Waking up in sweaty pajamas or breaking out in a heated flush (when everyone else in the room seems to be cool and comfortable) can be really disconcerting. But hot flashes aren’t just an annoying symptom of menopause. A new study finds that women who experience regular hot flashes may face a much greater risk of having a heart attack or stroke later in life.

Preliminary findings to be presented Thursday at the North American Menopause Society’s (NAMS) annual meeting in Chicago suggest that women and their doctors should take frequent or persistent hot flashes as a potential warning of future cardiovascular woes.

“For both patients—women—and the people who are caring for them, this is a wake-up call,” Stephanie Faubion, MD, NAMS medical director and director of Mayo Clinic’s Center for Women’s Health, tells Health.

Researchers had already suspected there might be some connection between hot flashes and heart health. But the link was based on studies of older women who were asked to recall their prior hot flash experiences, as well as research involving markers of heart disease, like coronary calcifications or blood flow disturbances—and not actual heart attacks or strokes.

The new study connects the dots in a more compelling way by following more than 3,300 pre- and early menopausal women in their 40s and early 50s and checking in with them about once a year over the course of 20 years. This allowed researchers to collect information on the women’s hot flashes as they were going through the menopause transition and to record cardiovascular events.

“This is the first study that’s actually done that,” Dr. Faubion points out.

Overall, 231 women in the study had a heart attack or stroke during two decades of follow-up.

Women who had frequent hot flashes at the beginning of study were twice as likely as other women to experience such events. Women with persistent hot flashes over time had an 80% increased risk of having a heart attack or stroke—even after adjusting for heart disease risk factors.

Rebecca Thurston, PhD, incoming NAMS president and lead author of the study, tells Health it doesn’t mean that any individual woman who has hot flashes is destined to go on to have heart attack or stroke. “But relative to a woman who doesn’t have hot flashes, she is at increased risk,” says Thurston, a researcher specializing in midlife women’s health and cardiovascular risk.

As for why hot flashes may be a harbinger of heart disease, Thurston suspects it says something about the women’s vasculature, aka her blood vessels.

Will treating your hot flashes reduce your heart disease risk? “We just don’t know because we haven’t done that research yet,” Thurston acknowledges. However, she does think the study findings underscore the need to engage in heart-healthy behaviors, such as quitting smoking, losing weight if you’re overweight, and getting your blood pressure under control.

“It definitely underscores the importance of women who are having severe hot flashes to just be on top of their cardiovascular health,” Thurston says.

What this study doesn’t tell us is whether knowing a woman’s hot flash history will boost the accuracy of predicting who will have a heart attack or stroke, Dr. Faubion says. But that, of course, is the hope.

It could be the “canary in the coal mine,” Arianna Sholes-Douglas, author of The Menopause Myth and found of the Tula Wellness Center in Tucson, Arizona, tells Health—pointing out that heart disease in the number one killer of women in the U.S. “Hot flashes are no laughing matter.”

The study findings reported at NAMS are considered preliminary because they have yet to be published in a peer-reviewed medical journal.