There has been a lot of response in the medical media and the public domain to the ten-year follow-up study concerning ejaculation as a reversible risk factor for prostate cancer. This is especially because there are so few risk factors for this disease that men can do anything about.
The prospective study that has launched this topic again into the media is the “Ejaculation Frequency and Risk of Prostate Cancer: Updated Results with an Additional Decade of Follow-up” study, published online this year in the Journal European Urology.
Originally, in 1992, 31,925 men from the Health Professionals Follow-up Study were questioned about their average monthly ejaculation frequency during ages 20-29 and 40-49 years of age and in the previous year 1991. Follow-up was through to 2010. There was a reference group of four to seven ejaculations a month. Ejaculation frequency at age 40 to 49 years was positively associated with age-standardised body mass index, physical activity, divorce, history of sexually transmitted infections, and consumption of total calories and alcohol. Prostate-specific antigen (PSA) test utilization by 2008, number of PSA tests, and frequency of prostate biopsy were similar across frequency categories. Associations were driven by low-risk disease, were similar when restricted to a PSA-screened cohort, and were unlikely to be explained by competing causes of death.
The relative risk reduction was significant at 10% in men who reported eight to twelve ejaculations per month at 40 to 49 years, and at 20% in men who reported thirteen to twenty ejaculations at 40 to 49 years (P trend < .0001). Importantly, there was no association between ejaculation frequency and high-grade, advanced, or lethal prostatic cancers.
“These 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… men who reported more frequent ejaculation in adulthood had a lower risk of total incidence of prostate cancer. Ejaculation frequency represents a potentially modifiable risk factor for prostate cancer.”1
Regarding the conclusion above, Dr Janet Stanford, PhD, a prostate cancer researcher at the Fred Hutchison Cancer Research Center in Seattle, who was not involved in the study, said about the observational data:
“Association does not mean causation, so one has to be cautious about interpretation,”2
In a 2007 analysis of the Health Professionals Follow-up Study cohort by another research group:
“Only four factors had a clear statistically significant association with overall incident prostate cancer: African–American race, positive family history, higher tomato sauce intake (inversely) and α-linolenic acid intake… In contrast, for fatal prostate cancer, recent smoking history, taller height, higher BMI, family history, and high intakes of total energy, calcium and α-linolenic acid were associated with a statistically significant increased risk. Higher vigorous physical activity level was associated with lower risk.”2
This group state that there are many issues that are difficult to take into account with this research, although it is generally agreed it was well done. One major problem is the fact that low-grade prostatic cancers are so much more common than high grade cancers and the behaviour of the two types is very different. This may have something to do with the underlying reason for no relationship found between ejaculation frequency and high-grade, advanced and fatal prostatic cancers in the previous study. One obvious aspect of bias is that the group studied are health professionals, and hence may have a healthier lifestyle in some than that of the general population.
1. Rider, J. et al. Ejaculation Frequency and Risk of Prostate Cancer: Updated Results with an Additional Decade of Follow-up European Urology, March 2016
2. Mulcahy, N. Study: Ejaculate More, Have Less Prostate Cancer Risk, Medscape, March 31, 2016
3. Giovannucci, E., Liu, Y et al. Risk factors for prostate cancer incidence and progression in the health professionals follow-up study. International Journal of Cancer. 2007 Oct 1; 121(7): 1571–1578.