Waking up feeling cold, even when nestled under blankets, is a common experience. This sensation can be perplexing, especially when the surrounding environment does not seem overtly chilly. Various factors, both external and internal, contribute to this nocturnal temperature dip, leading to a chilly awakening.
Environmental Factors
The bedroom environment directly influences body temperature regulation during sleep. A room temperature that is too low can significantly contribute to feeling cold upon waking; experts recommend 60 to 67 degrees Fahrenheit (15.6 to 19.4 degrees Celsius) for optimal sleep, as this range supports the body’s natural cooling process. Inadequate bedding, such as sheets or blankets not warm enough for the ambient temperature, can also lead to a chilly sensation; materials like cotton are breathable but may not provide sufficient insulation in cooler settings. Drafts from windows or doors can introduce cold air currents, creating localized cold spots. The use of air conditioning or fans, while beneficial for cooling a room, can inadvertently lower the temperature too much or create excessive air movement, causing the body to feel colder during the night.
The Body’s Natural Temperature Cycle
The human body undergoes a natural temperature fluctuation throughout a 24-hour cycle, known as the circadian rhythm. As bedtime approaches, the core body temperature begins to gradually decrease, signaling sleep preparation. This temperature dip continues through the night, typically reaching its lowest point in the early morning hours, often one to two hours before waking.
During non-rapid eye movement (NREM) sleep, the body’s temperature continues to fall; this reduction in core temperature is part of the sleep initiation process and helps facilitate restorative sleep. The body’s metabolic rate also slows, generating less internal heat. While thermoregulation is generally well-maintained during NREM sleep, it becomes less efficient during rapid eye movement (REM) sleep, making individuals more susceptible to external temperature changes and potentially leading to a cold sensation upon waking.
Underlying Health Considerations
Certain medical conditions can affect the body’s ability to maintain a stable temperature, leading to feelings of coldness. Hypothyroidism, an underactive thyroid gland, can cause a person to feel colder than usual due to a slowed metabolism; the thyroid gland produces hormones that regulate metabolism and energy use, and insufficient levels can reduce the body’s capacity to generate heat. Anemia, characterized by a low red blood cell count, can also contribute to cold sensations, as red blood cells are responsible for transporting oxygen throughout the body, and a reduced count leads to less efficient oxygen delivery. Poor circulation limits blood flow to the extremities, often resulting in cold hands and feet. Additionally, some medications can influence body temperature regulation as a side effect, and early signs of infection might also manifest as chills upon waking.
Lifestyle and Behavioral Influences
Daily habits and choices can impact body temperature regulation during sleep. Inadequate calorie intake or restrictive eating habits can reduce energy production, leading to a lower basal metabolic rate and a tendency to feel cold. Insufficient hydration can also impair temperature regulation, as water plays a role in heat dissipation through perspiration and respiration, and dehydration can hinder this process. The timing of exercise before bed can also influence body temperature; while exercise initially elevates body temperature, a subsequent drop can occur as the body cools down, potentially leading to feeling cold later in the sleep cycle. Alcohol consumption affects body temperature, initially causing warmth due to vasodilation but ultimately leading to a decrease in core body temperature as the body processes it, while sleepwear choice also affects warmth, with thicker materials like flannel providing more insulation than breathable fabrics like cotton.