If someone asked you to give some sage advice on ways to boost a couple’s sex life, a clunky CPAP mask probably wouldn’t even make your list. But a surprising new study shows that this device might be just what’s needed—at least for women with sleep apnea.

That’s good news for females who have this sleep-disturbing breathing disorder, but why didn’t men get the same boost?

The researchers had set out to investigate how CPAP (known clinically as continuous positive airway pressure) affects sexual quality of life for both male and female sleep apnea sufferers. The disorder is known to reduce libido in men and women and contribute to erectile dysfunction, but most of the previous research has focused on men—perhaps because fewer women have the condition.

It was a good bet that the use of CPAP, which delivers continuous air to keep the airway open and prevent snoring, gasping and waking up, would improve the sex lives of sleep apnea patients who used the device. After all, a good night’s sleep works wonders in knocking out the troubling symptoms of sleep apnea, including daytime sleepiness, depression and irritability.

But not all the findings lined up the way the researchers had expected.

Study details: A total of 182 men and women who were newly prescribed CPAP to treat obstructive sleep apnea took part in the research, and information about the participants’ quality of life, including their sex lives, was collected before and after the nearly three-year study.

Researchers then analyzed the difference in sexual quality of life scores between the 72 CPAP “users” who wore the mask for more than four hours per night and the 110 “nonusers” who wore the mask for fewer than 30 minutes per night. The CPAP users came out on top—averaging 0.6 points (12%) higher (on a scale of zero to 5) than the scores for the nonusers.

Here’s the surprising kicker: With further analysis, the researchers discovered that the higher sex scores applied only to the women in the study—not the men. This finding contradicted many of the earlier studies, which tended to focus on men with sleep apnea and a sexual dysfunction such as erectile dysfunction.

Compared with the current research, the men who were previously studied “might have been starting from a relatively worse-off place, which may have resulted in higher self-reported improvement,” explained Sebastian Jara, MD, the study’s lead author and a resident physician in otolaryngology-head and neck surgery with UW Medicine/Seattle.

Even so, the health benefits of CPAP, which include reduced risk for heart disease, stroke and diabetes, are so well-recognized that men with sleep apnea should still be motivated to use CPAP—even if this study didn’t show that their sex lives would improve.

A larger future study may indicate that both sexes enjoy better sleep—and a better sex life—with CPAP.

Bottom line: If your doctor prescribes CPAP to treat obstructive sleep apnea, it’s definitely worth using. The mask may not be a turn-on, but a well-rested partner with a renewed sex drive certainly can be!