Can sleep quality and wellbeing be improved by changing the indoor lighting in the homes of healthy, elderly citizens?

The study investigated the effect of bright blue-enriched versus blue-deprived indoor light on sleep and wellbeing of healthy participants over 65 years. Twenty-nine participants in 20 private houses in a uniform settlement in Copenhagen were exposed over 3 weeks to blue-enriched (280 Lux) and 3
weeks to blue-deprived (240 Lux) indoor light from 8 to 13 pm in a randomized cross-over design. The two light epochs were separated by one week neutral indoor light. Participants were examined at baseline and at the end of each light epoch. The primary endpoint was sleep duration during the last week of each light epoch measured by diary. Sleep quality was assessed using Pittsburg sleep
questionnaire index (PSQI). Circadian rhythm was measured by Morningness-Eveningness questionnaire (MEscore), chromatic pupillometry and melatonin sampling. Actiwatches were used to monitor light exposure and activity. The subjective response to changes in light was assessed by a visual analog scale (VAS).