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How Heat May Affect Male Infertility

According to the World Health Organization, if a man's sperm count is less than 20 million per milliliter, he is considered at risk of being infertile. Low sperm count, otherwise known as oligospermia, is one of the most common causes of male infertility. There are several factors that can lead to a low sperm count, but one of the most preventable is exposure to excessive heat.

Researchers have found that the reason why a man's testicles rest outside the body in the scrotum rather than in the abdomen like the ovaries is because the ideal temperature for sperm production is three to four degrees below normal body temperature. Any warmer will affect sperm count, slashing it by about 40 percent per one-degree rise. Temporary overheating of the testicles can result from exposure to things such as saunas, hot tubs, heating blankets, even waterbeds.

Research has shown that men who sleep in waterbeds are up to four times more likely to suffer fertility problems than those who prefer a traditional mattress. Frequent bike riding and wearing tight clothing can temporarily trap heat as well, although tight underwear has not been shown scientifically to cause any increase in testicular heat. Nevertheless, a change to looser clothing couldn't hurt when fertility is a concern.

Other factors that can cause overheating and decreased sperm production inside the testicles include climate and work environment. One study found that "semen specimens obtained in New Orleans during the summer had significantly lower sperm concentration, total sperm per ejaculate, percent motile sperm and motile sperm concentration than samples provided at other times of year," suggesting that men may be more fertile in cooler climates and during cooler months of the year. Sperm counts are about 30 percent lower in summer and, while heat may play a role, the seasonal rise and fall may be a legacy of our ancestors who bred seasonally.

In addition, exposure to heat over an extended period of time, such as in occupations which involve long hours of sitting, may result in permanently impaired fertility. One experiment showed that scrotal temperature rises by up to 2.2 degrees within two hours of driving a vehicle, putting truckers and taxi drivers at risk for a low sperm count. As for those who work with computers, another recent study warned young men to limit the time they use laptops on their laps after tests showed the heat from the battery might impair sperm production.

According to Dr. Yefim R. Sheynkin, director of male infertility and microsurgery at the State University of New York, Stony Brook, men who balance their laptops on their laps risk infertility problems because of the combination of pressing their legs together, which constricts the scrotum, and the heat from the laptop, which raises its temperature. The study found that after sitting with a computer in their laps for 15 minutes, men's scrotal temperatures had risen 1.8 degrees, and 2.8 degrees after an hour. It is not known whether the effects of the exposure would cause permanent damage, but the study recommended that men keep laptops off their laps to avoid the potential for "irreversible changes."

As far as damage from other factors, such as saunas, hot tubs and heating blankets, it is believed that sperm generally recover quickly from heat exposure, so a man's sperm count should return to normal within about a week. However, at least one study has shown that the production of sperm is a process requiring approximately three months, which suggests that even when a factor that may be harmful to production is taken away, a normal sperm count may not occur again for at least three months.

Whatever the case, when considering future fertility, it is important for men to consider the impact of prolonged exposure to heat. The best way for a man to protect his fertility is to avoid high-heat situations whenever possible.



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Cord Blood Registry
March of Dimes
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