Physical activity and risk of gastric cancer: a meta-analysis of observational studies

Background Studies evaluating the relationship of physical activity and stomach cancer risk have yielded inconsistent and largely inconclusive results. We therefore conducted a systematic review and meta-analysis of observational studies that assessed the relationship between physical activity and risk of gastric cancer. Methods Following a standard protocol, we searched medical literature databases (PubMed, EMBASE, CINAHL, PsycINFO and Google Scholar) from inception to July 2012, and conducted a random effects meta-analysis. Results Seven prospective cohorts and four casecontrol studies of physical activity and gastric cancer risk, with 1 535 006 people and 7944 cases of gastric cancer were included. We found a modest protective association between sufficient physical activity and gastric cancer risk (relative risk: 0.81 (95% CI 0.69 to 0.96); I-2=68.5%) in the prospective studies and (relative risk: 0.78 (95% CI 0.66 to 0.91); I-2=0%) in case-control studies. The association appeared weaker in smokers than in non-smokers (p heterogeneity=0.035). The association may also be weaker for gastric cardia cancer relative to the distal non-cardia subtypes. Physical activity type (recreational or occupational), intake of alcohol, total energy intake, consumption of fruits and vegetables and infection with Helicobacter pylori had no influence on the association. The effect measure from cohort studies (relative risk: 0.82 (95% CI 0.70 to 0.97); I-2=61.7%) and case-control studies (relative risk: 0.83 (95% CI 0.66 to 1.04); I-2=49.8%) did not differ materially at higher physical activity levels. Conclusions We conclude that a regular physical activity may be protective against stomach cancer risk.