Men who put laptops on top of their laps heat up their testicles - even when wearing clothes. This is bad for sperm quality, which in turn could affect fertility.

These are the findings of a State University of New York study of 29 men who agreed to have the temperature of their scrotum measured while using a laptop on their laps. To balance laptops, participants typically kept their legs closed.

Within 10-15 minutes, scrotal temperature had increased by up to 2.5 C, even for people who used a lap-pad. Participants in the study did not feel their balls getting hotter.

But such a temperature rise is "unsafe", according to urologist Yelim Sheynkin, who led the study. Other studies suggest that a 1 C rise in scrotal temperature could harm sperm production

Heavy laptop on lap users don't give their scrotums enough time to cool down, according to Sheynkin.

This is all very well - actually it isn't. We would like to know if the temperature rise causes irreversible harm to male fertility.

SUNY possibly has had time to try and figure this out: the researchers ran a very similar laptop / scrotal temperature study which came to the same conclusions in 2004. We wrote about it then: Laptops go on sperm killing rampage. The 2004 SUNY findings were published in journal Human Reproduction.

Findings of SUNY's more recent study are published in the November 2010 issue of "Fertility and Sterility".