due to health disparities, at least partially driven by age and race. The phenogroups we identified have different mortality, bleeding, and stroke outcomes, and we also observed heterogeneity in revascularisation. Our findings agree with the current trend towards prioritising and assessing multimorbidity in patients admitted with AMI, and CVD overall, to better understand the care needs of patients beyond the recommendations from the conventional single-disease oriented guidelines.

Supporting information

S1 Fig. Latent class membership (percentage) by age, sex, age/sex, and race.

Radar charts present the percentage proportion of patients per latent class starting from 0% (chart centre).

(PDF)

S2 Fig. Individual radar charts for percentage prevalence of comorbidities per latent class.

(PDF)

S3 Fig. Radar charts for percentage prevalence of in-hospital outcomes per latent class.

(PDF)

S4 Fig. Predictive margins (95% CI) of probabilities of outcomes per latent class.

(PDF)

S1 Table. ICD-10 and procedure codes for outcomes.

(PDF)

S2 Table. Comparison of AIC/BIC values between models.

(PDF)

S3 Table. Significance testing for baseline characteristics and comorbidity burden across latent classes.

(PDF)

S4 Table. Crude rates of in-hospital outcomes in patients admitted with AMI in 2018.

(PDF)

S5 Table. Odds ratios (95% CI) for risks of in-hospital outcomes in patients admitted with AMI in 2018.*.

Includes haemorrhagic stroke. ^ Class 3 is the largest class and was selected as the reference group. $ The ‘Other’ race group for these outcomes includes Hispanic, Asian/Pacific Islander, Native American and ‘Other’ categories. CABG: coronary artery bypass graft; CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; IABP: intra-aortic balloon pump; PCI: percutaneous coronary intervention; PVD: peripheral vascular disease; VD: valvular disease.

(PDF)

S6 Table. Regression coefficients (95% CI) of predictors of hospital costs in patients admitted with AMI in 2018.

^ Class 3 is the largest class and was selected as the reference group. CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; PVD: peripheral vascular disease; VD: valvular disease.

(PDF)

S7 Table. Incidence rate ratios (IRRs) (95% CI) of predictors of length of hospital stay in patients admitted with AMI in 2018.

^ Class 3 is the largest class and was selected as the reference group. CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; PVD: peripheral vascular disease; VD: valvular disease.

(PDF)

Data Availability

The third party data underlying the results presented in this study are available upon request from the Healthcare Cost and Utilization Project (HCUP) - National (Nationwide) Inpatient Sample (NIS) via their website (https://www.hcup-us.ahrq.gov/nisoverview.jsp). All interested researchers can access the data through HCUP directly. The authors of this study are not permitted to share the data or make it publicly available as per the data use agreement with HCUP. The authors did not have any special access privileges to this data.

Funding Statement

This study is funded by The University of Manchester as part of the Presidential Fellowship provided to SSZ. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Amirmohammad Khalaji

18 Sep 2023

PONE-D-23-21645Comorbidity clusters and in-hospital outcomes in patients admitted with acute myocardial infarction in the USA: a national population-based studyPLOS ONE

Dear Dr. Zghebi,

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[Note: HTML markup is below. Please do not edit.]

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Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: Yes

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: Zghebi et al. have performed a population-based study in order to identify comorbidity phenotypes of worse clinical outcomes following acute MI. The study is well performed and the findings are interesting. There are some minor points to add.

- The authors are encouraged to explain the clinical implications of their findings. In other words, what are the main lessons a clinician can learn from these?

- The advantages of LCA over other clustering methods could be added to the discussion section.

Reviewer #2: Few Questions:

1. How do authors explain high morbidity in Class 2 least burdened group as compared to Class 3 (CHD/dyslipidemia) group.

2. What explains the higher proportion of female in the Class 1 cluster?

3. What is the explanation of higher preponderance of afib/flutter in Class 4 patients.

4. What explains higher CKD rates in Class 4 patients?

5. One would imagine higher HF rates in CHD class, and yet HF rates are towards the lower side in Class 3 compared to Class 1, 4 and 5

6. What explains higher HF rates in Class 1

**********

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Reviewer #1: No

Reviewer #2: Yes: Nadeem Afridi

**********

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PLoS One. 2023 Oct 26;18(10):e0293314. doi: 10.1371/journal.pone.0293314.r002

Author response to Decision Letter 0


3 Oct 2023

Dear Editor,

Re. PONE-D-23-21645

Thank you for the opportunity to submit a revision of our manuscript.

Below, we provide a point-by-point response to the received comments. The changes are highlighted on the revised manuscript and numbered by the Reviewer and comment number to facilitate the review process.

We hope to have satisfactorily responded to the comments, which have strengthened our manuscript.

Looking forward to receiving your decision.

Yours sincerely,

Dr Zghebi, on behalf of the authors.

Journal requirements

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf [journals.plos.org] and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf [journals.plos.org]

Authors response

We thank the Editor for this comment. The manuscript has been reviewed and the formatting now adheres to the Journal's style as advised.

2. Thank you for stating the following in the Competing Interests section:

“SSZ, LYS, EK, MKR, DS, DMA MAM, MR declare no competing interests. SW is a currently an employee of GSK.” Please confirm that this does not alter your adherence to all PLOS ONE policies on sharing data and materials, by including the following statement: "This does not alter our adherence to PLOS ONE policies on sharing data and materials.” (as detailed online in our guide for authors http://journals.plos.org/plosone/s/competing-interests). [journals.plos.org] If there are restrictions on sharing of data and/or materials, please state these. Please note that we cannot proceed with consideration of your article until this information has been declared. Please include your updated Competing Interests statement in your cover letter; we will change the online submission form on your behalf.

Authors response

We confirm that the declared competing Interests statement does not alter our adherence to PLOS ONE policies on sharing data and materials. The updated Competing Interests statement has been added to the cover letter, as requested.

3. In your Data Availability statement, you have not specified where the minimal data set underlying the results described in your manuscript can be found. PLOS defines a study's minimal data set as the underlying data used to reach the conclusions drawn in the manuscript and any additional data required to replicate the reported study findings in their entirety. All PLOS journals require that the minimal data set be made fully available. For more information about our data policy, please see http://journals.plos.org/plosone/s/data-availability [journals.plos.org].

Upon re-submitting your revised manuscript, please upload your study’s minimal underlying data set as either Supporting Information files or to a stable, public repository and include the relevant URLs, DOIs, or accession numbers within your revised cover letter. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories [journals.plos.org]. Any potentially identifying patient information must be fully anonymized.

Important: If there are ethical or legal restrictions to sharing your data publicly, please explain these restrictions in detail. Please see our guidelines for more information on what we consider unacceptable restrictions to publicly sharing data: http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions [journals.plos.org]. Note that it is not acceptable for the authors to be the sole named individuals responsible for ensuring data access. We will update your Data Availability statement to reflect the information you provide in your cover letter.

Authors response

An updated Data Availability statement has been added to the cover letter as requested. Also copied below:

The data underlying the results presented in the study are available for purchase from the Healthcare Cost and Utilization Project (HCUP) - National (Nationwide) Inpatient Sample (NIS) via their website https://www.hcup-us.ahrq.gov/nisoverview.jsp. All interested researchers can access the data through HCUP directly and authors are not permitted to share the data (even as minimal underlying dataset) or make it available as per the data use agreement with HCUP. The authors did not have any special access privileges to this data.

4. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Authors response

We confirm that the reference list is complete and correct, and we have not cited any retracted references. New references numbered 44 to 49 and 53 to 55 have been added to the revised manuscript as part of the response to the reviewers' comments.

Review Comments to the Author

Reviewer #1

Zghebi et al. have performed a population-based study in order to identify comorbidity phenotypes of worse clinical outcomes following acute MI. The study is well performed and the findings are interesting. There are some minor points to add.

1. The authors are encouraged to explain the clinical implications of their findings. In other words, what are the main lessons a clinician can learn from these?

Authors response

We thank the reviewer for the positive remarks on our study and findings.

The findings provide a new insight on the clustering of comorbidity burden in patients admitted with AMI which can help clinicians to identify higher-risk patients with AMI with specific multimorbidity phenotypes as a starting point to assess personalized interventions to minimise adverse outcomes and reduce premature mortality.

Alongside our mapping of comorbidity profile, we provide an interpretation of possibly why certain comorbidities grouped together in people with AMI which may support healthcare professionals (HCPs) towards developing tailored prevention and timely screening programmes of some conditions may help early detection and better management of these comorbidities in people with AMI.

As outlined in the revised manuscript, we observe the following main lessons from our findings to clinicians, wider HCPs and policy makers:

- Understanding of the detailed mapping of the comorbidity profile by patient factors in adults admitted with AMI derived from modern clinical data.

- Understanding of possibly why certain comorbidities group together in people with AMI which can inform screening schemes and the adoption of alternative multidisciplinary therapeutic pathways tailored for high-risk groups with a specific multimorbidity phenotype e.g. our interpretation of the drivers of COPD, VD, and PVD clustering in Class 4, or the clustering of DM, CKD, and HF in the Black-dominant Class 5.

- Inform clinical guidelines and healthcare policy developers on class membership to move away from current individual-condition guideline.

Changes to the paper

In response to this comment, we have revised the 'Potential clinical and research implications' section of the Discussion and it now reads as follows:

'In current clinical practice, patients with CVD without comorbidities are increasingly an exception. Based on contemporary US data, our detailed mapping of comorbidity profile by patient characteristics and association with outcomes improves the understanding of AMI multimorbidity burden which has possible implications in supporting clinicians, wider healthcare professionals (HCPs), and policy makers towards developing timely and tailored screening, prevention, and care programmes of these comorbidities in people with AMI. These implications include helping clinicians to identify higher-risk patients with AMI with specific multimorbidity phenotypes as a starting point to assess personalized interventions to reduce premature mortality and possibly prioritising interventions for those at greatest risk of poor outcomes, and defining multidisciplinary therapeutic pathways and novel technologies tailored to the multimorbidity burden in these specific groups. In addition, our findings on the associations of some comorbidity classes with worse outcomes, and our hypotheses as to why certain comorbidities are grouped together (e.g. the clustering of diabetes, CKD, and HF in the Black-dominant Class 5), highlight that prevention and timely screening programmes of some conditions may help in early detection and better management of these comorbidities, in people with AMI. Our identification of higher risk phenotypes may be useful in highlighting patients that may have greatest benefit from early outpatient follow up, and involvement of multi-speciality teams for inpatient or follow-up care. Furthermore, our defined phenotypes can also inform developers of clinical guidelines to consider multimorbidity in their decision-making algorithms,[5] primarily in relation to the use of invasive treatments (e.g. NSTEMI), where there may be equipoise, particularly in elderly comorbid patients, thus moving away from current classic individual-condition guidelines.

Areas for future work include the external validation of our findings in a distinct and independent cohort, developing more inclusive research study designs to accommodate people with multimorbidity, examining longitudinal multimorbidity patterns, understanding why comorbidities cluster and how non-cardiovascular comorbidities possibly interact with outcomes in AMI.'

2. The advantages of LCA over other clustering methods could be added to the discussion section.

Authors response and Changes to the paper

In response to this comment, we now added the following section to the Discussion section:

'LCA is reportedly an optimum multimorbidity clustering algorithm and superior when compared to other existing clustering methods with many advantages e.g., accommodating different types of data, having a high within-method repeatability, and uniquely identifying small comorbidity clusters possibly not identified by most other clustering methods.[12]'

Reviewer #2

Few Questions:

1. How do authors explain high morbidity in Class 2 least burdened group as compared to Class 3 (CHD/dyslipidemia) group.

Authors response

As shown in Table 2 and S2 Figure (both copied in below), we observe that Class 2 has a consistently lower morbidity burden compared to people in Class 3, apart from 'rheumatoid arthritis and collagen vascular diseases' where the proportion is at 1.9% in both classes and weight loss that is more common in C2. Notably, in some conditions the burden is much lower in Class 2 e.g., for HTN (40% vs. 95%), dyslipidaemia (35% vs. 93%), diabetes (6% vs. 51%), and CKD (0% vs. 6%).

Comorbidities, % proportion (95% CI) Class 2 (Least burdened) Class 3 (CHD/ dyslipidaemia)

Hypertension 40.4 (39.7; 41.2) 95.0 (94.8; 95.2)

CHD 67.2 (66.5; 67.9) 90.6 (90.3; 90.9)

Dyslipidaemia 35.2 (34.5; 35.9) 92.6 (92.3; 92.9)

Diabetes (DM) 5.8 (5.5; 6.2) 51.2 (50.6; 51.7)

Heart failure (HF) 5.5 (5.1; 5.8) 18.1 (17.7; 18.5)

COPD 11.3 (10.8; 11.8) 16.9 (16.5; 17.3)

CKD 0 5.9 (5.7; 6.2)

Obesity 10.2 (9.7; 10.7) 29.2 (28.7; 29.6)

Anaemias 2.7 (2.5; 3.0) 3.6 (3.4; 3.8)

Valvular disease (VD) 5.5 (5.2; 5.8) 7.0 (6.7; 7.2)

Hypothyroidism 7.2 (6.8; 7.6) 11.0 (10.6; 11.3)

Atrial fibrillation (AF)/flutter 3.3 (3.0; 3.5) 5.1 (4.9; 5.3)

PVD 3.2 (2.9; 3.4) 4.5 (4.3; 4.7)

Depression 5.0 (4.7; 5.4) 9.9 (9.6; 10.2)

TIA/Stroke 1.7 (1.5; 1.9) 6.6 (6.31; 6.8)

Coagulopathy 1.1 (1.0; 1.3) 3.1 (2.90; 3.3)

Weight loss 0.4 (0.4; 0.6) 0.2 (0.2; 0.23)

Cancer 1.0 (0.8; 1.1) 1.2 (1.1; 1.3)

RA & collagen vascular diseases 1.9 (1.7; 2.1) 1.9 (1.7; 2.0)

Liver disease 0.5 (0.4; 0.6) 1.8 (1.7; 2.0)

Psychoses 1.3 (1.2; 1.5) 2.2 (2.0; 2.3)

2. What explains the higher proportion of female in the Class 1 cluster?

Authors response

Overall, Class 1 is dominated by a higher prevalence of liver disease, coagulopathy, and cancer, compared to other classes. Previous studies show that female sex is associated with higher risk of acute on chronic liver failure (ref 44), and with hypercoagulation (ref 45), which possibly explains why Class 1 had more females (45%) than other classes (proportion ranging from 34% in Class 2 to 43% in Class 4).

As shown in the female-specific heat map (Figure 2), Class 1 combines higher prevalence of comorbidities known to be more common in females: liver disease (5% in C1 vs. 0.4-2.9% in C2-C5), coagulopathy (11% vs. 0.7%-8.2% in C2-C5), and is the class with the lowest burden of dyslipidaemia (5.7% vs. 33-91%) that is known to be less common in females, possibly due to the reported high prevalence of diagnostic inertia of dyslipidaemia in women (ref 46).

Changes to the paper

In response to this comment, the following text is now added to the Discussion section: 'Class 1 includes a higher proportion of females (45%) than Classes 2-5 which is possibly explained by the combination of higher prevalence of comorbidities known to be more common in females, e.g., liver disease[44] (5% in C1 vs. 0.4-2.9% in C2-C5), and hypercoagulation (coagulopathy)[45] (11% vs. 0.7%-8.2% in C2-C5). Class 1 also has the lowest burden of dyslipidaemia (5.7% vs. 33-91% in C2-C5) that is known to be less common in females, possibly due to the reported high prevalence of diagnostic inertia of dyslipidaemia in women.[46]'

3. What is the explanation of higher preponderance of afib/flutter in Class 4 patients.

Authors response

The high prevalence of AF/flutter in Class 4 (28%) is likely attributed to the highest prevalence of baseline stroke (18%) that often co-exists with AF. It is widely known that AF is an important risk factor for ischaemic stroke (ref 53) as people with AF are up to five times more likely of having stroke (ref 54). This is also evident by the results in S4 Table showing that Class 4 members are the top 2 among all classes in developing acute ischemic stroke outcome (1.7%).

Changes to the paper

In response to this comment, this text has been added to the Discussion section of the paper: 'In addition, the high prevalence of AF/flutter in Class 4 is likely attributed to the highest prevalence of baseline stroke that often co-exists with AF. AF is an important risk factor for ischaemic stroke[53] as people with AF are up to five times more likely of having stroke,[54] which is also shown in S4 Table.'

4. What explains higher CKD rates in Class 4 patients?

Authors response

The rates of CKD in Class 4 (35%) are probably linked to the fact that CKD is generally prevalent in adults with CVD, hence its prevalence ranges between 0-25% in Classes 1-3 and up to 79% in Class 5. Previous literature show that ~50% of patients with HF have CKD, [36] where HF is a risk factor for CKD and vice versa, [37-39] where Class 4 has the second highest proportion of HF.

Age may also explain the observed higher CKD rates in Class 4. As highlighted in the paper, people in Class 4 are the oldest group compared to the other classes and The Centers for Disease Control and Prevention (CDC) report that CKD is more common in US people aged 65+ years (34%) than in younger people (ref 55) which is in agreement with our estimates.

Changes to the paper

In response to this comment, the following text in the Discussion section now reads as: 'Furthermore, ~50% of patients with HF have CKD,[36] where HF is a risk factor for CKD and vice versa.[37-39] This may also explain the relatively high prevalence of CKD in Class 4 (35%) that has the second highest proportion of HF. The later observation may also be linked to the fact that CKD is more common in US people aged 65+ years than in younger people,[55] where people in Class 4 are the oldest across all classes.'

5. One would imagine higher HF rates in CHD class, and yet HF rates are towards the lower side in Class 3 compared to Class 1, 4 and 5

Authors response

The chosen clustering approach expectedly classifies the patient population into distinct phenogroups based on the more relevant or inter-related comorbidities (e.g. conditions with shared pathophysiology) and socio-demographic factors (and possibly other unrecorded characteristics). In other words, LCA determined that patients with AMI and with high rates of HF are likely 'more similar' to AMI patients with highly prevalent diabetes and CKD (and so were grouped in Class 5) than to AMI patients with prevalent CHD and dyslipidaemia in Class 3. However, as the reviewer noted, HF is prevalent in Class 1 and Classes 3-5, but the resulted LCA phenogroups are driven by several factors as we explain above.

6. What explains higher HF rates in Class 1

Authors response

Our findings show that no comorbidity was exclusive per a latent class, especially for the most common comorbidities in AMI population e.g. HTN, HF and CHD. While we acknowledge that LCA grouped people with AMI into the most distinct clusters as possible leading to some clusters with a few dominant comorbidities, the observation of high HF rates in Class 1 may be basically driven by HF being a common comorbidity in people with AMI and so it is most prevalent at 74% in the DM/CKD/HF group (Class 5), while is also diagnosed in 62% of people in Class 1. Reportedly, HF leads to activation of coagulation (increased levels of thrombin formation and activation of fibrinolysis) (ref 47 & 48) and also due to possible cardiohepatic interactions related to the commonly co-existing liver disease and heart failure. (ref 49) Collectively, these may explain the observed rates of HF in this Cancer/Coagulopathy/Liver disease dominant group (Class 1).

Changes to the paper

This text has been added to the Discussion section to explain this observation: 'Our findings show that no comorbidity was exclusive per a latent class, especially for the most common comorbidities in AMI population e.g., HF that is most prevalent at 74% in the DM/CKD/HF group (Class 5) while it is also diagnosed in 62% of people in Class 1. Reportedly, HF leads to activation of coagulation (increased levels of thrombin formation and activation of fibrinolysis)[47, 48] and also due to possible cardiohepatic interactions related to the commonly co-existing liver disease and HF.[49] Collectively, these may explain the rates of HF in this Cancer/Coagulopathy/Liver disease dominant group (Class 1).'

Attachment

Submitted filename: Response to Reviewers.pdf

Decision Letter 1

Amirmohammad Khalaji

10 Oct 2023

Comorbidity clusters and in-hospital outcomes in patients admitted with acute myocardial infarction in the USA: a national population-based study

PONE-D-23-21645R1

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Acceptance letter

Amirmohammad Khalaji

16 Oct 2023

PONE-D-23-21645R1

Comorbidity clusters and in-hospital outcomes in patients admitted with acute myocardial infarction in the USA: a national population-based study

Dear Dr. Zghebi:

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Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Fig. Latent class membership (percentage) by age, sex, age/sex, and race.

    Radar charts present the percentage proportion of patients per latent class starting from 0% (chart centre).

    (PDF)

    S2 Fig. Individual radar charts for percentage prevalence of comorbidities per latent class.

    (PDF)

    S3 Fig. Radar charts for percentage prevalence of in-hospital outcomes per latent class.

    (PDF)

    S4 Fig. Predictive margins (95% CI) of probabilities of outcomes per latent class.

    (PDF)

    S1 Table. ICD-10 and procedure codes for outcomes.

    (PDF)

    S2 Table. Comparison of AIC/BIC values between models.

    (PDF)

    S3 Table. Significance testing for baseline characteristics and comorbidity burden across latent classes.

    (PDF)

    S4 Table. Crude rates of in-hospital outcomes in patients admitted with AMI in 2018.

    (PDF)

    S5 Table. Odds ratios (95% CI) for risks of in-hospital outcomes in patients admitted with AMI in 2018.*.

    Includes haemorrhagic stroke. ^ Class 3 is the largest class and was selected as the reference group. $ The ‘Other’ race group for these outcomes includes Hispanic, Asian/Pacific Islander, Native American and ‘Other’ categories. CABG: coronary artery bypass graft; CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; IABP: intra-aortic balloon pump; PCI: percutaneous coronary intervention; PVD: peripheral vascular disease; VD: valvular disease.

    (PDF)

    S6 Table. Regression coefficients (95% CI) of predictors of hospital costs in patients admitted with AMI in 2018.

    ^ Class 3 is the largest class and was selected as the reference group. CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; PVD: peripheral vascular disease; VD: valvular disease.

    (PDF)

    S7 Table. Incidence rate ratios (IRRs) (95% CI) of predictors of length of hospital stay in patients admitted with AMI in 2018.

    ^ Class 3 is the largest class and was selected as the reference group. CHD: coronary heart disease; DM: diabetes; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; HF: heart failure; PVD: peripheral vascular disease; VD: valvular disease.

    (PDF)

    Attachment

    Submitted filename: Response to Reviewers.pdf

    Data Availability Statement

    The third party data underlying the results presented in this study are available upon request from the Healthcare Cost and Utilization Project (HCUP) - National (Nationwide) Inpatient Sample (NIS) via their website (https://www.hcup-us.ahrq.gov/nisoverview.jsp). All interested researchers can access the data through HCUP directly. The authors of this study are not permitted to share the data or make it publicly available as per the data use agreement with HCUP. The authors did not have any special access privileges to this data.


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