Study Links Earlier Indoor Light Use With Activity and Sleep Measures in Older Adults

Older adults living in three European cities showed differences in activity, sleep and daily rest–activity patterns linked to their exposure to light, according to a University of Surrey study published in the Journal of Pineal Research. The researchers examined whether bright-light therapy lamps could provide useful daytime light supplementation in everyday settings.

The study enrolled more than 200 people ages 63 to 92 in Tartu, Bologna and Amsterdam. The cities were selected in part because they have different cultural settings and seasonal daylight patterns. After two weeks of baseline assessments, participants were assigned either to receive a light-therapy lamp or to a control group without one. The study was repeated across all seasons.

Participants given lamps were asked to position them at head height in the room where they spent the most time at home. They were instructed to switch the lamp on within an hour of waking and turn it off no later than four hours before their usual bedtime. Over the 12-week study period, all participants wore wrist actigraphy monitors to track activity and rest, along with pendant sensors that measured light exposure.

The researchers reported that participants who had higher natural-light exposure at baseline were more active during the day, had more consolidated daytime wakefulness and reported better sleep quality than those with lower exposure. Baseline data also showed that participants who reported metabolic disorders—including high blood pressure, diabetes, obesity or cardiovascular conditions—had lower total light exposure than participants who did not report a metabolic disorder.

Timing appeared to matter. Participants identified as morning types who began using the lamps earlier had higher daytime activity and less disrupted rest–activity rhythms than morning types who started later. Those who ended supplementation earlier, reducing their exposure to light in the evening, also had less fragmented rest–activity patterns.

The findings build on controlled laboratory research cited by the University of Surrey, where similar lamps have been reported to reduce circadian misalignment. The new study was designed to test whether those observations were reflected under real-world conditions involving different homes, behaviors, seasons and levels of natural daylight.

The researchers described indoor light supplementation as a potentially low-cost, nonpharmacological approach that could be considered in community-care and care-home settings. However, the reported results also highlight the importance of individual behavior and environmental conditions: when participants used the lamps, how much natural light they received and how much evening light they experienced all varied. The study therefore provides evidence about light exposure and daily rhythms in older adults, but does not establish that lamp use prevents chronic disease or extends lifespan.