Prolonged stress can hurt sperm quality, according to a study by researchers at Ben-Gurion University of the Negev and Soroka University Medical Center in Be’er Sheva.

The study, presented at the International Summit on Assisted Reproduction and Genetics in Israel in late May, indicated that 37 percent of the sperm samples taken during a stressful period had low sperm motility, making fertilization less likely.

“Mental stress is known to have an adverse effect on fertility, but there is little research on the impact of stress on sperm quality,” said Eliahu Levitas, a member of the Ben-Gurion University Faculty of Health Sciences and the director of the in-vitro fertilization unit at Soroka. “This study shows that prolonged stress can have an effect on sperm quality.”

The findings have implications for birthrates during times of conflict.

The study involved 10,536 samples donated during stress-free periods from 2009 to 2017 and 659 samples taken during and up to two months after military conflicts between Israel and Gaza in 2012 and 2014. The average age of the men was 32, and 44 percent were smokers.

“Our reasoning was that even men who heard incoming rocket warning sirens during a conflict experienced stress throughout the day over a longer period,” said Levitas, who directs the Soroka Sperm Bank.

In general, the probability of weak motility in sperm samples taken during periods of prolonged stress was 47 percent higher. Weak motility makes it less likely that the sperm will fertilize an egg.

Levitas said, “We were surprised to discover that there is a connection between the security situation and the sperm counts.”