Ejaculation Frequency and Prostate Cancer Risk

Summarized by Robert W. Griffith, MD
June 4, 2004

Introduction

It's been thought in the past that increased sexuality activity reflected increased androgen activity and was thus an indicator of increased risk of prostatic cancer. And some experts thought that increased sexual activity was an indicator of increased risk of exposure to sexually transmitted disease, which is also a risk factor for prostate cancer. So a new report from the US National Cancer Institute comes as a bit of a surprise. It's been published in JAMA, and summarized here.

Method

The data were derived from the Health Professionals Follow-up Study, which was started in 1986. Over 50,000 male health professionals between 40 and 75 were enrolled, and completed questionnaires about their possible risk factors for cancer and other chronic diseases. Follow-up questionnaires were sent every two years; in 1992 the questionnaire included questions about the frequency of ejaculation. The term 'ejaculation' covered sexual intercourse, nocturnal emission, and masturbation.

A total of 29,342 men provided adequate information to be included in the analysis, and they were followed carefully for the next 8 years. The participants were asked to report the average number of ejaculations they had per month during the ages 20 to 29, 40 to 49, and during the previous year (i.e. 1991); they could check either 1-3, 4-7, 8-12, 13-20, or ≤21 ejaculations per month.

Each subsequent questionnaire asked whether the participant had been diagnosed with prostate cancer in the previous two years. A positive answer led to further investigation to ascertain the accuracy of the diagnosis.

Results

There were 222,426 person-years available for analysis. During this time, 1449 cases of prostate cancer were diagnosed. As expected, the mean number of ejaculations per month fell with increasing age, from 15.1 at age 20-29, to 5.0 for men over 60. Put another way, 58% of men reported 3 or more ejaculations per week at 20-29, falling to 32% at ages 40-49, 22% at ages 50-59, and 5% in the over 60s.

Men with greater ejaculation frequency over their lifetime tended to be more active physically, and were more likely to have a history of a sexually transmitted disease, prostatitis, and vasectomy. They were also more likely to be divorced or separated, and consume more total calories, lycopene, fish, alcohol, and supplemental vitamin E and zinc.

Multivariate analyses were used, adjusting for current age, time period, racial group, family history of prostate cancer, vasectomy, BMI at age 21, height, smoking pack-years, type 2 diabetes, physical activity, and calorie, fructose, vitamin E, zinc, meat, fish, and alcohol intake. They showed the following relative risk (RR) of total prostate cancer, setting the RR for 4-7 ejaculations per month as 1.00:

* statistically significant (95% confidence intervals don't contain 1.0)

	Number of Ejaculations Per Month
	0-3	4-7	8-12	13-20	≥21
Age 20-29	1.09	1.00	1.06	0.95	0.89
Age 40-49	0.83	1.00	0.96	0.98	0.68*
Previous year	1.06	1.00	1.06	1.07	0.49*
Lifetime	0.89	1.00	0.89	0.86*	0.67*

It can be seen that an average ejaculation frequency of 21 or more times per month at ages 40-49, or 13 or more times per month over a lifetime, is associated with a decreased risk of prostate cancer. Similar results were obtained for prostate cancer that was confined to the organ itself.

Comment

This study shows that higher ejaculation frequency was not associated with an increased risk of prostatic cancer; indeed, a high ejaculation frequency may be associated with a decreased risk of total and organ-confined prostate cancer. These findings are not explained by interference of known risk factors such as age, family history, sexual transmitted disease, smoking, or diet.

How can these findings be explained? The authors of the study suggest that frequent ejaculations may modulate the presence of carcinogenic compounds in prostatic fluid. Candidates for this role are xenobiotics and chemical carcinogens, which are known to accumulate in prostatic fluid. Alternatively, frequent ejaculation may reduce the development of intraluminal prostatic crystalloids, which have been associated in some studies with prostate carcinoma.

In view of the conflicting studies reported to date, confirmation of the results obtained in the present study would be desirable before they become accepted as gospel. In the meantime, another, accepted, risk factor for prostate cancer that can readily be modified - a high animal fat diet (meat, cheese, high-fat dairy produce) - should receive greater attention. And one should eat more tomatoes!

Source

• Ejaculation frequency and subsequent risk of prostate cancer. MF. Leitzmann, EA. Platz, MJ. Stampfer,  et al., JAMA, 2004, vol. 291, pp. 1578--1586

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