"Heated seats may be frying your sperm", reports New Scientist (issue 2671), citing the rather less exciting "Influence of heated car seats on scrotal temperatures", from Fertility and Sterility (vol 90 issue 2).

Just to show how much fun some scientists have, Andreas Jung et al, from the Center of Dermatology and Andrology, Giessen University, Germany, attached temperature sensors to the testicles of 30 healthy men and recorded the temperature changes as they sat for a maximum of 90 minutes on heated car seats. Just to make sure the raised temperatures were not due to the act of sitting, each volunteer did two sessions to compare the heated and unheated seat scenarios.

To nobody's surprise the heated seats caused a small but significant rise in scrotal temperature compared to the unheated seats. Also, that the maximum temperature is reached after just 30 minutes.

Now, the optimum temperature for sperm production is 1-2 degrees below normal body temperature of about 37 C. New Scientist also states that a previous study suggests that couples take longer to conceive if the man drives for more than 3 hours a day. We shall put to one side the opportunities to conceive whilst driving, but a lot of other questions spring to mind. Does anybody really drive with the car seat heater on all the time? If it takes 30 minutes to reach maximum temperature would it not take about the same time to cool back down to normal? Could those cotton/wool mix trousers be the real source of heat, or the ubiquitous faux leatherette seating?

Anyway, the one burning question,"Do heated seats fry your sperm?", was not answered because the experimenters did not perform any tests on the sperm itself. So what was the point? I guess we'll have to wait for the next research grant to find out. In the meantime, the advice is to keep cool if you want to be hot.