Scientists have found out why you need to go to bed earlier in winter

(ORDO NEWS) — A new study has shown that adjusting your sleep patterns to reflect the changing seasons is essential, at least for people with insomnia.

How artificial light sources – street lamps, spotlights, lamps in the house, light bulbs on electrical appliances – affect human sleep has been the subject of quite a lot of recent scientific work.

However, we don’t know much about the long-term effects caused by the seasons.

Scientists from the Berlin Institute of Health, the University Hospital Charité – Universitätsmedizin Berlin and St. Hedwig’s Hospital (Germany) decided to fill this gap.

The aim of their retrospective study was to study the seasonal fluctuations in sleep rates in patients living in a large city.

“Light affects the structure of sleep (it consists of two phases – REM (REM) and non-REM sleep.

The effect of duration of periods of darkness and melatonin secretion in healthy individuals has been demonstrated in vitro.

Participants in one previous study slept 3.3 hours longer with a 10-hour photoperiod (length of daylight) than with a 16-hour photoperiod.

Thus, the most important factor in the change in sleep duration may be the natural change in light during the year.

The light entering the retina serves as the main time signal for the biological clock,” the authors of the work said.

However, although biological processes and experimental results suggest seasonal changes in how long a person sleeps throughout the year, scientists tried to challenge these findings in the 1990s.

The new study was carried out in a laboratory at St. Hedwig’s Hospital in Berlin for one year.

It involved 188 patients: 98 women and 90 men aged 17 to 81 with neuropsychiatric sleep disorders, who were examined in different months in groups of no more than 20 people.

The subjects did not take drugs that could disrupt nighttime sleep (antidepressants, dopamine receptor agonists, antipsychotics, stimulants, and so on).

Each person underwent polysomnography during sleep for three nights: alarm clocks were prohibited, but some patients insisted that they should be woken up anyway – for this, the latest possible awakening time was determined.

The windows of the laboratory faced east or west and could be either fully curtained or open.

The results of the experiment confirmed previous observations that the duration of night rest varies depending on the time of year.

So, in winter, the subjects slept an average of 62 minutes longer, although scientists considered this to be a negligible difference.

The period from the moment of falling asleep to the beginning of the REM phase (REM) was shorter in autumn than in spring, the difference was about 25 minutes.

In winter, this phase itself was longer than in spring, by about 30 minutes: in September, December, and January, it lasted an average of 100 minutes, and in April and June, 70 minutes each.

Slow-wave sleep – characterized by low-frequency activity of the cerebral cortex, at which time the brain really rests – turned out to be generally stable in winter and summer (lasted about 60-70 minutes, peaking from December to May), but decreased in autumn, especially in September – the difference was 31 minutes compared to February.

“For many people, the time to wake up depends more on the work schedule or study than on the biological clock. This means that the sleep schedule can only be adjusted by adjusting the time for going to bed.

According to our findings, improvements can be achieved by taking into account the increased need for sleep in winter and going to bed earlier.

In addition, changing the clock twice a year can alleviate seasonal changes in human physiology. For example, standard time (winter) provides more natural light when people drive to work in the morning.

On the other hand, a reduced need for sleep in the summer may lead to longer periods of wakefulness before school or work, which are better spent in free time after lunch and in the evening, ”the scientists concluded.

Of course, the experiment would have to be repeated with participants without sleep disturbances. Then, according to the authors of the article, they will receive unequivocal evidence that the sleep pattern needs to be adjusted taking into account the time of year.


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