Workplace exertion among factors linked to male infertility

It’s the perfect storm for male fertility problems: working in a physically demanding job, taking multiple medications, and having high blood pressure. That’s according to a recent study examining relationships among workplace exertion, certain health factors, and semen quality.

An expert in men’s health gave the research high marks for its population-based design, but urged caution in interpreting its results.

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For the study, which was published online in Fertility and Sterility (March 9, 2015), researchers from the National Institutes of Health, Bethesda, MD, and Stanford University, Palo Alto, CA followed 501 couples who stopped using contraception and were trying to conceive for a year. Of those, 473 men provided one semen sample; 80% provided a second sample. The final study group included 456 men, with an average age of 31.8 years. More than three-quarters of participants were Caucasian, more than 90% were college educated, and more than half had never fathered a pregnancy.

Thirteen percent of men who reported heavy work-related activity had lower sperm counts, compared to 6% of the men who reported no workplace exertion.

While heavy exertion at work seemed to impact semen quality, other work-related exposures, such as shift work, night work, vibration, heat, noise, or prolonged sitting, did not appear to have an effect.

Among men who said they had received a diagnosis of high blood pressure, diabetes, or high cholesterol, only those with hypertension had a lower percentage of normally shaped sperm, compared to men who reported no high blood pressure.

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"As men are having children later in life, the importance of diseases we once thought as separate from fertility must be re-explored. Future investigations need to examine whether it's the high blood pressure itself or the treatment that is driving these trends," principal investigator Michael L. Eisenberg, MD, of Stanford University, said in a press release from the NIH.

The authors also observed that while 7% of the men who did not take medications had sperm counts below 39 million, 15% of those who reported taking two or more medications had low counts.

NEXT: Dr. Hotaling discusses study's strengths, weaknesses

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James M. Hotaling, MD, MS, of the University of Utah Health Care, Salt Lake City, wrote in an email to Urology Times that this study has notable strengths and weaknesses.

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“The main strengths of this study are its population-based design and rigorous semen analysis metrics as well as in-depth examination of exposures. Perhaps the most novel component of the study is that it examined a cohort of patients from the population, not men from an infertility clinic,” said Dr. Hotaling, who was not involved with the study.

“However, its conclusions that increased occupational exertion, hypertension, and increased medication use were associated with poorer semen quality need to be interpreted with caution. Although these results are statistically significant, they are unlikely to be clinically significant. Further, lack of information on motility, and inability to ascertain the total motile count, is a major limitation of the study. Nonetheless, this is an important and relevant examination of the determinants of sperm parameters in a population-based cohort, that, sadly, is very hard to find in the male infertility literature.”

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