Warm vs. cool light before bed: the colour is only part of the story.
Brightness, timing and duration matter alongside the apparent colour of a bulb or screen.
What research supports
Short-wavelength light is relevant, but product labels oversimplify it.
A systematic review of light exposure and circadian rhythm concluded that the timing and spectrum of light can affect melatonin-related measures and circadian timing. It also found substantial variation in research methods and many small samples.[1] A separate review of sleep outcomes found that timing moderated the relationship between light and sleep.[2]
A practical interpretation
For the wind-down period, use the smallest, least bright light that lets you read, get ready and move safely. A warm-looking lamp can feel more relaxed, but dimming and placement are equally useful controls.
Avoid a false promise
There is no universal “best colour temperature” that guarantees sleep. Do not choose a product solely because its marketing calls it sleep-friendly.
What to compare in a lamp
Control beats a single fixed setting.
Prioritise a dimmable range, easy bedside controls, a shade that reduces glare, timer options if useful, and a return policy. These features help you adapt light to the task rather than relying on one colour claim.
Return to the lighting guide →References
Research cited in this article
- Tähkämö L, Partonen T, Pesonen A-K. Systematic review of light exposure impact on human circadian rhythm. Chronobiology International. 2019;36(2):151–170. doi: 10.1080/07420528.2018.1527773. PMID: 30311830.
- Dautovich ND, Schreiber DR, Imel JL, et al. A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults. Sleep Health. 2019;5(1):31–48. doi: 10.1016/j.sleh.2018.09.006. PMID: 30670164.