What can we learn about sleep from the land of the polar night

The 24-hour darkness during the winter near the Poles can disrupt sleep – this is how the people who live there cope.

Imagine not seeing the Sun for weeks or even months. It's dark, the air has a freezing sharp bite and everything is covered with thick snow.

But even in the midst of the polar night, it isn't pitch black. At times the rays of the Sun filter weakly through the upper layers of the atmosphere, creating twilight shades of blue, pink and purple.

There's also light from the Moon and the stars. The northern lights make a frequent appearance and the snow reflects all artificial light, creating a "snowglow" that makes everything look brighter.

It is a stunningly beautiful time of year for those living in the Arctic. For locals, the polar night is part of life, and many thrive, embracing the season. Some even say they sleep better than they do at other times of the year.

"Polar night is too short," says Esther Berelowitsch, 42, who lives in Inari, Finland, where the polar night lasts for six weeks. "I'd love if it lasted for two months. Nature shows itself even when there's no sunlight... I go to bed earlier and sleep better. I don't want spring to come."

Yet research shows that others become sad and sluggish when winter starts – deprived of the sunlight, their mood drops and depression can set in.

Sleep in the Arctic can be a unique challenge. The midnight sun during the summer months can play havoc with the human circadian rhythm, the natural clock that governs many of our bodily functions. The almost perpetual darkness of the polar night can also delay the normal sleep/wake cycle, especially in those who spend a lot of time indoors. Insomnia can be a particular problem for some people in the winter months.

But people who live and work in Arctic have also learned to cope with the challenges that the dramatic change in the seasons can mean for their sleep. There is certainly some evidence that local people are better acclimatised to the sleeping problems they might encounter during the polar night than those visiting from lower latitudes. So, what can the rest of us learn from Arctic residents about our own sleep?

In the far north of Norway, Sweden, Finland, Greenland, Russia, Canada and Alaska, the Sun remains below the horizon for much of the winter. For how long exactly depends on the location: in Rovaniemi, the capital of Finnish Lapland, right on the Arctic Circle, polar night lasts for only two days during winter solstice. In Tromsø, the largest town in northern Norway, 350km (217 miles) north of the Arctic Circle, it's about six weeks, from late November to mid-January. At the far end of the spectrum, servicemen live in darkness for almost four months a year at a Canadian military facility at Alert, in Nunavut, the world's northernmost permanently inhabited place, roughly 1,776 km (1,101 miles) north of the Arctic Circle – and just 817km (508 mi) from the North Pole.

With so little daylight, combined with the cold weather, the long winter months can affect people's mood. Perhaps the most well-known effect of the dark, cold winter months is seasonal affective disorder (Sad) – a significant slump in mood thought to be caused by a lack of sunlight during the shorter winter days. Symptoms include low energy, overeating and oversleeping, and appear in the autumn or winter, followed by spontaneous remission in the spring or summer. Disrupted sleep is also a hallmark of Sad. (Read more about how the dark days of January shape your mood, intelligence and sex drive.)

In Europe, Sad is estimated to affect some 2-8% of the population – approximately 8-14 million people, although rates vary country to country. It is also thought to afflict millions of people in the US, with rates ranging from about 1% in the south of the country to nearly 10% of the population in the north.

The same effects of latitude can be seen in countries with territory within Arctic circle. Communities living in the north of Greenland, for example, suffer far higher incidence of Sad than those in the south. Inuit communities in the Canadian Arctic also experience elevated rates compared to those further south – twice those in Ontario for example, and four times the rates found in southern parts of the US.

But the research is far from conclusive. Other studies have cast doubt on the idea that symptoms of depression are linked to seasonal changes in daylight or to latitude. One study of nearly 9,000 people in Tromsø found no seasonal differences in mental distress reported by the people taking part. Other studies, though, have found there is a strong seasonal relationship between elevated feelings of depression as well as what time people went to sleep and got up in the morning.

How you think about the winter months may be an important factor here.

A study of 238 people in Norway found that having a positive mindset about the winter can transform the way people experience polar night.

"Cold and darkness affects all of us," says one of the study's authors, Kari Leibowitz, a psychologist who researches people's wellbeing in the winter. "What makes a difference is how we respond to them emotionally and behaviourally."

The study found that people who look forward to enjoying the opportunities that winter brings, such as skiing and cozy nights spent with loved ones in front of a fire, reported better winter wellbeing.

Another study in northern Norway found that indigenous Sámi people were less likely to suffer from insomnia or rely upon medication to help them sleep compared to the non- Sámi population. The researchers found the Sámi tended to have a more relaxed attitude towards sleep, with even children being left to self-regulate their own sleep rather than sticking to regular bedtimes.

It is well known that depression, stress, anxiety and emotional conflict can all play a significant role in insomnia. But how you think about your sleep can also have a very real effect on how rested you feel after a night in bed too. In other words, the mood you are in when you wake can influence how you feel you slept the night before and how tired you will feel through the day. (Find out more about how the right mindset can improve your sleep in this article by Amanda Ruggeri.)

For Michèle Noach, an artist who shares her time between the UK and Vadsø, a town in the far north-east of Norway close to the Russian border, the polar night induces a feeling of coziness where she just wants to curl up and snooze.

But Leibowitz thinks something else might be going on too.

"Those with a negative mindset are fighting against winter," says Leibowitz. "For example they put on big lights to push away the darkness. But that just makes things worse: they create a contrast that makes the outside world even darker – and overlighting may also disrupt their sleep." 

The amount of light we are exposed to during the day plays an important role in setting our circadian rhythm, helping to regulate the amount of melatonin our bodies produce. Melatonin is a hormone produced by the brain from the evening onwards, preparing our body for sleep and so playing a crucial role in regulating our sleep-wake cycles.

The almost perpetual winter darkness in the Arctic can play havoc with melatonin production, with some studies showing a large spike in melatonin at the peak of the polar night in mid-January. Melatonin levels then decrease as the sunlight begins to return at the end of the month. This would be fine, except for those working on a set daily schedule that requires them to be at work or up and about at a certain time. During the periods of highest melatonin production, participants in a study by researchers at the University of Tromsø reported feeling much more tired in the mornings than they did in the summer months.

Artificial lighting, however, cannot fully replicate the levels of sunlight needed to maintain stable sleep patterns.

But research on soldiers in the Canadian Arctic suggests that it is possible to realign someone's melatonin production with their sleep pattern using a specialised light visor fitted with LEDs emitting a bluish green light at a wavelength of 505nanometres (nm). The military personnel who used the device reported an improvement in the quality of their sleep and mood over an 11-day period. Using lamps enriched with blue-light has also been found to be beneficial for people overwintering at Antarctic bases.

Håkan Långstedt, an engineer based in Helsinki, Finland, and managing director of lighting design company SAAS Instruments, recommends soft lighting during the polar night.

"If you have a lot of darkness, you don't need a lot of light to compensate," he says. "You only need low-level lighting."

Crucially, he says, it is best to gradually reduce the amount of light as it gets closer to bed time. "It's not something cut with a knife: it gradually goes from light to something darker." Certainly, research has shown that gradually reducing the amount of blue light we are exposed to up to two hours before bed can help to prepare us for sleep. Dimming the lights before we want to go to sleep can also help to shift when our bodies begin producing melatonin.

Leibowitz, who suffers from a sleep disorder herself, also recommends using soft lighting and natural light, such as candlelight and a fire, in the hours before going to bed to improve the quality of sleep.

"Low-level lighting stimulates the production of melatonin: the hormone that makes you sleepy," she says. "Going to the sauna or taking a hot bath has the same effect: the body temperature drops after you get out, which also triggers the release of melatonin."

Physical exercise also has an important effect on our circadian rhythm and seems to be particularly good for our sleep if we do it in the morning.

Jumping on an exercise bike shortly after waking and again in the afternoon, but doing so 20 minutes earlier each day, can help to shift our sleeping schedule, for example. A two hour bout of intense physical exercise during our usual night-time hours can also be a dramatic way of shifting our sleep pattern – although that wouldn't really be recommended unless you are trying to adjust to night shifts or a new time zone.

And there is some evidence from a study of students in Alta in northern Norway that adopting a regular exercise regime – such as a regular training session for a team sport or a spell on a treadmill – reduces the amount of melatonin produced in the afternoon, meaning you are less likely to feel sleepy at this point in the day.

Esther Berelowitsch, who moved to Inari in northern Lapland from Paris eight years ago to learn Sámi languages, spends two hours a day walking or skiing outside the house during the polar night.

"It's important to be outdoors when we have a little light," she says. "I only stay indoors when it's -40C (-40F) or colder. Otherwise I go out for a walk or go skiing."

But while cold weather workouts may help to burn more calories, most research on physical activity in the open air and sleep tends to have been done at lower latitudes where exposure to sunlight goes hand-in-hand. This makes it tricky to unravel whether being in the open air during the polar night would bring additional benefits or not.

"What we see is that the sleep-wake cycle is delayed in winter," says Arne Lowden, an associate professor who studies sleep and stress at the University of Stockholm, Sweden. "People go to bed later and if they have to wake up at a certain hour because they have to go to work, their sleep will be cut short," he says.

Lowden and his colleagues conducted a sleep study involving office workers in Kiruna in northern Sweden where the polar night lasts for 28 days. He found that they went to sleep 39 minutes later in the winter than in the summer, and they got 12 minutes less sleep per week in the winter.

"Cold temperatures and fewer daylight hours disrupt the circadian rhythm, that is, our body clock," Lowden says. "Our bodies operate a 24-hour cycle in which to perform their functions. Almost all our organs are organised in cycles, in a way that one time of the day they're active, and another time they're recuperating and restoring cells."

Certainly, exercising in the morning rather than the evening during the Arctic's dark month of January has been shown to have a beneficial effect on the heart's circadian rhythm, as well as overall sleep quality.

"If your circadian rhythm is disrupted, you'll be sleepy during the day," says Lowden. "If it's badly disrupted, you'll wake up at totally the wrong time and you won't be able to hold a job."

There is also evidence that humans may actually need more sleep during the winter than we do in the summer.

Researchers in Germany analysed sleep recordings of 188 people with disturbed sleep patterns and found that they experienced seasonal variations in rapid eye movement (REM) sleep – the stage of sleep when we dream. In December their REM sleep was 30 minutes longer than in June. (Find out more about how the seasons change our sleep in this article by Isabelle Gerretsen.)

Some evidence gathered by fitness trackers seems to support this idea. Based on data from 45,000 users of the Oura Ring, a wearable sleep and activity tracker, sleep duration was found to increase by 3%, or about 10 minutes, in the winter.

"We've seen a change in users' resting heart rates as well: they increase by 3% from summer to winter," says Heli Koskimäki, head of future physiology at Finland-based technology company Oura Health. He confirmed that most of the users were in the Nordic countries, Canada and the US, but was unable to say how many lived in places that experienced the polar night.

Koskimäki says users who follow a daily schedule according to their chronotype seem to sleep better. Put simply, this means getting up early in the morning and going to bed early in the evening if you're an early bird, and getting up and going to bed later if you're a night owl.

Modern society tends to favour morning types, says Koskimäki. "If you're more of an evening type, there's a danger that you'll sacrifice some of your sleep to meet society's demands. If you can't follow your own chronotype, try to be at least as consistent as possible with your sleep schedule: you'll sleep better and feel better for it."

Taken together, these findings suggest that sticking to the exact same daily schedule throughout the year may not be the best idea.

"If you have flexibility in your private life and in your job, you're better off if you adapt your schedules to the seasons and give yourself more time to sleep in the winter than the summer," says Leibowitz.

Berelowitsch, who loves the polar night, says it gives her an opportunity to slow down and engage in quiet pursuits.

"I've noticed that in my free time I do everything slower – I walk slow, eat slow, sleep slow," she says. "When it's too cold to go out, I remember my handicraft projects and my guitar. But I also enjoy socialising on dark winter evenings."

Maintaining social contacts and attending events is well-known to benefit mental health. And there is some evidence that social interactions can help with regulating our emotions and so improve our sleep, particularly if we surround ourselves with supportive relationships.

"Polar night is a time for gathering with family and friends," agrees Lowden.

Noach says there have been times when she has sat with friends at the fireplace for nine hours, unaware of the passing time. Polar night also gives Noach a unique opportunity to absorb herself in art. "For two months, everything's happening in the dark," she says. "I find that I'm very creative then. I'm mining myself.

"In the Arctic they say during polar night you have to switch your internal lights on," she adds. "So you have to draw on very deep resources in yourself. There are people who find it difficult and depressing. But the majority up here get a real kick out if it."

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