Men's sperm count acts a marker of general health, with low counts indicating men are more likely to have other health conditions.
Men who have low sperm counts are 12 times more likely to have low testosterone levels, according to a study of 5177 men from infertile couples, presented at the Endocrine Society Annual Meeting last week in Chicago, Illinois. Half of the men with low testosterone had low bone mass or osteoporosis.
The study, carried out at the University of Padova in Italy, also found that men with lower sperm counts were more likely to have high blood pressure, diabetes and more body fat. A low sperm count was considered to be less than 39 million spermatozoa per ejaculate.
'Evidence suggests that infertile men are at increased risk for hypogonadism, metabolic [differences] and osteoporosis, [and] have higher long-term morbidity and mortality than controls,' said Dr Alberto Ferlin, who carried out the research. He added that at present there was insufficient data in this area to draw conclusive results.
'Our study clearly shows that low sperm count by itself is associated with metabolic alterations, cardiovascular risk and low bone mass,' he said.
The study only found an association, but did not assess whether other health conditions caused the low sperm count in men or vice versa.
'There is currently no suggestion that male sub-fertility causes health problems later in life and in my opinion, it is more likely that they both have a common cause,' said Professor Allan Pacey at the University of Sheffield, who was not involved in the study.
'However, this highlights why we need to design better studies to investigate male sub-fertility as it could be an important 'canary in the coal mine' for other aspects of male health.'
The researchers maintained that couples would benefit from being given information on risk factors associated with infertility as part of their medical care, in addition to getting treatment for their specific condition.
'Infertile men are likely to have important co-existing health problems or risk factors that can impair quality of life and shorten their lives,' said Dr Ferin. 'Fertility evaluation gives men the unique opportunity for health assessment and disease prevention.'