What if a simple change in your morning light exposure could help you sleep better? Our sleep patterns change across our lifespan, and, as we get older, we tend to have difficulty getting a good night’s sleep and feeling well rested the next day.
Older adults – 60 years old and over – generally have less deep sleep and wake up more often at night. They also sleep for shorter periods, wake up earlier in the morning and feel sleepy during the day.
Light, especially blue-enriched light (which has a higher amount of blue colours in it, like the light at midday), plays an important role in how well we sleep. This is because our sleep timing and quality is influenced by our internal body clock in the brain – the circadian clock – which relies on light and dark to stay in sync with the external environment.
To achieve this, humans have specialised photoreceptors – light-detecting cells on the retinas at the back of the eyes – that are highly sensitive to blue light. This is likely because we evolved to see the natural bright blue sky during the day, rather than indoor electric lights at night which are much less bright – or blue.
As we age, our eyes change: the lens becomes thicker and yellow, and our pupil size and number of photoreceptors reduce. Less light, then, reaches the biological clock in our brain, making it more difficult to time and regulate our sleep-wake cycles.
To make matters worse, modern society’s electric light and bright screens at night trick our body clock into thinking it is still seeing daylight. Bright light at night contributes further to disruptions in our circadian system – and sleep quality and timing.
So, can improving indoor lighting offer an easier, affordable – and medication-free – solution to these problems? Our latest study, published in GeroScience, suggests it can.
Staying bright
We recruited older adults (over 60 years old) with sleep problems to take part in the study. We asked them to follow a light therapy routine in which they administered blue light to themselves, at home, by sitting in front of light boxes. Each morning and evening, they spent two hours exposed to either blue-enriched or regular white light while going about their usual activities, such as reading or watching TV.
Study participants wore trackers on their wrists to measure their activity levels and sleep patterns. We found that people exposed to more hours of blue light in the morning had better sleep and more stable daily activity – likely due to improved synchronisation of their internal body clock with the external environment.
Our findings are especially exciting because despite the messiness of real-world conditions – morning people naturally started light therapy earlier, while night owls delayed it – they align with the findings of controlled laboratory studies, highlighting the real-life potential of home-based light interventions for better sleep. We also found that those who spent more time outdoors in natural daylight were more active during the day and went to bed earlier. This might be because bright light helps keep us alert during the day, making us naturally more tired by bedtime.
Light and dark
Good light exposure isn’t just about bright light in the morning, it is equally about having enough darkness at night. Our study showed that those who spent more time exposed to light in the evening – either blue or white – actually experienced worsened sleep, taking more time to fall asleep and having more restless nights.
This could be explained by the alerting effects of light and suppression of the night hormone, melatonin, which can delay the body’s natural wind-down process.
Sleep problems aren’t just frustrating, they can also lead to health issues such as cardiovascular disease, diabetes, depression and anxiety, cognitive decline and reduced productivity.
While we cannot solve the many sleep problems affecting people, we can offer a possible solution for some: exposure to more morning light – by opening the curtains, stepping outside for a walk, or indeed using a bright, blue-enriched light source indoors.
So, why not try it yourself for a few days – and let us know how you get on. (The Conversation)