In a new study in the Journal of Sleep Research, men who slept fewer than six hours or more than nine were more likely to have an elevated high DNA stainability (HDS), an index that reflects sperm quality.

“Higher HDS indicates immaturity of the sperm production process (spermatogenesis), which means they may not perform well to reach the egg and achieve pregnancy,” explains study author Jia Cao, Ph.D., director of the toxicology institute at Third Military Medical University in China. It’s possible poor sleep behavior negatively interferes with your circadian clock (which controls spermatogenesis) and oxidative stress levels (how well your body can fight free radicals). “Although these results are interesting, and perhaps a springboard to stimulate further research, we don’t know if there is a causal relationship between sleep duration and sperm DNA integrity, and more importantly, if this translates to infertility,” adds Joseph Clark, M.D., program director of Penn State Hershey Medical Center’s urology residency program canadianviagras.net.

Aiming to get between seven and seven and a half hours of sleep per night if you’re a guy trying to conceive is probably not going to hurt your odds, Clark says. Also important is keeping stress levels in check, another key factor in male fertility. If you still can’t conceive after a year, Clark advises heading to a specialist.