Racial/ethnic differences in lifestyle-related factors and prostate cancer risk: the Multiethnic Cohort Study.

Purpose: Older age, African ancestry, and family history of prostate cancer are well-established risk factors for prostate cancer, and all are non-modifiable. Various lifestyle factors have been examined in relation to prostate cancer risk, including diet, obesity, and physical activity; however, none of them has been consistently related to risk. In the Multiethnic Cohort Study, we investigated whether lifestyle-related factors are associated with prostate cancer risk and whether such factors explain the racial/ethnic differences in risk.

Methods: During a mean follow-up of 13.9 years, 7,115 incident cases were identified among 75,216 white, African-American, Native Hawaiian, Japanese American, and Latino men. Cox proportional hazards models were used to calculate relative risks (RRs) and 95 % confidence intervals (95 % CIs) for prostate cancer.

Results: Among selected lifestyle-related factors including body mass index, height, education, physical activity, and intakes of alcohol, calcium, legumes, lycopene, and selenium, only smoking (RR for current (≥20 cigarettes/day) vs. never smoking = 0.72; 95 % CI 0.63-0.83) and history of diabetes (RR for yes vs. no = 0.78; 95 % CI 0.72-0.85) were significantly associated with prostate cancer risk. Compared to whites, the risk of incident prostate cancer was twofold higher in African-Americans and 16 % higher in Latinos. Additional adjustment for a history of PSA testing did not change the results.

Conclusions: The findings suggest that racial/ethnic differences in prostate cancer risk are not explained by the lifestyle factors examined and that underlying genetic factors may be involved.