Sedentary behavior and cancer-an umbrella review and meta-analysis

Abstract

Several systematic reviews and meta-analyses have summarized the association between sedentary behavior (SB) and cancer. However, the level of evidence and the potential for risk of bias remains unclear. This umbrella review summarized the current data on SB in relation to cancer incidence and mortality, with a particular emphasis on assessing the risk of bias. We searched PubMed, Web of Science and Cochrane Database for systematic reviews and meta-analyses on the association between SB and cancer incidence and mortality. We also searched for recent observational studies not yet included in existing meta-analyses. We re-calculated summary risk estimates for cancer incidence and mortality using random effects models. We included 14 meta-analyses covering 17 different cancer sites from 77 original studies. We found that high SB levels increase the risk for developing ovarian, endometrial, colon, breast, prostate, and rectal cancers, with relative risks of 1.29 (95% confidence interval (CI) = 1.08-1.56), 1.29 (95% CI = 1.16-1.45), 1.25 (95% CI = 1.16-1.33), 1.08 (95% CI = 1.04-1.11), 1.08 (95% CI = 1.00-1.17), and 1.07 (95% CI = 1.01-1.12), respectively. Also, we found an increased risk of cancer mortality of 1.18 (95% CI = 1.09-1.26). Most associations between SB and specific cancer sites were supported by a "suggestive" level of evidence. High levels of SB are associated with increased risk of several types of cancer and increased cancer mortality risk.

Keywords: Cancer mortality; Cancer prevention; Meta-analysis; Sedentary behavior; Sitting time; Umbrella review.

Fig. 1

Flow diagram of literature search and study selection for systematic reviews and meta-analyses

Fig. 2

Flow diagram of literature search and study selection for additional individual studies

Fig. 3

Grading the level of evidence of both case–control and cohort studies for the relationship between sedentary behavior and cancer incidence or cancer mortality. Number of studies is referred to the number of studies included in the individual meta-analysis. Number of cases is referred to the number of cancer conditions. Small study bias is considered positive if the p-value in Egger's test is less than 0.10. The excess significance bias is considered positive if the number of significant studies is greater than the number of significant studies expected (based on the largest study with the smallest SE) and the p-value is less than 0.10. Abbreviations: REM random effect model, NS not statistically significant, NP not performed

Fig. 4

Grading the level of evidence of cohort studies for the relationship between sedentary behavior and cancer incidence or cancer mortality. Number of studies is referred to the number of studies included in the individual meta-analysis. Number of cases is referred to the number of cancer conditions. Small study bias is considered positive if the p-value in Egger's test is less than 0.10. The excess significance bias is considered positive if the number of significant studies is greater than the number of significant studies expected (based on the largest study with the smallest SE) and the p-value is less than 0.10. Abbreviations: REM random effect model, NS not statistically significant, NP not performed