Association of smoking, body mass, and physical activity with risk of prostate cancer in the Iowa 65+ Rural Health Study (United States)

Smoking, obesity, alcohol, and physical activity can modulate theendocrine system, and therefore have been hypothesized to play a role in theetiology of prostate cancer. At baseline in 1982, 80 percent (n = 3,673) ofthe noninstitutionalized persons age 65+ in two rural Iowa (United States)counties were enrolled into the Iowa 65+ Rural Health Study. Follow-up formortality was complete through 1993, and cancer experience was determined bylinkage to the State Health Registry of Iowa cancer database for the years1973-93. We analyzed data on 1,050 men aged 65 to 101 years (mean age 73.5)with a full interview in 1982 and with no documented cancer in the 10 yearsprior to baseline. Through 1993 (8,474 person-years of follow-up), there were71 incident cases of prostate cancer. In a multivariate model, age, cigarettesmoking (relative risk [RR] = 2.9 for currently smoking 20 or more cigarettesper day compared with never smoking; P trend = 0.009), greater body massindex (BMI) (wt/ht 2 ) (RR = 1.7 for BMI > 27.8 kg/m 2 compared with <23.6; P trend = 0.1), and greater level of physical activity (RR = 1.9 forhigh activity level cf inactive; P trend = 0.05) were independent predictorsof prostate cancer, and these associations were stronger for regional ordisseminated disease at diagnosis. Percent change in BMI from age 50 tobaseline was associated positively with risk (P trend = 0.01), and thisassociation appeared to be stronger in heavier men. There were no data ondiet. These findings suggest that smoking, overweight, and weight gain inlater life are risk factors for prostate cancer and support a hormonaletiology; the positive association for physical activity confirms someprevious reports, but remains without a credible biologicmechanism.