Strenuous occupational physical activity - potential association with esophageal squamous cell carcinoma risk
The impact of leisure time or recreational physical activity (RPA) on cancer risk has been extensively studied. However, the association of the occupational physical activity (OPA), which differs in dose and intensity from RPA, with different cancers including esophageal squamous cell carcinoma (ESCC), has received less attention. Here, we present data from a case-control study which was conducted for assessing the risk factors for ESCC. Histopathologically confirmed 703 ESCC cases and 1664 controls, individually matched to the respective cases for age, sex and district of residence were recruited. Information on type, duration and intensity of physical activity was obtained in face-to-face interviews with participants using a structured questionnaire. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). A high level of occupational physical activity was associated with increased ESCC risk (OR = 2.17, 95% CI; 1.41 - 3.32), compared to subjects with moderate occupational physical activity. The association with ESCC risk was stronger in strenuous workers (OR = 3.64, 95% CI; 2.13 - 6.20). The association of strenuous OPA with ESCC risk persisted only in subjects that were involved in strenuous activities for equal to or greater than 5days/week. Our study suggests a possible association of strenuous occupational physical activity with ESCC risk. Although, our results were adjusted for multiple factors including indicators of socioeconomic status, more replicative occupational epidemiological studies are needed to rule out any residual confounding.