In a new study, older men and those with higher work stress had more fragmentation of the DNA in their sperm, which might affect their ability to conceive as well as the genes they pass on to their children. (De Agostini/Getty Images)

Certain lifestyle factors are linked to higher rates of damage in the genetic material in men’s sperm. This could affect men’s ability to conceive as well as the genes they pass on to their children.

According to researchers, the damage may stem from factors such as obesity, stress and even cellphone use.

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 such procedures as in vitro fertilization, the scientists 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 said by email.

The study looked at 286 men younger than 45 who were attending an infertility clinic. Most of the men were overweight nonsmokers, and most had moderate levels of work stress and life stress. Half had been using a cellphone for six 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 cellphone 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, such as 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 said 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 cellphone 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.