Humans have evolved for many millions of years on Earth with a reliable daily cycle of 12 hours of bright full-spectrum light, and 12 hours of dark (season & latitude permitting). Yet it has only been since the advent of electric lighting some 135 odd years ago that we have begun to have the dark period dramatically eroded. The benefits of electric lighting are obviously many, but as with so many things, there is a price to pay, and part of that price are adverse health effects on human health (as well as on many other life forms).
Previously, I’ve written on the importance of sunlight for good health, in particular its role in vitamin D synthesis, but the natural daily sunlight and dark cycle is also important on their effect on creating and maintaining our circadian rhythm, which is our 24 hour internal clock, which is tied to a great many physiological processes in the body, such sleeping and feeding patterns, brain wave activity, hormone production, cell regeneration and a whole lot more.
So, what happens when we start messing with millions of years of natural night and day cycles? A lot, apparently. Researchers have correlated light-at-night (LAD) to everything from breast, prostate, endometrial and colon cancer, to heart disease, diabetes, obesity, mood disorders and more.
The problem is that it is difficult to assess scientifically because almost everyone in the modern world uses electric light! Therefore a series of predictions have been made to test the LAD theory, especially in regards to breast cancer, including: (i) non-day shift workers would be at higher risk; (ii) blind people would be at lower risk; (iii) sleep duration, as a surrogate for hours of dark, would be inversely associated with risk; (iv) light level in bedrooms at night would be directly associated with risk; and (v) population level studies would show associations of community light level with risk.
In a nutshell, studies have by and large over the years confirmed all five predictions, so much so that the International Agency for Research on Cancer has concluded ‘shift-work that involves circadian disruption is probably carcinogenic to humans’.
So, what can we do to minimize circadian disruption to maximize our health and well being?! Well, the best thing would be to sleep when it’s dark, and wake when the sun rises! If that’s out of the question for you, here are some other ideas that will help: dim lights while awake at night; don’t use night lights; close curtains/blinds to shut out street lights (or greenhouse light if you live in Otterburne!); install a dim light (red is best) in the bathroom for night time use, as typical vanity lights will lower melatonin secretion in just a couple of minutes!
Lastly, there are a couple of free apps that everyone should be using to combat this problem for using their laptops and phones at night. The most popular ones are f.lux for PCs and Twilight for phones. Basically, as the sun is setting, they gradually adapts your screen to the changing light levels by reducing the amount of blue light emitted, which gives it more of a softer red tinge. As the sun rises, the process reverses, until your screen looks the same as it would without the apps running in the background. Try them out and see!