Evening Light Reduction

Ordinary household lighting is bright enough to matter. In a controlled study, room light under 200 lux in the eight hours before bed pushed melatonin onset later in 99% of participants and shortened melatonin duration by about 90 minutes; a separate trial found four hours of an LED reader before bed delayed circadian timing, lengthened sleep onset, and reduced next-morning alertness. What is not settled is how much dimming any particular household needs — individual sensitivity to evening light varies widely between people. Treat the targets below as starting points and judge them on how long you take to fall asleep.

Supported. Useful evidence exists, but outcomes or dosing vary. How Compound evaluates evidence

• Gooley et al., Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans (J Clin Endocrinol Metab, 2011)
• Chang et al., Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness (PNAS, 2015)