Combined risk assessment of physical activity and dietary habits on the development of colorectal cancer. A hospital-based case-control study in Poland.

The purpose of the study was to assess the importance of physical activity performed both in occupational settings and in leisure time on the risk of colorectal cancer, considering the possible confounding effects of dietary habits. The hospital-based case-control study was carried out in Poland. In total, 180 incident cases of colorectal cancer were recruited. An equal number of controls, individually matched by gender and age, were chosen from patients with no history of cancer. A food frequency questionnaire combined with quantity of foods eaten was used to assess the usual dietary pattern for 148 food items. The average physical load of the interviewed patients before the occurrence of disease was ascertained by self-assessment. The degree to which patients' recreational time was sedentary was measured by the number of hours spent watching TV. The adjusted risk of colorectal cancer was reduced by half in those active in leisure time (OR 0.45, 95% CI 0.24-0.84). The effect of occupational physical activity was of about the same order of magnitude in terms of risk reduction (OR 0.61, 95% CI 0.29-1.29) and both activities combined acted as independent protective factors. The protective effect of healthy nutrition appeared to be independent from that attributed to physical effort.