Laptops should be used as desktops if men want to protect their reproductive health, according to a new study published Thursday.
A combination of the heat generated by a laptop and the position of the thighs that is needed to balance the computer leads to higher temperatures around a man's genitals and over time can result in decreased sperm production, according to the study "Increase in scrotal temperature in laptop computer users," published in the U.K. journal Human Reproduction.
Though further research is needed, teenage boys and young men should limit the use of computers on their laps, said Dr. Yefim Sheynkin, the leader of the State University of New York at Stonybrook research team responsible for the article. "It's possible that external protective devices could help," Sheynkin added.
There will be 60 million laptops in the U.S. and 150 million worldwide by next year, Sheynkin said. Laptops have become more popular with teenage boys and young men due to continued improvements in power, size and price, and are currently outselling desktop computers, he added.
Twenty-nine volunteers between the ages of 21 and 35 took part in the study. Researchers measured their scrotal temperature, with and without laptops, during two one-hour sessions performed on different days, in a room where the temperature was about 22 C (degrees Celsius) or 71.6 F (degrees Fahrenheit).
When the men held their thighs together in order to balance a laptop that was turned off, their scrotal temperatures rose by 2.1 C. But when the laptop was in use, temperatures rose by 2.6 C on the left of the scrotum and 2.8 C on the right. The laptops were turned on and allowed to run for 15 minutes before being placed on the subjects' laps.
"The body needs to maintain a proper testicular temperature for normal sperm production and development," Dr. Sheynkin said. "Portable computers in a laptop position produce scrotal hyperthermia by both the direct heating effect of the computer and the sitting position necessary to balance the computer." Scrotal hyperthermia leads to decreased fertility, known as clinical subfertility, in men.
The study found that scrotal temperature in the men had risen by 1 C in 15 minutes of computer use. After one hour of use, the surface temperature of the laptops rose from around 31 C to nearly 40 C.
Sheynkin said it was unclear just how much additional heat could cause scrotal hyperthermia, but past studies suggest that a scrotal temperature increase of more than 1 C above baseline temperatures could have negative effects.
Sheynkin warned that years of heavy laptop use "may cause irreversible or partially reversible changes in male reproductive function."