Changes in daylight can affect the length and timing of sleep. Understanding the biological mechanisms that impact sleep during season and time changes can help ease transitions and improve sleep.
Despite the body’s consistent need for sufficient, restful sleep, the world around us is continually changing. Whether it be through changes in the total amount of natural daylight each season or an artificial jump in time due to daylight savings or travel, both the brain and body react to changes in the amount and timing of light each day, which can greatly affect when and how long a person sleeps.
Even in industrialized societies where artificial light is abundant, seasonal changes in the duration of natural daylight affects the body’s 24-hour circadian rhythms that regulate the sleep-wake cycle. A recent study measuring sleep in adults observed several seasonal changes in sleep that correlate to differences in the average amount of daylight.
These observations include:
“The tendency for seasonal fluctuations in sleep time is more pronounced in younger children.”
The tendency to increase sleep time in the winter, when the daylight hours are decreased compared to spring and summer, is more pronounced in younger children, the elderly, preindustrial societies and environments that lack artificial light. Additionally, seasonal changes in the sleep-wake cycle are more commonly observed in people that live in more northern versus southern U.S. latitudes, presumably because seasonal changes in natural daylight are more pronounced at higher latitudes.
One way that increased daylight hours may decrease sleep is by inhibiting the release of melatonin, a sleep-promoting hormone, in the brain. Melatonin is produced and released at higher levels when it is dark, and it is thought that both natural and artificial light can interfere with melatonin secretion at night, which may make falling asleep difficult. Melatonin is often used as a supplement to help induce sleep and is also used therapeutically for circadian rhythm disorders in the blind.
“Both natural and artificial light can interfere with melatonin secretion at night, which may make falling asleep difficult.”
There are several sleep hygiene and other measures that can improve sleep timing and duration as seasons change, at daylight savings time and with artificial light exposure, including:
Changes in the duration and quality of sleep are not always considered with the natural progression of seasons. Research not only supports this phenomenon, but also suggests that changes in melatonin secretion may be to blame. Fortunately, there are simple ways to adjust to changes in daylight and improve sleep naturally since adequate, restful sleep is required year-round.
“How to sleep well despite changes in your schedule” (2022) by Johns Hopkins Medicine. Johns Hopkins Health System.
“Melatonin” (2021) by Mayo Clinic Staff. Mayo Clinic.
“The effects of seasons and weather on sleep patterns measured through longitudinal multimodal sensing” (2021) by Stephen M. Mattingly et al. npj Digital Medicine.
“This is why the changing season could be affecting your sleep” (2022) by Imy Brighty-Potts. The Independent.
“Why is my sleep so messed up in the summer?” (2022) by Rachel Rabkin Peachman. The New York Times.