Sitting Time, Fidgeting, and All-Cause Mortality in the UK Women's Cohort Study.

INTRODUCTION Sedentary behaviors (including sitting) may increase mortality risk independently of physical activity level. Little is known about how fidgeting behaviors might modify the association. METHODS Data were from the United Kingdom (UK) Women's Cohort Study. In 1999-2002, a total of 12,778 women (aged 37-78 years) provided data on average daily sitting time, overall fidgeting (irrespective of posture), and a range of relevant covariates including physical activity, diet, smoking status, and alcohol consumption. Participants were followed for mortality over a mean of 12 years. Proportional hazards Cox regression models estimated the relative risk of mortality in high (versus low) and medium (versus low) sitting time groups. RESULTS Fidgeting modified the risk associated with sitting time (p=0.04 for interaction), leading us to separate groups for analysis. Adjusting for covariates, sitting for ≥7 hours/day (versus <5 hours/day) was associated with 30% increased all-cause mortality risk (hazard ratio [HR]=1.30, 95% CI=1.02, 1.66) only among women in the low fidgeting group. Among women in the high fidgeting group, sitting for 5-6 hours/day (versus <5 hours/day) was associated with decreased mortality risk (HR=0.63, 95% CI=0.43, 0.91), adjusting for a range of covariates. There was no increased mortality risk from longer sitting time in the middle and high fidgeting groups. CONCLUSIONS Fidgeting may reduce the risk of all-cause mortality associated with excessive sitting time. More detailed and better-validated measures of fidgeting should be identified in other studies to replicate these findings and identity mechanisms, particularly measures that distinguish fidgeting in a seated from standing posture.