Relationship of sedentary behavior and physical activity to incident cardiovascular disease: results from the Women's Health Initiative

Abstract

Objectives: The aim of this study was to examine the independent and joint associations of sitting time and physical activity with risk of incident cardiovascular disease (CVD).

Background: Sedentary behavior is recognized as a distinct construct beyond lack of leisure-time physical activity, but limited data exist on the interrelationship between these 2 components of energy balance.

Methods: Participants in the prospective Women's Health Initiative Observational Study (n = 71,018), 50 to 79 years of age and free of CVD at baseline (1993 to 1998), provided information on sedentary behavior, defined as hours of sitting/day, and usual physical activity at baseline and during follow-up through September 2010. First CVD (coronary heart disease or stroke) events were centrally adjudicated.

Results: Sitting ≥10 h/day compared with ≤5 h/day was associated with increased CVD risk (hazard ratio: 1.18, 95% confidence interval: 1.09 to 1.29) in multivariable models including physical activity. Low physical activity was also associated with higher CVD risk (p for trend < 0.001). When women were cross-classified by sitting time and physical activity (p for interaction = 0.94), CVD risk was highest in inactive women (≤1.7 metabolic equivalent task-h/week) who also reported ≥10 h/day of sitting. Results were similar for coronary heart disease and stroke when examined separately. Associations between prolonged sitting and risk of CVD were stronger in overweight versus normal weight women and women 70 years of age and older compared with younger women.

Conclusions: Prolonged sitting time was associated with increased CVD risk, independent of leisure-time physical activity, in postmenopausal women without a history of CVD. A combination of low physical activity and prolonged sitting augments CVD risk.

Figure 1. Multivariable-adjusted hazard ratios for total cardiovascular disease for the joint association between sedentary time and physical activity

The multivariable model was stratified by age and includes race, education, income, marital status, smoking, family history of myocardial infarction, depression, alcohol intake, hours of sleep, intake of total calories, saturated fat, fiber, and body mass index. The P for interaction is 0.94. HR = hazard ratio; CVD = cardiovascular disease; MET = metabolic equivalent task.

Figure 2. Multivariable-adjusted hazard ratios for total cardiovascular disease according to sedentary time in subgroups defined by body mass index (BMI), age, and employment status

The multivariable model was stratified by age and includes physical activity, race, education, income, marital status, smoking, family history of myocardial infarction, depression, alcohol intake, hours of sleep, intake of total calories, saturated fat, fiber. The P for interaction for BMI is 0.04, age is 0.03, and employment is 0.22. HR = hazard ratio; CVD = cardiovascular disease; BMI = body mass index.