Give daytime and evening different lighting
Healthy adults with a regular daytime schedule can start with three everyday actions: use daylight during the day and spend time outdoors when conditions allow, reduce unnecessary bright lighting before bed, and keep the sleep environment dark. These concern light reaching the eyes and its timing, not increasing skin UVB.
Daytime: make room for natural light
For example, spend a break outdoors in daylight or use suitable window light for daytime reading. Choose shade, comfort and a safe setting; check local UVI and weather outside. Window light can provide visible light without being a skin UVB source: the purposes differ.
Evening: reduce unnecessary bright light
Near bedtime, dim unnecessary overhead or bright lighting while retaining safe light for movement and reading. A phone is only part of the light environment; room lighting and timing also matter. During sleep, consider outside light and indicator lights that keep the room bright.
Who the guidance addresses
This article draws on a 2022 expert consensus on indoor light in healthy adults aged 18 to 55 with regular daytime schedules, translating its direction into everyday observations and actions. Children, older people, shift workers, travellers and those with specific conditions need appropriate individual arrangements. Persistent sleep problems warrant professional help.
The same light can matter differently at different times; indoor illuminance, light reaching the eyes and skin UVI are not equivalent measures. Use the everyday steps without converting weather UVI into an eye-light target or looking directly at the sun.
An ordinary workday example
Someone working indoors by day and using bright lights at night could start with one manageable change: take a lunch break outdoors when weather and protection allow, then adjust unnecessary evening lighting. Observe feasibility and routine rather than change everything at once or assume one change has already improved sleep.
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