Hot flashes and night sweats, the discomforting symptoms often linked to menopause, can have effects beyond disrupted sleep. A new study has found that women who experience hot flashes during sleep are at a higher risk of Alzheimer's.

Alzheimer's is a progressive brain disorder that affects memory, thinking and behavior. More than 6.5 million people in the U.S. above the age of 65 live with Alzheimer's disease, out of which more than 60% are women.

The increased risk in women might be due to their longer life expectancy. Another possibility is the occurrence of decreased estrogen levels during menopause, the stage that marks the end of a woman's menstrual cycle. Menopausal transition most often begins between ages 45 and 55. During this period, women experience various symptoms such as hot flashes, night sweats, irregular periods, sleep problems, mood changes, weight gain and hair thinning.

A previous study found that women who underwent premature menopause (before the age of 40) have higher levels of tau, the protein buildup in the brains linked to Alzheimer's.

A hot flash is a sudden warm feeling experienced on the upper body, engulfing the face, neck and chest, which is often accompanied by sweating. Rapid heartbeat and feelings of anxiety are the other signs of a hot flash.

"There has been a convergence of findings showing that hot flashes – particularly when objectively measured and occurring during sleep – are associated with poorer memory performance, as well as greater markers of small vessel disease risk in the brain, which has been linked to future dementia. This study further adds to the literature linking hot flashes – and particularly sleep hot flashes — to markers of poorer brain health," Dr. Rebecca Thurston, a study author, said.

In the latest study, researchers from the University of Pittsburgh and the University of Illinois evaluated skin temperature changes in 250 middle-aged women and found an association between hot flashes and increased occurrence of white matter hyperintensities, a recently identified biomarker for Alzheimer's disease.

The findings were presented at the annual meeting of The North American Menopause Society in Philadelphia.

The study does not indicate that hot flashes cause dementia and has not examined the potential mechanism that explains the association.

"We do not yet know the underlying mechanisms, as some most intuitive potential mechanisms such as sleep and estradiol levels did not explain the associations seen here. Interestingly, these associations were not explained by sleep itself. There may be something particularly important about these nocturnal hot flashes that we have not appreciated up to this point," Thurston said.

Researchers hope the findings will help women who experience hot flashes to reduce other controllable risk factors of Alzheimer's such as a sedentary lifestyle, poor sleep and diet.

"Right now, some of the best ways to preserve brain health are to engage in all of those healthy behaviors we know are important – such as engaging in regular exercise, eating a healthy diet, sleeping adequately, treating any mental health conditions, and treating any risk factors such as high blood pressure and diabetes," Thurston said.