Extreme hot weather can affect sperm count, concentration of Singapore men: Study

SINGAPORE: Exposure to blistering heat can affect men’s fertility, a wide-ranging study by the National University of Singapore (NUS) has found.

From analysing the sperm samples of 818 men, a majority of whom had issues with conceiving, a team from NUS Medicine found that there was a higher risk of low sperm concentration and low sperm count in men who were exposed to such heat in the months before sperm collection.

“We found that the quality and the quantity of the sperm that was produced was linked to whether the men were exposed to extreme heat conditions in the last 75 days, because that is the time it takes for sperm to be produced and to be in the ejaculate,” said Associate Professor Chan Shiao-Yng from the Department of Obstetrics and Gynaecology at NUS Yong Loo Lin School of Medicine, one of the study’s principal investigators. 

“We found that if the average temperature over the previous 75 days was over 29.8 degrees Celsius, then it significantly reduced the sperm count in the men.”

Exposure between one and three months before sample collection was associated with a 46 per cent increased risk of low sperm count and a 40 per cent increased risk of low sperm concentration, NUS said in a press release on Monday (Mar 18). 

Assoc Prof Chan noted that it is well-documented that increased heat reduces sperm production, survival, quality and motility.

“What wasn't clear before was … in a tropical country where the temperature is fairly even, whether small changes in ambient temperature can also have an impact on sperm quantity and quality,” she said.

She urged men trying to conceive with their partners to wear loose underwear, avoid saunas and hot baths, and keep the temperature low.

Singapore’s resident total fertility rate dropped to a historic low of 0.97 last year, below the 1.0 mark for the first time.

The research was part of Project HeatSafe, the first large-scale study in Singapore and the region aimed at investigating the impact of rising heat levels.

It also looked at the productivity and well-being of workers in tropical climates such as Singapore, on an individual level, as well as the impact of heat stress on a macroeconomic and national level.

IMPACT ON HEALTH, WELL-BEING AND PRODUCTIVITY

The study found differences in perception between employees and their employers on how heat affects workers’ health, well-being and productivity

From surveys with 355 workers and 214 employers in Singapore, researchers found that the higher the physical and mental exertion faced in the job role, the higher the productivity and economic losses. 

The economic loss significantly increased in conditions such as working under the sun or semi-outdoor spaces, or being exposed to additional sources of heat like machinery.

It is estimated that for every hot day, the reduced workers’ productivity during working hours translates into a median income loss of S$21 (US$15.7) per worker, which amounts to about a quarter of the daily median salary of the surveyed workers.

However, around 70 per cent of employers surveyed did not feel that these productivity losses of the workers from heat represented a problem for their companies.

Employers’ low level of awareness on the impact of heat means that they do not put in place measures to help their workers, said Dr Natalia Borzino, postdoctoral researcher from research hub Singapore-ETH Centre.

Dr Borzino, who led the study, added that workers and employers need to be educated on the impacts, and that there needs to be better communication at the workplace.

From the survey results, the team found that 88 per cent of the workers had experienced mild to moderate heat stress symptoms, while 37 per cent of the workers had experienced severe heat stress symptoms.

“We found that workers tend to push themselves to the limits, even though they are feeling heat stress symptoms in order to finish the work and not disappoint supervisors and employers. And this could be prevented if they feel free or more comfortable to communicate freely to the supervisors: ‘I need to stop, so I need a break’,” she told CNA’s Singapore Tonight. 

IMPACT OF HEAT ON CONSTRUCTION SECTOR 

Another study under Project HeatSafe surveyed construction workers. Six in 10 of them said they felt fatigued due to heat stress.

Nearly two in five also complained of headaches brought on by prolonged heat exposure.

Workplace safety and health officer Periyasamy Saravanan said heat stress symptoms manifest in several ways, including physical symptoms like rashes and breathing problems and mental symptoms like confusion. These can lead to accidents happening on the job.

“For drivers, or operators, also workers working under the hot sun, the roles require higher mental faculties and decision-making abilities on the construction site, and (they) have susceptibility to impairment by heat stress,” he told CNA.

Companies have stepped up efforts to educate workers on heat stress, and ensure they have what they need to cool down like using mist fans and taking more water breaks.

"The management has been closely monitoring, to see if there is anything we can improve along the way. But, all workers are instructed in the sense that if they feel unwell, or they feel that the heat is something that is not bearable for them, all workers are allowed to rest, at any time,” said executive director of construction firm OKP Holdings Daniel Or.

More hot days are expected as Singapore nears the end of the century - even if the world takes a path of sustainable growth.