Sleep apnea and night sweats: can sleep apnea make you sweat at night?

Sleep apnea can cause night sweats. In a large Icelandic study, people with untreated sleep apnea were about three times as likely as the general population to report sweating at night several times a week, and the sweating usually eased once they used CPAP regularly. Night sweats have many other causes, from menopause to medicines, so they're a clue rather than a diagnosis. If you sweat at night and also snore, gasp or wake up tired, it's worth asking your doctor about sleep apnea.

What counts as night sweats?

Night sweats are heavy sweating while you sleep, enough to soak your clothes or bedding. The NHS says it's normal to sweat if your room or bedding is too warm, and defines night sweats as sweating so much that your night clothes and bedding are soaking wet even though where you're sleeping is cool.

Cleveland Clinic describes night sweats as much more intense than normal sweating. It says you may feel a sudden wave of heat, especially in your neck, chest and upper body, notice your heart beating faster, and then feel cold once the sweating stops.

They're common. A 2012 systematic review in the Journal of the American Board of Family Medicine found prevalence estimates ranging from 10% among older primary care patients to 60% among women on an obstetrics ward. If your bedroom simply runs hot, start there; our guide to the best bedroom temperature for sleep covers the basics.

Can sleep apnea cause night sweats?

Yes, sleep apnea is one recognized cause. Cleveland Clinic lists sleep disorders such as sleep apnea among the conditions that may lead to night sweats.

It's an easy symptom to miss, because it isn't on the standard lists. The NHS lists loud snoring, gasping or choking noises, breathing that stops and starts, waking up a lot and feeling very tired in the day. The NHLBI adds dry mouth, headaches, insomnia and waking up often to pee. Neither list mentions sweating, so many people never connect the two. The authors of the 2013 Icelandic study, which we cover below, noted that only a minority of patients bring night sweats up with their doctor at all.

Night sweats are worth mentioning for another reason too. The Icelandic researchers found that people who sweated at night were also more likely to report daytime sleepiness and insomnia symptoms, and suggested that in the general population, night sweats may be a marker of increased risk of sleep apnea.

What does the research show?

The research shows a fairly consistent link between sleep apnea and reported night sweats, with one notable exception. Most of the studies rely on people's own reports of sweating, and none are randomized trials, so the evidence is still emerging.

The Icelandic cohort

The strongest evidence comes from the Icelandic Sleep Apnea Cohort, published in BMJ Open in 2013. Researchers asked 822 people with untreated moderate-to-severe sleep apnea, meaning an apnea-hypopnea index (AHI) of 15 or more, how often they sweated at night. They compared them with 703 randomly selected adults from the general population.

Frequent night sweating, defined as three or more times a week, was reported by 30.6% of men and 33.3% of women with sleep apnea. In the general population, the figures were 9.3% of men and 12.4% of women. The difference held after the researchers adjusted for demographic factors. Night sweating was more common in younger patients and was linked with heart disease, high blood pressure, sleepiness and insomnia symptoms.

The authors noted that the study was observational and relied on people's own reports of sweating. They also didn't find a link between how severe the sleep apnea was and how much people sweated, though most of their patients had moderate-to-severe disease.

Oxygen levels and sweating

A 2023 study in Sleep and Breathing, from sleep labs in Buenos Aires, looked at 1,397 adults who filled in a sleep questionnaire before a sleep study. About 17.5% reported night sweats. They were more common in people with sleep apnea than in those without it, at 18.9% versus 12.2%.

After accounting for other factors, night sweats were independently linked with body mass index, low oxygen levels during sleep, nightmares, frequent body movements or awakenings, and excessive daytime sleepiness. The authors concluded that in people with sleep apnea, night sweats were associated with a higher hypoxic burden, meaning more time with low oxygen. The study looked back at existing records, so it shows a link, not cause and effect.

The study that found no link

Not every study agrees. A 2008 study in the Journal of the American Board of Family Medicine reviewed data from two sleep labs in Oklahoma City. Patients who reported night sweats were more likely to report snoring, nighttime breathing trouble, morning headaches and daytime fatigue, and they scored higher on a sleepiness questionnaire. But the researchers found no statistically significant link between night sweats and the apnea-hypopnea index or other sleep study measures.

The 2012 systematic review by the same lead author concluded that night sweats appear to be a nonspecific symptom, and that many questions about their causes remain unanswered. That's a fair summary. Night sweats on their own don't tell you much. Night sweats alongside snoring, gasping or heavy daytime tiredness are more telling.

Why would sleep apnea make you sweat?

Sleep apnea most likely makes you sweat through your stress response. A 2023 narrative review in the Journal of Sleep Research explains that excessive sweating happens when the sympathetic nervous system, the part that drives your fight-or-flight response, overstimulates the sweat glands in your skin. The review lists sleep apnea, insomnia, restless legs syndrome and narcolepsy among the sleep disorders linked with night sweating, and names sympathetic overactivity as the major cause.

The Icelandic researchers describe sleep apnea as repeated closure of the airway during sleep, with drops in oxygen, brief awakenings or both. That fits with the 2023 study linking night sweats to lower oxygen levels. In the Icelandic study, people who sweated at night were also more likely to have high blood pressure, a condition often found alongside sleep apnea; see sleep apnea and high blood pressure.

Does CPAP stop night sweats?

CPAP often reduces night sweats, as long as it's used most nights. In the Icelandic cohort, 700 patients were reassessed two years after starting treatment with positive airway pressure (PAP). Among those who used it fully, defined as at least 4 hours a night on at least 5 days a week, frequent night sweats fell from 33.2% to 11.5%, which the authors described as general population levels.

Partial use didn't bring the same benefit. The researchers found that a minimum of about 4 hours a night, 5 nights a week, was needed. The paper also mentions two earlier, smaller studies that found the same pattern; in one of them, 34% of 98 men with untreated sleep apnea reported night sweats, falling to 12% on PAP.

If you already use CPAP and still sweat, check how many hours you actually get each night. Our guide to getting used to CPAP has tips if the mask is keeping you from using it longer. If you're consistent and still sweating, other causes are worth a look with your doctor. Our overview of sleep apnea treatment options covers the alternatives to CPAP.

What else causes night sweats?

Night sweats have many causes besides sleep apnea, and most are more common. The NHS lists the most common ones as:

• menopause symptoms (hot flushes)
• anxiety
• medicines, such as some antidepressants, steroids and painkillers
• low blood sugar (hypoglycaemia)
• alcohol or drug use
• hyperhidrosis, a harmless condition that makes you sweat too much all the time

It adds that sometimes the cause is unknown.

Cleveland Clinic gives a longer list. It says night sweats happen more often in women because of changes in hormones such as estrogen and progesterone, during perimenopause and menopause, pregnancy and after childbirth, and occasionally around a period. Other causes it lists include bacterial and viral infections such as flu or COVID-19, an overactive thyroid, diabetes, cancers such as leukemia and lymphoma, cancer treatments, anxiety and panic disorders, and alcohol. Its list of medicines that can cause sweating includes some blood pressure medicines, antidepressants, some migraine medicines, pain relievers like ibuprofen, narcotic pain medicines, breast cancer treatments and steroids.

Menopause deserves a special mention, because it overlaps with sleep apnea. Cleveland Clinic says that if you're close to 50 and waking up drenched in sweat, menopause is the likely cause. But the two can overlap, and a 2007 study of 406 people with sleep apnea at a US sleep center found that women reported night sweats more often than men. Our articles on sleep apnea and menopause and sleep apnea in women go into this overlap.

Alcohol is on both lists, too. It can cause sweating and it can make breathing during sleep worse, which we cover in sleep apnea and alcohol.

Don't stop or change a prescribed medicine on your own. If you think a medicine is behind your sweating, the NHS says a GP may be able to prescribe a different one.

When should you see a doctor?

See your doctor if night sweats are regular and bother you. The NHS says to see a GP if:

• you have night sweats regularly that wake you up or worry you
• you also have a very high temperature, or feel hot, cold or shivery, a cough or diarrhoea
• you have night sweats and you're losing weight for no reason

Cleveland Clinic suggests seeing a provider if night sweats disrupt your sleep.

When you go, mention any sleep apnea signs as well. The NHS says to see a GP if your breathing stops and starts while you sleep, you make gasping, snorting or choking noises, or you always feel very tired during the day. It suggests bringing along someone who has seen your symptoms. A partner's account of snoring or pauses can steer your doctor toward a sleep test rather than a long search for other causes. The NHS says you can usually do that test at home; our guide to the home sleep apnea test explains what's involved, and our list of sleep apnea warning signs covers the other clues.

A few other situations call for a call to your clinician. If you're pregnant, raise night sweats, snoring or breathing pauses at your next appointment, since Cleveland Clinic notes pregnancy hormones can cause sweating too. And if you snore and your nose is blocked most nights, mention that as well.

It helps to keep notes for a week or two before your appointment: how often you wake up soaked, what time, how warm the room was, whether you drank alcohol, what medicines you took, and whether anyone noticed snoring or gasping. If you also wake from vivid dreams, our article on sleep apnea and nightmares is worth reading, since the 2023 study found nightmares and night sweats often went together.

This article is general information, not medical advice. Talk to your doctor about your own symptoms.

Read next

• Sleep apnea and nocturia: why sleep apnea can make you get up to pee at night
• Why do I wake up at 3am?
• Sleep apnea warning signs

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.