Two in three adults in the UK struggled to sleep during recent high temperatures, according to polling by YouGov, as the country endures its fifth heatwave.
A separate study by One Poll revealed that 48 per cent of UK adults regularly lose sleep because they become too hot at night. Among the 2,135 people surveyed by YouGov during June, almost half reported losing at least three hours of rest each night as elevated temperatures disrupted normal sleep patterns.
Dr Maja Schaedel, a clinical psychologist and director of the Good Sleep Clinic in Kent, explained that elevated bedroom temperatures prevent the human body from initiating its natural rest process. Schaedel stated that when the body is too warm, it struggles to lower its core temperature, which is an essential requirement for falling and staying asleep. She noted that the ideal bedroom temperature is typically between 16C and 18C.
Schaedel added that when weather conditions are hot, the body must work harder to cool down. This extra strain leads to a faster heart rate to pump oxygenated blood and causes quicker breathing. According to Schaedel, these physical responses mimic symptoms of alertness, making it difficult for the brain to recognise that the body is safe to return to sleep.
Hormonal fluctuations make women particularly vulnerable to heat-related sleep loss, according to Russell Foster, a professor of circadian neuroscience at the University of Oxford. Speaking to the Daily Mail, Foster explained that body temperature increases prior to ovulation. He added that menopausal women experience hot flushes from fluctuating hormones, which create an additional rise in core temperature.
Foster noted that high nighttime temperatures prevent people from securing restorative deep wave sleep, even if they succeed in falling asleep. Furthermore, the physiological cooling mechanisms require energy that generates internal heat, leaving individuals exhausted the following day regardless of how long they slept.
Guy Leschziner, a consultant neurologist and professor of neurology and sleep medicine based in London, noted that heat fatigue may share neural pathways with illness. Leschziner stated that brain cells that induce fatigue during sickness might follow the same route during hot weather. Foster warned that short-term sleep deprivation impairs cognitive and emotional responses, suggesting people avoid making serious decisions, while elevated levels of the stress hormone cortisol suppress the immune system.
Home cooling and ventilation
Many residential properties in the UK are not constructed to manage severe heat. A study conducted last year by Loughborough University found that one in five homes was ill-equipped for hot weather due to inadequate shading and poor ventilation. Chris Sansom, a professor of solar power at the University of Derby, told the Daily Mail that residents should keep windows closed during daylight hours with curtains or blinds drawn to trap cooler indoor air, or position a fan facing an open window to push warm air outside.
Foster advised waiting until the outdoor temperature drops below 20C, or 68F, in the evening before opening front and back doors or windows to create an airflow through the property. To prepare for bed, Leschziner recommended taking a tepid bath or shower. He explained that warmth causes blood vessels near the skin surface to dilate, increasing blood flow so the body releases heat more efficiently. Conversely, cold showers cause blood vessels to constrict, temporarily reducing skin heat loss.
Dr Hana Patel, a general practitioner at online retailer Time4Sleep, recommended placing bedsheets inside a plastic bag in the freezer for about half an hour before bedtime to cool the bed without freezing the fabric. Lindsay Browning, a neuroscientist at the Trouble Sleeping clinic in Berkshire, suggested using a hot water bottle filled with crushed ice and cold water, or spraying skin with a misting bottle. Sleep consultant Ilona Andrews, founder of organic babywear company Sleeping Stars, suggested using the Scandinavian sleep method where partners use separate lightweight sheets or duvets to avoid trapping body heat in a single pocket.
Nighttime awakenings
Sleep fragmentation increases during hot spells, making early awakenings more likely, according to Browning. Schaedel stated that when she wakes up feeling hot at night, she wipes a flannel soaked in warm water across her skin. She explained that warm water brings heat to the surface of the skin, where it evaporates quickly to rapidly cool the body.
Schaedel advised against staying in bed to toss and turn when awake. Instead, she recommended reading a book, walking on cool tiles, or moving downstairs where air is cooler because heat travels upwards, returning to bed only when feeling sleepy. General practitioner Dr Roger Henderson warned that staying in bed requires keeping the room dark, suggesting an eye mask to block early daylight. Henderson also urged people not to scroll on mobile phones, as bright light and visual stimulation make returning to sleep much harder.
Managing daytime fatigue
For individuals suffering from heatwave sleep disruption, catching up on sleep can help combat daytime tiredness. Leschziner noted that while maintaining a fixed sleep routine is normally advised, lying in bed longer in the morning or at weekends is reasonable for a few days during extreme weather. However, Leschziner warned that excessive napping disrupts the body clock, recommending that naps be kept to 20 to 30 minutes during the natural circadian dip in the early afternoon after lunch.
Foster recommended placing ice cubes in front of an electric fan to generate cooler air during the day. Foster revealed that he purchased a small ice machine to ensure a continuous supply of ice cubes for this purpose.
Preventing fan cough
Sleeping with an electric fan blowing directly at the face can lead to a condition known as fan cough, according to Dr Edward Nash, a consultant respiratory physician at George Eliot Hospital in Warwickshire. Nash explained that direct airflow dries out the mucous membranes lining the nose, mouth, and throat. In response, the body produces extra mucus that drains down the throat, leading to irritation and coughing.
Dr Anindo Banerjee, a consultant respiratory surgeon at Southampton General Hospital, added that uncleaned fan blades blow accumulated dust directly into sensitive airways. Banerjee advised dusting fan blades weekly, placing a bowl of cool water underneath or in front of the fan to add humidification, and directing the fan towards the body rather than the face to safely cool the skin.
