In a study led by researchers from The Cleveland Clinic, men who used their cell phones the most had poorer sperm quality than those who used them the least.
The lowest average sperm counts seemed to be in men who had the most cell phone use (more than four hours a day); those who didn't use cell phones seemed to have the highest. Although the sperm count appears to go down with increasing cell phone use, the difference in numbers wasn't significant.
The findings do not prove a link between cell phone use and semen quality, researcher Ashok Agarwal, Ph.D., tells WebMD.
Agarwal presented the study in a poster session at the 62nd annual meeting of the American Society for Reproductive Medicine in New Orleans.
"This is still very preliminary and I would not want these findings misinterpreted as showing that cell phone use is a definite cause of decreased [male] fertility," he says. "There are still many unanswered questions."
About a billion people worldwide now use cell phones, and some projections suggest that within the next five years that number could double.
A link between cell phone use and reduced sperm counts has been suggested in several earlier studies, but none has been considered conclusive.
Sperm Quality and Cell Phones
The new study included 364 men being evaluated for infertility between September 2004 and October 2005.
In addition to undergoing tests to determine sperm quantity and quality, the men answered questions about their cell phone habits.
Most of the men had sperm counts that were well above the 20 million sperm per milliliter level that is considered the lower limit of normal. But the more the men in the study used their phones, the lower their sperm count tended to be.
The average sperm count among men who said they did not use cell phones was 86 million per milliliter, compared with 76 million/mL for men who used cell phones less than two hours a day and 71 million/mL for men who used cell phones two to four hours a day.
Men who reported using their cell phones more than four hours a day had the lowest average sperm counts — 66 million/mL.
Significant downward trends were seen when other sperm-quality parameters were measured, such as percentages of sperm swimming well, alive sperm, and normal sperm shape.
Laptops and Diapers
Cell phones are not the only modern conveniences suspected of influencing sperm counts. At least one study has suggested that wearing disposable diapers as a baby can influence adult fertility, and another proposed a link between laptop use and sperm quality.
But none of these suspected environmental influences has been proven to influence male fertility, says Rebecca Sokol, M.D., Ph.D., president of the Society for Male Reproduction and Urology.
Her own research suggests a link between air pollution and declining sperm quality.
Sokol calls the cell phone study "provocative" but far from conclusive.
"This is an interesting observation that may lead to larger, more controlled studies to see if the observation holds up," she tells WebMD.
But she acknowledges that such studies may be difficult to do.
An infertility specialist at the University of Southern California's Keck School of Medicine, Sokol says there isn't a lot she can tell patients when they ask about suspected environmental influences on male fertility.
"I tell them what we know, which isn't a lot," she says. "We know that high (scrotal) temperature is bad for sperm, and we think that smoking, drinking, and marijuana use are probably bad. But we still have a lot to learn."
SOURCES: 62nd annual meeting of the American Society for Reproductive Medicine New Orleans, Oct. 21-25, 2006. Ashok Agarwal, Ph.D., director, Clinical Andrology Laboratory and Reproductive Tissue Bank; director of research, Reproductive Research Center, The Cleveland Clinic. Rebecca Sokol, M.D., Ph.D., president, Society for Male Reproduction and Urology; professor of medicine and obstetrics and gynecology, Keck School of Medicine, University of Southern California.
By Salynn Boyles
Reviewed by Louise Chang, M.D