Body Clock: Sleep, Light and Melatonin

jetlag man unsure of time body clock

Have you ever wondered why you feel sleepy at night and awake in the day? This daily fluctuation is your natural body clock working correctly. Humans are naturally diurnal, meaning that we are meant to be active whilst it’s light, and should go to sleep when it’s dark.

Eyes and the brain

Our eyes don’t work very well in the dark, so it makes sense that we use this time to sleep and recover. Our feelings of sleepiness or wakefulness are dictated by light and what it does to our brains.

When light hits the back of our eyes, a cascade of information zips through the brain, telling a small gland deep in its center to stop the release of an important hormone, melatonin. When light diminishes at night the brakes are taken off. This hormone, sometimes nicknamed “the vampire hormone”, is now released in abundance and sets up our bodies for sleep. Melatonin lowers our blood pressure and body temperature, telling us that now is the time to go to bed [1][2].

Synchronization

Unfortunately, our internal body clock isn’t perfectly matched to the celestial clock of the Earth. Whilst the Earth does a full rotation in twenty-four hours, our body clock exceeds this by about fifteen minutes. Left to its own devices, our brains would switch between nocturnal and diurnal every month [2].

Light and melatonin brings our rhythm back in line with the day/night cycle of our planet. Artificial light can also influence melatonin release which is why SnoreLab uses darker colors.

Jet lag

Now consider long-haul flights, something that nature and evolution didn’t take into consideration. When we travel to a different time-zone, despite changing the clocks on our watches and phones, our body clock takes a bit more time to reset.

With the different patterns of light in far-flung destinations we can slowly coax our clock into synchronizing with our location. In the meantime, we have to put up with the uniquely miserable phenomenon of jet lag.

Let’s imagine we’ve travelled east, it’s 11pm local time but our body is convinced it’s only 4pm. We are not ready for sleep just yet but we try to force the issue, eventually falling asleep at 2am local time. Time to wake up at 7am for an important meeting, but internally, it’s midnight – time to sleep. But now we’ve got to get up and face the day perpetually in a state of groggy under-functionality.

Every day we are in this new environment, the new light pattern we are exposed to brings our rhythm back in line by about an hour. It will therefore take roughly seven days to fully get over this seven-hour difference [3].

Age

Jet lag isn’t the only shift in our internal cycle. Melatonin’s daily pattern changes throughout life. During adolescence, its release is delayed to later in the night which is why teenagers go to sleep and wake later. As we age, melatonin production diminishes, meaning we wake up earlier and generally sleep less [2].

Conclusion

Light, or lack thereof, is vital for good sleep hygiene, and good sleep hygiene keeps exhaustion and snoring at bay. When you set SnoreLab before bed, make sure it’s the last thing you do with your phone at night.

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References

  1. Waterhouse J. Jet-lag and shift work: (1) circadian rhythms. Journal of the Royal Society of Medicine 1999; 92(8): 398-401. https://www.ncbi.nlm.nih.gov/pubmed/10656004
  2. Walker M. Why We Sleep. London; Penguin, 2017: p107.
  3. Vosko AM, et al. Jet lag syndrome: circadian organization, pathophysiology, and management strategies. Nature and Science of Sleep 2010; 2: 187-198. https://dx.doi.org/10.2147%2FNSS.S6683 

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