Most women expect hot flashes as a part of the "change of life," but more than half start sweating before menopause has actually begun, according to a survey.
The study and others "indicate that women start having hot flashes and night sweats, the primary symptoms of the menopause transition, before they have their final menstrual period, contrary to the perception of many clinicians," according to Ellen Gold, of the University of California, Davis School of Medicine.
Previous studies put the number of women with hot flashes at 15 or 20 percent, but those specifically asked about hot flashes in the past two weeks, which may be a better measure of early onset menopause symptoms than the current study, which asked "have you ever had a hot flash," said Gold, who was not involved in the study.
The findings, published in the journal Menopause, shouldn't be a concern for women, but it may change how researchers look at hot flashes, according to lead author Dr. Susan Reed who studies women's mid-life health at the University of Washington in Seattle.
Usually associated with menopause, hot flashes and night sweats occur when hormone changes cause blood vessels near the surface of the skin to open rapidly. Women with regular menstrual cycles should have enough estrogen to stave off hot flashes, but they may have to reevaluate that idea, Reed said by email.
Reed and her coauthors sent questionnaires to 18,500 women between 45 and 56. About half responded. Of the 1,500 who still had regular cycles and weren't taking medications such as antibiotics or hormone replacement, 55 percent reported having experienced a hot flash or night sweat at some point in their lives.
More than half of white, black and Native American women reported the symptoms, compared to 30 percent or fewer of Asian and Hispanic women.
The study was funded by Otsuka Pharmaceutical Co., Ltd., which is developing S-Equol, a compound that may mimic estrogen and could be a potential treatment for menopausal symptoms.
Many women have hot flashes but don't find that they disrupt daily life, said Ellen Freeman, of the University of Pennsylvania Perelman School of Medicine in Philadelphia.
"Note that only 22% were ‘bothered,'" so more than half of the women who had experienced a hot flash weren't troubled by it, Freeman said by email.
Though it wasn't their primary aim, the researchers also looked at how much soy the women reported eating. Soybeans contain weak estrogen-like compounds, which are not as strong as estrogen but have been linked to reduced fertility and early puberty in women.
Among white women, those with menopausal symptoms seemed more likely to eat soy regularly, while white women without symptoms were more likely to never have eaten soy. There was no relationship with soy in the other ethnic groups.
Though a recent study found that eating soy doesn't alleviate hot flashes (see Reuters Health story of November 27, 2012 here reut.rs/YnBtFG), it's also too early to say that soy causes hot flashes, Freeman said.
Given the design of the study, "it is possible that those women with hot flashes had increased soy intake to try to manage their hot flashes - we don't know which came first," Reed's coauthor Katherine Newton said.