Joan Bengtson, MD

Q: I'm a 46-year-old woman going through perimenopause. Why do I only get hot flashes in the middle of the night?

A: Perimenopause is the period of time leading up to menopause. Menopause officially starts once a woman has not had a menstrual period for 12 months.

Hot flashes can start in perimenopause. How often they occur during the day and the time of day varies considerably. And many women don't have hot flashes during perimenopause. We don't know exactly how hormone changes cause hot flashes, but they seem to result from the temporary instability of the heat regulation center in the brain. This center functions like a thermostat.

When a hot flash occurs, the brain thinks the body's temperature is too high. The body reacts by dilating blood vessels in the skin to release what it thinks is excess heat. When this happens, an uncomfortable warm sensation spreads across the chest, neck, and face. This often comes with flushing and a fast or irregular heartbeat.

When hot flashes happen probably has to do with the erratic rise and fall of estrogen levels that come with perimenopause. For you, this might be at night.

Hot flashes may also be due to other factors that affect your heat regulation center. For example, hot flashes are more common when the room temperature is high. Sleeping under too much bedding might also contribute to your middle-of-the-night hot flashes.

Other reasons for the different patterns of hot flashes include:

-- What you eat and drink, such as spicy food and alcohol

-- Changes in other hormones, such as testosterone or thyroid hormone

-- Stress

-- Medications

Hot flashes tend to decrease over time. If your hot flashes are so bad that treatment is required, several options are available:

Lifestyle changes.

Drink plenty of water, avoid foods that trigger hot flashes, and get regular exercise may help.

Short term use of estrogen.

This is very effective, but you must consider the potential risks.


Antidepressants known as selective serotonin uptake inhibitors (SSRIs) may help. Gabapentin and clonidine may also be prescribed.

Soy, herbal products, and other supplements.

These may help some women but they have not been shown to improve symptoms more often than a placebo in most scientific studies.

Talk to your doctor about these options if your hot flashes are disrupting your sleep or causing other problems in your life.

Joan Bengtson, M.D., is an assistant professor of obstetrics, gynecology and reproductive biology at Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts. Dr. Bengtson is a Senior Medical Editor at Harvard Health Publications.)


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Women's Health - Could Hot Flashes Only Occur at Night?