The assessment of sperm morphology, determined by the cells’ shape and size, is an important part of male fertility testing. Previous research has suggested that only sperm with good sperm morphology are able to make their way to the egg in the woman’s body and fertilise it. 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. To investigate the effects of lifestyle factors on sperm morphology, a team of UK scientists based at the University of Sheffield (Professor Harry Moore and myself), the University of Manchester (Dr Andrew Povey and Professor Roseanne McNamee), and the University of Alberta (Professor Nicola Cherry), conducted this landmark research.
In a break from previous investigations into sperm morphology, this research was a substantial case-referent study with 318 cases and 1,652 referent controls. Cases had poor sperm morphology (<4% normal forms based on 200 sperm assessed), and exposures included self-reported use of alcohol, tobacco, and recreational drugs, as well as occupational and other factors. Participants were recruited from 14 fertility clinics across the UK during a 37-month period from January 1999. To ensure that the research was as unbiased as possible, all lifestyle details were disclosed before the subjects knew the results of their semen analysis, a major strength of study design.
So what did this study determine? Do factors such as body mass index (BMI), type of underwear, smoking, or the use of cannabis have an impact on the size and shape of a man’s sperm? Previous studies claimed that environmental factors may contribute to declining sperm quality. Contrary to these findings, our research demonstrated that lifestyle makes little contribution to the risk factors for poor sperm morphology. No significant association was found with BMI, underwear type, smoking, or alcohol consumption—suggesting that an individual’s lifestyle has very little impact on sperm morphology.
Of the risk factor variables for poor sperm morphology, only two proved noteworthy: the use of cannabis in young men in the three months before sample production, and sample production in the summer. Men who produced ejaculates with less than four percent normal sperm were nearly twice as likely to have produced a sample in the summer months (June to August), or be under 30 years old and used cannabis in the three month period prior to ejaculation.
The results overturned the findings of previous less well-controlled and underpowered studies, which suggested that eating, smoking, and drinking habits might contribute to poor sperm qualities in young men. While it is recommended that cannabis users stop using the drug if they are planning to start a family, overall it is reassuring to find that there are very few identifiable risks.
Since many couples undergoing assisted conception treatments such as IVF attempt to make lifestyle adjustments in order to maximise their chances of success, our data suggests there is little evidence to suggest that these will be able to improve sperm morphology. Our previous study, published in 2012 reached a similar conclusion about the number of motile sperm. Both these papers together suggest that modifiable lifestyle risks for semen quality are relatively few and far between.
With no clear link between lifestyle factors and sperm morphology, which factors affect the size and shape of sperm? A major contribution to good sperm morphology will inevitably be down to genetic factors. Moreover, infertility in men is now compounded by age-related changes in both partners. Participant recruitment began over 15 years ago, when lifestyle was much different from today, particularly with regards to mobile phone use. There are still unanswered questions in this area of research and we would like to repeat the study, to see if life in the mid-2010s has any more pronounced effects on sperm morphology than it did 25 years ago.
Featured image: Cigarette by realworkhard. CC0 Public Domain via Pixabay.