During summer, we are exposed daily to air conditioning for long hours. Many wonder whether exposure to air conditioning and sleeping in air-conditioned rooms leads to morning lethargy or changes in the body’s circadian rhythm or biological clock. Japanese researchers tested this hypothesis in a scientific study published in the journal Physiological Anthropology, where cortisol hormone levels were repeatedly measured throughout the day in two groups of volunteers: one exposed to air conditioning for short periods during summer, and the other for long periods.

It is known that measuring cortisol is one of the best indicators of the body’s biological clock. Normally, cortisol increases early in the morning, causing increased activity and vitality, decreases at night, and reaches its lowest levels during sleep. The study showed that those exposed to air conditioning for long hours had lower cortisol levels early in the morning, and the rise in hormone levels was delayed compared to those with less exposure. This supports the theory that artificial air conditioning may cause lethargy.

We understand that the summer heat is unbearable and air conditioning is necessary, but readers should take precautions by trying to get enough hours of sleep.