Circadian rhythms: embedded within our genes
Light and the modern world
Most life on earth has adapted to the 24-hour light-dark cycle that underpins our physiology. Before industrialization and widespread availability of electricity, daily life was restricted to natural day-night periods. The introduction of electric lighting led to changes in our environment and the way we interact throughout the day.
55% of the world’s population now inhabit the cities, and we, the urban dwellers, no longer rely on the natural light-dark periods for our sleep-wake cycles. More importantly, we spend more than 90% of our time indoors exposed to artificial lighting. However, lighting standards in our environments are not tailored to be optimal for our health and well-being and often meet only minimal illuminance levels. This has had a profound impact on our physiology considering that light is the strongest environmental cue regulating the body’s circadian rhythms.
The evolution of light from 1879 to present.