Television Viewing and Risk of Type2 Diabetes, Cardiovascular Disease, and All-Cause Mortality. A Meta-analysis. JAMA, 2011;305(23):2448-2455
To determine the association between TV viewing and risk of type2 diabetes, fatal or nonfatal cardiovascular disease, and all-cause mortality, a meta-analysis of all prospective cohort studies were performed. And the dose-response relationship between TV viewing with the risk of these health outcomes was quantified.
＜Data Sources and Study Selection] Relevant studies were identified by searches of the MEDLINE database from 1970 to March 2011 and the EMBASE database from 1974 to March 2011 without restrictions and by reviewing reference lists from retrieved articles. Cohort studies that reported relative risk estimates with 95% confidence intervals (CIs) for the associations of interest were included.
Data were extracted independently by each author and summary estimates of association were obtained using a random-effects model.
Of the 8 studies included, 4 reported results on type 2 diabetes (175 938 individuals; 6428 incident cases during 1.1 million person-years of follow-up), 4 reported on fatal or nonfatal cardiovascular disease (34 253 individuals; 1052 incident cases), and 3 reported on all-cause mortality (26 509 individuals; 1879 deaths during 202 353 person-years of follow-up) (Figure1). The mean (SD) follow-up duration was 8.5(1.9) years for type2 diabetes, 10.4(7.4) years for fatal or nonfatal cardiovascular disease, and 6.8(2.6) years for all-cause mortality. Outcome assessment was Self-report for Type2 diabetes, Registry for Cardiovascular disease and All-cause mortality (Table). The pooled relative risks per 2 hours of TV viewing per day were 1.20 (95% CI, 1.14-1.27) for type 2 diabetes, 1.15 (95% CI, 1.06-1.23) for fatal or nonfatal cardiovascular disease, and 1.13 (95% CI, 1.07-1.18) for all-cause mortality (Figure2). While the associations between time spent viewing TV and risk of type 2 diabetes and cardiovascular disease were linear, the risk of all-cause mortality appeared to increase with TV viewing duration of greater than 3 hours per day (Figure3). The estimated absolute risk differences per every 2 hours of TV viewing per day were 176 cases of type 2 diabetes per 100 000 individuals per year, 38 cases of fatal cardiovascular disease per 100 000 individuals per year, and 104 deaths for all-cause mortality per 100 000 individuals per year (based on incidence rate in the United States).
Longer duration of TV viewing time is consistently associated with higher risk of type 2 diabetes, fatal or non fatal cardiovascular disease, and all-cause mortality. Further study is needed to determine whether reducing prolonged TV viewing can prevent chronic disease morbidity and mortality.
The followings are the limitation of this study; A possibility of publication bias, the relatively small number of studies, the possibility of residual or unmeasured confounding, the possibility of the participants with subclinical stages of chronic disease, Single point measurement (the assessment of TV viewing relied on self-report at baseline), inappropriate control for physical activity, and miss of studies (eg, non-English-language studies).