There may be one more reason to put away the cellphone.
New research suggests daily cellphone use could have a negative impact on male fertility.
The findings, published in the International Journal of Andrology, add to growing evidence that suggests a link between cellphone use and lower quality sperm.
In the study, researchers from Canada and Austria examined the sperm of more than 2,000 men collected from 1993 to 2007 at an Austrian infertility clinic.
At the time of collection, men were also asked whether they had cellphones. Men who talked on them every day were classified as cellphone users.
After examining the data, the researchers found that the cellphone users had lower quality sperm than men who didn't use cellphones. The variation in sperm quality wasn't drastic, but there was enough of a difference to conclude there is a link between cellphones and lower quality sperm, said Rany Shamloul, a sexual-medicine researcher at Queen's University in Kingston and one of the study's authors.
The message of the study is that "cellphones may have a potential to negatively affect the fertility of men," he said.
Men who reported using cellphones had higher levels of circulating testosterone but lower levels of luteinizing hormone, which is secreted by the pituitary and a key reproductive hormone.
Although it's not entirely clear, researchers believe that the electromagnetic waves coming from cellphones increase the number of testosterone-producing cells. But at the same time, those waves may also lower the levels of luteinizing hormone, which may interfere with sperm production and fertility.
However, it is too early and there is not enough evidence to advise men to avoid using the technology, according to Keith Jarvi, director Murray Koffler Urologic Wellness Centre and head of urology at Mount Sinai Hospital in Toronto, who was not involved in the study.
"There is no evidence we can tell guys that cellphones are causing infertility," Dr. Jarvi said. "I don't even know if you can tell guys to move cellphones away from their nether regions." One important point to keep in mind, he said, is that there is no proof cellphone use is what caused the men in the study to have lower-quality sperm.
It's possible that men who use cellphones and those who don't possess different characteristics or socioeconomic factors that could have accounted for the difference. Dr. Jarvi also pointed out that differences in how sperm quality was measured throughout the length of the study could have had an impact on the results.
Despite the study's limitations, Dr. Jarvi said there is growing evidence that suggests a definitive link between increased cellphone usage and poorer sperm quality.
The problem is that researchers have more questions than answers about that relationship and its potential implications.
"The jury is still out," said Ashok Agarwal, director of the Center for Reproductive Medicine at the Cleveland Clinic and professor at the Lerner College of Medicine at Case Western Reserve University.
One of the chief difficulties in understanding that link, Dr. Agarwal said, is that there haven't been any comprehensive, rigorous scientific studies.
It's possible that might soon change, however. Dr. Jarvi said there has been an explosion in interest on the subject of male fertility and cellphones, which could lead to more research and a clearer understanding of what the risks may be.
"It's a huge unknown right now," he said. "But there's something there."