Sedentary behavior and cardiovascular disease in older women: The Objective Physical Activity and Cardiovascular Health (OPACH) Study

Abstract

Background: Evidence that higher sedentary time is associated with higher risk for cardiovascular disease (CVD) is based mainly on self-reported measures. Few studies have examined whether patterns of sedentary time are associated with higher risk for CVD.

Methods: Women from the Objective Physical Activity and Cardiovascular Health (OPACH) Study (n=5638, aged 63-97, mean age=79±7) with no history of myocardial infarction (MI) or stroke wore accelerometers for 4-to-7 days and were followed for up to 4.9 years for CVD events. Average daily sedentary time and mean sedentary bout duration were the exposures of interest. Cox regression models estimated hazard ratios (HR) and 95% confidence intervals (CI) for CVD using models adjusted for covariates and subsequently adjusted for potential mediators (body mass index (BMI), diabetes, hypertension, and CVD-risk biomarkers [fasting glucose, high-density lipoprotein, triglycerides, and systolic blood pressure]). Restricted cubic spline regression characterized dose-response relationships.

Results: There were 545 CVD events during 19,350 person-years. Adjusting for covariates, women in the highest (≥ ~11 hr/day) vs. the lowest (≤ ~9 hr/day) quartile of sedentary time had higher risk for CVD (HR=1.62; CI=1.21-2.17; p-trend <0.001). Further adjustment for potential mediators attenuated but did not eliminate significance of these associations (p-trend<.05, each). Longer vs. shorter mean bout duration was associated with higher risks for CVD (HR=1.54; CI=1.27-2.02; p-trend=0.003) after adjustment for covariates. Additional adjustment for CVD-risk biomarkers attenuated associations resulting in a quartile 4 vs. quartile 1 HR=1.36; CI=1.01-1.83; p-trend=0.10). Dose-response associations of sedentary time and bout duration with CVD were linear (P-nonlinear >0.05, each). Women jointly classified as having high sedentary time and long bout durations had significantly higher risk for CVD (HR=1.34; CI=1.08-1.65) than women with both low sedentary time and short bout duration. All analyses were repeated for incident coronary heart disease (MI or CVD death) and associations were similar with notably stronger hazard ratios.

Conclusions: Both high sedentary time and long mean bout durations were associated in a dose-response manner with increased CVD risk in older women, suggesting that efforts to reduce CVD burden may benefit from addressing either or both component(s) of sedentary behavior.

Keywords: Patterns of sedentary behavior; aging; epidemiology; lifestyle; physical activity; sedentary time.

Figure 1:

Continuous dose-response relation of sedentary time and mean sedentary bout duration with cardiovascular disease events, estimated using linear Cox regression models adjusted for age, race/ethnicity, education, smoking status, alcohol consumption, self-reported health, multimorbidity, physical functioning, and family history of myocardial infarction (blue lines). Results following additional adjustment for moderate-to-vigorous physical activity (MVPA) are shown using black dotted lines. The reference category was set to the 10th percentile of each exposure (sedentary time = 7.3 hours per day; mean bout duration = 4.7 minutes). Results for sedentary time were trimmed at the 1^st and 99^th percentiles and results for mean bout duration were trimmed at the 1^st and 95^th percentiles.

Figure 2:

Joint association of sedentary time (ST) and mean bout duration (BD) with cardiovascular disease events. Model 1 is adjusted for age and race/ethnicity, Model 2 is additionally adjusted for smoking status, alcohol consumption, self-reported health, multi-morbidity, physical functioning, and family history of myocardial infarction. ST and BD were split at their respective median values (9.3 hr/day and 6.8 min). Grey diamonds represent hazard ratios with the top and bottom error bars designating the 95% confidence interval. The total number of women (number of cases) for each group were: Low ST, Low BD = 2322 (154); low ST, high BD = 498 (42); high ST, low BD = 497 (49); high ST, high BD = 2321 (300).