The quality of light people live with matters to their physical and mental wellbeing. And by quality I really mean its dynamics. Not brightness. Not colour temperature. But the dynamic, ever-shifting quality of natural light that has helped to shape human physiology.

The Problem We’ve Created

Walk into most care settings and you’ll find lighting designed for efficiency and safety. Bright enough for staff to work. Uniform enough to eliminate shadows. Static enough to forget it’s even there.

This makes perfect sense from an operational perspective, but put simply, it removes a powerful environmental cue the body relies on to function well.

The circadian system – that body clock that governs sleep, hormone release, and countless other processes – depends on light as its primary time signal. Morning light contains more blue wavelengths, signalling alertness, and evening light shifts toward warmer tones, allowing melatonin to rise and sleep pressure to build.

Remove these transitions, and the system is adrift. For people with dementia, whose internal clocks are already compromised, this can lead to confusion, agitation, and the distressing sundowning behaviours that make evenings so challenging.

What We’re Learning

Research into circadian lighting, which tries to replicate natural light rhythms, has shown remarkable promise. Studies in care homes have documented reductions in nighttime waking, improvements in daytime alertness, and decreases in agitation.

Simply dimming lights in the evening isn’t enough. The human circadian system responds most strongly to blue wavelengths. This means even dim light can be alerting if it contains significant blue content, which is not always easy to spot in blended white lights. Brighter light can be appropriate for the evening if the blue wavelengths are reduced enough.

The Broader Impact

Lighting is only one piece of the care environment puzzle. But it seems so fundamental to bring back this natural influence. Good sleep makes medication more effective. Stable circadian rhythms improve cognitive function. Appropriate environmental cues reduce behavioural symptoms without additional interventions.

When we get the basics like light, sleep and daily rhythms right, we create the conditions for everything else to work better.

For too long, we’ve accepted disrupted sleep and behavioural challenges as inevitable consequences of dementia. We can do better – not through heroic interventions, but through careful attention to fundamentals: the daily rhythm of light and dark that has shaped human biology since the beginning.

It’s time we brought that rhythm back into places where people need it most.

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