Chilly Morning Wake-Up Calls: Why You Feel Cold After Sleep

Feeling cold when you wake up is a common problem that most people have experienced at some point. Our core body temperature follows a circadian cycle, dropping to a minimum about halfway through our sleep cycle. This drop in temperature signals to our brain that we are ready to sleep. By the time we wake up, our bodies have warmed up slightly, but often not to our typical body temperature. This variation in body temperature may be why some people struggle to wake up and feel alert in the morning. There are many reasons why you might feel cold when you wake up, from external factors like the temperature of your bedroom to internal factors like your body weight or hydration levels.

Core body temperature drops during sleep

Our core body temperature follows a circadian rhythm, which means that it rises and falls across a 24-hour cycle. Typically, our body temperature is at its lowest in the early hours of the morning, around 2–4 am. This is usually halfway through our sleep cycle.

The drop in core body temperature is a signal for our bodies to prepare for sleep. This is common across all mammals, from mice to humans. As bedtime approaches, our body temperature starts to fall, which is linked to a reduction in the time it takes to fall asleep. This is because our bodies lose heat, which helps us fall and stay asleep.

The circadian decline of core body temperature triggers the initiation of human sleep, with core body temperature continuing to decrease during sleep. This is known as the trough of the circadian rhythm. The body's metabolism also decreases during sleep, which is thought to be regulated by our circadian rhythm.

The optimum temperature for a comfortable night's sleep is between 16–20°C. Both dehydration and low blood sugar levels can cause an individual to feel colder, as the body does not have enough energy to produce and retain heat.

Poor sleep hygiene and sleep deprivation

Poor sleep hygiene refers to bad sleep-related habits, which can lead to sleep deprivation. Sleep deprivation can happen for many reasons, and it is virtually impossible to prevent it entirely. However, there are strategies to reduce the risk of developing sleep deprivation and improve sleep quality.

Firstly, maintaining a consistent sleep schedule is crucial. Going to bed and waking up at the same time each day, even on weekends, helps regulate your body's circadian rhythm. Secondly, limit exposure to bright lights and electronics before bedtime, as the light from these devices can disrupt your body's natural sleep-wake functions. Creating a relaxing bedtime routine and avoiding stimulating activities can help prepare your mind and body for sleep.

Making lifestyle choices such as avoiding alcohol and heavy meals close to bedtime can also improve sleep quality. Alcohol may initially make you feel sleepy, but it can disrupt your sleep later in the night. Instead, opt for a light snack if you feel hungry. Incorporating physical activity during the day can also improve your sleep. Even a gentle walk can enhance the quality of your sleep.

It is important to address sleep deprivation as it can have real and negative consequences on your health. Sleep deprivation can lead to weight gain, mood swings, dark under-eye circles, impaired coordination, higher stress levels, lower body temperature, and a weakened immune system. It can also negatively impact your mental abilities, creativity, and decision-making processes.

If you are struggling with sleep deprivation, consider seeking professional help. A healthcare provider or sleep specialist can help diagnose and treat any underlying sleep disorders or conditions that may be contributing to your sleep deprivation. They can provide guidance and support to improve your sleep hygiene and sleep quality.

Dehydration, low blood sugar and poor circulation

Dehydration can impact the sleep-wake cycle and overall sleep duration. The body of the average adult is more than 50% water, and water plays an important role in many body functions, including sleep. Dehydration can cause a drop in blood volume, leading to a decrease in blood pressure and oxygen levels in the body. This can result in a constriction of blood vessels as the body tries to conserve water.

To prevent dehydration, it is important to drink plenty of fluids, especially in hot or humid weather, and eat foods with high water content, such as fruits and vegetables. Caffeine and alcohol should be consumed in moderation and not right before bedtime, as they are diuretics and can cause frequent urination, disrupting sleep. Additionally, certain conditions, such as vomiting, diarrhea, excessive sweating, and increased urination, can lead to dehydration.

Low blood sugar, or hypoglycemia, can also occur during sleep, known as nocturnal hypoglycemia. This condition is more common in people with diabetes, but it can also affect those without diabetes due to factors like excessive alcohol consumption or critical illnesses. Symptoms of nocturnal hypoglycemia may include restless sleep, sweating, crying out during sleep, nightmares, and feeling disoriented or confused upon waking up.

To manage low blood sugar, it is crucial to consult a healthcare provider, especially if you don't have diabetes, as the underlying cause may be serious. For those with diabetes, it is important to manage blood sugar levels through a balanced diet, exercise, and medication, if necessary.

Poor circulation, often associated with health conditions like diabetes and heart issues, can also contribute to feeling cold. When blood flow to the limbs is reduced, it can result in a cold sensation, particularly in the hands and feet. Treatment for poor circulation typically involves addressing the underlying cause, and compression stockings may also be beneficial. Additionally, vitamin B12 deficiency can impact circulation, and this can be addressed through dietary changes or supplements.

Lack of body fat and low body weight

Adipose tissue is a type of connective tissue composed of adipocytes

Stress, anxiety and underlying health conditions

There are several reasons why you might wake up feeling cold, and stress, anxiety, and underlying health conditions can play a role in this.

Stress and anxiety can impact your sleep quality and duration, which in turn can affect your body's ability to regulate temperature. When you're stressed or anxious, your body may produce higher levels of cortisol

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