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Daylight Saving Time (DST) marks the time to “spring” ahead one hour for most of the United States. Where it is observed, Daylight Saving Time begins this year on Sunday, March 13, 2022. This transition from Standard Time was first enacted to conserve energy and shift the timing of our activities to match more daylight during evening hours. The days grow longer and the nights get shorter as we head towards the summer solstice, which has been described as the longest day of the year. The extra sunshine and boost of Vitamin D may be a relief from the dark winter days and a sign of warmer weather ahead. The extra daylight hours may allow for more fun in the sun, but we may want to consider how these changes in light and time can influence our circadian system and disrupt our sleep.
How does the circadian system detect the light/dark cycles?
The circadian system is a complex coordination of biological rhythms which help our body function. Derived from the Latin terms “circa” meaning “around” and “diem” meaning “day,” the human circadian system cycles a little longer than 24-hours and is influenced by external environmental cues. The strongest cue is light exposure, such as sunrise and sunset, which keeps the circadian system regulated within our 24-hour day. Light entering the eyes is detected by the master circadian clock in the brain, which coordinates many bodily functions, including the functions that prepare the body for sleep and wake. For example, the hormone melatonin is released by the pineal gland at night and has been associated with control of the sleep–wake cycle. The detection of light brightness and wavelength allows the master clock to distinguish between the appropriate times for wakefulness and sleep (1). This is how morning light exposure can help us wake up in preparation for the day. Conversely, darkness signals it is time to sleep and is why we can feel sleepy when in a darker environment. These external cues can be powerful, in that light exposure at different times of the day can shift the circadian system timing and alter sleep patterns (1). While this is helpful for feeling awake during daylight hours, falling asleep can be more of a challenge when the...