Speaking to the Telegraph, Dr Gunther said the study was the first to look at the impact of heat on fertility in tropical regions – where temperatures remain high all year round and fluctuations are milder than in seasonal climates like the UK.
“That we still found detrimental impacts during key exposure periods suggests that it might not take much fluctuation in temperature to damage sperm health,” he said. “This study demonstrates how environmental exposure such as high ambient temperature and heat stress can impact male fertility, and signals us to pursue the link further.”
The study is part of the National University of Singapore’s Project HeatSafe programme, which is exploring the consequences of extreme heat on different elements of society.
As well as looking at male sperm counts, the researchers tracked the birth records of more than 30,000 mothers, and found that avoiding extreme heat during the third trimester of a pregnancy was associated with a lower risk of premature births.
This comes after researchers at the Sri Ramachandra Institute of Higher Education and Research tracked 800 pregnant women in southern India, and found the risk of stillbirth and miscarriage can double if women are exposed to extreme heat.
But Prof Huang Zhong Wei, from National University of Singapore’s department of Obstetrics and Gynaecology, told the Telegraph that men are likely worse affected because men’s testes are in the scrotum – outside their bodies.
This is because spermatogenesis (the process of producing sperm), occurs at 1-2°C below core body temperatures – “thus, it is no surprise that this effect is more pronounced in men”.
However, surveys from the researchers in Singapore also suggested that pregnant women were more aware of the need to avoid extreme heat than young potential fathers, and urged these men to avoid high temperatures if they want to conceive.
They also called for more research to better understand the link between sperm and hot weather, and develop mitigation strategies.
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