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PLOS ONE logoLink to PLOS ONE
. 2024 Sep 30;19(9):e0311312. doi: 10.1371/journal.pone.0311312

Association of visceral adiposity index and lipid accumulation products with prediabetes in US adults from NHANES 2007–2020: A cross-sectional study

Li-Ting Qiu 1, Ji-Dong Zhang 1, Bo-Yan Fan 1, Ling Li 1, Gui-Xiang Sun 1,*
Editor: Demitri Constantinou2
PMCID: PMC11441703  PMID: 39348367

Abstract

Background

The lipid accumulation product (LAP) and the visceral adiposity index (VAI) are suggested as dependable measures for assessing visceral fat levels. Prediabetes is recognized as a condition that precedes the potential onset of diabetes. The objective of this research is to investigate how VAI and LAP are related to prediabetes among the adult population in the United States.

Methods

Information from the 2007–2020 National Health and Nutrition Examination Survey (NHANES) was scrutinized in a cross-sectional study. To evaluate the connection between VAI or LAP and the presence of prediabetes, both univariate analysis and multivariate logistic regression were utilized. Threshold effect analysis and fitted smoothing curves were used to delve into the non-linear association between VAI or LAP and prediabetes. Additional analyses were performed on specific subgroups, along with tests to explore potential interactions.

Results

In general, 12,564 American adults were included. After full adjustment, prediabetes with VAI (OR: 1.128, 95% CI: 1.073–1.185) or LAP (OR: 1.006, 95% CI: 1.004–1.008) showed a positive correlation. Individuals in the 4th VAI quartile group faced a significant 61.9% elevated risk for prediabetes (OR: 1.619, 95% CI: 1.354–1.937) when contrasted to those in the 1st VAI quartile. Participants in the 4th LAP quartile group had a significant 116.4% elevated risk for prediabetes (OR: 2.164, 95% CI: 1.747–2.681) when contrasted to individuals of the 1st LAP quartile. Smooth curve fitting analysis revealed a nonlinear correlation of VAI or LAP and prediabetes, and threshold effect analysis was used to determine an inflection point of 4.090 for VAI and 68.168 for LAP.

Conclusions

The values of VAI and LAP are positively associated with the prevalence of prediabetes. The VAI and LAP indices may be used as predictors of prediabetes.

Introduction

Type 2 diabetes mellitus (diabetes) is a progressive metabolic disease that poses a significant risk to public health. Timely identification of high-risk individuals could help prevent and control diabetes. Prediabetes is a well-acknowledged risk factor for future diabetes, representing an intermediate state where plasma glucose levels range between normal glucose metabolism and diabetes [1, 2]. Research evidence indicates a link between prediabetes and cardiovascular disease (CVD), diabetic retinopathy, neuropathies, and kidney disease [36]. Identifying and addressing prediabetes at an early stage can successfully halt the progression to diabetes and its associated health issues [7]. Studies indicate that each year, approximately 5–10% of individuals with prediabetes develop diabetes [2], and the conversion rate can be up to 70% [8]. The International Diabetes Federation projects that by 2030, close to 470 million individuals will be affected by prediabetes. The challenge in diagnosing prediabetes lies in its non-specific symptoms, making it a condition that often goes undetected. Therefore, awareness of the prediabetes risk factors is essential, as timely and appropriate intervention may reverse the incidence of diabetes and related complications.

A substantial body of research indicates that individuals carrying excess weight or with obesity are at an increased risk for the onset of prediabetes [9, 10]. Particularly, individuals with centripetal distribution of adiposity (visceral adiposity) are believed to have a greater predisposition to prediabetes compared to individuals with subcutaneous adiposity [11, 12]. Techniques like magnetic resonance imaging (MRI) and computed tomography (CT) are accurate in assessing the distribution of body fat, but their high costs and practical limitations curtail their widespread application in both research and routine clinical settings. Traditional obesity-related indicators, such as body mass index (BMI) and waist circumference (WC), are non-invasive and readily available but fall short in accurately distinguishing between subcutaneous and visceral fat masses. The visceral adiposity index (VAI), which integrates both anthropometric measurements (including BMI and WC) and blood biomarkers (including triglyceride (TG) and high density lipoprotein-cholesterol (HDL)), has gained acceptance as an effective measure for assessing the function of visceral fat [13]. Accordingly, the VAI is particularly adept at detecting metabolically unhealthy profiles that are often linked with central fat accumulation, including cardiovascular disease, metabolic syndrome, and insulin resistance [1417]. Lipid accumulation product (LAP) is an index integrates WC and TG and is a measure of abdominal lipid accumulation [18]. LAP indicators are effective at identifying insulin sensitivity, diabetes, metabolic syndrome, and CVD when contrasted to traditional lipid profiles [1922]. There are several studies analyzing the relationship between VAI or LAP and prediabetes. In a study of the Montenegrin population conducted by Klisic et al. [23] a significant positive relationship with prediabetes was suggested for both VAI and LAP. Ramdas Nayak et al. [24] found that both VAI and LAP were generally more effective than WC, waist to hip ratio (WHR), and BMI at predicting prediabetes within the Asian Indian demographic. Ahn et al. [25] demonstrated the efficacy of VAI and LAP as valuable indicators for discerning prediabetes/diabetes within a German population. Nevertheless, the ethnic specificity of visceral fat mean their results may not be widely applicable. Moreover, there has been a lack of investigation into the connection between VAI, LAP, and prediabetes across a nationally representative cohort of adults in the United States.

Therefore, we explored the correlation between prediabetes and VAI or LAP in a larger and more representative sample of various ethnic groups in the United States. The hypothesize of this study is that lower levels of VAI or LAP are associated with a significantly lower risk of prediabetes.

Methods

Study design and participants

14 years of data (2007 to 2020) from the National Health and Nutrition Examination Survey (NHANES) were applied. The NHANES, a database compiled by the Centers for Disease Control (CDC) and Prevention’s National Center for Health Statistics (NCHS), is constructed from a population-based national survey for the evaluation of the noninstitutionalized American population’s nutritional status and health. Participants were recruited by a complex and multistage probability sampling design that continuously samples approximately 5000 participants annually in the United States to ensure the representation of diverse demographic groups [26]. Specifically, NHANES first selects primary sampling units (PSUs) across the country, followed by stratified random sampling within each PSU to choose households, and finally, individuals are randomly selected from eligible household members. Survey participants were requested to partake in a household interview, encompassing questionnaires regarding socio-demographic, dietary, and general health information, along with a medical examination conducted at mobile examination centers, encompassing medical, dental, and physiological measurements. Initially, 66,148 people were involved in the study from 2007 to 2020 in the NHANES database. The study did not include the following groups: (1) individuals below the age of 20; (2) participants with diabetes data; (3) participants without information on diabetes, prediabetes, and blood glucose levels; (4) those without available information regarding VAI and LAP. After applying these criteria, the study population comprised 12,564 subjects (Fig 1). This investigation adhered to the ethical principles outlined in the Declaration of Helsinki [27]. Written consent was obtained from all participants of the NHANES study, and the project received ethical clearance from the NCHS Research Ethics Review Board [28].

Fig 1. Flowchart of participant selection.

Fig 1

Abbreviation: NHANES, National Health and Nutrition Examination Survey.

Exposure variable and outcomes

Individuals were identified as having prediabetes based on one or more of the following criteria: an HbA1c range of 5.7 to 6.4%, an impaired fasting glucose range of 5.6 to 7.0 mmol/L, an impaired glucose tolerance range of 7.8 to 11.1 mmol/L, or having received a clinical diagnosis of prediabetes from a healthcare provider [29]. The calculations for VAI and LAP were performed using established equations [13, 18].For men, the VAI formula is [13]: [WC/[(39.68 + (1.88 × BMI))] × (TG/1.03) × (1.31/HDL)]; for women, it is: [WC/(36.58 + (1.89 × BMI))] × (TG/0.81) × (1.52/HDL). The LAP formula for men is [18] (WC−65) × TG; for women, it is: (WC−58) × TG. Within these formulas, WC is expressed in cm and BMI in kg/m2. TG and HDL cholesterol levels are measured in mmol/L.

Covariates

Based on previous related studies [30, 31], we evaluated the potential risk factors for prediabetes, which included sociodemographic data (age, sex, race, education, marital, poverty income ratio (PIR)), lifestyle behavior characteristics (smoking status, alcohol use, BMI, physical activity, daily energy intake), and disease history (hyperlipidemia, hypertension, cancer, CVD). The smoking habits of participants were classified into three distinct types: never, former, and current smoker. Participants’ alcohol consumption was assessed by the single choice questionnaire, "In the past 12 months, on those days that you drank alcoholic beverages, on the average, how many drinks did you have?" Physical activity was assessed by metabolic equivalent scores (METs) = sum of walking + moderate + vigorous MET-minutes/week scores [32]. The total daily energy intake (kcal) was calculated from the first day of 24-h dietary recall. Hyperlipidemia was characterized by either the use of medication to lower lipid levels or by meeting any of the following criteria: total cholesterol being equal to or more than 200 mg/dL, TG being equal to or more than 150 mg/dL, low-density lipoprotein levels being equal to or more than 130 mg/dL, or HDL cholesterol being equal to or less than 50 mg/dL for females and being equal to or less than 40 mg/dL for males [33]. Hypertension was identified in individuals with a systolic blood pressure of 140 mmHg or higher and/or a diastolic blood pressure of 90 mmHg or higher, those who reported a history of high blood pressure, or those taking medication to manage blood pressure. The presence of cancer was determined by a positive response to the question, "Have you ever been told you had cancer or a malignancy?" CVD was classified as having been diagnosed with conditions such as stroke, heart attack, angina, coronary heart disease, or coronary heart disease by a healthcare staff.

Statistical analysis

EmpowerStates (www.empowerstats.com) was used for all statistical analyses. SDMVSTRA and SDMVPSU were utilized to ensure accurate national estimates due to the complex survey design employed in NHANES. All continuous variables had the expression of mean values (95% CI) during the baseline analysis, while categorical variables had the expression of percentages (95% CI). Multiple imputation was conducted to adequately account for missing covariates. The univariate analysis was used to investigate the potential correlation of each covariate and prediabetes. Multiple regression analysis was conducted using three models with different adjustments for confounders: Model 1 was unadjusted, Model 2 adjusted for gender, age, and race, and covariates were retained in the full model 3 if the change in the effect estimate exceeded 10%. Subgroup analyses were conduced by age, gender, smoking status, alcohol use, BMI, physical activity, daily energy intake, hyperlipidemia, hypertension, cancer and CVD. Interaction P-values were used to evaluate the consistency of effects across subgroups. We carried out smooth curve fitting for discovering underlying nonlinear relationships. A threshold effect analysis was further performed to demonstrate the association and inflection point between VAI, LAP, and prediabetes. A P-value < 0.05 exhibited significance.

Results

Participant characteristics

Among the 12,564 participants, there were 7,051 with prediabetes and 5,513 with normal blood glucose. When contrasted to participants with normal blood glucose, those with prediabetes were more likely to be older (50.4, P < 0.0001); more frequently male (52.8%, P < 0.0001); have a lower proportion of some college and college graduates or above (P < 0.0001); be less often never married (14.3%, P < 0.0001); be less frequently non-smokers (52.0%, P = 0.0007); have a normal weight less often (23.5%, P < 0.0001); engage in physical activity < 600 MET-minutes/week more frequently (46.3%, P < 0.0001); and have higher VAI (2.1, P < 0.0001) and LAP (60.6, P < 0.0001); they also had a higher risk of hyperlipidemia (78.1%, P < 0.0001), hypertension (42.2%, P < 0.0001), cancer (10.9%, P < 0.0001), and CVD (9.1%, P < 0.0001) (Table 1).

Table 1. Characteristics of participants by prediabetes status, NHANES 2007–2020.

Variable Normal blood glucose (N = 5,513) Prediabetes (N = 7,051) P-value
Age, years 40.2 (39.5, 40.9) 50.4 (49.9, 51.0) <0.0001
Sex <0.0001
    Men 42.4 (40.9, 43.9) 52.8 (51.3, 54.3)
    Women 57.6 (56.1, 59.1) 47.2 (45.7, 48.7)
Race and ethnicity 0.1638
    Mexican American 7.9 (6.7, 9.4) 9.0 (7.5, 10.7)
    other Hispanic 6.2 (5.1, 7.6) 6.1 (5.1, 7.3)
non-Hispanic white 68.5 (65.6, 71.2) 66.8 (64.0, 69.5)
    non-Hispanic black 9.7 (8.4, 11.1) 10.1 (8.8, 11.5)
    other races 7.7 (6.7, 8.8) 8.1 (7.1, 9.1)
Education <0.0001
    < 9th grade 3.4 (2.9, 4.1) 5.9 (5.2, 6.8)
    9–11th grade 9.1 (7.9, 10.6) 11.1 (10.1, 12.2)
    high school graduate 19.4 (17.8, 21.0) 24.3 (22.6, 26.0)
    some college 32.2 (30.2, 34.1) 29.6 (28.0, 31.3)
    college graduate or above 35.9 (33.4, 38.5) 29.1 (26.9, 31.4)
Marital <0.0001
    Married/Living with partner 61.9 (59.9, 63.8) 66.2 (64.1, 68.1)
    Widowed/Divorced/Separated 13.5 (12.4, 14.8) 19.5 (18.1, 21.1)
    Never married 24.6 (22.6, 26.6) 14.3 (13.0, 15.7)
Smoking status <0.0001
    Never 61.0 (58.7, 63.3) 52.0 (50.0, 53.9)
    Former 19.8 (18.3, 21.4) 27.6 (25.9, 29.4)
    Now 19.2 (17.4, 21.1) 20.4 (19.0, 21.9)
Alcohol use 0.3845
    1–14 99.3 (98.9, 99.5) 99.4 (99.2, 99.6)
    ≥ 15 0.7 (0.5, 1.1) 0.6 (0.4, 0.8)
PIR 0.1848
    ≤ 1.3 22.3 (20.5, 24.2) 21.7 (20.1, 23.4)
    > 1.3 and ≤ 3.5 34.1 (31.9, 36.2) 36.1 (34.4, 37.9)
    > 3.5 43.6 (41.1, 46.3) 42.2 (39.8, 44.5)
BMI <0.0001
    Normal (<25 kg/m2) 43.0 (41.0, 44.9) 23.5 (22.0, 25.0)
    Overweight (25–30 kg/m2) 33.0 (31.4, 34.7) 35.4 (34.0, 36.9)
    Obese (≥30 kg/m2) 24.0 (22.4, 25.7) 41.1 (39.4, 42.8)
Physical activity 0.0007
    < 600 43.4 (42.0, 44.9) 46.3 (44.7, 47.9)
    600–1500 31.8 (30.3, 33.3) 28.0 (26.7, 29.4)
    > 1500 24.8 (23.4, 26.3) 25.6 (24.1, 27.2)
Daily energy intake (kcal) 2196.3 (2161.6, 2231.0) 2204.4 (2169.4, 2239.4) 0.7555
VAI 1.5 (1.4, 1.5) 2.1 (2.0, 2.1) <0.0001
LAP 38.8 (37.4, 40.2) 60.6 (58.6, 62.6) <0.0001
Hyperlipidemia <0.0001
    No 41.8 (40.0, 43.6) 21.9 (20.6, 23.4)
    Yes 58.2 (56.4, 60.0) 78.1 (76.6, 79.4)
Hypertension <0.0001
    No 79.3 (77.5, 81.0) 57.8 (56.0, 59.5)
    Yes 20.7 (19.0, 22.5) 42.2 (40.5, 44.0)
Cancer <0.0001
    No 93.5 (92.6, 94.4) 89.1 (88.0, 90.2)
    Yes 6.5 (5.6, 7.4) 10.9 (9.8, 12.0)
CVD <0.0001
    No 96.6 (96.0, 97.2) 90.9 (89.9, 91.9)
    Yes 3.4 (2.8, 4.0) 9.1 (8.1, 10.1)

Continuous variables were listed as weighted mean (95% CI). Categorical variables were listed as weighted percentage (95% CI). Abbreviations: BMI, body mass index; CVD, cardiovascular diseases; LAP, lipid accumulation product; NHANES, National Health and Nutrition Examination Survey; PIR, poverty income ratio; VAI, visceral obesity index.

Univariate analysis

With the aim of examining the correlation of variables and prediabetes, we carried out univariate analysis. Age was found to be positively associated with prediabetes (OR: 1.04, 95% CI: 1.04–1.05). When contrasted to men, women had a lower risk of developing prediabetes (OR: 0.63, 95% CI: 0.59–0.68). Among ethnic groups, non-Hispanic whites (OR: 0.80; 95% CI: 0.72–0.89) and other races (OR: 0.83, 95% CI: 0.72–0.95) showed a lower prevalence of prediabetes. Regarding education level, individuals with 9–11th grade education (OR: 0.67, 95% CI: 0.57–0.79), high school graduates (OR: 0.65, 95% CI: 0.56–0.76), some college education (OR: 0.51, 95% CI: 0.44–0.59), and college graduates or above (OR: 0.46, 95% CI: 0.39–0.53) had lower prevalence rates of prediabetes when contrasted to individuals with less than a 9th-grade education. When contrasted to being married/living with a partner, the widowed/divorced/separated group (OR: 1.34, 95% CI: 1.22–1.47) had a higher risk of prediabetes. Those who were never married (OR: 0.54, 95% CI: 0.49–0.59) had a lower prevalence of prediabetes. Former smokers (OR: 1.64, 95% CI: 1.50–1.79) and current smokers (OR: 1.16, 95% CI: 1.06–1.27) were at a higher risk of prediabetes than nonsmokers. Obesity (OR: 2.79, 95% CI: 2.56–3.06) and being overweight (OR: 1.87, 95% CI: 1.71–2.04) significantly elevated the odds of prediabetes when contrasted to normal weight. Engaging in physical activity of 600–1500 MET-minutes/week (OR: 0.84, 95% CI: 0.77–0.93) was associated with a lower risk of prediabetes than physical activity below 600 MET-minutes/week. Notably, VAI (OR: 1.26, 95% CI: 1.22–1.29) and LAP (OR: 1.01, 95% CI: 1.01–1.01) showed a positive correlation to the occurrence of prediabetes. Additionally, hyperlipidemia (OR: 2.35, 95% CI: 2.18–2.54), hypertension (OR: 2.79, 95% CI: 2.58–3.02), cancer (OR: 1.86, 95% CI: 1.62–2.14), and CVD (OR: 2.50, 95% CI: 2.15–2.91) were all positively related to prediabetes (Table 2).

Table 2. Association of unadjusted variables with prediabetes.

Variables OR (95%CI) P-value
Age, years 1.04 (1.04, 1.05) <0.0001
Sex
    Men Reference
    Women 0.63 (0.59, 0.68) <0.0001
Race and ethnicity
    Mexican American Reference
    other Hispanic 0.94 (0.81, 1.08) 0.3879
    non-Hispanic white 0.80 (0.72, 0.89) <0.0001
    non-Hispanic black 0.94 (0.83, 1.07) 0.3444
    other races 0.83 (0.72, 0.95) 0.0066
Education
    < 9th grade Reference
    9 –11th grade 0.67 (0.57, 0.79) <0.0001
    high school graduate 0.65 (0.56, 0.76) <0.0001
    some college 0.51 (0.44, 0.59) <0.0001
    college graduate or above 0.46 (0.39, 0.53) <0.0001
Marital
    Married/Living with partner Reference
    Widowed/Divorced/Separated 1.34 (1.22, 1.47) <0.0001
    Never married 0.54 (0.49, 0.59) <0.0001
Smoking status
    Never Reference
    Former 1.64 (1.50, 1.79) <0.0001
    Now 1.16 (1.06, 1.27) 0.0013
Alcohol use
    1–14 Reference
    ≥ 15 0.92 (0.54, 1.56) 0.7510
PIR
    ≤ 1.3 Reference
    > 1.3 and ≤ 3.5 1.03 (0.94, 1.12) 0.5078
    > 3.5 0.93 (0.85, 1.02) 0.1112
BMI
    Normal (<25 kg/m2) Reference
    Overweight (25–30 kg/m2) 1.87 (1.71, 2.04) <0.0001
    Obese (≥30 kg/m2) 2.79 (2.56, 3.06) <0.0001
Physical activity
    < 600 Reference
    600–1500 0.84 (0.77, 0.93) 0.0008
    > 1500 0.92 (0.84, 1.01) 0.0901
Daily energy intake (kcal) 1.00 (1.00, 1.00) 0.3300
VAI 1.26 (1.22, 1.29) <0.0001
LAP 1.01 (1.01, 1.01) <0.0001
Hyperlipidemia
    No Reference
    Yes 2.35 (2.18, 2.54) <0.0001
Hypertension
    No Reference
    Yes 2.79 (2.58, 3.02) <0.0001
Cancer
    No Reference
    Yes 1.86 (1.62, 2.14) <0.0001
CVD
    No Reference
    Yes 2.50 (2.15, 2.91) <0.0001

Abbreviations: BMI, body mass index; CI, confidence interval; CVD, cardiovascular diseases; LAP, lipid accumulation product; OR, odds ratio; PIR, poverty income ratio; VAI, visceral obesity index.

Multivariate regression analysis

Three multiple regression models were applied to explain the correlation between prediabetes and VAI and LAP. The VAI and LAP levels were stratified into quartiles, with the lowest quartile (Q1) serving as the reference. The results indicated a significant positive correlation between VAI and prediabetes in models 1 (OR: 1.294, 95% CI: 1.230–1.361), 2 (OR: 1.293, 95% CI: 1.226–1.363), and 3 (OR: 1.128, 95% CI: 1.073–1.185). When VAI was categorized into quartiles, participants in the highest quartile (Q4: ≥ 2.13) showed a positive correlation to the prevalence of prediabetes across models 1 (OR: 2.885, 95% CI: 2.520–3.302), 2 (OR: 2.912, 95% CI: 2.504–3.386), and 3 (OR: 1.619, 95% CI: 1.354–1.937). All P for trend < 0.0001 (Table 3).

Table 3. Association of VAI and LAP with prediabetes.

Exposure OR (95% CI), P-value
Model 1a Model 2b Model 3c
VAI
Continuous 1.294 (1.230, 1.361), <0.0001 1.293 (1.226, 1.363), <0.0001 1.128 (1.073, 1.185), <0.0001
Q1 (< 0.78) Reference Reference Reference
Q2 (0.78–1.27) 1.248 (1.099, 1.417), 0.0009 1.200 (1.052, 1.369), 0.0080 0.982 (0.853, 1.130), 0.7974
Q3 (1.27–2.13) 1.845 (1.626, 2.094), <0.0001 1.855 (1.605, 2.144), <0.0001 1.259 (1.074, 1.477), 0.0046
Q4 (≥ 2.13) 2.885 (2.520, 3.302), <0.0001 2.912 (2.504, 3.386), <0.0001 1.619 (1.354, 1.937), <0.0001
P for trend <0.0001 <0.0001 <0.0001
LAP
Continuous 1.014 (1.012, 1.016), <0.0001 1.012 (1.011, 1.014), <0.0001 1.006 (1.004, 1.008), <0.0001
Q1 (< 20.41) Reference Reference Reference
Q2 (20.41–36.77) 2.115 (1.840, 2.431), <0.0001 1.711 (1.467, 1.994), <0.0001 1.330 (1.137, 1.555), 0.0004
Q3 (36.77–62.28) 2.933 (2.541, 3.386), <0.0001 2.283 (1.963, 2.656), <0.0001 1.422 (1.197, 1.690), <0.0001
Q4 (≥ 62.28) 5.236 (4.499, 6.094), <0.0001 4.286 (3.649, 5.036), <0.0001 2.164 (1.747, 2.681), <0.0001
P for trend <0.0001 <0.0001 <0.0001

aModel 1: adjusted for no covariates.

bModel 2: adjusted for age, gender, race.

cModel 3: adjusted for age, gender, race, education, marital, smoking status, BMI, physical activity, hyperlipidemia, hypertension, cancer and CVD.

Abbreviations: BMI, body mass index; CI, confidence interval; CVD, cardiovascular diseases; LAP, lipid accumulation product; OR, odds ratio; VAI, visceral obesity index.

Prediabetes was significantly correlated with LAP in models 1 (OR: 1.014, 95% CI: 1.012–1.016), 2 (OR: 1.012, 95% CI: 1.011–1.014), and 3 (OR: 1.006, 95% CI: 1.004–1.008). Participants in the highest LAP quartile (Q4: ≥ 62.28) showed a substantially higher risk of developing prediabetes in models 1 (OR: 5.236, 95% CI: 4.499–6.094), 2 (OR: 4.286, 95% CI: 3.649–5.036), and 3 (OR: 2.164, 95% CI: 1.747–2.681) when contrasted to individuals in the lowest quartile (Q1: < 20.41). The P for trend was < 0.0001 across all models (Table 3).

Subgroup analysis

Our results indicated that the positive association between VAI and prediabetes was observed across all subgroups except for those with alcohol use over 15 drinks per week (OR: 1.362, 95% CI: 0.866–2.144), physical activity over 1500 MET-minutes/week (OR: 1.068, 95% CI: 0.995–1.145), and participants with CVD (OR: 1.148, 95% CI: 0.985–1.339). As shown in Fig 2, a significant interaction between age and sex was found; other interaction terms were not significant.

Fig 2. Subgroup analysis for the association between VAI and prediabetes.

Fig 2

Abbreviation: BMI, body mass index; CI, confidence interval; CVD, cardiovascular diseases; OR, odds ratio; VAI, visceral obesity index.

Fig 3 presents a subgroup analysis of the correlation of LAP and prediabetes. The results indicated statistically significant outcomes for all subgroups, including age, gender, smoking status, alcohol use, BMI, physical activity, daily energy intake, hyperlipidemia, hypertension, cancer, and CVD (P < 0.05). Meanwhile, except for the interaction terms for age, gender, BMI, and hyperlipidemia, nearly all other interaction terms were not statistically significant.

Fig 3. Subgroup analysis for the association between LAP and prediabetes.

Fig 3

Abbreviations: BMI, body mass index; CI, confidence interval; CVD, cardiovascular diseases; LAP, lipid accumulation product; OR, odds ratio.

Curve fitting and threshold effect analysis

The smooth curve fitting that received the full adjustment demonstrated a non-linear correlation of VAI and prediabetes (S1 Fig). We then conducted a threshold effect analysis and determined that the turning point of the curve was at 4.090 (Table 4).

Table 4. Threshold effect analysis of VAI and LAP on prediabetes using piece-wise linear regressiona.

Outcome Adjusted OR (95% CI) P-value
Inflection point of VAI
< 4.090 1.238(1.181, 1.298) <0.001
> 4.090 1.031(0.995, 1.068) 0.093
Log likelihood ratio test <0.001
Inflection point of LAP
< 68.168 1.012(1.009, 1.015) <0.001
> 68.168 1.003(1.002, 1.005) <0.001
Log likelihood ratio test <0.001

aAll models were adjusted for: age, gender, race and ethnicity, education, marital, smoking status, BMI, physical activity, hyperlipidemia, hypertension, cancer and CVD.

Abbreviations: BMI, body mass index; CI, confidence interval; CVD, cardiovascular diseases; LAP, lipid accumulation product; OR, odds ratio; VAI, visceral obesity index.

When VAI was less than 4.090, prediabetes was positively correlated with VAI (OR: 1.238, 95% CI: 1.181–1.298). However, the association was not significant when VAI exceeded 4.090 (OR: 1.031, 95% CI: 0.995–1.068).

Similarly, the correlation of LAP and prediabetes was non-linear (S2 Fig). The inflection point for LAP was at 68.168, as revealed by threshold effect analysis (Table 4). When LAP was below 68.168, a markedly positive correlation between LAP and prediabetes was observed (OR: 1.012, 95% CI: 1.009–1.015). Conversely, when LAP exceeded 68.168, the positive association between LAP and prediabetes still existed, although it was less pronounced (OR: 1.003, 95% CI: 1.002–1.005).

Discussion

This study is the first to merge and analyze data from the 2007–2020 NHANES to explore the potential correlation of VAI, LAP, and the presence of prediabetes in American adults. The results indicate that both VAI and LAP are closely associated with prediabetes, exhibiting a positive correlation. The values of VAI and LAP could potentially be used as predictors of prediabetes.

Individuals with obesity, particularly visceral obesity, have been linked to the development of prediabetes [9, 10]. Techniques used to directly assess visceral fat are expensive and require considerable time to perform; therefore, simple and reliable surrogates of visceral fat are widely used. Although BMI is the most common indicator for detecting obesity, it does not distinguish between fat and muscle or their respective distributions [34]. This limited discriminatory power is particularly relevant for Asians, who tend to exhibit visceral adipose tissue of higher levels compared to Europeans at the identical BMI [35, 36]. Moreover, the loss of muscle, bone mass, and height with age may lead to a reduction in BMI but an increase in fat content. As a result, BMI cut-points are less sensitive to body fatness in older adults than in younger adults, which can lead to misclassification in some older adults [37]. While WC and WHR may be more accurate for measuring abdominal obesity than BMI, they still fail to make a comparison of subcutaneous and visceral adipose tissue. Visceral adipose tissue impacts insulin metabolism because it releases more free fatty acids than subcutaneous fat [38, 39].

VAI combines anthropometric and metabolic measurements and has been reported to correlate highly with visceral adipose tissue as evaluated by MRI [40]. The LAP is an effective tool for indicating the combined anatomic and physiologic changes caused by the deposition of visceral fat [18]. Gu et al. [41] and Liu et al. [42] have indicated that VAI showed a positive correlation to prediabetes in Chinese adults. However, another Chinese study found no significant association [43]. This discrepancy might be due to the fact that VAI was developed for Caucasians and body fat distribution varies among ethnicities [44]; thus, VAI may not be suitable for the Chinese population. Song et al. [45] documented that LAP was positively correlated with impaired fasting glucose in Chinese people, especially in females. Since this study was limited to the Chinese middle-aged and elderly population, its applicability to younger populations and other ethnicities may be limited due to age and ethnicity factors [44, 46]. A German study [25] showed that VAI and LAP are useful indices for discriminating against prediabetes/diabetes in males and females, although it did not assess associations with VAI and LAP and prediabetes separately. Previous studies have established that VAI and LAP were superior to traditional anthropometric measurements (i.e., BMI, WHR, and WC) for prediabetes risk prediction [23, 24]. In another study, Nusrianto et al. [47] demonstrated that elevated LAP and VAI were correlated with a worsening glycemic status; VAI was associated with a risk of prediabetes in both sexes, while LAP was associated in women but not in men. These inconsistent results might be due to differences in sample size, race, region, and study design. Our study highlighted the strong association of VAI and LAP with prediabetes, consistent with previous findings. Therefore, in order to reduce the negative health outcomes of visceral obesity, individuals must take the initiative to change their unhealthy lifestyle behaviors, including eating habits, and employ other methods.

Our study demonstrated that the relationships between VAI or LAP and the risk of prediabetes were non-linear, with inflection points at 4.090 and 68.168, respectively. VAI was positively correlated with prediabetes when it was below 4.090; however, the risk of prediabetes remained essentially stable when VAI exceeded 4.090, though not significantly. The positive association between LAP and prediabetes persisted whether LAP was below or above 68.168. Qin et al. [48] found revealed a non-linear positive correlation between VAI and fasting plasma glucose levels, with an inflection point at 4.02. For individuals with VAI below 4.02, the FPG level increased rapidly with rising VAI (β: 0.73, 95% CI: 0.59–0.87). For those with VAI above 4.02, FPG displayed a relatively mild upward trend (β: 0.23, 95% CI: 0.07–0.40). In the study of Song et al. [45], it was observed that individuals with LAP values in the lowest quartile faced a markedly elevated risk of impaired fasting glucose when contrasted to individuals in the highest quartile.

Insulin resistance is a hallmark of prediabetes, which is linked to excessive visceral fat [49, 50]. VAI and LAP have been suggested as preliminary indicators that could signal the presence of insulin resistance [5153]. The potential mechanisms by which VAI and LAP influence the outcome of prediabetes may include: Visceral fat exhibits high lipolytic activity, leading to an increased free fatty acid load in the portal circulation, which promotes hepatic fat accumulation and insulin resistance [35, 36]. Visceral adipocytes produce and release a series of adipokines, including interleukin-6, adiponectin, and leptin, which may lead to increased insulin resistance [54, 55]. An excess of visceral adipose tissue activates macrophages secreting considerable inflammatory cytokines, resulting in diminished insulin sensitivity [56]. Adiponectin, an adipokine mainly secreted by adipocytes, can regulate glucose and lipid metabolism. Elevated visceral adipose tissue decreases adiponectin levels [57], potentially exacerbating insulin resistance [58].

Our research exhibits some advantages. Initially, we analyzed data drawn from a broad and demographically diverse sample spanning the entire nation, allowing the weighted results to be interpreted as reflective of the U.S. population. Second, we employed an advanced statistical method (multiple imputation) to address missing data, reducing potential bias and enhancing the statistical power of our results. Additionally, the study’s findings were stable and robust in subgroup analyses. Despite these strengths, we must acknowledge certain limitations. First, NHANES is a cross-sectional study; thus, the increases in VAI and LAP could be a consequence of elevated blood glucose or insulin resistance occurring after the onset of prediabetes, rather than the cause of prediabetes. Longitudinal studies will be necessary to validate the utility of VAI and LAP as predictive markers for prediabetes. Secondly, although we adjusted for known potential confounders, other residual confounding factors might remain, which could influence the associations. Lastly, our research merely covered American participants, and the findings might not extend to other countries and populations.

Conclusions

Drawing from a nationally representative population, the findings from this investigation indicate that VAI or LAP with higher levels may be linked to a greater likelihood of developing prediabetes. This insight is of considerable importance to public health, advocating for the use of VAI or LAP as simple and practical indicators for clinical assessment of prediabetes risk. To solidify the understanding of how these associations work and to verify their causative nature, further extensive, well-conducted research studies are required.

Supporting information

S1 Fig. Smooth curve fitting of VAI and prediabetes.

(TIF)

pone.0311312.s001.tif (960.7KB, tif)
S2 Fig. Smooth curve fitting of LAP and prediabetes.

(TIF)

pone.0311312.s002.tif (990.5KB, tif)

Acknowledgments

We thank the National Center for Health Statistics (NCHS) for providing the NHANES data used in this study. We also acknowledge the participants and staff of NHANES, and our colleagues for their support and feedback during the preparation of this manuscript.

Abbreviations

BMI

body mass index

CI

confidence interval

CVD

cardiovascular diseases

HDL

high density lipoprotein-cholesterol

LAP

lipid accumulation product

METs

metabolic equivalent scores

NHANES

National Health and Nutrition Examination Survey

OR

odds ratio

PIR

poverty income ratio

TG

triglyceride

VAI

visceral obesity index

WC

waist circumference

WHR

waist to hip ratio

Data Availability

The data for this study are already publicly available through the National Center for Health Statistics (NCHS), National Health and Nutrition Examination Survey (NHANES) website: https://www.cdc.gov/nchs/nhanes/about_nhanes.htm.

Funding Statement

This study was supportded by the National Natural Science Foundation of China (Grant No.81973670), Central Subsidized Chinese Medicine Special Funds - National Medical Master Sun Guangrong Hunan Workshop Project (2015). The funders had no role in study conceptualization, data curation, formal analysis, methodology, software, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.

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PONE-D-24-10840Association of Visceral Adiposity Index and Lipid Accumulation Products with Prediabetes in US Adults from NHANES 2007-2020: A Cross-sectional StudyPLOS ONE

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Reviewer #1: This cross-sectional study evaluated the association of the visceral adiposity index (VAI) and the lipid accumulation product (LAP) with prediabetes in 12,564 US adults from NHANES 2007-2020. VAI and LAP values were found to be positively associated with the presence of prediabetes. Based on their findings, the authors conclude that the VAI and LAP indices may be used as predictors of prediabetes. The topic is important and, generally, the manuscript is very well written. However, the manuscript could benefit from revisions to address the following concerns:

1. The authors appear to use the words "prevalence" and "incidence" as if they are interchangeable. For example, in 3.2, the authors use the term "incidence rates" when, given the cross-sectional as opposed to longitudinal study design, "prevalence" is the correct term. On a similar note, in the discussion, the statement that "This study is the first to merge and analyze data from the 2007–2020 NHANES to explore the potential correlation of VAI, LAP, and the incidence of developing prediabetes in American adults." should be changed to something like "This study is the first to merge and analyze data from the 2007–2020 NHANES to explore the potential correlation of VAI, LAP, and the presence of prediabetes in American adults." In the abstract, "To evaluate the connection between VAI or LAP and the incidence of prediabetes" should be changed to something like "To evaluate the connection between VAI or LAP and the presence of prediabetes".

2. Was information available on a family history of diabetes and gestational diabetes in women? If so, the authors should comment on why such data were not considered in their analyses. Also, if feasible, it would be of interest to know how the VAI and LAP compare to the ADA/CDC Prediabetes Risk Test

(https://nationaldppcsc.cdc.gov/s/article/New-American-Diabetes-Association-ADA-CDC-Prediabetes-Risk-Test).

3. When referring to METs in connection with physical activity volume, the authors should use the terminology "MET-minutes/week."

4. When discussing limitations of the study, the authors state that "First, NHANES is a cross-sectional study; thus, we can establish correlations but not causal relationships between prediabetes and VAI and LAP." That statement is correct but the authors should further elaborate by discussing the following even more relevant potential limitation: Given the cross-sectional nature of the study, it is conceivable that neither the VAI or LAP are actually strongly predictive of the future development of type 2 diabetes (or, predictive to a lesser degree than appears evident in this study) because it is possible that it is only once a person actually develops prediabetes that the elevated blood glucose and/or insulin resistance cause an increase in triglycerides and decrease in HDL (and, thus, an increased VAI and LAP). Prediabetes could be predictive of a future increase in VAI and LAP rather than an increase in VAI and LAP being predictive of the future development of prediabetes.

Reviewer #2: This research aims at two novel indices and its association with Prediabetes in US adults.

Introduction: The introduction does not include the research conducted with VAI and LAP on ethnicities other than South Asian population. The objective is stated but is deficient by hypothesis.

Methodology:

The study design is not mentioned and the sample size estimation using multistage probability sampling requires description. I understand the data is collected by NHANES. How are the anthropometric measurements recorded and We assume they follow standard guidelines but this requires a mention.

The covariates data such as social, demographics, caloric intake, physical activity, smoking and alcohol history, were they all available in the database or these information were later recorded from participants. This can make a difference because the biochemical and body composition measurements must match with the timing when history is collected from participants.

Statistical analysis:

The regression analysis adopted requires explanation stepwise. Was the multivariate analysis conducted based on the results from univariate analysis? Three models were adopted for multivariate analysis- this is mentioned later in the results but not in methodology. Why is the OR mentioned only once for three models of multivariate analysis (line 226 & 228). The table show the OR for all three models.

Table 3, first column, What is the meaning of reference? This requires description.

Table 4 mentions inflection point, but the determination of inflection point needs to be mentioned.

**********

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Reviewer #2: No

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Attachment

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pone.0311312.s003.docx (13.7KB, docx)
PLoS One. 2024 Sep 30;19(9):e0311312. doi: 10.1371/journal.pone.0311312.r002

Author response to Decision Letter 0


29 Aug 2024

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Association of Visceral Adiposity Index and Lipid Accumulation Products with Prediabetes in US Adults from NHANES 2007-2020: A Cross-sectional Study” (Manuscript ID: PONE-D-24-10840). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in highlight yellow (normal revision) in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Reviewer # 1

�This cross-sectional study evaluated the association of the visceral adiposity index (VAI) and the lipid accumulation product (LAP) with prediabetes in 12,564 US adults from NHANES 2007-2020. VAI and LAP values were found to be positively associated with the presence of prediabetes. Based on their findings, the authors conclude that the VAI and LAP indices may be used as predictors of prediabetes. The topic is important and, generally, the manuscript is very well written. However, the manuscript could benefit from revisions to address the following concerns.

Response: Thank you for your letter and your comments. Those comments are all valuable and very helpful for revising and improving our paper. Our study used data from the National Health and Nutrition Examination Survey from 2007 to 2020, ultimately enrolling and analysing 12,564 participants; and concluded that VAI and LAP levels were positively related to an increased prevalence of prediabetes in American adults. These data suggest that VAI and LAP can be used as a new anthropometric indicator for predicting prediabetes, providing clues for population screening and early clinical disease intervention. Our study has some limitations, including a cross-sectional design that limits causal inference, the potential impact of residual confounding, national differences, etc. If there are any other modifications we could make, we would like very much to modify them and we really appreciate your help.

�The authors appear to use the words "prevalence" and "incidence" as if they are interchangeable. For example, in 3.2, the authors use the term "incidence rates" when, given the cross-sectional as opposed to longitudinal study design, "prevalence" is the correct term. On a similar note, in the discussion, the statement that "This study is the first to merge and analyze data from the 2007–2020 NHANES to explore the potential correlation of VAI, LAP, and the incidence of developing prediabetes in American adults." should be changed to something like "This study is the first to merge and analyze data from the 2007–2020 NHANES to explore the potential correlation of VAI, LAP, and the presence of prediabetes in American adults." In the abstract, "To evaluate the connection between VAI or LAP and the incidence of prediabetes" should be changed to something like "To evaluate the connection between VAI or LAP and the presence of prediabetes".

Response: Thanks for this positive comment. We are very sorry for the incorrect use of the word. Based on your suggestion, we’ve changed “incidence” to “prevalence” (See Lines26, Page.1; Lines211, Page.9; Lines302, Page.15). Furthermore, in order to avoid similar problems, we have also carried out a thorough examination of the full-text.

�Was information available on a family history of diabetes and gestational diabetes in women? If so, the authors should comment on why such data were not considered in their analyses. Also, if feasible, it would be of interest to know how the VAI and LAP compare to the ADA/CDC Prediabetes Risk Test

(https://nationaldppcsc.cdc.gov/s/article/New-American-Diabetes-Association-ADA-CDC-Prediabetes-Risk-Test).

Response: Thank you for your thorough review and valuable feedback. Regarding the first question, the NHANES database does indeed contain information on family history of diabetes and gestational diabetes. However, due to a significant amount of missing data in these questionnaire items, including this information in our analysis could potentially bias the results. Therefore, we did not incorporate family history of diabetes or gestational diabetes into our analytical model.

Additionally, due to the extensive missing data on gestational diabetes and family history of diabetes in the NHANES database, we were unable to calculate the ADA/CDC Prediabetes Risk Test scores. Consequently, feel sincerely sorry that we could not directly compare LAP and VAI with the ADA/CDC Prediabetes Risk Test.

�When referring to METs in connection with physical activity volume, the authors should use the terminology "MET-minutes/week."

Response: We were really sorry for our careless mistakes. Thank you for your reminder. The “METs” has been corrected on “MET-minutes/week”(See Lines154, Page.6; See Lines195, Page.8; See Lines224-226, Page.10). At the same time, we have carefully reviewed the manuscript to avoid the same mistakes.

�When discussing limitations of the study, the authors state that "First, NHANES is a cross-sectional study; thus, we can establish correlations but not causal relationships between prediabetes and VAI and LAP." That statement is correct but the authors should further elaborate by discussing the following even more relevant potential limitation: Given the cross-sectional nature of the study, it is conceivable that neither the VAI or LAP are actually strongly predictive of the future development of type 2 diabetes (or, predictive to a lesser degree than appears evident in this study) because it is possible that it is only once a person actually develops prediabetes that the elevated blood glucose and/or insulin resistance cause an increase in triglycerides and decrease in HDL (and, thus, an increased VAI and LAP). Prediabetes could be predictive of a future increase in VAI and LAP rather than an increase in VAI and LAP being predictive of the future development of prediabetes.

Response: Thank you for your insightful suggestions on improving the discussion of the study’s limitations. We completely agree with your observation that, as a cross-sectional study, our research is inherently limited in its ability to determine the true predictive value of VAI and LAP for the future development of type 2 diabetes. Indeed, as you suggested, the observed elevations in these indices may result from metabolic changes associated with prediabetes, rather than being precursors to it.

To address this, we will expand the discussion in the revised manuscript to include this important point: NHANES is a cross-sectional study; thus, the increases in VAI and LAP could be a consequence of elevated blood glucose or insulin resistance occurring after the onset of prediabetes, rather than the cause of prediabetes. Longitudinal studies will be necessary to validate the utility of VAI and LAP as predictive markers for prediabetes (See Lines379-383, Page.18).

Reviewer # 2

�This research aims at two novel indices and its association with Prediabetes in US adults.

Response: Thanks very much for taking your time to review this manuscript. We really appreciate all your comments and suggestions. Our study utilized data from the National Health and Nutrition Examination Survey spanning from 2007 to 2020, ultimately enrolling and analyzing 12,564 participants. It was concluded that VAI and LAP levels were positively associated with an elevated prevalence of prediabetes among American adults. These data imply that VAI and LAP can serve as a novel anthropometric indicator for predicting prediabetes, offering cues for population screening and early clinical disease intervention. However, our study has certain limitations, such as a cross-sectional design which restricts causal inference, the potential influence of residual confounding, and national disparities, among others. Based on your comments and suggestions, we have made careful modifications to the original manuscript, and carefully proof-read the manuscript. We would like to thank the referee again for taking the time to review our manuscript.

�Comments:

The introduction does not include the research conducted with VAI and LAP on ethnicities other than South Asian population. The objective is stated but is deficient by hypothesis.

Response: Thank you for your valuable feedback. We have revised the Introduction section to include references to studies conducted on populations other than South Asians that have utilized the Visceral Adiposity Index (VAI) and Lipid Accumulation Product (LAP) (See Lines92-94, Page.4). These studies demonstrate that while the cutoff points for VAI and LAP may vary due to ethnic differences, their effectiveness in predicting prediabetes remains significant across diverse populations. To further enhance the rigor of our study, we have explicitly stated our hypothesis in the revised Introduction: "The hypothesize of this study is that lower levels of VAI or LAP are associated with a significantly lower risk of prediabetes." (See Lines101-102, Page.4) This hypothesis aims to provide a theoretical foundation for the diversity and broad applicability of our research.

�Methodology:

The study design is not mentioned and the sample size estimation using multistage probability sampling requires description. I understand the data is collected by NHANES. How are the anthropometric measurements recorded and We assume they follow standard guidelines but this requires a mention.

Response: Thank you for highlighting this important aspect of our study. In the revised Methods section, we have provided a detailed description of the study design. Our study is based on data from the National Health and Nutrition Examination Survey (NHANES) and employs a cross-sectional study design. NHANES utilizes a complex, multistage probability sampling method to select a sample that is representative of the non-institutionalized population of the United States. Specifically, NHANES first selects primary sampling units (PSUs) across the country, followed by stratified random sampling within each PSU to choose households, and finally, individuals are randomly selected from eligible household members.

Regarding sample size estimation. Although NHANES itself does not provide explicit sample size estimations for individual studies, it surveys approximately 5,000 individuals annually. The use of sample weights provided by NHANES allows for unbiased national estimates, a process we have described in our statistical analysis section. Specifically, the variables SDMVSTRA and SDMVPSU were utilized to ensure accurate national estimates due to the complex survey design employed in NHANES. We have now elaborated on this sampling process and its implications for the study's conclusions in the revised manuscript (See Lines111-116, Page.4-5).

�The covariates data such as social, demographics, caloric intake, physical activity, smoking and alcohol history, were they all available in the database or these information were later recorded from participants. This can make a difference because the biochemical and body composition measurements must match with the timing when history is collected from participants.

Response: Thank you for your insightful question regarding the covariate data. We have clarified this in the revised manuscript (See Lines116-120, Page.4-5). All anthropometric measurements, such as height, weight, and waist circumference, were recorded following NHANES' standardized protocols, ensuring accuracy and consistency. Regarding the covariates, including social and demographic information, caloric intake, physical activity, smoking, and alcohol history, these data were also sourced directly from the NHANES database. These variables were collected concurrently with the biochemical and body composition measurements during the participants' medical examinations at NHANES' Mobile Examination Centers (MECs). This synchronization ensures that the timing of the data collection is aligned, thereby maintaining the temporal consistency between the covariates and the primary variables in our study. As a result, there is no risk of temporal mismatch, which could otherwise compromise the validity of our findings.

�Statistical analysis:

The regression analysis adopted requires explanation stepwise. Was the multivariate analysis conducted based on the results from univariate analysis? Three models were adopted for multivariate analysis- this is mentioned later in the results but not in methodology. Why is the OR mentioned only once for three models of multivariate analysis (line 226 & 228). The table show the OR for all three models.

Response: We sincerely appreciate your insightful suggestions regarding the statistical analysis. To address your concerns, we have provided a more detailed explanation of the univariate and multivariate analyses in the revised manuscript.

In our study, the univariate analysis was conducted primarily to assess the strength and direction of the association between each individual covariate and the risk of prediabetes. Based on these initial findings, we developed three multivariate logistic regression models to further explore the relationship between the Visceral Adiposity Index (VAI), Lipid Accumulation Product (LAP), and prediabetes.

The Model 1, was constructed without any adjustments, serving as the baseline analysis. In Model 2, adjustments were made for key demographic variables, specifically gender, age, and race, to account for their potential confounding effects. Finally, Model 3 included a comprehensive set of covariates, which were retained in the model if their inclusion resulted in a change of more than 10% in the effect estimate. This stepwise approach allowed us to systematically evaluate the impact of these covariates on the relationship between VAI, LAP, and prediabetes.

We have now included these detailed explanations in the Methods section of the revised manuscript (See Lines174-179, Page.7). Furthermore, in response to your suggestion, we have clarified the presentation of OR for each of the three models in the Results section, ensuring that our analysis is both transparent and robust.

�Table 3, first column, What is the meaning of reference? This requires description.

Response: Thank you for your attention to the clarity of Table 3. In the revised manuscript, we have added an explanation (See Lines236-237, Page.11) to clarify the meaning of "reference" in the first column of Table 3. Specifically, the term "reference" refers to the control group, which typically represents the lowest quartile (Q1) or the group not exposed to a particular risk factor. This group serves as the baseline for comparison, allowing us to evaluate the OR of the other quartiles or categories relative to this reference group.

�Table 4 mentions inflection point, but the determination of inflection point needs to be mentioned.

Response: Thank you for your insightful comment regarding the determination of the inflection point mentioned in Table 4. In the revised manuscript, we have provided a detailed explanation of how the inflection point was identified. The inflection point was determined through a threshold effect analysis, which allows us to detect nonlinear relationships between the Visceral Adiposity Index (VAI), Lipid Accumulation Product (LAP), and the risk of prediabetes. Initially, we conducted a smooth curve fitting analysis to explore the potential nonlinear relationship between VAI, LAP, and prediabetes. Following this, we applied threshold effect analysis to pinpoint the specific values where the relationship between VAI and LAP with prediabetes risk exhibited significant changes. In this study, the inflection point for VAI was identified at 4.090, and for LAP, it was identified at 68.168. These details have been thoroughly described in the Methods section (See Lines182-185, Page.7).

We acknowledge the reviewer’s comments and suggestions very much, which are valuable in improving the quality of our manuscript. Thank you and all the reviewers for the kind advice.

Sincerely yours.

Attachment

Submitted filename: Response to Reviewers.pdf

pone.0311312.s004.pdf (130.1KB, pdf)

Decision Letter 1

Demitri Constantinou

10 Sep 2024

Association of Visceral Adiposity Index and Lipid Accumulation Products with Prediabetes in US Adults from NHANES 2007-2020: A Cross-sectional Study

PONE-D-24-10840R1

Dear Dr. Sun,

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Reviewers' comments:

Acceptance letter

Demitri Constantinou

20 Sep 2024

PONE-D-24-10840R1

PLOS ONE

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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. Smooth curve fitting of VAI and prediabetes.

    (TIF)

    pone.0311312.s001.tif (960.7KB, tif)
    S2 Fig. Smooth curve fitting of LAP and prediabetes.

    (TIF)

    pone.0311312.s002.tif (990.5KB, tif)
    Attachment

    Submitted filename: PONE_comments.docx

    pone.0311312.s003.docx (13.7KB, docx)
    Attachment

    Submitted filename: Response to Reviewers.pdf

    pone.0311312.s004.pdf (130.1KB, pdf)

    Data Availability Statement

    The data for this study are already publicly available through the National Center for Health Statistics (NCHS), National Health and Nutrition Examination Survey (NHANES) website: https://www.cdc.gov/nchs/nhanes/about_nhanes.htm.


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