The longest day of the year is a great opportunity to explore how light influences our circadian rhythm, and therefore our sleep.
Originating from Latin, the word ‘circadian’ means ‘about a day’ (circa ‘about’ + dies ‘day’). It’s the perfect way to describe how our internal clock is set to roughly 24 hours – and it’s no coincidence that it matches the Earth’s rotation with respect to the Sun!
For humans and other diurnal organisms that have naturally evolved to be active during the day and sleep during the night, our circadian rhythm helps us stick to our ‘day shifts’, ensuring that we are alert when the sun is out and that we relax when night falls.
However, our internal clocks are not perfect; they need some adjusting from time to time, and light (as well as the absence of it) is the fail-safe indicator they’ve learnt to rely on. After all, if it’s one thing we know for sure is that the sun will come out in the morning and that it will set in the evening! As a result, our brains have evolved to scan our environment for light and darkness, so that they can wind our internal clock and regulate our body’s processes accordingly.
If you’re wondering how your body knows to differentiate between light and dark, the answer is melatonin. Also known as “the sleep hormone” or “the darkness hormone”, melatonin is increasingly produced in your brain as it gets darker, signalling to your body that it’s time to wrap it up for the day. While you sleep, and as the sun begins to rise again, melatonin levels begin to fall. Eventually, the absence of melatonin in your body alerts your brain to the fact that the sun is up, and that perhaps it’s time for you to wake up, too.
Naturally Longer Days
As the days get longer in the summer, melatonin production is also delayed at night. Our brains and bodies can get tricked into staying up later, and we end up sleeping less. In the past, this natural delay may have been fine, as it just allowed for us to hunt and gather for longer. Then again, we didn’t need to get up for work in the morning!
The effect of longer days is felt even more strongly by those who naturally stay up later than others (owls), as it pushes their natural late tendency even later. On the flip side, however, if you struggle to get up, the early morning light can really help to give you the early morning boost you need!
What you can do: The best way to deal with longer days is to try to stick to a regular sleeping schedule, making sure you go to bed and wake up at the same time every day. By maintaining this routine, you’ll be training your internal clock, helping it to understand when you need to relax and when it’s time to get up and seize the day! Using an eye mask, heavy curtains or black-out blinds can also help you control the light and manage your sleep during this time.
Not-so-Naturally Longer Days
Nowadays, many of us suffer from the effect of longer days throughout the year. The reason? Our beloved smartphones, tablets, laptops and TVs. Digital screens emit blue light, which our brains recognise as sunlight and, unsurprisingly, respond accordingly: melatonin production is halted causing our brain to think it’s daytime when it’s actually dark outside, alpha waves in our brains are boosted causing us to be more alert, and delta waves which induce sleep are suppressed.
What you can do: The best way to deal with this problem is to switch off all your devices and dim the lights 40 minutes before bed. If you really need to use them, try installing a blue filter on your laptop, or activating this feature on your smartphone or tablet. Another great idea is to try using a traditional alarm clock, and leave your phone in another room. You can find more information on digital screens, blue light and how it affects your sleep here.