Postdiagnosis sedentary behavior and health outcomes in cancer survivors: A systematic review and meta-analysis

Background: High levels of sedentary behavior may negatively affect health outcomes in cancer survivors. A systematic review and meta-analysis was performed to clarify whether postdiagnosis sedentary behavior is related to survival, patient-reported outcomes, and anthropometric outcomes in cancer survivors. Methods: The Ovid MEDLINE, EMBASE, CINAHL (The Cumulative Index to Nursing and Allied Health Literature), and SPORTDiscus databases were searched from study inception to June 2019. Studies of adults who had been diagnosed with cancer that examined the association between sedentary behavior and mortality, patient-reported outcomes (eg, fatigue, depression), or anthropometric outcomes (eg, body mass index, waist circumference) were eligible for inclusion. Meta-analyses were performed to estimate hazard ratios for the highest compared with the lowest levels of sedentary behavior for all-cause and colorectal cancer-specific mortality outcomes. The ROBINS-E (Risk of Bias in Nonrandomized Studies-of Exposures tool) and the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) system were used to assess the risk of bias and the strength of evidence, respectively. Results: Thirty-three eligible publications from a total of 3569 identified articles were included in the review. A higher level of postdiagnosis sedentary behavior was associated with an increased risk of all-cause mortality (hazard ratio, 1.22; 95% CI, 1.06-1.41; heterogeneity [I² statistic], 33.8%) as well as colorectal cancer-specific mortality (hazard ratio, 1.53; 95% CI, 1.14-2.06; I², 0%). No clear or consistent associations between sedentary behavior and patient-reported or anthropometric outcomes were identified. The risk of bias in individual studies ranged from moderate to serious, and the strength of evidence ranged from very low to low. Conclusions: Although avoiding high levels of sedentary behavior after a cancer diagnosis may improve survival, further research is required to help clarify whether the association is causal.