5078 Background: A prospective study in the Health Professionals Follow-up Study (HPFS) cohort published in 2001 found significantly lower risks of prostate cancer (PCa) among men with more frequent ejaculation. Because associations were stronger among men at older ages, which could be indicative of reverse causation (i.e., men ejaculating less because of symptoms associated with PCa) and few advanced cases were included, we conducted an updated study with an additional 8 years of follow up. Methods: We included 31,929 men aged 46-81 years from the HPFS who answered ejaculation frequency questions on the 1992 questionnaire. We assessed average frequency per month at three time points: age 20-29, age 40-49, and in 1991 (the year prior to the questionnaire). These data were also combined to estimate average lifetime frequency. Using follow up through January 31, 2008, we used Cox proportional hazards models to estimate relative risks (RR) and 95% confidence intervals (95% CI) for total PCa risk, as well as risk of advanced, lethal, and high-grade (Gleason 8-10) disease. As sensitivity analyses, we also examined associations within a subgroup of highly screened men and a subgroup of men without erectile dysfunction at baseline. Results: During 16 years of follow up, 3403 men were diagnosed with PCa; 455 were advanced, 360 were high grade, and 304 were lethal. Three percent of men reported a lifetime average frequency of >21 times per month while 34% reported 4-7 times per month. Compared to a frequency of 4-7 times per month, multivariate RRs for total PCa for men with >21 ejaculations per month were 0.81 (95% CI: 0.71-0.91) for ages 20-29; 0.76 (95% CI: 0.66-0.88) for ages 40-49; 0.68 (95% CI: 0.53-0.86) in 1991; and 0.57 (95% CI: 0.43-0.75) for lifetime average frequency. RRs for advanced PCa were of similar magnitudes at ages 20-29 years and 40-49 years but not statistically significant. Results were similar when we included only highly screened men or men without a history of erectile dysfunction. Conclusions: With extended follow up, ejaculation frequency continues to be strongly inversely associated with risk of total PCa. These findings are unlikely to be attributable to underlying disease or screening frequency.
Ejaculation Frequency and Risk of Prostate Cancer: Updated Results with an Additional Decade of Follow-up
