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How does seasonality affect sleep?


Our sleep patterns are affected by our external environment and the changing seasons are no exception. Changing the clocks can affect how you sleep and the quality of it.

The importance of sleep

Our daily sleep-wake cycle is controlled by our circadian rhythm. You can think of this as the internal body clock. It runs on a 24 hours cycle and affects when you feel tired and when you’re more alert.

Sleep is essential for the recovery of both our brain and body; a lack of sleep is associated with poor mental and physical performance.

The change in seasons has been shown to influence human behaviour and physiology for centuries. Many scientific studies have found that people sleep longer in winter than in summer. This makes sense because the days are shorter in winter, so there is less sunlight and our bodies are more inclined to feel tired.

Vitamin D and sleep disorders

Vitamin D is a fat-soluble vitamin. Although it can be acquired from food, the amount is often not enough. Instead, the best way to acquire vitamin D is through sunlight exposure. When your skin is exposed to the UVB rays of the sun, it converts the rays into vitamin D.

Why should you care about vitamin D? Studies have shown that vitamin D deficiency contributes to sleep disorders, a poorer quality of sleep and shorter sleep duration.

What’s this got to do with seasonality? Well, vitamin D status is associated with sunlight exposure. In the winter, a lack of sunlight means vitamin D levels are likely to be low. That’s why it’s vital to expose your skin to the sun during the winter months to build up your supply. If this isn’t possible, you might need to take a vitamin D supplement.

What about your daily routine?

When it’s darker for longer, our daily routines can often be thrown out of sync. The lack of daylight can make it harder for us to wake up or make us less motivated to go for a run in the evening, for example.

But there are strategies you can adopt to help your body to adjust:

  1. Try to resist the urge to nap too frequently or too late in the day as this can affect your sleep
  2. Use relaxation techniques to help you wind down, like taking a bath, reading or meditating.
  3. Limit your phone usage at night as the blue light affects your ability to sleep
  4. Consider making your bedtime 10-15 minutes earlier every night to anticipate the time change
  5. Avoid drinking caffeine too late in the day
  6. Create a comfortable sleeping environment with clean sheets and a cool temperature

Let’s recap:

Seasonality undoubtedly affects our circadian rhythm and ultimately our sleep. But there are good practices you can adopt to make sure you still get a good night’s sleep, whatever the time of year.