Vasectomy and prostate cancer in US blacks and whites
Hayes, R. B., Pottern, L. M., Greenberg, R., Schoenberg, J., Swanson, G. M., Liff, J., ... Hoover, R. N. (1993). Vasectomy and prostate cancer in US blacks and whites. American Journal of Epidemiology, 137(3), 263-9.
A large population-based case-control study was carried out to investigate the association between vasectomy and prostate cancer risk in black and in white men in the United States. Study subjects resided in the geographic areas covered by the population-based cancer registries of the Georgia Center for Cancer Statistics, or the Metropolitan Detroit Cancer Surveillance System, or in 10 counties included in the cancer registry of the New Jersey State Health Department. Cases for this study were men aged 40-79 years identified from pathology and outpatient records at hospitals covered by these registries, newly diagnosed with pathologically confirmed prostate cancer between August 1, 1986, and April 30, 1989. Population controls less than age 65 years were selected at periodic intervals by random digit dialing. Older controls were systematically selected (after a random start) from computerized records of the Health Care Finance Administration. A statistically nonsignificant excess risk (odds ratio (OR) = 1.6, 95% confidence interval (CI) 0.5-4.8) for prostate cancer associated with vasectomy was noted in blacks. Overall, the risk for prostate cancer associated with vasectomy in whites was not elevated (OR = 1.1, 95% CI 0.8-1.7). An increase in risk was found, however, for white men who had had a vasectomy 20 years or more prior to study (OR = 1.7, 95% CI 0.9-3.3) or who had had a vasectomy at less than age 35 years (OR = 2.2, 95% CI 1.0-4.4). For the total study group, the odds ratio associated with men who had a vasectomy 20 or more years prior to study was 1.5 (95% CI 0.8-2.7), and the odds ratio associated with men who had had a vasectomy at less than age 35 years was 2.0 (95% CI 1.0-4.0). Further detailed analysis showed that young age at vasectomy (less than age 35 years) was a more important risk factor than was years since vasectomy.