Smoking may affect fertility in both men and women, new study finds

Smoking may affect fertility in both men and women by changing biological processes involved in reproduction, a new study has found.

Scientists at the Universities of Nottingham and Sheffield found a series of gene changes in male and female mice exposed to cigarette smoke that could help explain how the ovaries and testes are impacted.

According to the World Health Organisation, approximately one in six people globally experience infertility at some point in their lives. While links between smoking and poor fertility are well-established, how it affects the ovaries and testes is not well understood.

Published in the journal Frontiers, the study examined the structure of the ovaries and testes and gene activity in mice who were exposed to cigarette smoke extract at a lower or higher dose for 12 weeks.

They found that in female mice, the number and structure of ovarian follicles – where eggs develop – showed little change following even high exposure to cigarette smoke.

However, they identified gene changes similar to those that take place during biological processes associated with ovarian aging and reduced ovarian function.

In males, higher levels of smoke exposure were associated with changes to structures within the testes, including enlargement of the seminiferous tubules, where sperm develop. Researchers also identified changes in the activity of genes involved in sperm production, immune responses and cell signalling.

Some genes involved in sperm production became more active, while others involved in immune function became less active. Researchers said the findings suggest that cigarette-smoke exposure may “alter biological processes important for normal testicular function and sperm development”.

Professor Lucy Fairclough, from the University of Nottingham and co-author of the study, said the research had “identified potential biological mechanisms that could help explain the link between smoking and reproductive health in both men and women”.

“In females, we identified changes in gene activity associated with biological processes that have previously been linked to ovarian ageing and reduced ovarian function,” she explained. “In males, we found changes in genes involved in sperm production and testicular function.

“These findings are important because they help us understand how exposure to cigarette smoke could affect reproductive health. Further research will be needed to establish how these biological changes relate to fertility in humans.”

Previous research has linked smoking to a slew of fertility problems, including abnormal sperm shape, poor motility, lower sperm counts, and DNA damage. Scientists have also linked mothers’ smoking during pregnancy to infertility in their children later in life.