Body Temperature Fluctuations During Rem Sleep: What's The Science?

Sleep is a complex process that involves a variety of physiological changes in the body, including fluctuations in body temperature. The relationship between sleep and body temperature has been a subject of interest for researchers, who have found that body temperature plays a significant role in sleep quality and duration.

During the day, body temperature tends to vary slightly, and this pattern continues throughout the night. As bedtime approaches, the body's temperature begins to drop, creating favourable conditions for sleep. This decrease in body temperature is thought to be a signal for the body to prepare for sleep, and it is observed across various mammalian species, including humans.

Throughout the night, body temperature continues to drop, reaching its lowest point in the early morning hours, typically around 2-4 am. This drop in temperature aids in falling asleep and staying asleep. However, as morning approaches, the body temperature starts to rise again, preparing the body for wakefulness.

Sleep can be broadly categorised into two types: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. NREM sleep accounts for about 80% of an adult's sleeping time and is characterised by slow and regular breathing. On the other hand, REM sleep is associated with increased brain activity, faster and more irregular breathing, and vivid dreams.

Interestingly, body temperature fluctuations also occur as we cycle between REM and NREM sleep. The body cools down during NREM sleep and heats up slightly during REM sleep. This slight increase in body temperature during REM sleep has led some researchers to suggest that REM sleep acts like a thermostatically controlled brain heater.

According to a study by UCLA professor Jerome Siegel, warm-blooded animals with higher body temperatures tend to have lower amounts of REM sleep, while those with lower body temperatures experience more REM sleep. This relationship was observed across different animal groups, including birds, humans, placental mammals, marsupials, and monotremes.

In summary, body temperature plays a crucial role in sleep regulation, with a drop in temperature facilitating sleep onset and a rise in temperature promoting wakefulness. Additionally, the amount of REM sleep is influenced by body temperature, with a negative correlation between REM sleep duration and body temperature observed across warm-blooded animal groups.

Body temperature and insomnia are linked

Insomnia is a very generic term with the criteria including difficulty initiating sleep, maintaining sleep, and early morning awakening, accompanied by some form of daytime impairment. Sleep onset insomnia is associated with a delayed temperature rhythm, at least partly because sleep is attempted during a delayed evening wake maintenance zone. Conversely, early morning awakening insomnia has been associated with a phase-advanced temperature rhythm. Sleep maintenance insomnia has been associated with a 24-hour elevation of core body temperature.

The body temperature starts to fall as bedtime approaches, paving the way for a good night's sleep. The body also tends to lose heat, which helps one fall and stay asleep. That's one of the reasons experts say one shouldn't exercise close to bedtime. We sleep better when we're cooler. The body temperature starts to rise toward morning, preparing the body for wakefulness.

The amount of REM sleep is neither high nor low compared to other homeotherm animals, undermining some popular views suggesting a role for REM sleep in learning or emotional regulation. However, brain activity goes up during REM sleep, sometimes even more than during the day.

Thermoregulation keeps the core body temperature between 97.7 and 99.5 degrees Fahrenheit, which offers the best environment for the body to function at max capacity. The body temperature peaks in the afternoon and gets the lowest in the hour or two before one wakes up, which works in tandem with the internal clock, or circadian rhythm, to get the best sleep. A good goal for sleeping temperature is about 66 to 70 degrees Fahrenheit, but one can experiment to find what works best for their environment and sleeping preferences.

Chronic illnesses like cardiovascular disease and depression can mess with temperature regulation, especially when one has both. Disorders of the brain that affect movement like multiple sclerosis and Parkinson's disease often cause issues with regulating body temperature throughout the day and night. When the thyroid overproduces its hormones, the body uses energy differently, which can affect core temperature. Infections can ratchet up body temperature because of inflammation from immune cells meant to destroy the virus or bacteria.

In a perfect world, our bodies would shift our temperature exactly right all the time, but sometimes illness and other factors keep us from our best thermoregulation. Quite a few health issues can disrupt temperature controls. If one thinks they may have a condition, they should let their healthcare provider know, and they can help make a plan to get their thermoregulation back on track.

Body temperature changes throughout the day

The body's core temperature follows a circadian rhythm, rising and falling across a 24-hour cycle. At the start of the day, body temperature is low and rises steadily throughout the day. As evening approaches, it begins to drop again, which is thought to be a signal for the body to prepare for sleep. This pattern is common across all mammals, from mice to humans.

Body temperature is highest in the afternoon and lowest in the hour or two before waking up. It tends to fluctuate slightly during the day and night, and this is also true while sleeping. While sleeping, body temperature can be 1 to 2 degrees lower than during the daytime.

During non-REM sleep, which accounts for about 80% of an adult's sleeping time, breathing is slow and regular. In REM sleep, however, the breathing rate increases, and this is when we typically dream.

Brain temperature falls during non-REM sleep and then rises during REM sleep. This pattern allows homeothermic mammals to save energy during non-REM sleep without the brain becoming so cold that it becomes unresponsive to threats.

Body temperature is regulated through a process called thermoregulation, which keeps the core temperature between 97.7 and 99.5 degrees Fahrenheit. This offers the best environment for the body to function at maximum capacity.

As bedtime approaches, the body temperature starts to drop, and this downward trend is steepest when entering non-REM sleep. The body temperature continues to fall gradually throughout the night until approaching wake-up time.

The ideal bedroom temperature for sleep is somewhere between 15.5 and 21 degrees Celsius. A good average is around 18.3 degrees Celsius.

The body temperature can be influenced by various factors, such as exercise, diet, and room temperature. Exercising a few hours before bed can help reduce the time it takes to fall asleep and increase the amount of deep sleep. Eating a large or fatty meal too close to bedtime can increase body temperature and disrupt sleep.

Additionally, the body temperature is linked to melatonin production, a key hormone that helps prepare the body for sleep. As melatonin levels rise in the evening, heat loss from the hands and feet increases.

Understanding the changes in body temperature throughout the day and night can help create optimal conditions for a good night's sleep.

The ideal bedroom temperature for sleep

The ideal bedroom temperature for a good night's sleep is a topic that has been widely studied. Our bodies work hard to keep us at the right temperature using a process called thermoregulation, and how well our body can maintain its temperature can have a big impact on our sleep quality.

During the day, our body temperature tends to fluctuate a little, and the same is true at night. However, while we sleep, our body temperature can be 1 to 2 degrees lower than during the daytime. Our body temperature starts to fall as bedtime approaches, which helps us fall and stay asleep. Our body also tends to lose heat during sleep, which is why experts advise against exercising close to bedtime.

Our core body temperature generally hovers around 98.6 degrees Fahrenheit (37 degrees Celsius) but fluctuates by about 2 degrees Fahrenheit throughout the night. The drop in temperature starts about two hours before we go to sleep, coinciding with the release of the sleep hormone melatonin. Our body temperature continues to fall during sleep, reaching a low point in the early morning, and then gradually warming up as the morning progresses.

A good goal for sleeping temperature is about 66 to 70 degrees Fahrenheit, but this can vary from person to person, and you may need to experiment to find what works best for your environment and sleeping preferences, such as bedding and sleepwear. Most doctors recommend keeping the thermostat set between 65 to 68 degrees Fahrenheit (18.3 to 20 degrees Celsius) for the most comfortable sleep.

During REM sleep, the body ceases most temperature-regulation behaviors such as sweating or shivering, making us more sensitive to ambient temperature changes. Excessively hot ambient temperatures also appear to reduce the time spent in REM sleep. On the other hand, sleeping in a cold bedroom is not considered as detrimental as sleeping in a hot bedroom, but it can still cause discomfort and may impact REM sleep and blood pressure.

If your bedroom is too hot, you can try lowering the thermostat, using a fan or air conditioning, investing in cooling bedding, or wearing lighter sleepwear. If your bedroom is too cold, you can try turning up the heat a little, layering your sleepwear and bedding, or using a heated mattress pad or blanket.

Overall, maintaining a cool bedroom temperature of around 66 to 70 degrees Fahrenheit is generally recommended for optimal sleep.

Things that can affect your body temperature and interfere with sleep

Our bodies work hard to keep us at the right temperature using a process called thermoregulation. This process keeps our core body temperature between 97.7 and 99.5 degrees Fahrenheit, which is the best environment for our bodies to function at maximum capacity.

As bedtime approaches, our body temperature starts to fall, paving the way for a good night's sleep. Our body temperature is at its lowest in the early hours of the morning, around 2-4 am, and then it starts to rise again about two hours before we wake up.

• Room temperature: A too-hot or too-cold room can impact your body's ability to regulate its core temperature while you sleep. The ideal bedroom temperature for optimal sleep is between 66 and 70 degrees Fahrenheit (18.3-21 degrees Celsius).
• Bedding and clothing: The type of bedding and clothing you use can impact how hot or cold you feel at night. It's essential to strike a balance between a cooler bedroom temperature and a warmer temperature under the covers.
• Exercise: Exercising a few hours before bed can help you sleep by increasing your core body temperature and then allowing for a natural decrease at bedtime. However, high-intensity exercise right before bed may interfere with sleep.
• Stress: Stress can impact your body in various ways, including raising your core temperature. Practicing deep breathing exercises, meditation, or calming yoga before bed can help reduce stress levels and improve sleep.
• Alcohol and drug use: Alcohol can influence your body temperature by widening your blood vessels or affecting your nervous system. Stimulant drugs and opioids can make you more sensitive to a higher room temperature while sleeping.
• Chronic illnesses: Certain health conditions, such as cardiovascular disease and depression, can disrupt your body's ability to regulate temperature, especially when both conditions are present.
• Central nervous system disorders: Disorders that affect movement, such as multiple sclerosis and Parkinson's disease, can cause issues with regulating body temperature throughout the day and night.
• Hyperthyroidism: When the thyroid gland overproduces hormones, it can affect how your body uses energy, which can impact your core temperature.
• Fever: Infections can increase your body temperature due to inflammation caused by immune cells fighting off the virus or bacteria.
• Hot flashes: This symptom of menopause can cause unexpected and erratic jumps in body temperature during the day or night.
• Meal timing and composition: Eating a large or fatty meal close to bedtime can increase your body temperature and interfere with sleep. This is because your metabolic rate increases, causing your body to burn more calories and produce more heat.

By understanding how these factors can impact your body temperature and sleep, you can make adjustments to your environment and routines to optimize your sleep quality.

How to use temperature to create the best conditions for a good night's sleep

The ideal room temperature for a good night's sleep is between 60°F and 65°F (15.6°C to 18.3°C). However, this can vary from person to person, and factors such as age and health conditions can also play a role. For example, infants and older adults may need a slightly warmer room temperature.

• Regulate the room temperature: Set your thermostat to the desired temperature before going to bed. You can also use fans or air conditioning to cool the room during warm months, or a space heater for colder months.
• Swap out bedding: Use lightweight and breathable bedding during warm months to avoid overheating. In colder months, add extra layers of blankets and warmer sleepwear to stay cosy.
• Take a warm bath: A warm bath about an hour before bedtime can help decrease your core body temperature, promoting melatonin production and sleep onset.
• Consider your bedding: Invest in high-quality, natural bedding such as cotton blends or bamboo sheets, which are naturally cooler. Cooling pillowcases, blankets, and mattresses can also help improve sleep quality.
• Exercise: Avoid exercising close to bedtime as it can increase your body temperature and interfere with sleep. However, exercising a few hours before bed can be beneficial, as it increases your core body temperature and allows for a natural sleep-inducing decrease at bedtime.
• Manage stress: Stress can impact your body temperature and sleep quality. Try deep breathing exercises, meditation, or calming yoga before bed to reduce stress levels and improve sleep.
• Scandinavian sleep method: If you and your partner have different temperature preferences, try using separate sheets and blankets. This allows each person to adjust their bedding to their preferred temperature without affecting the other.

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