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February 17, 1993

Vasectomy and Prostate Cancer: Chance, Bias, or a Causal Relationship?

Author Affiliations

From the Department of Urology, University of Virginia Health Sciences Center, Charlottesville, Va (Dr Howards), and the Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Ga (Dr Peterson).

JAMA. 1993;269(7):913-914. doi:10.1001/jama.1993.03500070093036

This issue of The Journal includes two reports of cohort studies by Giovannucci et al that find an association between vasectomy and subsequent risk of prostate cancer.1,2 Both vasectomy and prostate cancer are common and any causal relationship between the two would be important both for individual and public health. Although the studies by Giovannucci et al are of high quality, whether the relationship they report on is causal remains unclear.

The age-adjusted relative risks for prostate cancer among men with vasectomy in the Nurses' Health Study and the Health Professionals Follow-up Study were 1.56 (95% confidence interval, 1.03 to 2.37) and 1.66 (95% confidence interval, 1.25 to 2.21), respectively. When risk estimates of this magnitude are derived from observational studies, they are considered to be weak associations that may be due to chance, bias, or a causal relationship.3 It is our

See also pp 873 and 878.