Research Article Physical Activity in Relation to Risk of Hematologic Cancers: A Systematic Review and Meta-analysis

Background: Despite the existence of numerous biologic pathways potentially linking increased physical activity to decreased risk of hematologic cancers, the associations between physical activity and subtype-specific hematologic cancers have not been comprehensively quantified. Methods:We conducted a systematic review and meta-analysis of physical activity in relation to subtype-specific hematologic cancers. We summarized the data from 23 eligible studies (15 cohort and eight case– control studies) and estimated summary relative risks (RR) and 95 % confidence intervals (CI) using random-effects models. Results:When comparing high versus low physical activity levels, the RR for non-Hodgkin lymphomawas 0.91 (95%CI, 0.82–1.00), forHodgkin lymphoma itwas 0.86 (95%CI, 0.58–1.26), for leukemia itwas 0.97 (95%CI, 0.84–1.13), and for multiple myeloma it was 0.86 (95 % CI, 0.68–1.09). When focusing on subtypes of non-Hodgkin lymphoma, the RR for diffuse large B-cell lymphoma was 0.95 (95 % CI, 0.80–1.14) and for follicular lymphoma it was 1.01 (95 % CI, 0.83–1.22). In an exploratory analysis combining all hematologic cancers, high versus low physical activity levels yielded a statistically significant RR of 0.93 (95 % CI, 0.88–0.99). Conclusions: Physical activity showed statistically nonsignificant associations with risks of non-Hodgkin lymphoma, Hodgkin lymphoma, multiple myeloma, and leukemia. These findings may not represent a true lack of associations given the variation in high versus low physical activity definitions, the quality of physical activity assessments, and the variability in hematologic cancer classification schemes in individual studies. Impact: Physical activity is unrelated to risks of subtype-specific hematologic cancers. Cancer Epidemiol Biomarkers Prev; 23(5); 833–46. 2014 AACR