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July 21, 2004

Frequency of Ejaculation and Risk of Prostate Cancer—Reply

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;292(3):329. doi:10.1001/jama.292.3.329-b

Reply: In response to Dr Giles and colleagues, our rationale for using the category of 4 to 7 ejaculations per month as the common reference group was that that category reflects a more typical ejaculation frequency than the category of 0 to 3 ejaculations per month. In addition, the category of 4 to 7 ejaculations per month had sufficient numbers of cases across the different age groups, which ensured reasonable stability of the relative risk estimates. When we combined the first 2 groups as the reference category, the multivariate relative risks for men reporting 21 or more ejaculations per month at ages 20 to 29 years, ages 40 to 49 years, in the previous year, and across the lifespan were 0.88 (95% confidence interval [CI], 0.73-1.06), 0.69 (95% CI, 0.55-0.87), 0.42 (95% CI, 0.24-0.74), and 0.69 (95% CI, 0.52-0.91), respectively.