Men considering having a vasectomy, convinced by their doctors that there are no detrimental health effects, may want to think even more carefully about their decision. Two large studies reported recently add to earlier evidence that a vasectomy may increase a man's risk of developing prostate cancer. Moreover, vasectomies can cause chromosomal abnormalities in sperm itself.
As comedian Benny Ross has stated "the inventor of vasectomies must of been a prison warden...who else would prevent these rambunctious little swimmers from getting to their destination."
Humour aside, vasectomies are no laughing matter.
Experts not directly involved in the two large studies on vasectomies call the research scientifically well designed, adding that they underscore the need for further research to assess the possible hazards of one of the most effective and ...widely used methods of contraception.
The studies found that men who had a vasectomy more than 20 years earlier faced up to an 89 percent greater risk of prostate cancer than men who had not had a vasectomy. The studies also found that the more time that had passed since a vasectomy, the greater was the risk of developing prostate cancer.
The studies, reported in The Journal of the American Medical Association, were largely financed by the National Institutes of Health. They were conducted by a team headed by Dr. Edward Giovannucci from the Brigham and Women's Hospital and Harvard University in Boston.
In 1990, a small study from Edinburgh, Scotland, found that an unexpectedly large number of men who had had vesectomies later developed testicular cancer.
Experts said the findings show a statistical association that required further study. No plausible biological cause for the association is yet evident. They speculated that such a biological mechanism might be related to the decreased amount of prostate fluid after a vasectomy or to suppression of immune reactions that affect cancer. The experts also noted that the studies might have been influenced by other non-detectable factors.
The editorial urged men who have had a vasectomy to undergo annual checkups for prostate cancer, which is the recommendation made by the urological group and the American Cancer Society for men 50 to 70 years old.
Doctors should inform men seeking a vasectomy about the new findings, the editorial said.
The World Health Organization, a United Nations agency based in Geneva, said the studies were not definitive but "of high scientific quality" and that the scientific design of the studies avoided many of the methodological problems of earlier studies, some of which did not find a link between vasectomy and prostate cancer.
Experts in the United States and at the W.H.O. said that additional studies were urgently needed because confirmation of the latest findings would have a critical effect on family planning programs. Crucial information could come from at least six ongoing studies in the United States and Europe, the W.H.O. said.
Indications of a link between vasectomy and prostate cancer from recent studies led the World Health Organization to convene a committee of 23 experts from 10 countries in 1991. They concluded that no changes in family planning policies concerning vasectomies were justified on the basis of the biological and epidemiological evidence available then.
W.H.O. officials said that they did not know why reports from the meeting had not been published, as it had been announced they would be, in The European Journal of Cancer.
At an annual meeting of the British Fertility Society, researchers suggested that even if the surgical effect of a vasectomy can be undone, the longer term effects onĀ sperm production may not be so reversible.
Vasectomies work by deliberately obstructing the tube that carries sperm from the testis, thereby preventing sperm, which continues to be produced, from being ejaculated. Researchers from the School of Medicine, Obstetrics and Gynaecology at Queen's University, Belfast, studied men who had vasectomies as a form of contraception after having children ten years ago. Years after the vasectomy, they found the men had a much lower sperm production rate compared to those (fertile) men who hadn't ever had the operation.
Dr Carmel McVicar, who presented the work, said the research team did not expect to see 'this reduction in sperm count or pregnancy due to previous vasectomy and ongoing studies are attempting to decipher the reasons for it'. She added: 'Men attend our clinic every week wanting to have a second family with a new partner. Men who are considering vasectomy certainly need to think very carefully about the long-term consequences to their future fertility'.
Researchers from Thailand found
that rate of abnormalities dropped with time after a reversal operation - that is, the longer ago the reversal, the better the chances of producing normal sperm. Team leader Professor Nares Sukchareon said that the study raised important questions, such as 'is the abnormal spermatogenesis [sperm production] reversible, and if so, how long will it take to get back to normal?'
Professor Sukchareon said that the findings may not affect babies born to men who have had vasectomy reversals, since the healthiest sperm might naturally be selected for fertilisation. But he added that until further research is carried out, 'it would probably be safer to freeze ejaculated sperm before vasectomy'. Dr Allan Pacey, senior lecturer in andrology at the UK's University of Sheffield, and spokesperson for the British Fertility Society, agreed, saying 'I think it would be a sensible insurance policy'.