Professor Masashi Yanagisawa of the University of Tsukuba recommends keeping the head cool and feet bare to improve sleep quality during summer [1].
These guidelines address a widespread seasonal issue, as research indicates that 69% of people struggle with sleep during the summer, compared to 47% in the spring [4, 5].
Yanagisawa, a sleep scholar, said that the soles of the feet act as a radiator for the body. By keeping feet bare, the body can more effectively release heat to regulate internal temperature [1]. He said, "The soles of the feet are a radiator, in other words, a heat dissipator."
To optimize the sleeping environment, Yanagisawa said to keep the head relatively cool while avoiding socks or footwear that might trap heat [1]. He also said to wear pajamas with high breathability to assist in thermoregulation throughout the night [1].
Beyond temperature control, the timing of nutrition plays a role in sleep hygiene. Yanagisawa said it is important to finish eating two to three hours before going to bed [1].
The professor also said that sleep requirements vary significantly by age. For adults in their 20s, the necessary sleep duration is slightly over eight hours [1]. In contrast, adults in their 70s typically require slightly over six hours [1]. On average, the recommended sleep duration for most adults is around seven hours [1].
Yanagisawa's guidance focuses on the physiological need for heat dissipation to trigger the onset of deep sleep [1].
“"The soles of the feet are a radiator, in other words, a heat dissipator."”
These recommendations emphasize the biological link between core body temperature reduction and the ability to fall asleep. By utilizing the feet as heat exchangers and managing digestive timing, individuals can mitigate the disruptive effects of summer heat on the circadian rhythm.
