Hot Flashes at Night: Why They Happen and What Helps

The short answer

Hot flashes at night, usually called night sweats, happen because menopause shrinks the band of core temperatures your brain tolerates, so a tiny rise in body heat sets off flushing and sweating (Freedman 2013). Up to 80% of women get hot flashes or night sweats, and each episode typically lasts 1 to 5 minutes (Menopause Society). A cooler bedroom, layered bedding and a fan make nights easier (NIA hot flashes), and effective treatments exist if they still wreck your sleep. Night sweats with fever, weight loss or other new symptoms need a doctor.

What are night sweats and hot flashes?

A hot flash brings a sudden, intense wave of heat to the face, neck and chest. Sweating, chills, anxiety and a racing heartbeat can come with it. Night sweats are simply hot flashes that strike during sleep, and the chills afterward can leave you shivering in damp sheets (Menopause Society).

Doctors group the two together as vasomotor symptoms. They often begin before the final period and can last a long time. In the Study of Women's Health Across the Nation (SWAN), which followed more than 3,300 women at seven US sites, frequent hot flashes and night sweats lasted a median of 7.4 years. They continued a median of 4.5 years after the last period. Women whose symptoms started early in the transition had them longest, and African American women reported the longest duration, a median of 10.1 years (Avis 2015).

Why do hot flashes happen?

Your brain normally holds core body temperature inside a comfortable band. Above the top edge you sweat; below the bottom edge you shiver. Researchers call that band the thermoneutral zone.

In lab studies, women without hot flashes had a zone about 0.7°F (0.4°C) wide. In women with frequent hot flashes, the zone shrank to essentially zero (Freedman 2013). With no buffer, a rise of a fraction of a degree tips the body into full heat-dumping mode: blood rushes to the skin, and sweat follows. Core temperature crept up before most recorded hot flashes, and warm surroundings or heating the skin could set one off (Freedman 2013).

Falling estrogen plays a part, though it doesn't explain everything. The brain's stress-signaling system also seems to narrow the zone (Freedman 2013).

Why are hot flashes worse at night?

Hot flashes don't necessarily happen more often at night. In one small study that tracked women around the clock, hot flashes peaked in the early evening, around 6:25 p.m. (Freedman 2013). Night ones hurt more because of what they interrupt.

• They wake you up. Researchers measured hot flashes and sleep together in 168 midlife women at home. A wake episode lined up with 78% of nighttime hot flashes, and women were about five times more likely to wake during a flash than in the minutes before it. That held even when women didn't remember the flash (Thurston 2019).
• Your bed traps heat. Covers, a warm partner and a stuffy room all add the small amount of heat a narrowed zone can't tolerate.
• You lose sleep twice. The flash wakes you hot, the sweat leaves you cold and damp, and getting back to sleep takes time.

Sleep trouble in menopause has more than one cause, and hot flashes explain part of it (Freedman 2013). Still, for many women they drive the worst nights.

Best bedroom temperature for menopause

No study has named a single ideal bedroom temperature for women in menopause. The general advice for good sleep still applies, so start at the cool end of the range in our best temperature for sleep guide and adjust from there. The sleep temperature calculator lowers its suggestion for night sweats and shows you why.

The National Institute on Aging suggests these steps for hot flashes that keep you up (NIA hot flashes):

• Lower the bedroom temperature.
• Sip a small amount of cold water before bed.
• Layer your bedding so you can peel it back during the night.
• Turn on a fan.

A few more practical moves:

| Setup | Why it helps | |---|---| | Separate blankets for each sleeper | One partner can sleep warm while the other kicks off covers | | Light, breathable sheets and sleepwear | Sweat dries faster, so the chill afterward hits less hard | | A fan aimed at you | Moving air speeds evaporation and cools skin quickly | | Drier summer air | Muggy air slows sweat evaporation; see ideal indoor humidity | | A spare shirt and towel by the bed | A quick change beats lying awake in damp clothes |

Be realistic about what a cool room can do. In clinical trials, cooling techniques such as adjusting clothing or room temperature haven't been shown to cut the number of hot flashes (Menopause Society). They make each episode easier to ride out and help you fall back asleep, which matters plenty at 3 a.m. Your ideal setting can also shift with the weather and the season; that's why the perfect temperature changes. If you use an Apple Home thermostat, Just Right can lower the bedroom setting for nighttime and learn from the corrections you make.

What to track

The NIA suggests noting what seems to trigger your hot flashes and how much they bother you (NIA hot flashes). A simple log over two to four weeks gives you and your clinician something concrete to discuss:

• Bedtime room temperature and what bedding you used
• How many times you woke hot or sweaty, and how you felt the next day
• Alcohol, caffeine and spicy food that evening, which the NIA lists as possible aggravators
• Any new medication or supplement
• Fever, unplanned weight loss or other new symptoms

Expect your log to undercount. Many hot flashes during sleep don't wake you, and memory of the ones that do runs poor by morning (Freedman 2013). Score the nights by how rested you feel too.

Other causes of night sweats

Menopause causes a lot of night sweats, but plenty of other things do too. A review for family physicians lists these among the causes (Viera 2003):

• Infections, including tuberculosis, HIV, endocarditis and others
• Cancers, especially lymphoma and leukemia
• Hormone problems, such as an overactive thyroid or low blood sugar at night in people with diabetes
• Medications, including fever reducers like aspirin and acetaminophen, some blood pressure drugs and others
• Alcohol and some other substances
• Sleep apnea, acid reflux and anxiety
• Over-bundling, meaning a room or bed that runs too hot

Tuberculosis and lymphoma cause night sweats less often in modern practice, yet doctors still check for them when the story fits (Viera 2003). Men get night sweats too, so menopause can't explain every case. If you run hot during the day as well, why am I always hot covers other reasons.

Treatments to discuss with your clinician

If bedroom changes don't give you decent sleep, effective treatments exist. Hormone therapy works best for bothersome hot flashes. Several nonhormone prescriptions also help, and cognitive behavioral therapy and clinical hypnosis can ease symptoms without medication (Menopause Society). Risks shift with your age and health history, so the right choice differs from one woman to the next (NIA hot flashes). Talk them through with your clinician and skip the internet's miracle supplements: the NIA notes that products such as black cohosh and soy haven't been proven to work, and some carry risks such as liver damage.

When to see a doctor

See a doctor or other clinician if:

• Night sweats regularly break your sleep or leave you exhausted during the day.
• Drenching sweats come with fever, chills, cough, unexplained weight loss, swollen glands or deep fatigue.
• Night sweats started after a new medication.
• You haven't reached the age of menopause, you're past it and the sweats are new, or you're a man with night sweats.
• You also snore loudly, gasp in your sleep or have heartburn at night.
• You have a racing heart, shakiness or weight loss that could point to a thyroid problem.

Call 911 for chest pain, trouble breathing, fainting or sudden confusion, whether or not you're sweating.