ASSOCIATION OF SMOKING, BODY-MASS, AND PHYSICAL-ACTIVITY WITH RISK OFPROSTATE-CANCER IN THE IOWA 65-STATES)( RURAL HEALTH STUDY (UNITED)

Smoking, obesity, alcohol, and physical activity can modulate the endo crine system, and therefore have been hypothesized to play a role in t he etiology of prostate cancer. At baseline in 1982, 80 percent (n = 3 ,673) of the noninstitutionalized persons age 65+ in two rural Iowa (U nited States) counties were enrolled into the Iowa 65+ Rural Health St udy. Follow-up for mortality was complete through 1993, and cancer exp erience was determined by linkage to the State Health Registry of Iowa cancer database for the years 1973-93. 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 years prior to baseline, Through 1993 (8,474 person-years of follow-up), there were 71 incident cases o f prostate cancer. In a multivariate model, age, cigarette smoking (re lative risk [RR] = 2.9 for currently smoking 20 or more cigarettes per day compared with never smoking; P trend = 0.009), greater body mass index (BMI) (wt/ht(2)) (RR = 2 compared with < 23.6; P trend = 0.1), a nd greater level of physical activity (RR = 1.9 for 1.7 for BMI > 27.8 kg/m(2) high activity level cfinactive; P trend = 0.05) were independ ent predictors of prostate cancer, and these associations were stronge r for regional or disseminated disease at diagnosis. Percent change in BMI from age 50 to baseline was associated positively with risk (P tr end = 0.01), and this association appeared to be stronger in heavier m en. There were no data on diet. These findings suggest that smoking, o verweight, and weight gain in later life are risk factors for prostate cancer and support a hormonal etiology; the positive association for physical activity confirms some previous reports, but remains without a credible biologic mechanism.