Impossible to fall asleep, soaked sheets, repeated awakenings… During heatwaves, the nights quickly become tiring. But behind this well-known fatigue lies another, more discreet problem: these too hot nights can also put a strain on the heart.
Because when temperatures rise, the body never really rests. And in certain fragile people, this accumulation of nighttime stress can have real consequences on cardiovascular health.
Why does the heat tire the body so much at night?
Normally, the body lowers its temperature slightly to help you fall asleep. But during periods of extreme heat, this mechanism is disrupted. Result: we have more difficulty falling asleep, we wake up more often and sleep becomes much less restorative.
However, throughout the night, the heart continues to work to help the body dissipate heat. “The heart must pump faster to send more blood to the skin to cool the body“, explains Dr. Gérald Kierzek, emergency physician and medical director of True Medical.
Consequence: even at rest, the heart rate can increase by 10 to 15 beats per minute. An extra effort that is repeated for several nights in a row.
Nocturnal awakenings which also weigh on the heart
These frequent awakenings are not trivial. Because deep sleep – the phase during which the heart and arteries truly recover – becomes shorter, or even almost absent during scorching nights.
According to Dr. Kierzek, this sleep fragmentation gradually increases cardiovascular stress.
“Lack of sleep and repeated awakenings promote a rise in morning blood pressure and maintain a state of stress for the heart“, he explains.
In the long term, these disturbed nights can:
- Promote hypertension;
- Increase inflammation in the body;
- Increase the risk of cardiovascular problems;
- And, in fragile people, aggravate existing heart disease.
Dehydration also plays an important role. When you sweat a lot without drinking enough, the blood becomes “thicker”, forcing the heart to exert even more effort to maintain good circulation.
The most vulnerable people during heatwave nights
Some people must be particularly vigilant during episodes of high heat at night:
- People suffering from hypertension;
- Those with heart failure or coronary artery disease;
- People who have already had a heart attack;
- Seniors, whose ability to regulate temperature is reduced;
- But also people suffering from sleep apnea, already faced with fragmented sleep.
For them, several bad nights in a row can quickly become difficult for the body.
Advice from Dr Gérald Kierzek to sleep better despite the heat
Take a lukewarm shower before sleeping
“Take a lukewarm shower before going to bed. This helps cool the body without causing thermal shock“, advises Dr. Gérald Kierzek. This drop in temperature also helps to promote sleep.
Drink regularly, even at night
Dehydration increases heart fatigue. The emergency doctor therefore recommends keeping a bottle of fresh water near the bed so that you can drink regularly during the night.
Focus on light bedding
Synthetic materials and thick blankets encourage perspiration. “Use lightweight cotton sheets and avoid fabrics that retain heat“, recommends the doctor.
Circulate the air
When temperatures drop slightly in the evening, opening opposite windows creates an effective draft. “Ventilate ideally at night or early in the morning, when the outside air is cooler“, specifies Dr. Kierzek.
Use a fan wisely
The fan can improve thermal comfort, especially if you place a bottle of iced water or a damp cloth in front of it to further cool the ambient air.
Keep the heat out
Closing the shutters and curtains during the day remains one of the most effective ways to keep things cool inside.
Eat light in the evening
Heavy meals increase body temperature and make it harder to fall asleep. During heatwaves, it is better to favor raw vegetables, fruits rich in water and cold soups.
Refresh yourself regularly
A mist, a damp cloth on the back of the neck or legs, or even running your wrists under cool water can help the body better tolerate the heat before bed.
Because during a heatwave, sleeping well is not only a question of comfort: it is also a way of protecting your body… and your heart.