Dim light in the evening

Lower light intensity in the last hours before bed so the clock can wind down.

Why it works

Light in the evening delays the circadian clock and suppresses melatonin, the hormone that signals biological night. Bright artificial light after dusk effectively tells the brain it is still daytime, pushing your sleep window later and blunting the nighttime melatonin rise.

How to do it

1. Drop overall light levels for the last hour or two before bed — fewer, dimmer, lower lamps.
2. Favor warm, low light over bright overhead lighting in the evening.
3. Keep the bedroom dark for sleep; even small light sources can intrude.

Evidence

Evening light exposure delaying circadian phase and suppressing melatonin is well documented; brighter evening light produces larger melatonin suppression and phase delay. Ordinary room light before bed measurably suppresses and shortens the nightly melatonin rise, showing that everyday indoor brightness — not just screens — is enough to push the clock later. (rct)

The dominant lever is overall light intensity and timing, not just screen "blue light"; reducing total brightness matters more than the color filter alone.

Sources

• Gooley et al. (2011), exposure to room light suppresses melatonin, J. Clinical Endocrinology & Metabolism
• Gooley JJ, Chamberlain K, Smith KA, Khalsa SBS, Rajaratnam SMW, Van Reen E, Zeitzer JM, Czeisler CA, Lockley SW (2011). Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. The Journal of Clinical Endocrinology & Metabolism, 96(3), E463-E472.
• Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA (2000). Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. The Journal of Physiology, 526(3), 695-702.
• Cajochen C, Frey S, Anders D, Späti J, Bues M, Pross A, Mager R, Wirz-Justice A, Stefani O (2011). Evening exposure to a light-emitting diode (LED)-backlit computer screen affects circadian physiology and cognitive performance. Journal of Applied Physiology, 110(5), 1432-1438.

Common mistake

Trusting a blue-light filter while leaving bright overhead lights on — total light intensity is the main driver, not screen color alone.