A morning dose of blue light might help older people sleep better in the evening, giving them a boost for their daily activities the following day.
Researchers from the University of Surrey in the UK ran an experiment involving 36 volunteers aged 60 or over, testing their response to two-hour-long sessions of blue and regular white light twice a day over several weeks.
The focus on the elderly was deliberate: as we get older, we tend to spend less time outdoors and more time exposed to artificial light, while our aging eyes also let in less blue light. These different factors can all affect the body's circadian rhythms, and subsequently our sleep patterns.
"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," says chronobiologist Débora Constantino from the University of Surrey.
The results were striking: the blue light treatment preceded significantly better quality sleep an increase in regular daily activity. However, this was only true for morning doses, with evening exposure correlating with greater difficulties falling and staying asleep.
Timing is crucial, in other words. The researchers suggest morning doses help train our daily rhythms and teach the body when to be awake, and therefore when to sleep. Evening doses, on the other hand, disrupt the same patterns, which is also why your phone or laptop might come with a blue light filter for evening use.
"Morning blue-enriched light may have increased the signal for wakefulness during the day, increasing sleep pressure and the homeostatic drive for sleep in the evening, thus improving sleep consolidation," write the researchers in their published paper.
The study also showed that daylight exposure – exposure to light above an intensity equivalent to the ambient light of an overcast day – boosted daily activity levels and meant participants tended to get to bed earlier. This fits in with what we know about daylight, which has more blue wavelength light in it, and can boost our mood and levels of alertness.
This idea that blue light therapy could be helpful as we get older has also been shown in previous studies, though those studies usually involved elderly people with dementia who were living in controlled environments. This new research represents more of a real world test.
"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," says chronobiologist Daan Van Der Veen from the University of Surrey.
"By focussing on morning blue light and maximizing daytime light exposure, we can help older adults achieve more restful sleep and maintain a healthier, more active lifestyle."
The research has been published in GeroScience.