Tuning environmental lighting improves objective and subjective sleep quality in older adults

This study investigated the effects of two whole-day ambient lighting interventions applied in living rooms on the objective and subjective sleep quality in older adults. Both lighting interventions were designed to apply a direct/ indirect ambient illumination that delivered a high illuminance level (500lux) in the morning (8:00-12:00). The illumination was gradually dimmed throughout the day and reached 100lux in the evening (after 20:00). One lighting condition (L1) provided a constant Correlated Color Temperature (CCT) of 2700 K. In the other lighting condition (L2), the CCT changed in a range of 6500 K - 2700 K from the morning to the evening. Twenty-one older adults (mean age = 78.81, 16 female) from three residential communities participated in a counterbalanced crossover study. Participants were exposed to each lighting intervention for nine days. Using 41-day actigraphy and standard questionnaires, objective and subjective data of sleep were collected before, during, and after exposure to interventions. Both interventions significantly increased sleep duration at night compared to the baseline with significantly more increase after L2 intervention. Additionally, the L2 intervention significantly improved sleep efficiency and sleep quality and decreased sleep disturbance, sleep-related impairment, and sleep onset latency compared to Baseline and L1. These results provided promising evidence that daily exposure to a whole-day lighting scheme that follows the light/dark cycle could improve sleep quality in older adults; thereby it could be considered as an effective design solution in creating healthy living environments for the senior population.