Sedentary behaviour and life expectancy in the USA: a cause-deleted life table analysis

Abstract

Objectives: To determine the impact of sitting and television viewing on life expectancy in the USA.

Design: Prevalence-based cause-deleted life table analysis.

Setting: Summary RRs of all-cause mortality associated with sitting and television viewing were obtained from a meta-analysis of available prospective cohort studies. Prevalences of sitting and television viewing were obtained from the US National Health and Nutrition Examination Survey.

Primary outcome measure: Life expectancy at birth.

Results: The estimated gains in life expectancy in the US population were 2.00 years for reducing excessive sitting to <3 h/day and a gain of 1.38 years from reducing excessive television viewing to <2 h/day. The lower and upper limits from a sensitivity analysis that involved simultaneously varying the estimates of RR (using the upper and lower bounds of the 95% CI) and the prevalence of television viewing (±20%) were 1.39 and 2.69 years for sitting and 0.48 and 2.51 years for television viewing, respectively.

Conclusion: Reducing sedentary behaviours such as sitting and television viewing may have the potential to increase life expectancy in the USA.

Figure 1

Risk of all-cause mortality associated with sitting. Level 3 corresponds to ¾/all of the time for Katzmarzyk et al and ≥6 h for Patel et al. Level 2 corresponds to ½ of the time for Katzmarzyk et al and 3–5 h for Patel et al. Level 1 corresponds to none/¼ of the time for Katzmarzyk et al and <3 h for Patel et al.

Figure 2

Risk of all-cause mortality associated with television viewing. Level 3 corresponds to ≥4 h for Dunstan et al and Stamatakis et al and >3.6 h for Wijndaele et al. Level 2 corresponds to 2–3.9 h for Dunstan et al and Stamatakis et al and 2.5–3.6 h for Wijndaele et al. Level 1 corresponds to <2 h for Dunstan et al and Stamatakis et al and <2.4 h for Wijndaele et al.

Figure 3

Prevalences of (A) sitting and (B) television viewing in the US National Health and Nutrition Examination Survey (NHANES). *Adjusted prevalences of sitting and television viewing using the weighted average case:source prevalence ratio obtained from cohort studies of sedentary behaviour and all-cause mortality.