Manual workers more fertile than those who labour at desk

MEN who do physical jobs, such as building workers, are more fertile than office workers, a study found.

Researchers said that those who regularly lift heavy objects have higher sperm counts than those who are sedentary at a desk for most of the day.

About four in 10 cases of infertility can be traced to problems such as sperm count, semen quality and sexual function among men. In particular, sperm count and semen quality are thought to be the major drivers.

Dr Lidia Mínguez-alarcón, a reproductive epidemiologist in the Channing division of network medicine at Boston’s Brigham and Women’s Hospital, said: “These findings suggest that physical activity during work may also be associated with significant improvement in men’s reproductive potential.

“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.”

Analysis led by the Environment and Reproductive Health (Earth) study found that among men seeking fertility treatment, sperm count and quality declined by as much as 42 per cent between 2000 and 2017. Earth is a clinical study which aims to explore how exposure to environmental chemicals and lifestyle choices affect reproductive health.

The project has collected samples and survey data from more than 1,500 men and women and the current study focused on a sub-set of these participants, including 377 male partners living in couples who are seeking treatment at a fertility centre.

The researchers found that men who said they regularly lifted or moved heavy objects at work had 46 per cent higher sperm concentration and 44 per cent higher total sperm count than those with less physical jobs.

Men who reported more physical activity at work also had higher levels of the male sex hormone, testosterone, and the female hormone oestrogen.

Dr 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 hypothesise that excess testosterone is being converted into oestrogen, which is a known way for the body to keep normal levels of both hormones. More evidence suggests that male infertility can give us insight into broader public health issues, including chronic diseases.”