By Amy Norton

NEW YORK (Reuters Health) - Heated seats are a luxury in some cars, but they may be a little too hot for men, a preliminary study suggests.

Researchers found that 90 minutes on a heated car seat created a significant increase in men's scrotal temperature. Because heat stress on the testicles has been shown to impair sperm quality, the findings raise the possibility that over time, heated car seats could affect a man's fertility.

However, the study looked only at short-term changes in scrotal temperature, and not the effects on sperm, stressed lead researcher Dr. Andreas Jung, of Justus Liebig University Giessen in Germany.

"It is too early to (make) any conclusions concerning the influence of heating car seats on semen quality," Jung told Reuters Health.

Normal sperm production is temperature-dependent and requires a testicular temperature that is slightly below the body's core temperature, the researchers explain in the journal Fertility and Sterility.

In tests of 30 male volunteers, Jung's team found that, on average, 90 minutes on a heated car seat raised the men's scrotal temperature enough to nearly match their core body temperature.

Sitting for prolonged periods, on its own, raises a man's scrotal temperature, and the effect of a heated car seat is actually weaker by comparison, according to the researchers. However, they add, even a small additional effect on scrotal temperature might be enough to affect a man's sperm quality.

According to Jung, studies should now directly examine sperm quality to see if there is, in fact, a risk from heated car seats.

SOURCE: Fertility and Sterility, August 2008.

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