Male biological clock is ticking
Scientists from Bristol and Brunel Universites believe that they have shown evidence for a male "biological clock."
The study, described in
Human Reproduction (2000;
15(8):1703-8), showed that
conception takes longer when
the man is older, irrespective
of his partner's age. Out of
8000 pregnancies studied, 74%
were conceived in under six
months, 14% in the second six
months, and 12% after more
than a year. After adjustment
for independent variables it
was found that women with
older partners were significantly less likely to conceive in
under six or 12 months. It is
not apparent from the study
whether the conception took
longer because older men's
sperm was less fertile or
because older men have intercourse less frequently.
David Bowie in 1997, shortly after his 50th birthday, with his wife Iman. A much wanted child, Alexandria, has just been born to the happy couple(CHRIS PIZELLO/AP)
The researchers used questionnaires to analyse families
who had babies in 1991 and
1992 in the Avon Health
Authority. The questionnaires
completed by both partners
were designed to evaluate the
effects of specific fertility factors, such as paternity or alcohol consumption, on the rate of
conception.
The researchers claim that
this study shows for the first time
the existence of a male "biological clock," and concludes that
even for a fertile couple, the likelihood of taking more than a
year to conceive doubles when
the man is over 35. The implication is that paternal age should
be another factor that is taken
into account when looking at
the chances of conception in
subfertile couples.
Richard Tingay, London
studentBMJ 2000;08:303-346 September ISSN 0966-6494
