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New research suggests we may need more sleep during the colder months. Whether we are early risers or night owls, our biological clocks are set by the sun. This is why we would need to adapt our habits, in particular our working hours, according to the season.
A team of researchers from the Clinic for Sleep and Chronomedicine at St Hedwig’s Hospital in Germany suggests that even in an urban population with disrupted sleep, humans experience longer REM sleep in winter than in summer and a less deep sleep in autumn.
Longer REM sleep in winter
The results, published in the journal Frontiers in Neuroscience, show that seasonality is related to sleep quality in humans. “REM sleep” is the period of very deep sleep during which we perform rapid eye movements (called REM). This is also the period when most dreams occur.
To carry out this study, the researchers studied 188 patients who have difficulty sleeping, but who do not use sleeping pills. The latter slept naturally in a special laboratory, without waking up. Their sleep quality and duration were monitored throughout a year.
Although total sleep time appeared to be about an hour longer in winter than in summer, this result was not statistically significant. However, REM sleep was 30 minutes longer in winter than in summer. REM sleep is known to be directly related to the circadian clock, which is affected by changes in light.
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Adjust your sleep according to the seasons
“Seasonality is omnipresent in every living thing on this planet. Even though our performance remains unchanged during the winter, human physiology is down-regulated, with a feeling of ‘dry running’ in February or March“, explains Dr Dieter Kunz, author of the study, to the Guardian who relayed the study.
Although the team recognized that these results should be validated with a population without sleep disorders, seasonal changes could be even greater in a healthy population. “Societies should adjust sleep patterns, including length and timing of the season, or adjust school and work schedules to seasonal sleep needs“, concludes Dr. Kunz.