Just two months of stress may damage a man's sperm and slash his chances of having children, a new study suggests.
Israeli scientists found men are 47 per cent more likely to have swimmers with weak motility if they are under intense pressure.
Weak motility – known to be affected by lifestyle choices - makes it less likely that the sperm will successfully fertilise an egg.
The findings were derived from 11,000 sperm samples, including those of adults exposed to 'regular rocket warning sirens' in the Gaza Strip.
Israeli scientists found men are 47 per cent more likely to have swimmers with weak motility if they are under intense pressure
Researchers at Ben-Gurion University of the Negev and Soroka University Medical Center in Beer-Sheva led the study.
They analysed 10,535 sperm samples donated by men during periods in Israel deemed ‘unstressful’ between 2009 and 2017.
These were then compared to 659 samples from men take up to two months after fierce military battles between Israel and Gaza.
The men had an average age of 32, which, according to figures, is the average age for first time fathers in the UK.
Even though the findings related to just those living in conflict zones, the researchers argued they could apply to any mental stress.
Dr Eliahu Levitas, study author, said: ‘This study shows that prolonged stress can have an effect on sperm quality.
‘Mental stress is known to have an adverse effect on fertility, but there is little research on the impact of stress on sperm quality.’
The findings were presented at the International Summit on Assisted Reproduction and Genetics in Tel Aviv.
The results follow a landmark study last July that warned humans could face extinction if sperm counts continue to plummet.
Western lifestyles have more than halved the sperm count of men in the US, Europe and Australia since the 1970s, it revealed.
Researchers at Hebrew University of Jerusalem and the Icahn School of Medicine at Mount Sinai claimed it was an 'urgent wake-up call' to investigate lifestyle factors.
Lead author Dr Hagai Levine told Daily Mail Online at the time that ‘if we do not make a drastic change to how we live I am worried about the future.’
An array of previous evidence has also revealed sperm quality can be affected by chemicals found in soap, sunscreen and plastic.
Dr Hana Visnova, medical director at European fertility clinic IVF Cube in Prague, said the research hints at a ‘vicious circle’ when it comes to stress and infertility.
She told MailOnline: 'Those who suffer fertility problems often endure an emotional rollercoaster.
'And if stress has led to the infertility problems in the first place, we could be looking at a vicious circle when it comes to sperm quality and infertility.
'For men, there there’s this notion - an outdated and dangerous one - that fertility problems reflect poorly on a man’s masculinity, and that they have to stay strong and stoic and strong for the sake of their relationship.
'And that results in men are often going unsupported in their journey to becoming a parent, as the focus shifts primarily to the female. A more open dialogue would be helpful.'
WHAT SHOULD MEN DO TO HAVE HEALTHIER SPERM?
Maintain a healthy weight
The majority of male fertility issues relate to sperm disorders, writes Professor Luciano Nardo, a consultant gynaecologist at the Reproductive Health Group in Cheshire.
But there are changes men can make to try and improve their overall wellbeing. Lifestyle can have a major impact on general health, including fertility.
Excess weight can put extra pressure on your body and there is a link between a higher BMI and a decrease in testosterone and erectile dysfunction.
It's for these reasons it is wise to maintain a healthy weight, especially if you want to start a family.
Quit smoking
For both men and women trying to get pregnant the advice is to quit smoking.
A large volume of research has shown a link between smoking tobacco and having difficulty conceiving. Smoking can also damage sperm and cause erectile problems - making it harder to get pregnant.
Ditch the booze
Enjoying the occasional drink is fine but excessive or binge drinking could harm sperm, and sperm that is damaged is unlikely to lead to a successful conception.
Wear looser pants
Professor Nardo recommends avoiding tight fitting underpants
It is normal for up to 96 per cent of sperm to appear abnormal in some way. However where there are higher numbers there could be an underlying cause for this.
One cause could be the increased temperature of the testes.
A number of studies in the past have tried to find a definitive link between tight fitting underpants and a higher count of abnormal sperm.
Although we can't say for certain, it is recommended that men wear loose boxer shorts rather than briefs.
Get enough sleep
Having a good sleep routine can help you feel rested even during the busiest of times.
When you're tired it can also make you more likely to reach for sugary quick fixes and caffeinated drinks, sending blood sugar levels up and down throughout the day and making it harder to sleep well.
Keep stress in check
Stress is generally bad news for your overall health, and it's not great for fertility, either.
Stress is associated with hormonal changes and damage to cells in the body.
Many people think keeping stress in check while trying to conceive is purely for women, but it's important men keep calm and take time to de-stress too.
Keep fit
Moderate exercise two or three times a week is important for overall health and studies have indicated it can also help improve the shape and concentration of sperm.
We never recommend people go on crash diets and start an intensive exercise regimes when they are trying to conceive a child, but small changes to improve overall health and well-being are really important.
Exercises like running can also improve mental health, and help to de-stress the body.
Don't leave it too long
If you're having regular unprotected sex with your partner for 12 months and haven't conceived, get checked.
You may initially feel uncomfortable speaking to a doctor about these things but the earlier you talk to someone about it, the better.
Doctors can carry out a semen analysis and also check for chlamydia, which can affect fertility.