Morning blue light exposure improves sleep and activity levels in older adults

Want to improve sleep and feel more active during the day? For older adults, the answer might be as simple as switching to blue-enriched light in the mornings. A recent study published in GeroScience shows that this type of light can positively influence the body’s natural rhythms, resulting in better sleep and increased daytime engagement for seniors at home.

As people get older, their sleep patterns often change, and they may find it harder to get restful sleep. These changes can include sleeping less deeply, waking up more during the night, and feeling tired during the day. One reason for this is that as we age, our eyes become less effective at letting in light, which is important for regulating our body’s natural sleep-wake cycle. Think of our bodies as having an internal clock that is set by daylight. Reduced light input can weaken this clock, making it harder to maintain a consistent sleep schedule. Furthermore, older adults may spend less time outdoors in bright daylight and more time indoors under artificial light, which can also disrupt their natural rhythms.

Past research has indicated that blue light, which is a type of short-wavelength light, is particularly powerful in influencing our body’s biological clock. It is known to have a strong effect on alertness and can shift our sleep-wake cycle. Previous studies have explored the use of blue-enriched light to help older adults, especially those in care facilities or with dementia. These studies suggested that such light could boost daytime activity and improve sleep.

However, many of these studies were conducted in controlled environments like hospitals or care homes, and often for short periods. This left a gap in understanding how blue-enriched light might help generally healthy older adults living independently at home over a longer duration.

The researchers behind the new study wanted to investigate the effects of different types of light, administered in people’s own homes over several weeks, on their sleep, daily activity, and exposure to light. They aimed to see if using blue-enriched light, compared to regular white light, could improve sleep and activity patterns in older adults experiencing sleep problems in their everyday lives.

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To conduct this study, the researchers recruited 36 adults aged 60 and older who lived at home and reported having sleep difficulties. Participants were not working full time and were generally healthy, without major medical conditions, and not taking medications that heavily affect sleep. The study was designed as a crossover trial, meaning each participant experienced both types of light being tested. The study lasted for 11 weeks and was conducted during the autumn and winter months, when natural daylight is typically reduced.

The study began with a week of baseline measurements to understand participants’ usual sleep and activity patterns. Then, for three weeks, participants used either a blue-enriched white light box or a standard white light box in their homes. After this, there was a two-week break period where they did not use any special lights.

Following the break, they then used the other type of light box for another three weeks, followed by a final two-week break. This design ensured that each person experienced both the blue-enriched light and the control light conditions. Participants were randomly assigned to start with either the blue-enriched light or the standard white light.

The light boxes were designed to be used for two hours each day, once in the morning and once in the evening. Participants were instructed to complete their morning light session before 11:00 AM and their evening session before 10:00 PM. They could choose the exact times within these windows and were asked to sit about two feet away from the light box while doing activities like reading or watching television. They also kept a diary to record when they used the light. The researchers used two different intensities for each light type, but the main comparison was between the blue-enriched white light and the standard white light.

Throughout the study, participants wore small activity monitors on their wrists to track their movements and sleep-wake patterns. They also wore a light sensor around their neck during the day to measure their personal light exposure levels. These devices recorded data continuously. Additionally, participants completed daily sleep diaries to record their bedtime, wake-up time, and how well they slept. At several points during the study, they also filled out questionnaires about their sleep quality.

The researchers analyzed the data collected from the activity monitors and sleep diaries to assess various aspects of sleep and daily activity. They looked at the regularity of participants’ activity patterns, how fragmented their sleep was, and their overall activity levels during the day and night. They also examined how these measures changed when participants used the blue-enriched light compared to the standard white light.

The study’s findings showed that using blue-enriched light in the morning had a positive impact on the participants. Specifically, longer morning exposure to blue-enriched light was linked to more stable daily activity patterns and less fragmented sleep. This means that their daily routines became more consistent, and their sleep was less disrupted.

However, using the same blue-enriched light in the evening did not have the same beneficial effects; in fact, it seemed to negatively affect sleep in some ways. For instance, longer evening light exposure was associated with taking longer to fall asleep and experiencing less efficient sleep overall.

“Our research shows that carefully timed light intervention can be a powerful tool for improving sleep and day-to-day activity in healthy older adults,” said Daan Van Der Veen, a senior lecturer in sleep and chronobiology at the University of Surrey. “By focusing on morning blue light and maximising daytime light exposure, we can help older adults achieve more restful sleep and maintain a healthier, more active lifestyle.”

Interestingly, the study also found that spending more time in bright outdoor light, indicated by higher light levels measured by the neck sensors, was associated with several benefits. Participants who spent more time in bright light during the day tended to have stronger daily activity rhythms, higher levels of daytime activity, and earlier bedtimes.

Débora Constantino, a postgraduate research student at the University of Surrey added: “We believe that this is one of the first studies that have looked into the effects of self-administered light therapy on healthy older adults living independently, to help aid their sleep and daily activity. It highlights the potential for accessible and affordable light-based therapies to address age-related sleep issues without the need for medication.”

The study, “The bright and dark side of blue-enriched light on sleep and activity in older adults,” was authored by Débora Barroggi Constantino, Katharina A. Lederle, Benita Middleton, Victoria L. Revell, Tracey L. Sletten, Peter Williams, Debra J. Skene, and Daan R. van der Veen.