How light sensitivity affects sleep and circadian rhythm

23 May How light sensitivity affects sleep and circadian rhythm

Over exposure to artificial evening and night lighting used in our home and work environments in industrialised societies has the potential to affect our biological 24hr circadian rhythm, mental alertness, emotional wellbeing and our sleep-wake cycles.

Predictions show that over the past 10 years approximately 10% to 23% of the world’s land mass shows artificial light, including sky glow, at night. Individuals in industrialised societies are increasing exposed to low natural daytime light levels, inadequate indoor daytime light, and high evening artificial light exposure. This exposure includes artificial room lighting, smartphones, and visual display units.

Evidence indicates that differences in photosensivity, in reponse to overexposure of artificial evening night light, and the affects on sleep-wake circadian rhythm, varies greatly across individuals. Biological differences in age, sex, chronotype and genetic predisposition all create individual differences within the retina and the downstream biological mechanisms that control melatonin production and the regulation of the central circadian clock. Understanding individual variations in sensitivity to artificial night light exposure may provide guidelines for lighting specifications to improve sleep and circadian rhythms and optimizing personalized lighting solutions.


Sarah L Chellappa. Individual differences in light sensitivity affect sleep and circadian rhythms. Sleep, Volume 44, Issue 2, February 2021, zsaa214,