Men who do physical jobs such as builders are more fertile, a new study suggests.
Scientists found that men who regularly lift heavy objects at work have higher sperm counts than desk-bound workers.
About four in ten cases of infertility can be traced to problems such as sperm count, semen quality and sexual function.
In particular, sperm count and semen quality are thought to be the major drivers of growing infertility rates among men.
First author Dr. Lidia Mínguez-Alarcón, a reproductive epidemiologist in Brigham’ and Women’s Hospital’s Channing Division of Network Medicine said: “What these new findings suggest is that physical activity during work may also be associated with significant improvement in men’s reproductive potential.
“We already know that exercise is associated with multiple health benefits in humans, including those observed on reproductive health, but few studies have looked at how occupational factors can contribute to these benefits.
“Further, there is increasing evidence that male infertility is associated with common chronic diseases such as cardiovascular disease and autoimmune disease, highlighting the broader importance of male reproductive health.”
A previous analysis led by the Environment and Reproductive Health (EARTH) study to which Mínguez-Alarcón is co-investigator found that among men seeking fertility treatment, sperm count and quality declined by as much as 42% between 2000 and 2017.
EARTH is a clinical study which aims to explore how exposure to environmental chemicals and lifestyle choices affect reproductive health.
They have collected samples and survey data from over 1,500 men and women, and the current study focused on a subset of these participants, including 377 male partners in couples seeking treatment at a fertility center.
The researchers found that men who reported often lifting or moving heavy objects at work had 46% higher sperm concentration and 44% higher total sperm count compared to those with less physical jobs.
Men who reported more physical activity at work also had higher levels of the male sex hormone testosterone and, surprisingly, the female hormone estrogen.
Mínguez-Alarcón added: “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.
“Reproductive health is important in its own right, but more and more evidence suggests that male infertility can give us insight into broader public health issues, including the most common chronic diseases,.
“Uncovering actionable steps people can take to improve their fertility stands to benefit all of us, not just couples trying to conceive.”
They hope the study, published in the journal Human Reproduction, will pave the way for revealing the underlying biological mechanisms at play and confirm if these findings hold true for men from the general population.
Produced in association with SWNS Talker.
