Young men who use cannabis may be putting their fertility at risk by affecting their sperm quality, according to a new study. However, other common lifestyle factors, including smoking cigarettes and drinking alcohol, appear to have little effect.
“Our knowledge of factors that influence sperm size and shape is very limited, yet faced with a diagnosis of poor sperm morphology, many men are concerned to try and identify any factors in their lifestyle that could be causing this. It is therefore reassuring to find that there are very few identifiable risks, although our data suggest that cannabis users might be advised to stop using the drug if they are planning to try and start a family,” said lead author Dr Allan Pacey, Senior Lecturer in Andrology at the University of Sheffield, United Kingdom.
Although many studies have claimed that men's lifestyle can affect sperm morphology, the evidence is weak with studies often underpowered and poorly controlled. In the world’s largest study to investigate how common lifestyle factors influence sperm morphology, a research team from the Sheffield and Manchester universities recruited more than 2200 men from 14 fertility clinics around the UK. The men filled out detailed questionnaires about their medical history and their lifestyle.
Reliable data about sperm morphology were available for only 1970 men, so the researchers compared the information collected for 318 men who produced sperm of abnormal morphology (less than 4% sperm of normal size and shape) and a control group of 1652 men who had normal sperm morphology.
Men who produced ejaculates with less than 4% normal sperm were nearly twice as likely to have produced a sample in the summer months (June to August), or if they were younger than 30 years, to have used cannabis in the 3-month period before ejaculation.
No significant association was found with body mass index, type of underwear, cigarette smoking, alcohol consumption, or having a history of mumps, all factors that have been associated with fertility risk in men.
This research builds on a study of 2 years ago that looked at the risk factors associated with sperm motility concentration in men’s ejaculates, said Dr Andrew Povey, from the University of Manchester’s Institute of Population Health.
“This previous study also found that there were relatively few risk factors that men could change in order to improve their fertility,” said Dr Povey. “We therefore have to conclude again that there is little evidence that delaying fertility treatment to make adjustments to a man’s lifestyle will improve his chances of a conception.”
Although the study failed to find any association between sperm morphology and other common lifestyle factors, such as cigarette smoking or alcohol consumption, it remains possible that they could correlate with other aspects of sperm that were not measured, such as the quality of sperm DNA, the researchers noted.
They published their results online on June 4, 2014, in Human Reproduction.