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Many of us have experienced waking up in the middle of the night, sweating and panicking, having frequent dreams or nightmares.
As a “natural function the body uses to regulate body temperature,” notes Jewel Kling, MD, associate director of women’s health at the Mayo Clinic, sweating has many benefits. However, this can also be a cause for alarm.
For example, some people worry that sweat causes body odor, while others worry that sweating is a sign of anxiety or nervousness (which it probably is, but they don’t want other people to know that). However, for those who sweat a lot at night, sweating can be especially costly because of the amount of laundry it creates and can disrupt regular sleep routines.
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What are night sweats?
The Mayo Clinic defines night sweats as frequent, profuse sweating while you sleep. The sweat is often so intense that it soaks through your nightwear or bedding. Whether a person sleeps in a hot or cold environment can trigger these episodes.
“Night sweats can be moderate to heavy,” says Kling. Similar to periods of profuse daytime sweating, night sweats are commonly referred to as generalized hyperhidrosis or profuse sweating. Such sweating may occur spontaneously or in conjunction with other medical conditions such as fever or nausea.
What causes night sweats?
While many factors can cause or worsen night sweats, such as medications and medical problems, Kling advises that if you have persistent night sweats, you should check with your doctor for the cause.
Hormonal changes, such as menopause, are another common cause of night sweats. These changes can make it harder for the brain to regulate body temperature. Night terrors and nightmares can also cause it, as can infection. “There are many stimuli that can cause night sweats, including stress and an increased heart rate,” explains Anthony Beutler, MD, associate medical director of sports medicine at Intermountain Health in Salt Lake City.
Endocrine conditions such as vitamin B12 deficiency, being overweight, autonomic nervous system problems, or thyroid problems can also cause night sweats.
And each of these factors can cause night sweats to varying degrees. According to Columbia University physical medicine and rehabilitation professor Lauren Fishman, MD, “the composition of sweat varies significantly depending on its cause.”
How are night sweats different than exercise-related sweat?
It is also important to remember that there are two main differences between sweating during activity and sweating throughout sleep. “Night sweat, like other emotional or endocrine causes, has a different chemical composition than exercise-induced sweat,” says Fishman. They explain this by saying that sweat produced during regular activity contains more lactate, a byproduct of metabolism, than sweat produced during sleep.
Although the processes that cause sweating are similar, Kling notes that night sweats and sweating during activity have different motives. “The body produces exercise-related sweat during exercise to regulate body temperature,” she says. “Night sweats are usually caused by something else.”
More: Sweating cools us down, but does it burn calories?