Sperm counts halve over decade

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Sperm production by middle-aged men has deteriorated by as much as 50 per cent in the last 10 years and testicles are smaller, according to a study by Finnish scientists which provides further evidence of declining male fertility.

The proportion of men in Finland aged between 35 to 69 with normal spermatogenesis - the production of sperm - fell from about 56 per cent to 27 per cent between 1981 and 1991.

Over the same period there was a significant increase in the number of men with no mature sperm cells, a condition known as spermatogenic arrest. The incidence of complete spermatogenic arrest rose from 8 per cent to 20 per cent, and of partial spermatogenic arrest from 31 per cent to 48.5 per cent.

The post-mortem study of two groups, one comprising 264 men who died in 1981 and the other of 264 men who died in 1991 showed that the weight of the men's testicles had also diminished over the study period; seminiferous tubes were smaller, and there was increased fibrosis (thickening) of testicular tissue. The mean age of the groups was 53, and there were no significant differences in cause of death between the two groups. More than half died from diseases and a third died violently or from intoxication (accidents or suicide).

Writing in tomorrow's issue of the British Medical Journal, Dr Jarkko Pajarinen from the Department of Forensic Medicine at Helsinki University, and colleagues write: " ... the incidence of normal spermatogenesis has decreased significantly among middle-aged men, with a parallel increase in the rate of disorders of spermatogenesis ... between 1981 and 1991. This finding suggests that the quality and dispatch of spermatogenesis are deteriorating in middle-aged men and also confirms earlier presumptions on deteriorating sperma- togenesis being the main cause of decreasing sperm counts."

Another Scandinavian team first alerted the scientific community in 1992 to declining sperm counts. Professor Niels Skakkebaek at Copenhagen University reviewed studies involving almost 15,000 men between 1938 and 1992 and found the average sperm count had fallen from 113 million per millilitre in 1940 to 66 million in 1990. The definition of a "normal" sperm count fell from 60 million per millilitre to 20 million in the same period. Critics claimed fundamental flaws in the data but two studies in France and Belgium in 1994 confirmed the findings.