Based on the data, researchers further found that lifestyle factors like use of recreational drugs, smoking, drinking and body weight had little effect. For instance, the proportion of men with low swimming sperm counts was similar whether they smoked over 20 cigarettes a day or if they had never smoked before. Alcohol use was also unrelated to fertility among men.
"The message of 'No smoking, drinking in moderation, no street drugs and not be too overweight' is clearly sound and should be offered to men as good health advice," says study author Dr. Andrew Povey of University of Manchester's School of Community Based Medicine. "However, the evidence from this study is that even if the man changes his lifestyle in such a fashion, such changes are unlikely to improve his chances of conceiving a child."
The findings came as a surprise to the researchers. "I expected to find a link with smoking, as studies have often reported that smoking is bad for semen quality," says Povey. "When I looked again at the evidence for such statements, I found that it wasn't necessarily that strong and that if there was an effect of smoking, it was more likely to occur within the normal range of semen quality and not then directly affect whether a man was likely to be infertile or not."
Image: Man drinking alcohol, via Shutterstock