“Probably one of the most precious achievements in human evolution is the almost invisibility of the weather at the behavioral level,” said Dr. Dieter Kunz, corresponding author of the study based at the Clinic of Sleep and Chronomedicine at St. Hedwig’s Hospital. Berlin. “In our study we show that the architecture of human sleep varies significantly by season in adult populations living in urban environments.”
A team of scientists led by Ms. Eileen Seidler recruited 292 patients who were treated in Dr. Kunz’s working group at the University of Charitable Medicine in Berlin.
At St. Hedwig’s Hospital. These studies are routinely performed on patients who experience sleep-related difficulties, using a specialized laboratory where patients are asked to fall asleep naturally without an alarm clock, and sleep quality and Along with the type as well as the duration of sleep can also be monitored. Although sleep disorders could potentially affect the results, this takes a large study group spread evenly throughout the year, allowing the investigation of month-to-month differences.
The team excluded patients who were taking drugs affecting sleep, had technical failures during polysomnography, and had REM sleep latency longer than 120 minutes, which suggested that the first REM sleep episode had been omitted. Once these exclusions were made, 188 patients remained. Most of their diagnoses showed no seasonal pattern, but insomnia was typically diagnosed toward the end of the year.
winter sees more REM sleep
Even though the patients were based in an urban environment with low natural light exposure and high light pollution, which affect any season controlled by light, the scientists found subtle but surprising changes across all seasons. Although total sleep time seemed to be approximately one 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 thought to be directly linked to the circadian clock, which is affected by changing light. Although the team acknowledged that these results would need to be validated in a population that does not experience sleep difficulties, the seasonal changes may be even greater in healthy populations.
“This study needs to be repeated in a larger group of healthy subjects,” cautioned Kunz.
Although most people’s waking hours are currently largely out of their control, due to school or work schedules, society could benefit from habitats that would allow humans to respond more effectively to the changing seasons . Meanwhile, going to bed earlier in winter may help humans adjust to the season.
“Weathering is ubiquitous in any living creature on this planet,” Kunz said. “Even though we still perform unchanged, human physiology in winter is down-regulated with a sensation of ‘running-on-empty’ in February or March. In general, societies adjust sleep habits to length and season.” need to be accommodated, or adjust school and work schedules to seasonal sleep needs.”
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