Television viewing and time spent sedentary in relation to cancer risk: a meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational studies
PubMed 24935969 · doi:10.1093/jnci/dju098
What was done
Authors conducted a systematic search across Cochrane, EMBASE, Medline, and SciSearch through February 2014 for observational studies examining sedentary behavior and cancer incidence. Data from 43 observational studies (including 68,936 cancer cases) were independently extracted and pooled using random-effects meta-analysis and meta-regression.
What was found
Comparing highest versus lowest levels of sedentary time: - Colon cancer risk was increased for TV viewing time (RR = 1.54; 95% CI: 1.19 to 1.98), occupational sitting time (RR = 1.24; 95% CI: 1.09 to 1.41), and total sitting time (RR = 1.24; 95% CI: 1.03 to 1.50). - Endometrial cancer risk was increased for TV viewing time (RR = 1.66; 95% CI: 1.21 to 2.28) and total sitting time (RR = 1.32; 95% CI: 1.08 to 1.61). - Overall sedentary behavior was associated with increased lung cancer risk (RR = 1.21; 95% CI: 1.03 to 1.43). - Sedentary behavior was unrelated to cancers of the breast, rectum, ovaries, prostate, stomach, esophagus, testes, renal cell, and non-Hodgkin lymphoma.
Why it matters
This meta-analysis quantitatively synthesizes observational data to show that prolonged sedentary behavior, particularly TV viewing, is selectively associated with higher risks of colon, endometrial, and lung cancers.
Limits
All included data were observational, precluding causal conclusions. The abstract does not specify cutoffs for exposure categories, whether sedentary behavior was self-reported or objectively measured, or how individual studies controlled for key confounders such as physical activity, diet, and obesity.
Cited by
- supports Sedentary behavior is an independent risk factor for cancer.