Physical activity and colon cancer: a comparison of various indicators of physical activity to evaluate the association.

We compare categories of physical activity, based upon self-reported leisure time and occupational activity, with categories of activity based upon coded job titles using the Dictionary of Occupational Titles. For people under 65 years of age, self-reported total activity, total nonintense activity, and occupational activity were not strongly associated with coded occupational activity in men (Spearman r = 0.36, 0.27, and 0.32, respectively); even weaker associations were noted in women (r = 0.23, 0.27, and 0.10). Associations between total activity and coded occupational activity were generally weaker for people who were 65 or older. Despite these weak associations, all indicators of physical activity assessed were associated with a decreased risk for colon cancer in men. Comparing those in the highest category of activity with those in the lowest, the OR for total self-reported activity was 0.7; for self-reported occupational activity, 0.7; and for coded occupational activity, 0.6. Whereas self-reported total activity was associated with colon cancer among women, estimates of activity based upon occupation (both self-reported and coded from job titles) were not.