Source: HARVARD HEALTH BLOG
May 13, 2020
- By: Lawrence Epstein, MD, Contributor
- By: Syed Moin Hassan, MD, Contributor
It’s no accident that most people tend to sleep at night and are awake during the day. Our sleep-wake cycle is determined by our circadian rhythm, the body’s internal clock. Like old-time clocks, this internal clock needs to be reset every day, and is adjusted by first exposure to light in the morning.
How does circadian rhythm work?
Our circadian rhythms are controlled by multiple genes and are responsible for a variety of important functions, including daily fluctuations in wakefulness, body temperature, metabolism, digestion, and hunger. Circadian rhythm also controls memory consolidation (the formation of long-term memories occurs during sleep); the timing of hormone secretion (for example, the hormones controlling body growth work mostly at night); and body healing.
While the circadian sleep phase typically occurs at night, there are a range of times during which the sleep phase can occur, with some people programmed to sleep from early evening to early morning (known as morning larks), while others stay up late and sleep late (known as night owls). In addition to determining the timing of their sleep, a person’s circadian tendency can also affect their choice of emotional coping skills, such as assertiveness or rationalization, and their predisposition to psychological disorders.