Elevated air temperatures in the bedroom can significantly impair the quality of nighttime rest, increase the duration of wakefulness, and reduce the amount of deep sleep. When the room temperature rises from 25 to 30 degrees Celsius, sleep efficiency in older adults decreases by 5–10%, according to the results of a scientific study published in the journal *Science of The Total Environment*.
Scientists studied the effect of bedroom temperature on the duration, quality, and restlessness of sleep among older adults living in their own homes. The study involved 50 participants with an average age of about 79 years. Observations continued for 18 months. The researchers used wearable sleep monitors and environmental sensors that recorded air temperature and humidity.
The results showed that participants experienced the most restful and uninterrupted sleep at air temperatures between 20 and 25 degrees. When the temperature rose to 30 degrees, sleep efficiency decreased by 5–10%.
However, the researchers found significant individual differences, so the temperature values obtained cannot be considered a universal standard for people of all ages.
An additional experimental study, published in the journal *Building and Environment*, also demonstrated the negative impact of high temperatures on the sleep of older adults.
During the experiment, raising the bedroom temperature from 27 to 30 degrees resulted in a 26.3-minute reduction in total sleep duration. Sleep efficiency decreased by 5.5%, the duration of rapid eye movement (REM) sleep decreased by 5.3 minutes, and nighttime wakefulness increased by 27 minutes.
The researchers also found that improved ventilation led to an increase in deep sleep duration by 10.3 minutes and in REM sleep duration by 3.7 minutes.
Experts attribute the effect of temperature to the body’s thermoregulatory mechanisms. Before falling asleep, the body’s core temperature naturally begins to drop. To achieve this, the body redistributes heat to the skin’s surface and releases it into the environment.
If the air temperature is too high, the cooling process is hindered. This can delay the onset of sleep, disrupt the alternation of sleep stages, and increase the number of nighttime awakenings.
According to the scientific review “Thermoregulation in Sleep Disorders,” published on April 12, 2026, in the *Journal of Clinical Medicine*, disruption of the natural drop in body temperature is associated with sleep fragmentation and the onset of daytime symptoms, including fatigue and reduced alertness.
Poor-quality sleep can negatively affect concentration, memory, emotional stability, and performance the following day. However, the severity of these consequences depends on the duration and severity of the sleep disturbance, the person’s age, and other factors.
A separate problem during the heating season is the decrease in indoor relative humidity.
Heating cold outdoor air without additional humidification leads to a decrease in its relative humidity. Dry air can cause discomfort in the nose and throat, as well as dryness of the mucous membranes and skin. For some people, this can exacerbate nasal congestion and further interfere with restful sleep.
The U.S. Environmental Protection Agency (EPA) recommends monitoring indoor humidity and preventing it from rising above 50% when using household humidifiers. Excessive humidity can promote the growth of mold and other biological contaminants.
According to the Sleep Foundation, for many adults, a comfortable bedroom temperature falls within the range of approximately 16–20 degrees Celsius. However, choosing the optimal setting depends on individual characteristics, age, sleepwear, and the type of blankets used.
In particular, research findings on older adults suggest that in some cases, higher temperatures—around 20–25 degrees—may be most beneficial.
To improve sleep conditions, experts recommend avoiding overheating the bedroom, regularly ventilating the room, using season-appropriate bedding, and controlling humidity levels.
