Tests conducted with male volunteers found that holding a computer on the lap raises the temperature of the testicles and could affect sperm quality, says a study in the journal Fertility and Sterility.
Researchers measured scrotal temperatures of 29 subjects in three separate 60-minute sessions in which they varied their sitting positions–keeping legs close together or spread apart, and alternately using or not using a lap pad beneath the computer.
“Within 10 to 15 minutes their scrotal temperature is already above what we consider safe, but they don’t feel it,” Dr. Yefim Sheynkin, a urologist at the State University of New York at Stony Brook and leader of the study, told Reuters.
A lap pad made little difference in reducing scrotal temperature. Only when subjects sat with legs open at about a 70-degree angle was there a change in the heating effect. Even in those cases, the effect was only delayed and it took about 30 minutes to reach an elevated temperature.
There have been no studies on how laptops may affect male fertility, but earlier research has shown that warming the scrotum more than one degree Celsius (1.8 degrees Fahrenheit) is enough to damage sperm.
Dr. Sheynkin suggested that the effects may not be permanent, but could take months to go away.


