Certain lifestyle factors are linked to higher rates of damage in the genetic material in men's sperm, a study suggests.

The damage - which may stem from factors like obesity, stress and even cell phone use - could affect men's ability to conceive as well as the genes passed to their children, researchers say.

Semen analysis usually looks at the numbers and the condition of whole sperm. But the authors of a small study in Poland believe the degree of breakage, or fragmentation, in DNA strands in the sperm might be a better indicator of fertility. DNA carries the cell's genetic information and hereditary characteristics.

Men with fragmentation have lower odds of conceiving naturally and through procedures like in vitro fertilization, they write in the International Journal of Impotence Research.

Researchers have noticed before that lifestyle factors can influence the level of sperm DNA fragmentation, said Ricardo P. Bertolla of Sao Paulo Federal University in Brazil, who was not part of the new study.

"More importantly, we do expect that environmental and lifestyle factors may influence male fertility, but the degree of response is highly variable among individuals," Bertolla told Reuters Health by email.

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Dr. Marian Radwan of Gameta Hospital in Rzgow, Poland, focused their study on 286 men under age 45 who were attending an infertility clinic.

Radwan did not respond to a request for comment.

Most of the men were overweight, nonsmokers, and with moderate levels of work stress and life stress. Half had been using a cell phone for 6 to 10 years.

The men all had normal semen concentrations, but older men and those with higher work stress had more fragmentation of the DNA in their sperm.

Men who were obese or had used a cell phone for more than 10 years also tended to have a higher percentage of immature sperm than others.

Coffee or alcohol use, smoking and physical activity levels were not linked to DNA fragmentation, the researchers report.

There is some evidence that DNA damage, beyond affecting a man's fertility, may be passed along to offspring, raising their risk of gene mutations linked to various illnesses, the study team notes.

Even men with otherwise normal sperm parameters, like ejaculate volume and sperm concentration, may have increased levels of free radicals and DNA damage in their sperm, said Rima Dada of the All India Institute of Medical Sciences in New Delhi, who was not part of the new study.

Up to 40 percent of reproductive-age men have some issue with sperm production, Dada told Reuters Health by email.

But they wouldn't know it, because standard semen analysis does not involve testing for DNA damage in sperm, she added.

"The important thing is that majority of factors which cause oxidative stress which result in DNA damage are due to our poor social habits and unhealthy lifestyle, and simple lifestyle interventions and quitting smoking and doing yoga and meditation can reduce both psychological stress and oxidative stress and oxidative DNA damage," she said.

Bertolla, however, is "currently not convinced" that cell phone use damages sperm. "I do not see any definitive proof that this is true," he said.

The new study does not prove that any lifestyle factors cause DNA damage in sperm, only that they are associated with each other, he noted.

"There are some companies that produce antioxidants specifically designed to improve male fertility, but it is my opinion that antioxidants are useful only for those men that need it," he said. "I know this sounds very simple and obvious, but there are many men that end up taking antioxidants without a real need for them (or who will not benefit from them), and this ends up giving a general notion that antioxidant supplementation will not work."