Human Sleep in Winter: Biometrics, Adaptations, and Cultural Narratives Sleep during winter represents a complex phenomenon at the intersection of physiology, ecology, and cultural studies. Its changes are caused both by objective biological reactions to environmental seasonal changes and by socio-cultural factors shaping a unique "winter" perception of rest and dreams. This period is a natural experiment demonstrating the subtle tuning of the human body to the rhythms of nature. 1. Physiological Basis: The Influence of Photoperiod and Temperature. The key external factor regulating sleep during winter is the shortening of the day length (photoperiod). The retina of the eye detects the decrease in intensity and duration of sunlight, which is transmitted to the suprachiasmatic nucleus of the hypothalamus — the main "biological clock" of the body. Melatonin production: In response to early twilight and late sunrise, the pineal gland (epiphysis) begins to secrete the hormone melatonin ("the hormone of night and sleep") earlier and in greater amounts. This leads to increased evening sleepiness, a desire to go to bed earlier, and potentially to a longer night's sleep. Studies show that in populations living in high latitudes without artificial lighting, the duration of winter sleep may increase by 1-2 hours. Temperature regime: The decrease in ambient temperature also affects the architecture of sleep. Natural lowering of body temperature is necessary for falling asleep. In a cold, but well-ventilated bedroom (at an ideal temperature of about 18-19°C), this process is easier. However, extreme cold can, on the contrary, disrupt sleep, forcing the body to spend energy on thermoregulation. Sleep quality and structure of cycles: Some studies indicate a possible increase in the proportion of slow sleep (deep sleep) during winter, which is related to its restorative function and role in thermogenesis. The REM sleep phase, associated with emotional regulation and dreams, may al ... Read more