The study, published in September 2026 in the Journal of Pineal Research, involved 202 participants aged 63 to 92 from Amsterdam, Bologna, and Tartu.
One group of participants in the experiment received special bright lamps for light therapy, while the other group continued with their usual lighting. Sensors recorded when and how much light participants in both groups were exposed to, as well as their physical activity.
Participants who received a lamp were advised to switch it on within an hour of waking, but not before sunrise, to use it for at least two hours a day, and to switch it off at least four hours before bedtime.
The study investigated whether daytime alertness, sleep, and cognitive functions could be supported by changing lighting conditions without deliberately changing physical activity or diet.
The researchers found that people who were exposed to more light during the day:
- Were more physically active (according to accelerometer measurements).
- Had longer uninterrupted periods of activity during the day, with fewer transitions between activity and rest.
- Reported better sleep quality.
However, these were observational associations. Perhaps people move more because they receive more light. But the reverse is also possible: more active people spend more time outdoors and therefore receive more light. In addition, health status may influence both physical activity and time spent outdoors. Therefore, we cannot conclude that light itself caused all these differences.
Another interesting finding was that participants who started using their lamps earlier in the day were more active and switched less frequently between activity and rest than those who switched their lamps on later. Wiley Online Library
Light performs two distinct functions in the body. Its visual function enables us to read, recognize objects, and navigate our surroundings. Its regulatory function provides the nervous system with information about the time of day.
The retina contains specialized light-sensitive cells that transmit information about ambient light to the brain, helping synchronize internal physiological processes with the external cycle of day and night (regulation of circadian rhythms).
As we age, the lens of the eye becomes less transparent to short-wavelength light, and the pupil becomes smaller. As a result, less light reaches the retina. Lighting that is sufficient for reading may therefore not provide as strong a circadian signal as it does in younger people. Wiley Online Library
A practical conclusion follows: Regularly spending time outdoors during the first half of the day is a sensible way to increase exposure to natural daylight.
However, no differences in cognitive functions were found between the two experimental groups.