Artificial light is a core environmental change; it will sway our biological sleep cycles
All living things have a circadian rhythm; evidence of a ‘clock’ can be found in early life forms, though that clock was closer to 22 hours, not the 24 hours that we see today. Circadian is a Latin derivative from circa about + di (es) day. It gives a sense of the time. The pattern probably helped humans build communities because it gives an anticipation of social patterns, of when most people do the same thing – that of being awake or being asleep. Humans tend to sleep less than other primates, but in all creatures sleep is a powerfully busy time of repair and reconciliation. The fatigue we feel is fatigue in our brains, not in our bodies – muscles do not tire in the same manner as a brain.
Sleep depends on a central pacemaker, an oscillator so to speak, and it is set to the external world of light and dark. The eye sends light or dark signals to our clock circuitry — this consists of about 10,000 cells and is known as the supra-chiasmatic nuclei. The appearance of morning light stops the sleep program and lets the body switch to the awake program.
Needless to say, individuals vary in their sleep cycles and needs. Some have broken sleep, and some wake up without the ‘the morning’ signal. Others awaken because of pain, full bladders, babies’ crying, outside noises, room temperature, and so on. Age, caffeine, tobacco, some psychiatric conditions or medicals, and alcohol do modify sleep. There are many variables, but on the whole, the basic system is to sleep when it is dark and be awake when it is light. The arrangement is so critical that the visually blind still respond to a light-dark circadian rhythms via a relatively newly discovered other light sensitive cell in the retina known as the photosensitive retinal ganglion cells. Certain genes turn on with sleep to allow the brain restore itself. We may sleep, per se, but the brain does not. Nature is serious about this age-old cycle.
And that’s the way it was for uncountable years.
But now, because of artificial lighting, we can disrupt that venerable biological clock; things have changed.
To start, we tend not to think of artificial light as a core environmental change. But it is.
Sleep is better in the quiet and dark. So television’s noise and light can indeed disable some of the sleep processes. Many people say they cannot sleep in the dark – the question is why? Is it a fear? We should not be afraid of the dark. Likewise some people need noise to sleep – again, the question is why? Does it distract them from their own thoughts as they fall asleep? We should not be afraid of quiet. Or might there be other biological abnormalities, such as within the orexin or adonsine system, causing sleep problems.
The sleeping impaired might need some outside help. But first try simple good sleep hygiene. And turn off the lights and TV.
We eat organic foods to give our bodies a better environment. We need to think of sleep with the same environmental mindset.