Hot flashes can last a decade, and scientists traced them to a thermostat in the brain

Key takeaways

• In a federally funded study of 1,449 U.S. women with frequent hot flashes, the median length was 7.4 years, and more than half had them for over seven years¹².
• Hot flashes appear to start in a small cluster of brain cells that loses estrogen’s restraint, and that discovery led to a new class of hormone-free drugs³⁴⁵.
• Women who reported frequent hot flashes at more than a third of study visits had a 77% higher rate of later heart attacks, strokes and similar events than women who reported them less often, a link that doesn’t prove hot flashes cause heart disease⁶.
• Across 24 trials, hormone therapy cut weekly hot flashes about 75% more than a placebo did, while acupuncture did no better than a fake version in a 327-woman trial⁷¹¹.
• In hot flash trials, women on dummy treatments improve by as much as two-thirds, so a remedy that seemed to work may not beat a placebo⁷⁸.

If your hot flashes started while your periods were still regular or just starting to change, you may be in for a long season. In a large federally funded study, women whose hot flashes began that early had them for a median of more than 11.8 years².

That finding comes from the Study of Women’s Health Across the Nation, or SWAN². Among the 1,449 women in the analysis who had frequent hot flashes, the median was 7.4 years¹. More than half had them for longer than seven years².

The researchers wrote that clinical guidelines tend to underestimate how long hot flashes last². That gap matters if you were told to wait them out, or to treat them only briefly.

Researchers have also traced hot flashes to a few brain cells, linked frequent ones to heart risk, and sorted treatments that work from those that mostly ride the placebo effect. This is what they found.

Seven years is the middle of the range, not the end

SWAN enrolled more than 3,000 women in their 40s and early 50s and checked on them about once a year from 1996 to 2013¹². For this analysis, published in JAMA Internal Medicine in 2015, the team focused on women who had hot flashes or night sweats on at least 6 of the previous 14 days¹². Nancy Avis of Wake Forest University led the work¹.

When the first hot flash arrived mattered most. Women whose hot flashes began while their periods were still regular, or early in the transition, had them for a median of more than 11.8 years, including 9.4 years after their last period². Women whose hot flashes started only after their periods ended had them for a median of 3.4 years².

Length also differed by group¹:

Women in SWAN	Median years of frequent hot flashes
African American	10.1
Hispanic	8.9
Non-Hispanic white	6.5
Chinese	5.4
Japanese	4.8

Women with more depressive symptoms, anxiety or stress, and those with less schooling, also had hot flashes longer¹. The study can’t say why.

Some women were still having hot flashes when the study ended, so the authors said the true duration may be longer¹. NIH agencies funded the work, and one author reported ties to drug companies¹.

If yours run long, you have plenty of company, and you aren’t doing something wrong. That’s a good reason to look for options that are safe to use for years, not weeks.

Hot flashes start in a small cluster of brain cells

As recently as 2013, a review by University of Arizona researchers called the cause of hot flashes unknown, though their own lab work held the leads⁴.

Naomi Rance, a University of Arizona professor of pathology and neurology, spotted the first clue while training at Johns Hopkins University. In brain tissue from women past menopause, a group of nerve cells in the hypothalamus had grown larger³⁵. The team also found that these cells were more active and made more of a signaling chemical called neurokinin B⁵.

Because the cells also make kisspeptin and dynorphin, scientists call them KNDy neurons⁴.

Rat studies filled in the chain³⁴:

• KNDy cells send fibers to brain areas that manage heat loss, and those areas carry a receptor called NK3.
• Switching on NK3 in one of those areas lowered rats’ body temperature.
• Destroying KNDy cells reduced the widening of skin blood vessels that sheds heat, and it partly blocked estrogen‘s effect on body temperature.

The working idea is that estrogen normally keeps these cells in check. When estrogen falls, they release more neurokinin B into the brain’s temperature-control areas, which can switch on the body’s heat-release system³⁴. The 2013 review framed this as a hypothesis built mostly on animal data⁴.

Human tests came next. In a 2015 placebo-controlled study, an IV infusion of neurokinin B gave hot flashes to women who hadn’t reached menopause⁵. In a 2017 investigator-led trial in The Lancet, researchers tested an experimental pill that blocks NK3. Over four weeks, it cut weekly hot flashes by 45 percentage points more than a placebo, according to the trial’s first author⁵.

The FDA has since approved fezolinetant, a hormone-free drug that blocks NK3⁸. Our menopause sleep article covers it and a newer drug, elinzanetant, including their label warnings.

Rance credited federal funding for basic research³. For readers who see the body as a self-regulating system, the story fits: a hot flash is a temperature-control circuit reacting to a hormone change.

Frequent hot flashes travel with higher heart risk

In 2021, a SWAN team writing in the Journal of the American Heart Association reported on 3,083 women followed for up to 22 years, with as many as 16 study visits each⁶. The researchers counted heart attacks, strokes, heart failure and procedures to reopen blocked arteries, fatal or not. There were 231 such events⁶.

Women with frequent hot flashes at the start, on 6 or more days in two weeks, had a 51% higher rate of these events than women with none⁶. Occasional hot flashes, on 1 to 5 days, showed no link⁶.

Persistence mattered more. Women who reported frequent hot flashes at more than a third of their visits had a 77% higher rate than women who reported them less often⁶. Those figures held after the team accounted for standard heart risk factors, medicines and background⁶.

The study summary didn’t give event rates for each group, so we can’t turn those percentages into personal odds. Across all the women, 231 of 3,083 had an event, about 7.5% over as long as 22 years, by our math.

This was an observational study, so it shows a link, not a cause. It can’t tell you whether treating hot flashes protects the heart. The authors suggested that frequent hot flashes may be a heart risk factor unique to women⁶.

Treat that as a nudge, not a scare. If your hot flashes are frequent or long-running, know your blood pressure, cholesterol and blood sugar numbers. Our companion article on menopause covers heart changes after the final period.

In hot flash trials, dummy treatments work surprisingly well

Hot flashes respond strongly to placebo. In a Cochrane review of hormone trials, women on dummy pills saw their hot flashes drop 57.7% from start to finish⁷. The Menopause Society’s 2023 review of hormone-free treatments said placebo groups in those trials improve by 20% to 66%, and more anxious women respond more⁸.

Acupuncture shows why that matters. In a trial published in 2016 in the Annals of Internal Medicine, researchers in Australia enrolled 327 women with at least seven moderate hot flashes a day¹¹. Every woman also fit a traditional Chinese medicine pattern called kidney yin deficiency, so the trial respected the tradition’s own way of choosing patients¹¹.

Half got 10 real acupuncture treatments over eight weeks. The other half got a sham version with blunt needles that touch the skin but don’t pierce it¹¹¹².

Both groups improved by about 40%, and the gains lasted six months¹². But real needling beat the sham by almost nothing: end-of-treatment hot flash scores were 15.36 and 15.04¹¹. No serious side effects were reported, and Australia’s national health research council paid for the study¹¹¹².

Lead author Carolyn Ee, a family doctor trained in Chinese medicine, pointed to placebo, the value of talking through symptoms at a clinic, and hot flashes easing over time¹². The Menopause Society doesn’t recommend traditional acupuncture for hot flashes⁸. It called electroacupuncture, acupuncture with a mild electric current, more promising but wants more research first⁸.

If an herb or treatment eased your hot flashes, that relief was real. The open question is what caused it. Only a comparison with a convincing fake can separate the remedy from time, care and expectation.

Hormone therapy still sets the bar

The Menopause Society’s 2023 statement still ranks hormone therapy as the most effective hot flash treatment⁸. A Cochrane review, a pooled analysis of trials, measured the size of that edge⁷.

It combined 24 trials with 3,329 women who took estrogen pills, alone or with a progestogen, or a placebo for three months to three years⁷. Hormones cut weekly hot flashes 75% more than placebo, about 18 fewer a week⁷. That works out to roughly 2.6 fewer a day, by our math. Severity fell too⁷.

Side effects were somewhat more common on hormones, but women on placebo were far more likely to drop out because their treatment wasn’t working⁷. One caveat: the review dates from 2004, and its trials were short⁷.

Some women can’t take hormones. The 2023 statement names estrogen-sensitive cancers, heart disease, a past heart attack or stroke, and a history or inherited risk of blood clots⁸. Others would rather not. Our sibling article on hormone therapy walks through the risks in absolute numbers.

Older drugs and a nerve block found a second job

Several drugs made for other conditions turned out to cool hot flashes. Whether any fits you is a decision to make with your clinician.

Low-dose paroxetine. In 2013, the FDA approved a 7.5 mg bedtime capsule of this antidepressant as the first hormone-free drug for moderate to severe hot flashes⁸⁹. Its two trials enrolled 1,175 women for 12 or 24 weeks⁹. Headache, tiredness and nausea were the common side effects⁹. The label warns it may weaken the breast cancer drug tamoxifen⁹.

In a pooled analysis of three trials, low-dose estradiol cut 2.3 more hot flashes a day than placebo, and the antidepressant venlafaxine cut 1.8 more⁸.

Gabapentin. This anti-seizure drug reduced hot flashes at 900 mg a day⁸. In one trial, a much higher dose matched an estrogen pill for severity, but dizziness, headache and disorientation limited its use⁸. Dizziness and drowsiness usually fade within about four weeks⁸.

Oxybutynin. This bladder drug was tested in a Mayo Clinic-led trial of 150 women, first presented at a 2018 cancer meeting and published in 2020 in JNCI Cancer Spectrum¹⁰¹⁵. About 65% were taking tamoxifen or an aromatase inhibitor, another breast cancer drug¹⁰¹⁵. Over six weeks, hot flash scores fell about 70% on the lower dose and 86% on the higher one, compared with 27% on placebo, according to the meeting report¹⁰. By our math, that’s 43 and 59 percentage points beyond placebo. The published paper called the drug effective and relatively well tolerated¹⁵.

Dry mouth, belly pain and harder urination were common side effects¹⁰¹⁵. The Breast Cancer Research Foundation, a nonprofit, paid for the trial¹⁰. The Menopause Society warns that long-term use of drugs in this class may be linked to declines in memory and thinking, especially in older adults⁸.

Stellate ganglion block. This is an anesthetic injection into a nerve cluster. In one trial of 40 women, measured hot flashes fell 21% after three months with the real shot and not at all with a saltwater sham⁸. Larger trials are needed⁸.

Weight loss. Small studies tie weight loss to fewer hot flashes, and the Menopause Society lists it as an option while calling for bigger trials⁸. It’s the most natural-health-friendly item on this list.

The hot flash options table

This table is our own summary. The numbers come from different trials with different women and lengths, so compare them loosely.

Option	Typical effect in trials	Evidence	Main cautions	Source
Hormone therapy	About 18 fewer hot flashes a week than placebo (75% more reduction)	Strong evidence	Not for some health histories; see our sibling article	78
Fezolinetant	Fewer hot flashes than placebo through 12 weeks	Strong evidence	Rare liver enzyme rises; see our menopause sleep article for the FDA warning	8
SSRIs and SNRIs, including low-dose paroxetine	25% to 69% fewer across trials	Strong evidence	Nausea, headache; paroxetine may weaken tamoxifen	89
Gabapentin	Fewer, milder hot flashes	Strong evidence	Dizziness and drowsiness early on	8
Oxybutynin	70% to 86% lower scores vs. 27% on placebo in a 6-week trial	Strong evidence	Trials were short; dry mouth; possible memory effects with long use	81015
CBT or clinical hypnosis	Recommended; see our menopause sleep article	Strong evidence	Takes sessions and practice	8
Stellate ganglion block	21% fewer measured hot flashes in one 40-woman trial	Promising but early	A procedure; few trials	8
Weight loss	Fewer hot flashes in small studies	Promising but early	Needs larger trials	8
Electroacupuncture	Beat sham at 8 weeks in a 2021 analysis of 17 studies	Promising but early	Not yet recommended	8
Traditional acupuncture	No better than sham needles	Evidence says no, or unsafe	Both groups improved about 40%	81112
Cooling or avoiding triggers	Little or no trial evidence	Not enough evidence	Cheap comfort; fine to try	8

Herbal supplements, including black cohosh, aren’t recommended by The Menopause Society⁸. Our sibling article covers their trials.

Self-care deserves an honest word. One large survey of 4,595 women in China linked drinking to hot flashes, but other studies haven’t found the same pattern⁸. Our menopause sleep article covers what the small cooling studies showed. A fan and light layers still cost little and may make you more comfortable.

When night sweats may not be menopause

Night sweats can have other causes, too. The Menopause Society lists sleep apnea, an overactive thyroid, acid reflux, diabetes, infections such as tuberculosis and HIV, and some cancers, including lymphoma¹³. Many medicines can also cause sweating, among them some antidepressants, steroids, thyroid hormone and diabetes drugs¹³.

Cancer care can cause them, too. Tamoxifen, aromatase inhibitors and treatments that bring on early menopause can all trigger hot flashes and night sweats, and so can hormone treatment or testicle removal for men¹⁴.

See a clinician if¹³:

• night sweats come with fever, swollen glands or weight loss;
• sweating started soon after a new medicine (ask whether it could be the cause before changing anything);
• you have trouble breathing at night, which can point to sleep apnea;
• you still have regular periods, or sweats come back after they had gone away;
• sweats begin years after you stopped hormone therapy.

If you take fezolinetant, our menopause sleep article lists the liver warning signs the FDA says to watch for.

Questions readers ask

The bottom line

Hot flashes often last far longer than women expect, especially when they start early in the transition. They appear to begin with brain cells that react when estrogen falls, and that discovery has produced a new class of hormone-free medicine. Frequent, long-running hot flashes also travel with higher heart risk, which makes them worth taking seriously.

Hormone therapy works best, and several hormone-free prescriptions, CBT and hypnosis have solid evidence too. A nerve block and weight loss look promising, while traditional acupuncture and most self-care tricks haven’t been shown to work in fair tests. Bring your two-week count to a clinician and decide together.

Related reading

• Hot flashes aren’t the only thing stealing sleep in menopause
• Hormone therapy’s risks depend on which hormones, when and how, and most herbs fell short
• Placebos ease how you feel but rarely change what doctors measure
• The three numbers that explain the acupuncture argument
• A new calculator cut millions of heart risk scores while nothing inside those hearts changed

Sources

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2. The Hospitalist (MDedge). “Vasomotor Symptoms of Menopause Often Persist Longer Than 7 Years” (report on Avis NE, et al., JAMA Internal Medicine, 2015). community.the-hospitalist.org
3. University of Arizona. “Paving the Way for Promising Treatment for Hot Flashes” (news release on Naomi Rance’s research). ScienceDaily, June 28, 2017. sciencedaily.com
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7. MacLennan AH, Broadbent JL, Lester S, Moore V. “Oral Oestrogen and Combined Oestrogen/Progestogen Therapy Versus Placebo for Hot Flushes.” Cochrane Database of Systematic Reviews, 2004, Issue 4 (CD002978). cochrane.org
8. Shufelt CL, Brown V, Carpenter JS, et al. “The 2023 Nonhormone Therapy Position Statement of The North American Menopause Society.” Menopause, 2023;30(6):573–590 (copy hosted by the University of Washington). depts.washington.edu
9. Contemporary OB/GYN. “FDA Approves First Nonhormonal Treatment for Hot Flashes” (Brisdelle, low-dose paroxetine). July 11, 2013. contemporaryobgyn.net
10. The ASCO Post. “Oxybutynin for Managing Hot Flashes” (report on Leon-Ferre RA, et al., ACCRU SC-1603, San Antonio Breast Cancer Symposium, December 2018). January 25, 2019. ascopost.com
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