A study of 97 healthy non-smoking men aged from 22 to 80 has demonstrated that, as they age, men's semen quality declines. There was a continuous reduction in sperm motility (movement) and semen volume and the proportion of men with abnormal semen volume, sperm concentration and motility increased significantly across the age decades.
The research, from a team in California, confirms that men as well as women have a biological clock – even though it may not start ticking as abruptly as women's.
One of the lead researchers, Dr Brenda Eskenazi, Director of the Center for Children's Environmental Health Research at the University of California at Berkeley, said: "We measured semen volume, sperm concentration, sperm motility and progressive motility (the ability of sperm to move forward) in men with no known fertility problems and we found significant age-related decreases in semen quality, most notably for semen volume and sperm motility.
"However, unlike women, there appears to be no evidence of an age threshold, but rather a gradual change over time. Because semen quality is generally considered to be a proxy for fertility our findings suggest that men may become progressively less fertile as they age.
Over a quarter of cases of infertility are known to be due to male factors. Dr Eskenazi, who is Professor of Maternal and Child Health and Epidemiology, said that understanding the effect of male age on fertility had become increasingly significant in public health as a growing number of men are choosing to father children at older ages than in the past. In the USA, for example, the birth rate for fathers aged between 35 and 54 has risen by nearly a quarter since 1980.
Dr. Andrew Wyrobek, head of the Health Effects Genetics Division at Lawrence Livermore National Laboratory and another principal researcher on the study, warned: "These findings therefore have important implications for men who choose to delay fatherhood since they may reduce their chance of success the longer they delay."
Of the 97 men in the study, nearly two-thirds had fathered children earlier in life. Unlike most previous studies this one controlled for other demographic and lifestyle factors. It also included larger numbers of older men, enhancing the ability to detect an association between age and semen parameters.
The researchers found that semen volume fell by 0.03ml per year of age, motility decreased by 0.7% per year, progressive motility decreased by 3.1% per year and the total progressively motile sperm count decreased by 4.7% a year.
"For men aged 50, we predicted about an 80% probability of clinically abnormal motility, 35% probability of abnormally low semen volume and 15% probability of abnormally low sperm count. These probabilities rose to 100%, 80% and 50% respectively for men aged 80.
"Our findings support and extend those for semen quality in prior clinical studies of infertile patients and sperm donors, and were generally at the high end of changes observed in the clinical studies. For example, we saw a 20% decrease in semen volume in 50-year-olds compared to 30-year-olds. Our findings are generally consistent with some previous studies that demonstrated a decreased pregnancy rate and longer time to pregnancy in partners of older men."
Drs Eskenazi and Wyrobek said there were two possible explanations for changes with age – cellular or physiological changes in the genitourinary tract or the effect of reproductive damage from disease or exposure to exogenous factors.
[1] The association of age and semen quality in healthy men. Human Reproduction. Vol.18. No.2. Pp 447-454.
Notes:
1 PDF version of this press release and full embargoed text of the paper with complete results can be found from 09.00hrs GMT Monday 3 February on: http://www3.oup.co.uk/eshre/press-release/feb203.pdf or is available immediately from Margaret Willson.
2 Human Reproduction is a monthly journal of the European Society of Human Reproduction and Embryology (ESHRE). Please acknowledge Human Reproduction as a source. Dr Helen Beard, Managing Editor. Tel: 44-195-421-2404. Email: beardh@humanreproduction.co.uk
3 ESHRE's website is: http://www.eshre.com
4 Abstracts of other papers in ESHRE's three journals: Human Reproduction, Molecular Human Reproduction & Human Reproduction Update can be accessed post embargo from: http://www3.oup.co.uk/eshre/ Full text of papers available on request from Margaret Willson.
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