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Greater ejaculation frequency may reduce prostate cancer risk
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Ten-year follow-up data from add to prior evidence suggesting more frequent ejaculation may reduce prostate cancer risk.
“Our findings provide additional evidence of a beneficial role of more frequent ejaculation throughout adult life in the etiology of prostate cancer, particularly for low-risk disease,” Jennifer R. Rider, ScD, MPH, assistant professor in the department of epidemiology at Boston University School of Public Health, and colleagues wrote.
Rider and colleagues aimed to comprehensively evaluate the inverse association between ejaculation frequency and prostate cancer risk among 31,925 men.
Researchers used data from a 1992 questionnaire that included questions about ejaculation frequency. Men were followed through 2010.
Median monthly ejaculation frequency was assessed between the ages of 20 and 29 years, 40 and 49 years, and the year before questionnaire distribution. The researchers accounted for screening, clinically relevant disease subgroups and the effects of mortality from other causes.
The analysis included 480,831 person-years of follow-up.
During that time, 3,839 men were diagnosed with prostate cancer.
Multivariable analyses showed significantly reduced prostate cancer incidence among men who reported 21 or more ejaculations per month compared with those who reported four to seven ejaculations per month. HRs for prostate cancer incidence were 0.81 (95% CI, 0.72-0.92) for those aged 20 to 29 years, and 0.78 (95% CI, 0.69-0.89) for those aged 40 to 49 years.
HemOnc Today spoke with Rider about the study, the potential clinical implications of the findings, and how these data add to existing literature.
Question: Can you describe the evidence for this potential association prior to your study?
Answer: Previous population-based studies have investigated sexual behaviors and risk for prostate cancer, but most of these studies have used surrogate measures, including the number of sexual partners and age at first marriage. These measures are, of course, less than perfect measures of sexual activity. Our study is a follow-up to a publication in the same cohort — the Health Professionals Follow-up Study Cohort — published nearly a decade ago. In that study, researchers were specifically interested in evaluating a hypothesis that has been around for a long time, dubbed the prostate stagnation hypothesis, which is basically the idea that if things are allowed to accumulate in the prostate, there may be more of an opportunity for potential carcinogens to initiate tumors. The researchers found an inverse association between frequency of ejaculation and risk for prostate cancer. In both the original study and our follow-up study, we used questionnaire data on ejaculation frequency at ages 20 to 29, ages 40 to 49, and the year prior to the questionnaire. The initial study showed results were strongest within the 1 year before the questionnaire was administered. There were some concerns that perhaps the results could be due to early symptoms of prostate cancer, even before the cancer had been diagnosed, leading men to ejaculate less. This is one of the reasons we conducted the follow-up study. Men were followed 10 additional years, and there were many more prostate cancer outcomes, allowing us to more carefully assess whether symptoms of prostate cancer were accounting for the observed association.
Q: Can you elaborate on the results of your study?
A: Our study used the same data collected in 1992, but we followed men through 2010. During the study period, 3,839 men were diagnosed with prostate cancer. After controlling for a very long list of potential prostate cancer risk factors and other factors found to be associated with prostate cancer in this cohort previously, we identified a 20% reduction in total prostate cancer risk when we compared the highest category of ejaculation — 21 or more ejaculations per month — vs. the lowest, or four to seven ejaculations per month. We found this for the 20-to-29-year age group, as well as the 40-to-49-year age group. So, unlike the first study, we found stronger associations in these two age groups than in the year prior to the questionnaire, suggesting that it was not symptoms of prostate cancer that could be accounting for the observed association.
Q: What are the potential implications of these findings?
A: Before we suggest that men change their behavior in any way, we would like to see these results replicated in another independent cohort. However, I am not aware if those data exist.
Q: What should future research entail?
A: We are following up on these study results by conducting a study looking at changes in gene expression in the prostate associated with ejaculation. If some of the gene expression changes that we see are also related to prostate cancer development, that may provide us with more evidence suggesting that what we are seeing is truly a causal association. We hope to publish these results soon. As of right now, I would not suggest men change their behavior based upon our study. At the same time, men who have an active sex life and are practicing safe sex might be reassured about this additional potential benefit.
Q: Is there anything else that you would like to mention?
A: We were concerned that men who were more sexually active were less likely to undergo prostate cancer screening and, therefore, less likely to be diagnosed with prostate cancer. We took care to ensure that it was not just the frequency of PSA testing and prostate cancer screening that was accounting for our results. – by Jennifer Southall
Reference:
Rider JR, et al. Eur Urol. 2016;doi:10.1016/j.eururo.2016.03.027.
For more information:
Jennifer R. Rider, ScD, MPH, can be reached at Boston University School of Public Health,
715 Albany St., T317E, Boston, MA 02118; email: rider@bu.edu.
Disclosure: Rider reports no relevant financial dis