Health

Brigham & Women’s study: Men who lift heavy stuff have more sperm, apparently

Men who regularly lifted or moved heavy objects at work had 44 percent higher sperm counts than those who did not, researchers found.

David L Ryan/Globe Staff

February 24, 2023

2 minutes to read

Those men installing microwave ovens and moving refrigerators and color TVs that Dire Straits sang about may not have gotten their “money for nothing” like those guys who play the guitar on the MTV.

But, apparently they may have gotten more than their paychecks because of their strenuous work, a new study from researchers at Brigham & Women’s Hospital suggests.

Research recently published through a collaboration between the Harvard T.H. Chan School of Public Health and Mass. General Brigham found that men who regularly lift and move heavy objects at work have higher sperm counts than those who do not.

The study included 377 men who were male partners in couples seeking infertility treatment and who enrolled in the Environment and Reproductive Health study between 2005 and 2019, according to the research published in Human Reproduction earlier this month.

“Men who reported often lifting or moving heavy objects at work had 46% higher sperm concentrations and 44% higher total counts compared with men who reported never lifting or moving heavy objects at work,” the researchers wrote. “Similar results were found for men working in rotating shifts compared to those in day shifts, as well as for men involved in heavy levels of physical exertion compared to those with light levels at work.”

Additionally, men who performed “heavy/moderate levels of physical exertion” in the workplace had higher levels of testosterone and even higher concentrations of estrogen, according to the study.

“Contrary to what some people remember from biology class, ‘male’ and ‘female’ hormones are found in both sexes, but in different amounts. In this case, we hypothesize that excess testosterone is being converted into estrogen, which is a known way for the body to keep normal levels of both hormones,” first author Lidia Mínguez-Alarcón, a reproductive epidemiologist in Brigham’s Channing Division of Network Medicine and co-investigator of the EARTH study, said in a news release.

According to the study, the men involved in the research had a median age of 36 and were predominantly white, with 87% of them considered caucasian. Among them, 12% reported often lifting or moving heavy objects while working. Six percent reported completing heavy physical exertion at work and 9% also reported evening or rotating shifts.

“Due to our study design which recruited men from couples seeking fertility treatment, it may not be possible to generalize our findings to men from the general population,” researchers cautioned. “Also, as is the case of all studies based on self-reported questionnaires, measurement error and misclassification of the exposure are potential concerns.”

According to the study, research has long shown that semen quality has declined in the past few decades and “has been negatively correlated with higher risks of common chronic diseases and mortality, highlighting its public health importance beyond fertility and reproduction.”

“Uncovering actionable steps people can take to improve their fertility stands to benefit all of us, not just couples trying to conceive,” Mínguez-Alarcón said.