Shape and Size of Sperm in Young Men Affected by Use of Cannabis

Use of cannabis among young men affects the shape and size of sperm eventually leading to fertility problems, a new study suggests.

Researchers at the University of Sheffield investigated how certain lifestyle factors influence size and shape of sperm known as sperm morphology. 

In this study, researchers looked at 2,249 men from 14 fertility clinics around the U.K..  The participants were asked to complete questionnaires about their medical history as well as lifestyle.

The reliable data about sperm morphology was available on 1,970 men and this data was later compared with the data of 318 men who produced sperm in which less than four percent was of  correct size and shape. The study also included a control group of 1,652 men where the correct size and shape was more than four percent, which was deemed normal.

The researchers noticed that men who produced ejaculates with not more than four percent normal sperm were two times more likely to have produced the sample in summer months i.e. June -August. Or they were not more than 30 years old and used cannabis in a three month period before ejaculation.

Lead author Dr Allan Pacey, senior lecturer in Andrology at the University of Sheffield, said: "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 suggests that cannabis users might be advised to stop using the drug if they are planning to try and start a family."

A study conducted earlier showed that sperm with good sperm morphology only make it to the egg and fertilize it. And those with poor sperm morphology also swim less because the abnormal shape makes it difficult for the sperm to swim efficiently.

Dr Andrew Povey, from the University of Manchester's Institute of Population Health, said: "This research builds on our study of two years ago which looked at the risk factors associated with the number of swimming sperm (motile concentration) in men's ejaculates. This previous study also found that there were relatively few risk factors that men could change in order to improve their fertility. 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 their chances of a conception."

The finding was documented in the journal Human Reproduction.