Leisure-time physical activity and gastric cancer risk: a pooled study within the Stomach cancer Pooling (StoP) Project

Background Physical activity (PA) has been recognized as a protective factor against several types of cancer, though robust evidence related to Gastric Cancer (GC) are lacking. This study aimed to establish whether leisure-time PA can prevent GC using data from a large pooled analysis of case-control studies within the Stomach cancer Pooling (StoP) Project.Methods Five case-control studies from StoP project collected data on PA, for a total of 2,415 cases and 9,722 controls. Subjects were classified into three leisure-time PA categories, either none/low, intermediate or high, based on study-specific tertiles. We used a two-stage approach. Firstly, we applied multivariable logistic regression models to obtain study-specific odds ratios (ORs) and corresponding 95% confidence intervals (CIs). Afterwards, we used a random-effect models for estimating pooled effect estimates. Heterogeneity across studies was assessed using Q and I 2 statistics. We performed stratified analyses according to demographic, lifestyle and clinical covariates.Results The pooled ORs for GC risk were 0.90 (95% CI: 0.72, 1.13) for intermediate, and 0.72 (95% CI: 0.57, 0.91) for high levels of leisure-time PA. There was no evidence of significant heterogeneity in outcome estimates ( I 2 = 49.7%; p=0.094 for intermediate; I 2 = 42.9%, p=0.135 for high levels of exposure). GC risk estimates did not differ across strata of selected covariates.Conclusions Our study is the largest pooled analysis that provides insights about protective effects of high levels of recreational PA on GC risk. Although our results should be confirmed from large cohort studies, the implications have relevant public health significance.