Physical activity, sedentary time, and heart failure risk in low-income Black and white adults living in the southeastern United States

Race, sex, and socioeconomic disparities exist in the risk of incident heart failure (HF) with lower income individuals residing in the southeastern United States at particularly high risk.¹ Physical activity (PA) and sedentary time (ST) are modifiable risk factors for HF, although most studies from which this association is based were conducted among primarily middle-income or white cohorts.² Few studies simultaneously examined both PA and ST as independent risk factors for HF, let alone in high-risk low-income individuals who not only have a higher prevalence of traditional cardiovascular risk factors, but also a greater burden of adverse social determinants of health which may confer increased risk. Therefore, in the Southern Community Cohort Study (SCCS), we tested whether greater PA and less ST independently associate with lower risk for incident HF, accounting for socioeconomic and cardiovascular risk factors, and whether these associations vary by race-sex.

The SCCS is a prospective cohort of ~85,000 English-speaking, predominantly Black, female, and low-income adults (age 40-79) in the southeastern US enrolled between 2002-2009. The institutional review boards of Vanderbilt University Medical Center and Meharry Medical College approved SCCS protocols and all SCCS participants provided written informed consent. This analysis included self-identified non-Hispanic white or Black participants receiving Centers for Medicare/Medicaid Services (CMS) without prevalent HF who completed the SCCS PA questionnaire at enrollment. Requests to access the dataset from qualified researchers trained in human subject confidentiality protocols may be sent to the Southern Community Cohort Study at https://ors.southerncommunitystudy.org/.

From questions regarding vigor and duration of PA and ST, total Metabolic Equivalent of Task (MET)-hrs/day and total sit-hrs/day were calculated, respectively.³ Physiologically implausible MET-hr/day values were excluded using Tukey’s method and total sit-hrs/day exceeding 24 were assigned a value of 24. The final analysis sample size was 26,658 participants.

Incident HF was ascertained using the first claim with an International Classification of Diseases 9^th or 10^th revision diagnosis code of 428.x or I50.x. Censoring occurred at first incidence of HF, death, or last follow-up (December 31, 2016).

Stratification by race-sex group was prespecified. Multivariable-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident HF in relation to PA (MET-hrs/day) and ST (sit-hrs/day) as continuous variables. Restricted cubic spline terms to test non-linear associations between PA or ST with HF risk and a PA x ST interaction were included. Analysis was performed using R (R-project, Vienna, Austria).

Over 11.0 years median follow-up (interquartile range [IQR]: 8.7-12.7), 7,388 participants developed incident HF. In multivariable-adjusted Cox regression, the interaction between PA and ST was not significant (p=0.73) and each IQR increase in PA (~15 MET-hrs/day) associated with an 11% lower risk of HF (HR: 0.89, 95% CI: 0.86-0.93). In race-sex stratified analyses, a nonlinear association between PA and HF risk was observed among Black women (p=0.004), with the trend indicating greater PA associates with lower risk (p<0.001) (Figure 1A). Greater PA also associated with lower HF risk in white women (HR: 0.89, 95% CI: 0.82-0.97) and Black men (HR: 0.85, CI: 0.79-0.92) (Figure 1B–1C), but not white men (HR: 1.02, 95% CI: 0.92-1.13) (Figure 1D).

Figure 1. Associations of physical activity (PA) (Panels A-D) and sedentary time (ST) (Panel E) with the risk of incident heart failure (HF) in the Southern Community Cohort Study.

5-year predicted probability for incident HF according to PA (MET-hrs/day) in (A) Black women, (B) white women, (C) Black men, and (D) white men. The relationship between PA and HF among Black women was non-linear (p=0.004). (E) Forest plot of hazard ratios (HRs) and 95% confidence intervals for incident HF per 6.0 sit-hrs/day increase in ST overall and each of the race-sex groups. The association between ST and HF risk was linear in all groups. All results are from Cox regression adjusted for age, body mass index, Dietary Approaches to Stop Hypertension diet score, smoking status, history of myocardial infarction or coronary artery bypass graft, history of stroke or transient ischemic attack, diabetes, hypertension, high cholesterol, annual income, education, marital status, enrollment source, PA and ST. Results in Panel E for the overall cohort were also adjusted for sex and race.

Overall, each IQR increase in ST (~6 sit-hrs/day) associated with a 9% greater risk of incident HF (HR 1.09, 95% CI: 1.05-1.12) (Figure 1E). Results were similar in Black and white women; however, in Black and white men, increased ST was not significantly associated with HF. In three sensitivity analyses excluding participants with prevalent MI/CABG, stroke/TIA, or HF diagnosis within 3 months of enrollment, the results did not appreciably change for PA or ST overall or in race-sex groups.

The SCCS includes a large proportion of individuals who are underrepresented in most prior studies examining how PA and ST associate with HF risk. We found greater PA associated with lower risk of incident HF in Black and white women and Black men, but not white men.

The null association between PA and incident HF risk in white men in the SCCS is novel and contrasts with prior studies.^2,4 Heterogeneity in HF risk associated with PA is also described in the Atherosclerosis Risk in Communities study, which found a neutral association among individuals with prevalent atherosclerotic disease.⁴ In the SCCS, atherosclerotic disease is most common in white men;¹ however, our results persisted following exclusion of individuals with prior MI/CABG.

The association of more ST with greater HF risk particularly among women, regardless of race, and independent of PA, in high-risk, lower income individuals is also novel. Though we were unable to distinguish between HF with preserved vs. reduced ejection fraction, in the Multi-Ethnic Study of Atherosclerosis, the significant association between increased ST and HF was significant only for HF with preserved ejection fraction, which is more common in women.⁵

Compared with prior studies, our findings may be due to study population differences, greater socioeconomic factor adjustment, simultaneous adjustment for ST, sex/race-based differences in PA questionnaire response,³ and/or unmeasured factors, e.g. temporal changes in risk factor modification. Further study of mechanisms and clinical and public health implications of PA and ST on HF risk is needed.