Spring is here, why has my sleep quality deteriorated?

(Image source: pexels)

Written by | Ah Xian

Review | Ziv

When it comes to "spring is coming", many people's first reaction may be that the long and cold winter is finally over, the days are longer and the nights are shorter, the weather has become warmer, and the mountains are full of flowers, making it a perfect place for outings.

However, a change that you may not have noticed is also quietly happening with the change of seasons - sleep begins to decrease.

Seasonal changes affect countless creatures on Earth, from small deciduous trees that change color and shed their leaves in autumn and grow new leaves in spring, to large animals such as bears, squirrels and turtles that hibernate in the winter and wake up in the spring... A new study finds that humans also have seasonal sleep, and the duration and structure of sleep change significantly throughout the year. Compared with the summer, humans get more sleep in the cold winter.

Through polysomnography (including more than 10 physiological signal monitoring such as brain waves, electrocardiogram, electromyogram, oculoculogram, chest and abdominal respiratory tension graph, nasal and oral ventilation, body position and movement, and blood oxygen saturation), scientists divide human sleep into two distinct stages: rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM).

Scientists invited 292 volunteers to spend three nights in a laboratory environment at different times of the year (December 22nd when the daylight hours are shortest in the Northern Hemisphere and June 21st when the daylight hours are longest) in order to closely monitor their sleep.

(Photo source: Internet)

The data showed that subjects tended to sleep longer in winter, with a total sleep time of 60 minutes longer than in summer; the time they entered REM sleep in autumn was about 25 minutes shorter than in spring; the REM sleep time in winter was an average of 30 minutes longer than in spring; and in the autumn months, slow-wave sleep (the third sub-stage of non-REM sleep, during which we dream and consolidate memories) experienced a rapid and sudden decline.

Previous studies have found that looking at a phone or being exposed to artificial light for a long time before bed can suppress the body's melatonin secretion, but the findings of this study make people realize that even when exposed to artificial light, our sleep still has seasonal changes.

Spring sleepiness, autumn fatigue, summer naps, and sleepiness in winter and March... all have scientific reasons｜gifer

Should we consider changing our sleep habits year-round based on the season? Researchers believe that most people maintain similar sleep patterns year-round: going to bed around 11pm and waking up around 7am to go to work/school. Therefore, going to bed earlier in the winter could address the "increased need for sleep" issue.

Compared to the seasons that shorten your sleep time, if you learn that the sleeping patterns of ancient people are very different from those of modern people, you will definitely feel more surprised and unbelievable!

In 2004, Roger Ekirch, a historian at Virginia Tech, revealed the sleeping habits of the ancients through 500 references in his book At Day's Close: Night in Times Past - polyphasic sleep (also known as polyphasic sleep), which divides a single sleep into multiple sleep cycles.

Like many Romans, the ancient Roman historian Titus Livius was a practitioner of polyphasic sleep, and he mentioned this method in his magnum opus, The History of Rome. | wiki

A long time ago, a night's sleep cycle was like this: from 20:00 to 23:00, most people would fall asleep on a mattress filled with straw or rags; a few hours later, people would wake up from the first stage of sleep, and then stay awake from 23:00 to 02:00 to do things like eating, taking care of children, etc.

According to Ekirch's research, polyphasic sleep is very common, and evidence of this habit has even been found in Africa, South and Southeast Asia, Australia, South America and the Middle East. He believes that this sleeping habit is the main sleeping method that has been passed down for thousands of years. In fact, it is easy to understand that when resources were scarce, people basically had no other activities except daytime labor and daily activities, especially when the sun set, people had nothing to do.

Some people say that the sleeping habits of newborn babies are completely consistent with the polyphasic sleep cycle. | pixnio

Humans aren’t the only animals with polyphasic sleep habits. Many species in nature sleep in two or more distinct periods of time, which helps them stay awake at the most beneficial times of day. Ring-tailed lemurs, for example, have sleep patterns very similar to those of pre-industrial humans.

At the same time, Ekirch also explains why most people have abandoned polyphasic sleep since the beginning of the 19th century: Like other changes in our behavior (such as the shift to clock dependence), the answer is the increasing prevalence of artificial lighting and the impetus of the Industrial Revolution. The former made our nights a time of legal activity, and the colorful nightlife made spending hours in bed a waste of time. The latter made people who no longer went to bed at 21:00 have to get up at the same time the next morning to go to work.

If you suddenly wake up in the middle of the night, don't be too nervous. Think about your pre-industrial ancestors. This has been part of human physiology for thousands of years...

Source: "Bring Science Home" WeChat Official Account