Abstract
The prevalence of sleep problems in elderly care home residents may be explained by age-related changes in the circadian timing system, the homeostatic regulation of the sleep/wake cycle, reduced visual function and inadequate light exposure. This study investigated the effect of a continuous daytime light intervention in communal care home rooms on the light environment, on care home residents' light exposure and rest-activity rhythms. The 12-week study was conducted in recruited participants (11 males 69 females, 86±8 years) in seven care homes during the autumn/winter months. After a baseline week, each light intervention period (4000 K 200 lux or 17000 K 1000 lux) lasted 4 weeks, with a 3-week washout period in between (original care home lighting <100 lux). Light exposure (n = 44) and rest-activity (n = 52) data were recorded constantly using wrist worn Actiwatches. The 17000 K light condition significantly increased the light intensity of the room environment and the time that residents spent in bright light. In the 17000 K light condition, the peak time of activity (acrophase) was significantly advanced and the mean activity level during the day (M10) and night (L5) increased compared to the 4000 K light condition. Participants with the most light exposure (338±105 mins/day >100 lux) during the 17000 K light condition had significantly more advanced L5 and M10 onset times compared to the participants that spent the least amount of time in the light (46±21 mins/day >100 lux). Despite the heterogeneity of the study population (65% on medication and 64% wheelchair bound), this study demonstrated that the 17000 K light intervention was sufficient to affect some rest-activity parameters significantly.