You’ve probably heard of circadian rhythms. They govern the natural 24-hour operating cycles of plants and animals; in humans they’re better known as the ‘body clock’.
Our body clock is controlled by the suprachiasmatic nucleus (SCN), which keeps vital body systems – immune system, metabolism, and sleep–wake cycle – working in sync and at the right time.
The SCN communicates using hormones and neurotransmitters – for example, telling your body to produce melatonin when it’s time to sleep, and to release cortisol when it’s time to wake up.
But your SCN has its own natural master controller as well: light.
More than meets the eye
Humans evolved to use sunlight to sync our circadian rhythms with the natural environment.
The biomechanics behind this has only been understood in recent years through the discovery of a third photoreceptor in our eyes – the catchily named ‘intrinsically photosensitive retinal ganglion cells’ (ipRGCs). These cells do not contribute to vision; they send signals directly to the SCN about the light in our environment.
However, we now spend most of our time indoors, where our ipRGCs get the wrong inputs for most of the day. Circadian alignment requires our ipRGCs to get sufficient daytime exposure to light in the cyan-blue part of the spectrum, peaking at 490nm. This bandwidth is abundant in natural light, but weak to non-existent in the artificial light of workplaces and homes.
The direction of the light is also important. Light entering the eye directly gives a stronger signal to the ipRGCs than light reflected off walls, desks, and other indoor surfaces.
Moreover, our circadian system needs a clear delineation between day and night, something lacking in our built environment.
For example, exposure to blue light at night from screen-based devices misleads our system into thinking that it’s still daytime, which can delay the onset of sleep-inducing melatonin.
Conversely, for those of us who spend the day working (or studying) indoors, the amount of light we receive is not enough to send a strong daytime signal, adding to the problem. This combination is essentially a circadian twilight, and our circadian rhythm drifts out of sync over time.
This type of circadian misalignment is known as social jet lag – and it’s not at all as harmless as that term might sound.
The cost of social jet lag
Your circadian rhythm regulates about 60% of your body’s functions. When things drift out of alignment, there can be a significant impact on critical immune and metabolic systems over time.
This shows up as a decrease in general energy levels, that sluggish feeling during the day, and reduced sleep quality at night – all associated with reduced cognitive performance.
More severe consequences include a weakened immune system with an increased risk of cardiovascular and metabolic disease. All of which is less than ideal.
By supplementing the deficient working/living light with the correct circadian light – and limiting your exposure to bright light at night – you can realign your body clock and mitigate the effects of accumulated social jet lag.
Circadian light will quickly reduce the most noticeable adverse effects of social jet lag. Energy levels will increase, sleep quality will improve, and your overall mood should lift. You may notice an improvement in cognitive ability – or others might notice it for you!
The end of that sluggish, jet-lagged feeling indicates that your immune,
cardiovascular, and metabolic systems are functioning better, too.
Now you know a bit more about the science of social jet lag, check out the
clever Loop device to get your own body clock back in sync.