Light is a basic part of daily life, but its role in the body goes beyond vision. Daylight provides an important environmental signal for the biological clock, helping align daily patterns such as sleep and wakefulness with the day-night cycle. As people age, changes in the way the body responds to light can make this relationship particularly relevant for older adults. At the same time, older adults may receive less daylight because of changes in daily routines, time spent indoors and other age-related factors. This makes the relationship between daylight exposure and ageing worth a closer look. Could the light in an older person’s home have a role in healthy ageing?
Researchers examined this question by looking at how natural daylight exposure and supplemental indoor light relate to sleep, activity and daily rhythms in older adults. Their findings linked greater daytime light exposure with higher activity, more consolidated wakefulness and better reported sleep quality, while the timing of supplemental light was associated with measures of rest and activity. Because these functions are important aspects of daily life in later years, the findings help explain why light exposure may be relevant when considering healthy ageing.
What did the study find about light, sleep and activity in older adults?
Researchers from the University of Surrey and collaborators studied 202 adults aged 63 to 92 in Amsterdam, Bologna and Tartu as part of the European ENLIGHTENme project. Participants continued their usual daily routines while researchers measured their light exposure and activity. Wrist actigraphy recorded rest and activity patterns, while a pendant sensor measured personal light exposure. Participants also reported their sleep quality and daytime sleepiness. The researchers measured dim light melatonin onset, or DLMO, as a marker of circadian timing.
Participants with higher natural daytime light exposure were more active during the day. They also had more consolidated wakefulness and reported better sleep quality. The study also found lower total light exposure among participants who reported metabolic conditions such as high blood pressure, diabetes, obesity or cardiovascular conditions. This was an association observed at baseline. The study cannot establish that lower light exposure caused these conditions or that increasing light exposure would prevent them.
Can bright indoor light affect circadian rhythms?
The researchers randomly assigned participants to either a light supplementation group or a control group. The light group used a HALO lamp at home for 12 weeks. Participants were instructed to use the lamp within one hour of waking, not before sunrise, and to switch it off no later than four hours before their usual sleep time. The lamp was placed at head height in the room used most often. The researchers were interested not only in how much supplemental light participants received, but also when they used it. Participants who started supplementation earlier in the morning had higher daytime activity and less fragmented rest-activity rhythms.
Rest-activity fragmentation refers to interruptions and irregularity in periods of rest and activity. The researchers measured it using intradaily variability, or IV. Earlier supplementation was associated with lower IV, including after adjustment for chronotype and other factors. Chronotype describes a person’s preferred timing of sleep and activity. Morning types in the study tended to start their light exposure and daily activity earlier. The overall randomized intervention did not show significant differences between the light and control groups when the timing of supplementation was not considered. The results therefore do not show that simply receiving a bright light lamp improves sleep or activity.
Why might the timing of light matter?
Light exposure was related to participants’ daily routines and the season. Participants who spent less time outdoors tended to use supplemental light for longer. During winter, participants also tended to use the lamps for longer periods as daylight hours became shorter. The timing of supplementation was associated with activity and rest-activity measures. Participants who started supplementation before 10 a.m. had greater daytime activity and lower rest-activity fragmentation. Ending supplementation earlier was also associated with lower fragmentation in some analyses.
The study had several limitations. Objective light exposure was measured during two 14-day periods rather than throughout the entire 12-week intervention. Participants also controlled their own lamp use, and the distance between the lamp and the participant was not standardized. Use of the lamp varied among participants. At follow-up, 52 of the 98 people assigned to the supplementation group reported using the lamp every day. The study population was predominantly female and may have been more active and educated than the wider population of older adults. The number of participants also differed between the three study locations.
The researchers concluded that daytime light supplementation may have a role as a non-pharmacological approach for older adults, while emphasizing that supplemental light should complement natural daylight rather than replace it. Further studies are needed to test whether light schedules based on individual chronotype produce more consistent results. The researchers also identified reminder or timer systems and better measurement of light exposure as areas for future work. For this study, the clearest findings concern the relationship between daytime light exposure and activity, wakefulness and subjective sleep quality. The timing of supplemental light was also associated with measures of rest-activity organization. The randomized intervention itself did not show an overall effect when supplementation timing was not taken into account.
FAQs on Indoor Light Supports Healthy Ageing
Q: How can indoor light support healthy ageing in older adults?
A: The study found that older adults with higher natural daytime light exposure were more active during the day, had more consolidated wakefulness and reported better sleep quality. Supplemental indoor light was also associated with activity and rest-activity patterns when it was used earlier in the day.
Q: Can bright light therapy help older adults sleep better?
A: Higher natural daytime light exposure was associated with better reported sleep quality in the study. However, the randomized light supplementation intervention did not show an overall significant difference between the light and control groups when the timing of lamp use was not considered.
Q: What is the best time of day to use a light therapy lamp?
A: In this study, participants were instructed to begin using the lamp within one hour of waking and not before sunrise. Starting supplemental light earlier, particularly before 10 a.m., was associated with greater daytime activity and less fragmented rest-activity rhythms.
Q: Does morning light help regulate sleep patterns in older adults?
A: The study found that earlier supplemental light use was associated with lower rest-activity fragmentation. Morning types also tended to have earlier light exposure and activity patterns, but the study does not establish that morning light alone changes a person’s circadian rhythm.
Q: Is natural daylight better than indoor light for healthy ageing?
A: The researchers did not suggest replacing natural daylight with artificial light. Their findings support using supplemental indoor light as a possible complement to natural daylight when daytime exposure is limited.
Q: Who may benefit from using bright indoor light during the day?
A: The study involved adults aged 63 to 92 living in three European cities, so its findings are most directly relevant to a similar older population. It does not establish that every older adult will benefit, and the researchers noted that their participants may have been more active and educated than the general population.
Q: How long should older adults use a bright light lamp?
A: Participants in the study were asked to use the lamp for 12 weeks as part of the daytime light supplementation intervention. Actual use varied considerably, so the study does not establish a single daily duration that works for everyone.
Q: Can indoor light improve daytime activity in older adults?
A: The study found that greater natural daytime light exposure was associated with higher daytime activity. Earlier use of supplemental light was also associated with greater activity, although these findings do not prove that increasing indoor light directly causes people to become more active.
Q: Should you use a bright light lamp in the evening or before bed?
A: The study’s supplementation protocol focused on daytime use, with participants instructed to switch the lamp off no later than four hours before their usual sleep time. The researchers found that earlier ending of supplementation was associated with lower rest-activity fragmentation in some analyses. Q: How much does a bright light therapy lamp cost?
A: The study did not evaluate the purchase price of the lamp or compare the costs of different light therapy devices. It therefore cannot establish how much a suitable lamp should cost or whether using one is cost-effective for an individual.
References
- Constantino DB, Baccari F, Caporali L, Carelli V, Amore G, Gordijn M, et al. ENLIGHTENme: Translating the Benefits of Self-Administered Daytime Light Supplementation to Older Adults in the Real World. Journal of Pineal Research 78 (2026): e70174. Doi: 10.1111/jpi.70174.
- Li J, Wang T, Shao R, Yu C, Hao L, Wu Y. Quantitative Study of Indoor Light and Sleep Health in Elderly. HERD: Health Environments Research & Design Journal. 2026 Jul;19(3):31-49. Doi: 10.1177/19375867261426378.
- Barroggi Constantino D, Lederle KA, Middleton B, Revell VL, Sletten TL, Williams P, Skene DJ, van der Veen DR. The bright and dark side of blue-enriched light on sleep and activity in older adults. Geroscience. 2025 Jun;47(3):3927-39. Doi: 10.1007/s11357-025-01506-y.
- Cheng S, Zhang J, Li R, Cheng Y, Cheng L. Effects of bright light therapy on cognition, sleep and psychological stress in older adults with mild-to-moderate cognitive impairment: a pilot study in long-term care facilities. BMC geriatrics. 2026 Dec;26(1):789. Doi: 10.1186/s12877-026-07520-9.
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