A new study showed hot flashes tend to continue for five years after menopause, but a third of women experience them for up to 10.

This can be a problem in some women because medical guidelines do not recommend hormone therapy (which is generally used to treat hot flashes) for a period lasting more than five years, a Penn Medicine news release reported.

The study team believes "empirical evidence supporting the recommended [three] to [five] year hormone therapy for management of hot flashes is lacking," the news release reported.

Hot flashes are experiences of "radiating heat" that often occur in postmenopausal women, they are believed to be caused by hormonal changes.

"Our findings point to the importance of individualized treatments that take into account each woman's risks and benefits when selecting hormone or non-hormone therapy for menopausal symptoms," the study's lead author, Ellen W. Freeman PhDresearch professor in the department of Obstetrics and Gynecology at Penn  Medicine said in the news release. "While leading non-hormone therapies such as Paxil or Escitalopram may provide some relief of menopausal symptoms for some women, for others, they may not be as effective as hormone-based therapy."

The team looked at 255 women who naturally reached menopause over a period of 16 years.  Eighty percent of them complained of moderate to severe hot flashes while 17 percent reported mild flashes; only three percent reported a lack of hot flashes.

Those at the greatest risk of experiencing moderate to severe hot flashes were obese Caucasian women and both fit and obese African American women.  

"The increased risk of hot flashes in obese women has previously been associated with lower levels of estradiol (the most potent estrogen produced by women's bodies) before menopause, but the new finding that non-obese African-American women also have a greater risk of hot flashes remains unexplained," the news release reported.

The team also found a 34 reduced risk of hot flashes in women who had been educated beyond high school.