Independent and joint effects of sitting time with lifestyle factors on mortality, in post-menopausal, U.S. Women
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Abstract
Prolonged sitting has been linked to cardiovascular disease, diabetes, obesity, cancer and early mortality, independent of physical activity. As a result, it would be beneficial from a public health standpoint to examine the impact of sitting time amongst older populations who are prone to sitting. We grouped post-menopausal women of the Women's Health Initiative (n= 84 865; 50-79 years of age) into quartiles of total daily sitting time (Q1: <=5; Q2: 6-9; Q3: 10-13; Q4: 14+ hrs. /day). We also examined the joint effects of sitting time with other well-known risk factors on mortality. The two highest quartiles of sitting time had significantly higher all-cause (Q3: HR: 1.13, 95% CI: 1.04-1.22); (Q4: 1.26, 95% CI: 1.11-1.44) and cancer mortality (Q3: HR:1.17, 95% CI: 1.04-1.31 ); (Q4: 1.38, 95% CI: 1.13-1.67) risk in comparison to our referent group who sat less than or equal to 5 hours daily. Additionally, individuals who at baseline were smokers, or inactive in conjunction with high levels of sitting, were also at a considerably higher risk of all-cause and cancer mortality compared to women with a more optimal risk profile (non-smoker, or active and low sitting). These findings suggest that in older, post-menopausal women, limiting sitting time throughout the day may be a positive strategy to improve one's longevity. Further, high-risk individuals such as older women who exhibit high sitting with other behaviours such as, smoking, or inactivity should be of priority to limit sitting time.