A combination of the heat generated by a laptop and the position of the=
thighs that 's needed to balance the computer leads to higher temperatures=
around a man's genitals and over time can result in decreased sperm produc=
tion,=20
according to the study "Increase in Scrotal Temperature in Laptop Computer=
Users," which was published in the U.K. journal Human Reproduction.=

Though further research is needed, teenage boys and young men should li=
mit=20
the use of computers on their laps, said Dr. Yefim Sheynkin, the leader of =
the=20
State University of New York at Stonybrook research team responsible for th=
e=20
article. "It's possible that external protective devices could help," he sa=
id.=20

There will be 60 million laptops in the U.S. and 150 million worldwide b=
y=20
next year, Sheynkin said. Laptops have become more popular with teenage boy=
s and=20
young men due to continued improvements in power, size and price, and they'=
re=20
currently outselling desktop computers, he said.=20

Twenty-nine volunteers between the ages of 21 and 35 took part in the st=
udy.=20
Researchers measured their scrotal temperature, with and without laptops, d=
uring=20
two one-hour sessions performed on different days, in a room where the=20
temperature was about 71.6 degrees Fahrenheit.=20

When the men held their thighs together in order to balance a laptop tha=
t was=20
turned off, their scrotal temperatures rose by 3 degrees Fahrenheit. But wh=
en=20
the laptop was in use, temperatures rose by 4 degrees on the left of the sc=
rotum=20
and 5 degrees on the right. The laptops were turned on and allowed to run f=
or 15=20
minutes before being placed on the subjects' laps.=20

"The body needs to maintain a proper testicular temperature for normal s=
perm=20
production and development," Sheynkin said. "Portable computers in a laptop=
position produce scrotal hyperthermia by both the direct heating effect of=
the=20
computer and the sitting position necessary to balance the computer." Scrot=
al=20
hyperthermia leads to decreased fertility, known as clinical subfertility, =
in=20
men.=20

The study found that scrotal temperature in the men had risen by just ov=
er 1=20
degree Fahrenheit in 15 minutes of computer use. After one hour of use, the=
surface temperature of the laptops rose from around 88 degrees to nearly 1=
04=20
degrees.=20

Sheynkin said it was unclear just how much additional heat could cause=
scrotal hyperthermia, but past studies suggest that a small scrotal temper=
ature=20
increase above baseline temperatures could have negative effects.=20

Sheynkin warned that years of frequent laptop use "may cause irreversibl=
e or=20
partially reversible changes in male reproductive function."