17 May 2005
Results from a study of sperm counts among men attending Scottish fertility clinics between 1989 and 2002 were announced recently at the fourth joint meeting of the Association of Clinical Embryologists and the British Fertility Society, 5-6 January 2004. The SPIN (Semen Parameters in the Northeast) study measured sperm counts in more than 16,000 semen samples from over 7,500 men attending the Aberdeen Fertility Centre. They found that among men with sperm counts within the normal range (above 20 million sperm per millilitre), the average sperm count had fallen over 14 years from around 87 million sperm per ml to 62 sperm per ml. Although still well within normal parameters, this decrease represented a 29% drop in average sperm levels over this period.
Although men attending a fertility clinic are not necessarily representative of the male population as a whole, the results contribute to fears that environmental and genetic factors may be having serious adverse effects on male potency. Multiple potential causes for falling sperm counts have been proposed, including environmental toxins and chemicals, obesity and lifestyle factors such as smoking, drinking and drug use. However, there are as yet no firm conclusions. Researchers commented that in themselves the results could not be used to determine a corresponding fall in male fertility, although this is an issue of obvious concern. They next aim to investigate aspects of sperm quality (such as motility) to determine whether this has also declined over recent years. A recent US study found that the quality of sperm declined with age, in terms of increasing levels of DNA damage in sperm. They also observed an age-related decrease in levels of apoptosis of sperm cells (a process of self-destruction designed to remove genetically damaged cells), but were unable to attribute these features directly to ageing or to increased exposure to harmful environmental factors.