Would-be dads take note. Lifestyle choices from smoking to exercise to wearing tight underpants lead to subtle changes in your sperm that may affect the health and behaviour of your children.
鈥淲hat a man does throughout his life has an impact on his sperm,鈥� says Kenneth Aston at the University of Utah. 鈥淭hose changes may confer risk to offspring.鈥�
The focus is usually on mothers when it comes to smoking, but a father鈥檚 behaviour also affects his children鈥檚 health. One way this can happen is by pregnant women and children being exposed to fathers鈥� cigarette smoke.
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However, there is growing evidence that even smoking before conception increases children鈥檚 risk of developing a wide range of diseases, from autism to cancers. In part this is because the sperm (and eggs) of smokers have more mutations in their DNA.
Epigenetic changes
In 2017, Aston鈥檚 team showed that there are also epigenetic changes in the sperm of men who smoke. Epigenetic changes, such as the addition of methyl groups to DNA, don鈥檛 change the underlying DNA sequence but can alter the activity of genes.
Aston found . What wasn鈥檛 clear was whether these changes affect children. In theory, all the methylation changes might be wiped away in developing embryos.
So Aston鈥檚 team has now exposed male mice to cigarette smoke. The offspring of these mice had altered methylation patterns and altered gene expression in the prefrontal cortex of the brain compared with mice whose fathers were not exposed to smoke.
That strongly suggests that the epigenetic changes in sperm due to lifestyle factors such as smoking do indeed affect the health and behaviour of children, the team concludes.
Men need to be aware of this, Aston says. 鈥淚 don鈥檛 think many men think about the impacts that their behaviour prior to conception has on their offspring. That鈥檚 something I didn鈥檛 think about when I was having kids.鈥�
罢丑别谤别鈥檚 , says reproductive expert Michael Carroll at Manchester Metropolitan University in the UK.
What is notable about this latest study, Carroll says, is that it suggests that the epigenetic changes in the sperm are a result of oxidative stress 鈥� the production of high levels of damaging chemicals inside cells.
Oxidative stress occurs in the testes when they get too warm. This can be caused by obesity, diabetes, obstructions known as varicoceles, environmental toxins, injuries, infections and perhaps even tight underwear. So all these factors might affect children鈥檚 health, too, Carroll says.
On the plus side, Aston found that when male mice were no longer exposed to cigarette smoke, around half of the epigenetic changes reverted to normal after 30 days 鈥� the time it takes for sperm to develop from stem cells. In humans, this takes 67 days.
The team also found no changes in the sperm of mice whose sires were exposed to smoke, suggesting any adverse effects last only one generation. But Aston cautions that epigenetic effects can also be passed on in other ways 鈥� for instance, via RNAs in sperm 鈥� that the team did not check.
Epigenetic changes are not always bad. Last year another study showed that , due to RNAs passed on in sperm.
Smoking also reduces the fertility of both men and women.
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