Association between various sedentary behaviours and all-cause, cardiovascular disease and cancer mortality: the Multiethnic Cohort Study

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.

Keywords: Sedentary lifestyle; exercise; mortality; prospective studies; television.