Why is nighttime heat endangering our health?

High temperatures do not let up even after sunset. More and more often, especially in cities, the thermometer remains above 20 degrees all night and sometimes does not even drop below 25.

This is the "urban heat island" effect, where asphalt, concrete, buildings and road surfaces accumulate energy during the day and slowly release it after the sun has set, preventing the air from cooling.

But the problem isn't just discomfort. To recover from the day's fatigue and promote sleep, our bodies need to cool down.

When this doesn't happen, sleep becomes more fragmented, the heart works harder, the risk of dehydration increases, and digestion can become more difficult. The consequences are especially significant for the elderly, children, pregnant women, and people with chronic illnesses.

What happens to the body during a night of extreme heat?

And what are the best strategies, recommended by experts, to protect yourself? Below are some explanations:

Why does the body need cool nights?

During sleep, the body does not just rest: it lowers its internal temperature, slows down the work of the cardiovascular system, and activates repair and recovery processes. If the external temperature remains high, especially for several nights in a row, these mechanisms become less efficient. Therefore, heat waves are especially dangerous when even the minimum night temperatures remain high.

What to do: Keep the room as cool as possible; close windows and shutters during the day, ventilate only when it is cooler outside and, if you have one, use air conditioning at 24–26°C, avoiding large temperature changes.

Why do we sleep worse in the heat?

To fall asleep, the brain must lower its body temperature by about one degree. When the environment is hot or humid, the body works continuously to cool itself by sweating and dilating blood vessels. This delays falling asleep, increases awakenings during the night, and reduces the deep sleep phase. The result is fatigue, irritability, and difficulty concentrating the next day.

What to do: Take a lukewarm shower before bed, wear natural fiber sheets and pajamas, avoid physical activity in the evening and avoid alcohol; limit caffeine and heavy meals before bed.

What happens to the heart and blood pressure during a hot night?

To remove heat, blood vessels dilate and the heart pumps more blood to the skin, even during sleep. During the night we lose water through breathing and sweating. If we do not rehydrate properly, dehydration, low blood pressure, weakness and dizziness may occur. In the morning you may feel thirsty, headache, cramps, etc. In people with cardiovascular disease, this additional load increases the risk of complications. In the elderly, the problem is even greater, as the sensation of thirst decreases with age.

What to do: Drink water regularly throughout the day, consume fruits and vegetables, avoid alcohol in the evening, and do not change medical therapies on your own; people taking diuretics or blood pressure medications should follow their doctor's instructions.

Does heat also affect digestion?

Yes, although the evidence is more limited. A heavy, high-fat dinner increases heat production during digestion, adding to discomfort at night. Dehydration can also affect bowel movements.

What to do: Light dinner with grains, vegetables, fish or white meat; avoid fried and fatty foods, as well as alcohol. Eat 2–3 hours before bedtime.

Who is most at risk and when should help be sought?

Those most at risk are the elderly, young children, pregnant women, and people with heart, respiratory, kidney, or diabetes diseases. They have less ability to regulate body temperature and fluids.

When to seek help: If mental confusion, high fever, difficulty breathing, fainting, severe weakness or changes in consciousness occur, a doctor or the emergency number 112 should be contacted immediately.

During heat waves, it is also important to check on seniors who live alone daily.