A study conducted by the University of Southern Denmark has found evidence that suggests men who do not get enough sleep are likely to be less fertile. Many studies have been conducted to discover the link between sleep and healthy living, but this was the first to look specifically for a link between sleep and male fecundity.
The study was conducted by taking sperm samples from 953 Danish men in their late teens to early twenties and asking them to fill out a questionnaire on sleeping patterns. The researchers found that men who suffered from disturbed sleep patterns or got less than 6 hours sleep a night saw a reduction in sperm concentration by over a quarter and also had smaller testicles.
Sleep disturbance was determined by asking the men if they had difficulty falling asleep, how often they woke up during the night and how much time it then took them to get back to sleep. The answers were then scored and compared to the corresponding semen sample and there appeared to be a correlation between low-scoring low-sleep individuals and sperm concentration, sperm count, motility and quality.
Dr Tina Kold Jensen, the lead researcher, hopes the next avenue of research will be to find out whether stabilising the sleeping pattern or making sure males get the recommended seven to eight hours of sleep will reverse the effect and bring sperm levels back up to normal.
In a commentary on the Danish paper, Dr Rémy Slama from Joseph Fourier University in France, went on to say that there are many factors that affect sperm production, such as tobacco smoke, obesity, exposure to heavy metals and atmospheric pollutants.
Individually, these factors only add a small amount of stress to the sperm production mechanisms, but may accumulate to produce a complex series of interacting variables. The researchers in the Danish study pointed out that men who get less sleep tend to have unhealthier lifestyles and drink more alcohol, are more overweight or are more likely to be smokers.
They also explained that the production of testosterone may be affected by sleeping with lower levels of the hormone associated with poor sleeping patterns.
Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said it was unlikely that poor sleep would have a major impact on fertility, however.