Certain characteristics predispose women to different hot flash and night sweat patterns

Most women will get hot flashes or night sweats at some point in life. However, when these symptoms occur and how long they last can vary dramatically among women. New findings show that women fit into four distinct groups when it comes to getting hot flashes and night sweats, with potential ramifications for therapy and prevention of future health conditions, according to the research led by the University of Pittsburgh Graduate School of Public Health.

The epidemiological investigation followed hundreds of women for an average of 15 years and identified characteristics that predisposed them to certain trajectories for getting hot flashes and night sweats—collectively known as "vasomotor symptoms." The findings are published in today's issue of Menopause: The Journal of the North American Menopause Society and were funded by the National Institutes of Health.

"Most women get vasomotor symptoms, and we used to think these symptoms lasted from three to five years, right around the time of the final menstrual period," said senior author Rebecca Thurston, Ph.D., a professor in Pitt's Department of Psychiatry and an epidemiologist at Pitt Public Health. "We now know that these symptoms persist for far longer—typically seven to 10 years—and occur at different times for different women. This is strong evidence that we need to further investigate the underlying physiological causes of vasomotor symptoms and their link to potentially preventable health conditions."

Hot flashes and night sweats involve a sudden flush of feverish heat and are linked to menopause, the time when a woman's menstrual period stops.

Dr. Thurston and her colleagues followed 1,455 women enrolled in the Study of Women's Health Across the Nation (SWAN) who had not yet gone through menopause when they enrolled. The women lived in Pittsburgh, Boston, Detroit, Chicago, Los Angeles, Oakland, Calif., or Newark, N.J., and were not on hormone therapy, nor did they have a hysterectomy. Each year, the women reported their vasomotor symptoms, along with receiving a clinical examination and sometimes a blood test.

The researchers found that the women could be relatively equally divided into four distinct trajectories for vasomotor symptoms as they went through menopause transition, and that certain characteristics were more common in different categories:

• A consistently low chance of having symptoms throughout the menopause transition was more common in Chinese women.
• A consistently high chance of having symptoms throughout the transition was more common in black women, those with less education, those who reported drinking alcohol moderately or heavily, and those who reported symptoms of depression or anxiety.
• An early onset of symptoms in the decade before the final period with cessation thereafter was more common among women who were obese, had symptoms of depression or anxiety, were in poorer health than their peers and at an older age at menopause.
• A late onset of symptoms after the final period that gradually declined in the following decade was more common in women with a lower body mass index (ratio of weight to height), those who smoke and black women.

Hormonal fluctuations were correlated with vasomotor symptoms but were not perfectly consistent, indicating that they did not fully account for the symptoms.

"It's fascinating that we can distinguish these unique patterns and then pinpoint specific characteristics associated with each of these trajectories," said co-author Maria M. Brooks, Ph.D., professor of epidemiology and associate professor of biostatistics at Pitt Public Health, and principal investigator of the coordinating center for SWAN. "When we see patterns like this, it indicates that there's something going on beyond hot flashes and night sweats being a passing nuisance. Depending on which category a woman falls into, there may be important implications regarding her health."

In a different, recent study, Dr. Thurston found evidence that some of these trajectories were associated with risk factors for cardiovascular disease.

"At this point, we can't completely untangle any causal relationship between vasomotor symptoms and health outcomes or suggest preventative measures for vasomotor symptoms without further study," said Dr. Thurston. "But women and their doctors can use these findings now to help them get a better idea what they're likely to experience as they go through menopause and to plan the best ways to manage their symptoms."