Evening light exposure to computer screens disrupts human sleep, biological rhythms, and attention abilities

May 27, 2017Chronobiology international

Evening computer screen light may disturb sleep, body clock, and attention

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Abstract

Nineteen participants experienced significant sleep disruption under short wavelength light, regardless of intensity.

Short wavelength light exposure significantly disrupted sleep continuity and architecture.
Participants reported greater daytime sleepiness after exposure to short wavelength light.
Short wavelength light altered biological rhythms by reducing the normal nighttime drop in body temperature and lowering melatonin secretion.
Light intensity had a lesser, yet independent, effect on sleep quality.
Both light intensity and wavelength negatively impacted morning attention performance.
Short wavelength light may have a greater influence on sleep and biological functions compared to light intensity.

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The use of electronic devices with light-emitting screens has increased exponentially in the last decade. As a result, humans are almost continuously exposed to unintentional artificial light. We explored the independent and combined effects of two aspects of screen illumination, light wavelength, and intensity, on sleep, its biological regulation, and related functional outcomes. The 2 × 2 repeated-measure design included two independent variables: screen light intensity (low ([LI] versus high [HI]) and wavelength (short [SWL] versus long [LWL]). Nineteen participants (11F, 8M; mean age 24.3 [±2.8] years) underwent four light conditions, LI/SWL, HI/SWL, LI/LWL, and HI/LWL, in counterbalanced order. Each light exposure lasted for two hours (21:00-23:00), following which participants underwent an overnight polysomnography. On each experimental night, oral temperature and urine samples (for melatonin analysis) were collected at multiple time points. Each morning, participants filled out questionnaires and conducted a computerized attention task. Irrespective of light intensity, SWL illumination significantly disrupted sleep continuity and architecture and led to greater self-reported daytime sleepiness. SWL light also altered biological rhythms, subduing the normal nocturnal decline in body temperature and dampening nocturnal melatonin secretion. Light intensity seemed to independently affect sleep as well, but to a lesser degree. Both light intensity and wavelength negatively affected morning attention. In sum, light wavelength seems to have a greater influence than light intensity on sleep and a wide-range of biological and behavioral functions. Given the widespread use of electronic devices today, our findings suggest that screen light exposure at evening may have detrimental effects on human health and performance.

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Evening light exposure to computer screens disrupts human sleep, biological rhythms, and attention abilities

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