This is how much longer you need to sleep in the winter

Turns out humans could use a little hibernation in the winter.

A study published Friday in the peer-reviewed journal Frontiers in Neuroscience found that, in the winter, people with sleep deficiencies experience longer REM sleep — short for rapid eye movement, it’s a stage of deep sleep associated with dreaming and memory — compared to warmer months because it’s darker longer.

Researchers from the Charite Medical University of Berlin gathered 292 patients with sleep-related deficiencies or potential disorders to undergo sleep studies at a German hospital. The sleep studies consisted of asking patients to sleep naturally without an alarm clock. Researchers then monitored the quality, duration and type of sleep they were getting. Patients who were on medications that affect shut-eye were excluded. 

Total sleep time appeared to be about an hour longer in winter than in summer, while REM sleep — linked to the circadian clock — was 30 minutes longer in winter, signaling perhaps that folks are in deeper sleep longer and more tired due to the lack of light.

“Even though we still perform unchanged, over the winter human physiology is down-regulated, with a sensation of ‘running-on-empty’ in February or March,”  Dr. Dieter Kunz, an author of the study, said in a statement.

While most people have a strict, set wake-up time due to school or work schedules, individuals could benefit from going to sleep an hour early in the colder months to combat restlessness the next day, the authors suggest.

What’s more, the findings suggest that sleep changes with the seasons “may be even greater if generalized to a healthy population” outside of just those with sleep difficulties analyzed in the study.

“In general, societies need to adjust sleep habits including length and timing to season, or adjust school and working schedules to seasonal sleep needs.”