Feeling uncomfortably hot or waking up drenched in sweat is known as nocturnal hyperthermia, or more commonly, night sweats. While many people blame too many blankets, true night sweats involve excessive perspiration that soaks sleepwear and bedding, often regardless of the ambient temperature. This widespread issue can significantly disrupt sleep quality. Understanding the causes, from environmental factors to internal physiology, is the first step toward a cooler night’s rest.
How the Body Regulates Temperature During Sleep
The body’s internal temperature control, or thermoregulation, is closely tied to the sleep-wake cycle and directed by the hypothalamus in the brain. As the evening progresses, the body naturally begins to cool down, a physiological change that signals the onset of sleep. This cooling process involves a drop in core body temperature by about one degree Celsius.
To achieve this temperature reduction, the body initiates peripheral vasodilation, widening blood vessels near the skin’s surface. This increased blood flow to the hands and feet allows heat to move from the core to the periphery, where it dissipates into the surrounding air. An efficient drop in core temperature is associated with shorter sleep latency and more restorative sleep.
During the deepest stages of sleep, the body’s ability to actively regulate temperature through mechanisms like shivering or sweating is diminished. If the environment is too hot or too cold, a person is more vulnerable to thermal stress during the night. The body relies heavily on a neutral thermal environment to maintain its lowered temperature without needing to activate a heat-loss response like sweating.
Quick Fixes Optimizing Your Sleep Environment
The most common cause of feeling too hot at night is a sleep environment that prevents the body’s natural cooling process. Adjusting the room temperature is one of the most effective solutions, with experts suggesting a range between 60 and 67 degrees Fahrenheit (15–19°C) for optimal rest. A simple fan also helps significantly by improving air circulation and creating an evaporative cooling effect on the skin.
The materials used for sleepwear and bedding have a major impact on heat retention. Heavy or non-breathable fabrics like flannel or certain synthetics trap body heat and moisture, insulating the core too much. Switching to lightweight, breathable options such as cotton, linen, or moisture-wicking performance fabrics allows heat and sweat to escape more easily.
Layering bedding rather than using a single, heavy comforter provides better control over your thermal microclimate. If you wake up feeling too warm, you can simply remove a layer without fully disrupting your sleep. Taking a warm bath or shower about 90 minutes before bedtime can also be beneficial, as the rapid cooling of the skin signals the body to lower its core temperature.
Lifestyle choices made before bed also influence nocturnal temperature. Intense physical activity raises core body temperature, so heavy exercise should be completed at least three hours before trying to sleep. Consuming large or spicy meals close to bedtime can also increase metabolic heat production as the body works to digest the food.
When It Is More Than Just a Hot Room Medical and Hormonal Factors
When night sweats are persistent, severe, and occur even in a cool environment, the cause is often an internal health condition. Hormonal fluctuations are a frequent trigger, particularly in women experiencing perimenopause or menopause. Hot flashes result from changes in estrogen levels, making the body’s temperature control center hypersensitive and leading to sudden, intense sweating episodes.
Endocrine disorders, which affect hormone production, can also be a factor. An overactive thyroid (hyperthyroidism) accelerates the body’s metabolism, causing heat intolerance and excessive sweating, including at night. Low blood sugar (nocturnal hypoglycemia) can also trigger a sweat response as the body attempts to compensate for the drop in glucose, which is a concern for individuals managing diabetes.
Certain medications can interfere with the brain’s thermoregulatory signals, leading to night sweats as a side effect. Common culprits include some antidepressant medications, aspirin, pain relievers, and hormone therapy drugs. Conditions that increase the body’s metabolic rate or trigger the “fight or flight” response may also cause drenching sweats, such as obstructive sleep apnea.
Night sweats can sometimes be a sign of an underlying infection, such as tuberculosis, or in rare cases, certain types of cancer, like lymphoma. It is important to seek medical consultation if the sweating is persistent, drenching, or accompanied by other concerning symptoms. These warning signs include unexplained weight loss, recurring fever, or chronic fatigue, which suggest the need for a professional diagnosis.