Studies in which people self-rated their sleep duration have shown an increase in sleep duration in the winter. In the new study, researchers used more objective data: the duration and quality of sleep was measured using polysomnography.
Scientists analyzed data from 188 patients who underwent polysomnography at St. Hedwig’s Hospital because of sleep problems. They found that insomnia was diagnosed more often towards the end of the year.
Despite the fact that the patients were in an urban environment with low levels of natural light and high levels of light pollution, their sleep had pronounced seasonal patterns. Total sleep time did not change in winter, but people spent more time in REM sleep: 30 minutes more than in summer. It is known that REM sleep is directly related to circadian rhythms, which are affected by changes in lighting.
The scientists believe their results will need to be confirmed in healthy people with no sleep problems. They suggest that seasonal changes may be even more pronounced in healthy populations.