Waking up feeling overheated or drenched in sweat during the night is a common and often uncomfortable experience. This phenomenon, known as night sweats or simply feeling too hot while sleeping, can disrupt sleep quality and lead to daytime fatigue. Understanding the various factors that contribute to this nocturnal warming can help in addressing the issue and improving overall sleep. This article explores the physiological processes involved in sleep temperature regulation and common causes of overheating during the night.
Natural Sleep Physiology and Temperature
The human body’s temperature naturally fluctuates throughout a 24-hour cycle, a process governed by the circadian rhythm. As bedtime approaches, about two hours before sleep, the core body temperature begins to gradually decrease, coinciding with the release of the sleep hormone melatonin. This cooling trend continues into the early hours of sleep, reaching its lowest point two hours after falling asleep.
Maintaining an optimal body temperature is important for initiating and sustaining sleep. The body employs thermoregulation mechanisms to facilitate this cooling. Blood vessels in the skin, particularly in the hands and feet, widen, increasing blood flow to these areas. This allows heat to escape from the body’s core to the periphery, promoting a reduction in overall body temperature.
Sweating is another mechanism the body uses to cool down. As sweat evaporates from the skin, it draws heat away from the body. This natural drop in core body temperature is conducive to restful sleep and helps the body cycle through the various stages of sleep. Most doctors suggest keeping the thermostat between 60 and 68 degrees Fahrenheit (15.6 to 20 degrees Celsius) for comfortable sleep.
Common Causes of Feeling Too Hot
Feeling hot during sleep can stem from various factors, ranging from the immediate sleep environment to underlying physiological conditions. These elements can disrupt the body’s natural cooling processes, leading to discomfort and interrupted sleep.
Environmental factors play a role in sleep temperature. A bedroom that is too warm, heavy bedding made of synthetic materials, or sleepwear that traps heat can prevent the body from cooling down. Insufficient ventilation in the sleeping area also contributes to heat buildup around the body, hindering the evaporation of sweat.
Lifestyle choices made close to bedtime can also elevate body temperature. Engaging in late-night exercise raises core body temperature. While exercise can promote sleep, intense activity too close to bedtime might interfere with the natural cooling process needed for sleep onset.
Consuming spicy foods in the evening can increase metabolism and thermogenesis due to compounds like capsaicin. Alcohol consumption can initially create warmth by widening blood vessels, but it can later disrupt thermoregulation, leading to increased core body temperature. Caffeine, a stimulant, can also raise body temperature and interfere with sleep.
Physiological and medical factors are frequently implicated in nocturnal overheating and night sweats. Hormonal fluctuations during menopause or perimenopause can cause hot flashes and night sweats due to changes in estrogen and progesterone levels. Premenstrual syndrome (PMS) can also involve night sweats as estrogen levels decrease.
Certain medications, including antidepressants and hormone therapies, can cause night sweats as a side effect. Infections causing fever elevate body temperature and trigger sweating as the body fights illness.
Sleep disorders such as obstructive sleep apnea (OSA) are linked to night sweats; breathing interruptions trigger the release of stress hormones which activate sweat glands. Hyperthyroidism accelerates metabolism and generates excess body heat. Anxiety and stress can activate the body’s “fight or flight” response, increasing heart rate, blood pressure, and body temperature, resulting in sweating during sleep.