Introduction:
Sedentary behaviors such as television viewing are ubiquitous in modern society. Several prospective studies have demonstrated an association between television viewing and incident obesity and type 2 diabetes as well as cardiovascular disease and all-cause mortality.
Hypothesis:
We tested the null hypothesis that television viewing has no impact on life expectancy in the United States.
Methods:
A prevalence-based cause-deleted methodology was used to estimate the gains in life expectancy in the population that would be expected under current mortality patterns if television viewing was eliminated as a potential risk factor in the United States. The population attributable fraction (PAF, calculated using adjusted relative risk (RR) = ∑P(RR-1/RR)) was computed from the RR of all-cause mortality associated with television viewing (2–3.9 h and ≥4 h versus < 2 h) obtained from a meta-analysis of available prospective cohort studies, and the estimated case prevalence (P) of television viewing obtained from the U.S. National Health and Nutrition Examination Survey (2005–06) and the prospective cohort studies. The resulting PAF was applied to mortality rates among 18+ year olds living in the United States and an abridged life table analysis was used to estimate the potential gains in life expectancy.
Results:
Three prospective cohort studies contributed data to the meta-analysis, yielding summary RR estimates for all-cause mortality of 1.17 (95% CI: 1.04 – 1.32) and 1.49 (95% CI: 1.22–1.82) for 2–3.9 h and ≥4 h of television viewing versus <2 h, respectively. The estimated case prevalences of television viewing in the U.S. population were 23.8%, 45.7% and 37.2% for <2 h, 2–3.9 h and ≥4 h of television viewing, respectively. The estimated gain in life expectancy in the US population associated with television viewing was 1.38 years. The lower and upper limits from a sensitivity analysis which 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 0.48 years and 2.50 years.
Conclusions:
Reducing sedentary behaviors such as television viewing has the potential to increase life expectancy in the United States.
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