Of all the months in the year I’d like to sleep through, February is top of the list. Sure, it might be getting brighter out there, but as the cold, gloomy days linger on, spring is still very much un-sprung. The good news? It’s not just laziness making us want to hunker down and hibernate. According to scientists, humans actually need more sleep in the winter months. From November to March, experts say, we should be going to bed earlier or starting work later, to compensate for our tired bodies’ need to rest and recharge.
The eye-opening finding comes from a new study, published in the journal Frontiers in Neuroscience, which measured the sleep of 292 patients. Subjects slumbered for 43 minutes longer on average in the winter than the summer, and spent an extra 15 minutes in REM (rapid eye movement) sleep, the stage during which we dream, process emotions and form memories. It’s the first time human sleep habits have been directly linked to the seasons — and comes as a relief to those of us who seem to feel low in energy during the darker months.
So what is it about the winter that makes us yearn for 40 winks — and how much good could a few extra hours in bed do us? Dr Maja Schaedel, co-founder of The Good Sleep Clinic, says a seasonal approach to sleeping “makes sense from an evolutionary perspective...We would have been most productive during daylight hours, especially when we had no other sources of light, and therefore it made sense to maximise sleep during the winter months.”
We may now have electricity at our disposal, but natural darkness still triggers a biological response in our brains. “Our circadian, or sleep-wake, rhythms are heavily tied to daylight,” explains Dr Schaedel. “Levels of the hormone melatonin increase dramatically in the evening when the sun goes down. How long the darkness lasts at night can have an impact on our circadian rhythms.”
According to research by the Johns Hopkins University in the US, the body’s internal clock is controlled by an area of the brain called the SCN (suprachiasmatic nucleus), which is sensitive to signals of dark and light from the optic nerve in your eyes. When it’s dark, the SCN sends messages to the brain’s pineal gland, which triggers the release of melatonin. This, in turn, makes you feel sleepy and ready for bed.
There’s also the matter of temperature, which drops by several degrees — or more, in this perennially-chilly country — in the winter. “We know that in order to fall asleep and stay asleep, we need our core body temperature to drop by one or two degrees,” explains Dr Schaedel. “Lowering the room temperature from 24C to 18C has a significant impact on sleep quality, making it much better during cooler climates.”
So we’re naturally programmed to sleep longer, and more deeply, when it’s cold — and, according to a 2014 study published in the journal Diabetes, exposure to cold temperatures increases our metabolism, which actually requires more sleep at night.
Experts also point to our diet as a cause for drowsiness. With fresh fruit and veg less readily available, many of us gorge on sleep-inducing carbohydrates, refined sugar and snacks. We also tend to feel hungrier: research from the Nineties links this with thermoregulation, the process by which eating food generates heat in the body. In cold weather, it’s instinctive to increase our food intake because our body needs to make more heat. It’s also less practical — and, let’s be honest, less appealing — to exercise in the winter, a sluggish combination which lowers energy levels and makes us feel tired.
All the science points to one thing: stop what you’re doing and go back to bed. The benefits, experts say, range from fending off the dreaded cold and flu (research shows increased sleep improves our immune system) to helping regulate your appetite (banking a solid night’s kip will set you up for a healthier day) and fighting winter blues, anxiety and depression. A wide-ranging study in 2021 found that a good night’s sleep can have a direct impact on mental health. Dr Dieter Kunz, a clinical psychiatrist and lead author of the latest research, says getting more sleep at this time of year could stop the feeling of “running on empty in February or March”.
So go on: head back to bed.
