Association of sedentary behavior with the risk of breast cancer in women: update meta-analysis of observational studies.

PURPOSE Increasing studies focus on the health consequences of sedentary behavior, and whether sedentary behavior is associated with the risk of breast cancer remains uncertain. We applied quantitative techniques to synthesize relevant original observational studies to investigate this issue. METHODS PubMed and Embase were searched through September 2014 to identify cohort and case-control studies that evaluated the association between sedentary behavior and breast cancer risk in women. Information on the characteristics of the included studies, risk estimates, and control for possible confounding factors, was extracted independently by two authors. A random effects model of meta-analysis was used to calculate the pooled risk estimate. RESULTS Twenty one studies with 34 reports were included in our quantitative analysis. Sedentary behavior was found to slightly increase the risk of breast cancer in women and the pooled odds ratio (OR) and its 95% confidence interval (CI) were 1.08 and 1.04 to 1.13, without substantial heterogeneity (P = .579, I(2) = 0.0%). Subgroup analysis showed that the risks of breast cancer for different domains of sedentary behavior were similar, although only occupational behavior showed statistical significance (OR, 1.10; 95% CI, 1.02-1.18) and the combined ORs of breast cancer are of borderline significance for sedentary behavior of daily life (OR, 1.10; 95% CI, 1.00-1.20) and sedentary behavior of leisure time (OR, 1.08; 95% CI, 0.98-1.19). Exclusion of any single study did not materially alter the combined risk estimate. Visual inspection of funnel plot, Begg's and Egger's tests did not indicate evidence of publication bias. CONCLUSIONS Integrated evidence from observational studies suggests a statistically significant slightly positive association of sedentary behavior with breast cancer risk.