Leisure Time Spent Sitting in Relation to Total Mortality in a Prospective Cohort of US Adults

Alpa V. Patel; Leslie Bernstein; Anusila Deka; Heather Spencer Feigelson; Peter T. Campbell; Susan M. Gapstur; Graham A. Colditz; Michael J. Thun

Disclosures

American Journal of Epidemiology. 2010;172(4):419-429. 

In This Article

Abstract and Introduction

Abstract

The obesity epidemic is attributed in part to reduced physical activity. Evidence supports that reducing time spent sitting, regardless of activity, may improve the metabolic consequences of obesity. Analyses were conducted in a large prospective study of US adults enrolled by the American Cancer Society to examine leisure time spent sitting and physical activity in relation to mortality. Time spent sitting and physical activity were queried by questionnaire on 53,440 men and 69,776 women who were disease free at enrollment. The authors identified 11,307 deaths in men and 7,923 deaths in women during the 14-year follow-up. After adjustment for smoking, body mass index, and other factors, time spent sitting (≥6 vs. <3 hours/day) was associated with mortality in both women (relative risk = 1.34, 95% confidence interval (CI): 1.25, 1.44) and men (relative risk = 1.17, 95% CI: 1.11, 1.24). Relative risks for sitting (≥6 hours/day) and physical activity (<24.5 metabolic equivalent (MET)-hours/week) combined were 1.94 (95% CI: 1.70, 2.20) for women and 1.48 (95% CI: 1.33, 1.65) for men, compared with those with the least time sitting and most activity. Associations were strongest for cardiovascular disease mortality. The time spent sitting was independently associated with total mortality, regardless of physical activity level. Public health messages should include both being physically active and reducing time spent sitting.

Introduction

It is now well established that the US obesity epidemic will have major public health consequences. This epidemic is attributed, at least in part, to reduced overall physical activity expenditure. It has long been recognized that physical activity has a beneficial impact on the incidence and mortality of many chronic diseases, including cardiovascular disease, diabetes, stroke, and various types of cancer including colon and postmenopausal breast cancer.[1–5] Dose-response relations between physical activity and improved health outcomes have been reported, and substantial evidence supports health benefits even with physical activity below recommended levels.[1,3,6,7]

There is a growing body of evidence showing that reducing the amount of time spent sitting, regardless of the amount of physical activity, may improve the metabolic consequences of obesity.[8–11] However, current public health guidelines focus largely on increasing physical activity with little or no reference to reducing time spent sitting.[12–15] Numerous studies support an association with sitting time and endpoints such as obesity, type 2 diabetes, cardiovascular disease,[11,16,17] and unhealthy dietary patterns in children and adults.[18–20] However, to our knowledge, few studies have examined time spent sitting in relation to total mortality,[21–23] but they were limited by sample size[21,22] or qualitatively assessed time spent sitting.[21]

To better assess the relation between time spent sitting and total mortality, both independent of and in combination with physical activity, we conducted a detailed analysis in the American Cancer Society's Cancer Prevention Study II (CPS-II) Nutrition Cohort. This cohort has the advantage of being very large with approximately 184,000 US adults and over 19,000 deaths for whom detailed information on time spent sitting and physical activity was collected at baseline.

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