In winter, people experience hypersomnia, depressed moods, and a widespread sense of hopelessness. Even the risk of premature death in winter is significantly higher. Our biological clock is out of sync with our waking and working hours. Should we adjust our office hours to help improve our mood?
As a rule, people tend to see the world in dark colors when daylight hours become shorter and cold weather sets in. But changing our working hours according to the seasons can help lift our spirits.
For many of us, winter, with its cold days and lingering nights, creates a general feeling of ailment. In the semi-darkness, it becomes more and more difficult to break away from the bed, and as we hunched over desks at work, we feel our productivity draining along with the remnants of the midday sun.
For the small subset of the population experiencing severe seasonal affective disorder (SAD), it's even worse - winter melancholy mutates into something much more debilitating. Patients experience hypersomnia, depressed mood, and a widespread sense of hopelessness during the darkest months. Regardless of ATS, depression is more commonly reported in winter, suicide rates increase, and productivity declines in January and February.
While this is all easily explained by some vague idea of winter gloom, there may be a scientific basis for this depression. If our body clock is out of sync with our waking and work hours, shouldn't we adjust our office hours to help improve our mood?
“If our biological clock says it wants us to wake up at 9:00 am because it's a dark winter morning outside, but we get up at 7:00 am, we miss a whole sleep phase, says Greg Murray, professor of psychology at Swinburne University., Australia. Research in chronobiology - the science of how our bodies regulate sleep and wakefulness - supports the idea that sleep needs and preferences change in winter, and the limitations of modern life may be especially inappropriate during these months.
What do we mean when we talk about biological time? Circadian rhythms are a concept that scientists use to measure our inner sense of time. It is a 24-hour timer that determines how we want to post the various events of the day - and, most importantly, when we want to get up and when we want to sleep. “The body loves to do this in sync with the biological clock, which is the main regulator of how our body and behavior relate to the sun,” explains Murray.
There are a myriad of hormones and other chemicals involved in regulating our biological clock, as well as many external factors. The sun and its position in the sky are especially important. Photoreceptors located in the retina, known as ipRGCs, are particularly sensitive to blue light and are therefore ideal for adjusting circadian rhythm. There is evidence that these cells play an important role in regulating sleep.
The evolutionary value of this biological mechanism has been to promote changes in our physiology, biochemistry, and behavior depending on the time of day. “This is precisely the predictive function of the circadian clock,” says Anna Wirtz-Justice, professor of chronobiology at the University of Basel in Switzerland. "And all living beings have it."Given the change in daylight throughout the year, it also prepares organisms for seasonal changes in behavior, such as reproduction or hibernation.
While there hasn't been enough research on whether we would respond well to more sleep and different waking times in winter, there is evidence that this might be the case. “In theory, lowering natural light in the morning in winter should contribute to what we call phase lag,” says Murray. “And from a biological point of view, there is good reason to believe that this is probably actually happening to some extent. The delay in the sleep phase means our circadian clock wakes us up later in the winter, which explains why it becomes more difficult to fight the urge to set the alarm."
At first glance, sleep phase delay might seem to indicate that we will want to go to bed later in winter, but Murray suggests that this tendency is likely to be neutralized by a general growing desire to sleep. Research shows that people need (or at least want) more sleep in the winter. A study in three pre-industrial societies - where there are no alarms, smartphones, and no workday from 09:00 to 17:00 - in South America and Africa found that these communities collectively dozed for an hour longer during the winter. Given that these communities are located in equatorial regions, this effect may be even more pronounced in the northern hemisphere, where winters are colder and darker.
This hypnotic winter regimen is at least partially mediated by one of the main players in our chronobiology - melatonin. This endogenous hormone is controlled and influenced by the circadian cycles. This is a sleeping pill, which means that its production will gain momentum until we fall into bed. “Humans have a much broader melatonin profile in winter than in summer,” says chronobiologist Til Rönneberg. "These are biochemical reasons why circadian cycles can respond at two different times of the year."
But what does it mean if our internal clock does not match the times that our schools and work schedules require? “The discrepancy between what your body clock wants and what your social clock wants is what we call social jetlag,” says Rönneberg. "Social jetlag is stronger in winter than in summer." Social jetlag is similar to the one with which we are already familiar, but instead of flying around the world, we are unsettled by the time of our social demands - getting to work or school.
Social jetlag is a well-documented phenomenon and can have serious consequences for our health, well-being, and how well we can function in our daily lives. If it is true that winter produces a form of social jet lag, in order to understand what its consequences may be, we can turn our attention to the people who are most susceptible to this phenomenon.
The first group of people for potential analysis includes people living in the western ends of time zones. Because time zones can span large areas, people living on the eastern edge of the time zone experience the sunrise about an hour and a half earlier than those living on the western edge. Despite this, the entire population must adhere to the same working hours, which means that many will be forced to get up before sunrise. Basically, this means that one part of the time zone is constantly out of sync with circadian rhythms. While this may not seem like a big deal, it comes with a number of devastating consequences. People living on the western outskirts are more susceptible to breast cancer, obesity, diabetes and heart disease - the researchers determined that the cause of these diseases was primarily a chronic disturbance of circadian rhythms, which arises from the need to wake up in the dark.
Another striking example of social jet lag is observed in Spain, which lives according to Central European time, despite the geographic correspondence of Great Britain. This means that the country's time is moved forward one hour, and that the population must follow a social schedule that does not match their biological clock. As a result, the entire country suffers from a lack of sleep - getting an hour less on average than the rest of Europe. This degree of sleep loss has been associated with an increase in absenteeism, work injuries, and increased stress and school failure in the country.
Another population that may exhibit symptoms similar to those of people suffering from winter is the group that has a natural tendency to stay awake at night throughout the year. The average teen's circadian rhythms are naturally shifted four hours ahead of adults, which means adolescent biology forces them to go to bed and wake up later. Despite this, for many years they have to struggle with themselves to get up at 7 am and get to school on time.
While these are exaggerated examples, could the winter-exhausting consequences of inappropriate work schedules contribute to a similar but less significant impact? This idea is partially supported by the theory of what causes SAD. While there are still a number of hypotheses about the exact biochemical basis of this condition, a significant number of researchers believe that this may be due to a particularly severe response to the body clock being out of sync with natural daylight and the sleep-wake cycle - known as delayed sleep phase syndrome.
Scientists now tend to think of SAD as a spectrum of characteristics rather than a condition that is or is not, and in Sweden and other countries in the northern hemisphere, it is estimated that up to 20 percent of the population suffers from milder winter melancholy. In theory, weak ATS can be experienced by the entire population to some extent, and only for a few will it be debilitating. "Some people don't react too emotionally to out of sync," Murray notes.
Currently, the idea of reducing working hours or postponing the start of the working day to a later time in winter has not been tested. Even countries in the darkest parts of the northern hemisphere - Sweden, Finland and Iceland - work almost at night all winter. But chances are, if working hours more closely match our chronobiology, we will work and feel better.
After all, US schools that have moved the start of the day to a later time to match the circadian rhythms of adolescents have successfully shown an increase in the amount of sleep students receive and a corresponding increase in energy. A school in England, which moved the start of the school day from 8:50 to 10:00, found that thereafter there was a sharp decrease in the number of absenteeism due to illness and improved student performance.
There is evidence that winter is associated with more tardiness to work and school, and more absenteeism. Interestingly, a study published in the Journal of Biological Rhythms found that absenteeism was more closely related to photoperiods - hours of daylight - than other factors like weather. Simply allowing people to come later can help counteract this influence.
A better understanding of how our circadian cycles affect our seasonal cycles is something we could all benefit from. “Bosses have to say, 'I don't care when you come to work, come when your biological clock decides that you have slept, because in this situation we both win,” says Rönneberg. “Your results will be better. You will be more productive at work because you will feel how effective you are. And the number of sick days will decrease. Since January and February are already our least productive months of the year, do we really have much to lose?