Association Between Various Sedentary Behaviours and All-Cause, Cardiovascular Disease and Cancer Mortality

The Multiethnic Cohort Study

Yeonju Kim; Lynne R Wilkens; Song-Yi Park; Marc T Goodman; Kristine R Monroe; Laurence N Kolonel

Disclosures

Int J Epidemiol. 2013;42(4):1040-1056. 

In This Article

Abstract and Introduction

Abstract

Background It has been proposed that time spent sitting increases all-cause mortality, but evidence to support this hypothesis, especially the relative effects of various sitting activities alone or in combination, is very limited.

Methods The association between various sedentary behaviours (time spent: sitting watching television (TV); in other leisure activities; in a car/bus; at work; and at meals) and mortality (all-cause and cause-specific) was examined in the Multiethnic Cohort Study, which included 61 395 men and 73 201 women aged 45–75 years among five racial/ethnic groups (African American, Latino, Japanese American, Native Hawaiian and White) from Hawaii and Los Angeles, USA.

Results Median follow-up was 13.7 years and 19 143 deaths were recorded. Total daily sitting was not associated with mortality in men, whereas in women the longest sitting duration (≥10 h/day vs <5 h/day) was associated with increased all-cause (11%) and cardiovascular (19%) mortality. Multivariate hazard ratios (HR) for ≥5 h/day vs <1 h/day of sitting watching TV were 1.19 in men (95% confidence interval (CI) 1.10–1.29) and 1.32 in women (95% CI 1.21–1.44) for all-cause mortality. This association was consistent across four racial/ethnic groups, but was not seen in Japanese Americans. Sitting watching TV was associated with an increased risk for cardiovascular mortality, but not for cancer mortality. Time spent sitting in a car/bus and at work was not related to mortality.

Conclusions Leisure time spent sitting, particularly watching television, may increase overall and cardiovascular mortality. Sitting at work or during transportation was not related to mortality.

Introduction

Sedentary behaviours, conventionally defined as activities that do not increase energy expenditure above the resting level of 1.0–1.5 METs (metabolic equivalents) or as reclining postures, include activities such as sitting, lying down, watching television, writing and reading.[1–3] Time spent sitting during work and leisure has increased considerably with modern technological advances in transportation, the workplace and entertainment.[4]

An effect on disease status of time spent in sedentary behaviours, such as sitting, is unlikely to be due to confounding from time spent engaged in moderate to vigorous physical activity, as large cohort studies have shown no association between leisure sitting time and physical activity.[5,6] A cross-sectional study of 11 037 adults showed that time sitting for television or computer use was not correlated with time spent in physical activity.[7] Individuals can achieve high levels of moderate to vigorous physical activity while spending the remainder of the day being sedentary.[1]

Recently, results from a meta-analysis of several cohort studies suggested that prolonged television (TV) viewing was associated with an increased risk of the incidence of cardiovascular disease,[8] type 2 diabetes and all-cause mortality.[9] In addition to TV watching, people usually spend additional time doing other sitting activities at leisure, such as reading, listening to music, relaxing, using a computer or playing video games.[10]

Although evidence suggesting deleterious effects of prolonged sitting on premature mortality has been growing, most previous studies have focused on only one type of sitting behaviour, thus failing to address the problem more broadly. Sitting behaviours have different energy expenditure levels, depending on other activities performed simultaneously while sitting.[3] Moreover, the association between sitting and mortality across different racial/ethnic groups that may have different activity patterns[6,11–16] has rarely been examined, although a recent study compared Whites and African Americans.[5]

Our goal was to examine the association between total sitting, time spent in specific sitting behaviours (watching TV, doing other leisure activities, in a car or bus, at work and at meals) and mortality (all-cause and cause-specific) in a multiethnic population, adjusting for physical activity and other potential confounders. We also examined possible interactions with other factors, including age and ethnicity, as well as different types of physical activity and sedentary behaviours.

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