Combating Disrupted Sleep From Increasing Heat Explored in New Study

Sleep quality, including sleep disruptions, has been shown to be affected by a rise in ambient temperature, which in turn could have effects on general health, including mortality. A review published in Journal of Sleep Research compiled ways to mitigate adverse effects from heat to increase sleep quality.

According to the review, melatonin release coincides with the downregulation of core body temperature in the evening, thereby linking temperature regulation and sleep. Interfering with this process could disturb initiation and maintenance of sleep. Further, higher temperatures could lead to increased wakefulness and decreases in slow-wave sleep SWS and rapid eye movement (REM) sleep.

In an experimental study that saw higher ambient temperatures (35°C vs 29°C [95°F vs 84°F]) suppressing the normal decrease of body temperature at sleep onset, heat exposure was found to disrupt sleep, increase wakefulness, and decreased duration of Stage 3 and REM sleep. A second study suggested these effects can occur if a patient has not had an opportunity for gradual acclimatization to the temperature rises.

Older adults are particularly vulnerable to overheating at night, as studies have shown that higher temperatures lead to lower sleep quality and higher levels of physiological stress in this patient group.

The review gave the following advice to maintain sleep during heatwaves:

• Keep the bedroom temperature as close to 19°C (66°F) as possible
• If high ambient temperatures are present in the bedroom, a cool or lukewarm shower can help induce sleep and reduce stress
• Ventilators and electric fans can help to cool bedrooms
• Heat-induced awakenings during sleep can be shortened by cooling the body with water spray or mist
• Stay hydrated
• Try to keep the house and bedroom as cool and dark as possible
• Limit clothing and choose cotton clothing over other materials
• Take short naps of approximately 20 minutes and try to keep sleep-wake rhythm as regular as possible
• Avoid sleeping anywhere but your bed

Children’s sleep can also be affected by heatwaves. Alterations to thermal stability can lead to respiration instability in infants, and changes in circadian rhythm and shorter sleep duration during the summer months is associated with changes in body mass index and risk of obesity in children.

Children can learn to mitigate the effects of heatwaves on sleep by doing the following:

• Getting the correct amount of sleep each night
• Setting an age-dependent latest time to be in bed
• Staying hydrated
• Engaging in outdoor activities
• Naps can be useful and longer for children but shouldn’t be taken after 2:30 pm
• Participating in pleasing and calming activities, such as reading a book or listening to music, in the hour before bed

Lastly, heatwaves and climate changes can have a negative effect on women’s health, namely sexual maturation, fertility, pregnancy and neonatal outcomes, lactation, and menopause. Recent studies have found that exposure to heatwaves during pregnancy could be associated with health risks; therefore, during pregnancy and peripartum, attention should be given to women who seek sleep during heatwaves.

The researchers for this review suggest that more focus be placed on investigating and addressing how heat can affect the vulnerable patient groups mentioned in this review. They also suggest sleep researchers collaborate to understand the true effects of this phenomenon, as literature and studies on the topic are still scarce.

Reference

Altena E, Baglioni C, Sanz-Arigita E, Cajochen C, Riemann D. How to deal with sleep problems during heatwaves: practical recommendations from the European Insomnia Network. J Sleep Res. Published online September 8, 2022. doi:10.1111/jsr.13704