Laptops Pose Fertility Risk For Men

Men who frequently work with their notebooks on their laps are in danger of permanently lowering their fertility rate, researchers said Thursday.

Scientists at the State University of New York at Stony Brook have found that heat emitted from notebooks sitting on a man's lap can lower sperm count over time. As a result, the scientists are warning teenage boys and young men to consider limiting the time a notebook sits on their thighs.

The problem, according to the study published this month in the European medical journal Human Reproduction, is the scrotum's sensitivity to heat.

The research team, led by Dr. Yefim Sheynkin, found that a notebook sitting on a man's lap increases the left scrotal temperature by a median 2.6 degrees centigrade and the right by a median 2.8 degrees centigrade. The median refers to the middle of the lowest and highest measurements.

Studies have shown that increases in testicular and scrotal temperatures between 1 degree centigrade and 2.9 degrees centigrade can dramatically lower the body's ability to produce sperm, and, therefore, lower a man's ability to impregnate.

"The body needs to maintain a proper testicular temperature for normal sperm production and development," 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."

The ramifications of the study are significant, considering that by 2005, there is expected to be 60 million laptops in use in the United States, and 150 million worldwide, Sheynkin said. In addition, increasing power and portability, and lower prices have led to laptops outselling desktops and have added to their popularity among young people.

The researchers worked with 29 volunteers from 21 to 35 years old, measuring scrotal temperatures with and without laptops during two one-hour sessions on different days. The scientists found that scrotal temperatures rose by 2.1 degrees just by having the men sit with their thighs together. Adding a laptop increased the scrotal temperatures by the levels listed above.

The median surface temperature of Pentium 4 computers used in the study rose from nearly 31 degrees centigrade at the start of the experiment to nearly 40 degrees centigrade after an hour.

Researchers have found that sperm concentration can decrease by 40 percent for every 1 degree centigrade rise in scrotal temperature above a median daytime norm, Sheynkin said.

The SUNY researchers were unable to determine the exact frequency and time of heat exposure needed to produce irreversible changes in sperm production. Studies have shown that short-term heating produces reversible changes.

"Until further studies provide more information on this type of thermal exposure, teenage boys and young men may consider limiting their use of laptop computers on the laps, as long-term use may have a detrimental effect on their reproductive health," Sheynkin said.