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Guidance for optimising lighting in the home to support healthy circadian rhythms in older adults

Electric lighting can be problematic to the ageing eye in that human bodies and our respective functions are generally influenced by light, the most important time trigger for our circadian rhythm, or biological clock. Put simply, the sun rising in the morning lets us know it’s approaching the time to get out of bed, and the sun setting in the evening means it’s time to think about heading off to sleep. This becomes particularly prominent when it comes to those living with dementia, who can typically suffer from sundowning, which results in restlessness, confusion or irritability that can begin or worsen as daylight begins to fade. 

As we age, our eyesight changes dramatically, resulting in reduced visual acuity and colour discrimination and a slowing in the rate at which our eyes adapt to changing light levels and contrast. Studies have shown that these changes can lead to disrupted circadian cycles and sleep patterns if not addressed by the lighting design in care environments for older adults and those living with dementia. 

Without the right colour and intensity level of light at the right times of day, the human circadian system weakens and production of hormones critical to the sleep-wake cycle is affected. Disrupted human circadian rhythms cause negative health & wellbeing impacts, whereas supported human circadian rhythms are proven to improve the wellbeing of older adults and people living with dementia. 

The colour of light 

A good guide for when to use the right colour of LED lamps or bulbs is to try and imitate how our ancestors lived: out in the morning in sunlight and then back into the cave in the late afternoon/evening gathered around the only artificial light source available – fire. Cold white lights contain a lot of blue light which is important for circadian stimulus in the morning, like bright daylight. Warm white lamps are more like the evening fire, very little blue content and so providing much reduced levels of circadian stimulus. The general guide is to use cold white in the morning and warm white in the afternoon and evenings. This should be the same for every day of the year. 

 

The position of lights 

Like sunlight, the best angle for light to give us circadian stimulus in the morning is at or above eye level. This can come from ceiling downlights or reflected light from uplighters or tall lamps. The reason for this is the location of the photoreceptor cells in our eyes that are sensitive to the colour and intensity of light. They channel the light triggers to the part of our brain which “governs” our biological clock 

For late afternoon and evenings lamps at low levels and with warm white light will give minimal disruptive influence to our circadian rhythms. 

 

 

Lighting levels and darkness at night 

Lighting levels and contrast levels between rooms and spaces are also particularly important considerations for older adults. The retina receives less light as one ages because pupil size becomes smaller and other changes in the eye occur. It is estimated that for the same light level, a typical 60-year-old receives about one-third of the retinal illuminance of a 20-year old. So, the brighter the better for the all-important morning stimulus from wake to getting up and about. Even better if you can get outside in sunlight, but if not, bright cold white light from above will help to replace that spot of sun. 

In the evening, the levels should be reduced by dimming or switching to low level lamps with less powerful bulbs, and, of course, in warm white colours. This contrast during the day is signalling the time of day and the change from morning to afternoon to evening. 

To support sleep at night the bedroom should be capable of being completely dark. Use of blackout blinds may be required in addition to curtains in order to keep street lighting from encroaching. It’s also important to have a light to hand for use in the night and this should be sufficient for movement around to the bathroom, for instance, but should also be a warm white light and not cold white or blue. 

Bedrooms: The bedroom is a cosy and intimate space.  Lights should be capable of delivering circadian stimulus through colour and brightness settings, and also be able to provide enough light in the evenings and at night without any potential disruption to the circadian cycle. Bedside lights of a suitable colour and power are a good way to provide comfort and utility of lighting without introducing lighting complications for the circadian-supportive environment. 

Bathrooms: Being a functional space, the bathroom should have bright lights but also provide a good night-time light level and setting which does not disrupt circadian cycles. Sensor-activated lights may be useful and are also a good way to minimise energy use. 

Dining areas: Dementia-affected persons may find it difficult to eat without adequate lighting. A good even and wide level of illumination is important so ceiling and wall lights are particularly effective in dining areas and lounges. Care should be taken to avoid shadows and creating bright or dark areas within a room.  

Stairs, hallways and corridors: all should have good levels of lighting with no dark or shadow areas, if possible. Unless people are spending long periods of time in these areas the circadian-supportive considerations are less than for other areas of the home. A mid-white colour of lamp (i.e. 4000K) is useful for these spaces. 

These suggestions are provided by Circadacare and informed by our experience with circadian lighting in care homes and dementia care, as well as a significant body of research. For more detailed information our White Paper on Circadian Lighting Research may be downloaded from www.circadacare.com 

 

Recommended Reading: 

Life Time. Written by Russell Foster, Professor of Circadian Neuroscience, University of Oxford. Published by Penguin Life 

Chasing The Sun. Written by Linda Geddes published by Profile Books and Wellcome Collection