Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial.
Level 2 - randomized trial
Multicenter double-blind placebo-controlled factorial randomized trial
PubMed 18544724 · doi:10.1001/jama.299.22.2642
What was done
A double-blind, placebo-controlled, 2 x 2 factorial randomized trial evaluated long-term daily exposure to whole-day bright (+/- 1000 lux) versus dim (+/- 300 lux) light (randomized by facility) and evening melatonin (2.5 mg) versus placebo (randomized by participant). The study enrolled 189 residents (mean age 85.8 years; 90% female; 87% with dementia) across 12 group care facilities in the Netherlands. Participants were followed for a mean of 15 months (SD 12 months; maximum 3.5 years), with standardized cognitive, noncognitive, activities of daily living, and adverse effect scales assessed every 6 months.
What was found
Bright light attenuated cognitive deterioration by a mean of 0.9 points on the Mini-Mental State Examination (95% CI, 0.04 to 1.71; 5% relative benefit), reduced depressive symptoms by 1.5 points on the Cornell Scale for Depression in Dementia (95% CI, 0.24 to 2.70; 19% relative benefit), and attenuated functional limitation increases by 1.8 points per year on an activities of daily living scale (95% CI, 0.61 to 2.92; 53% relative difference). Melatonin shortened sleep onset latency by 8.2 minutes (95% CI, 1.08 to 15.38; 19%) and increased sleep duration by 27 minutes (95% CI, 9 to 46; 6%), but worsened positive affect (-0.5 points; 95% CI, -0.10 to -1.00), negative affect (0.8 points; 95% CI, 0.20 to 1.44), and withdrawn behavior (1.02 points; 95% CI, 0.18 to 1.86). Combined light and melatonin attenuated aggressive behavior by 3.9 points on the Cohen-Mansfield Agitation Index (95% CI, 0.88 to 6.92; 9%), increased sleep efficiency by 3.5% (95% CI, 0.8% to 6.1%), and reduced nocturnal restlessness by 1.00 minute per hour each year (95% CI, 0.26 to 1.78; 9%).
Why it matters
Environmental whole-day bright light provides modest cognitive, mood, and functional stabilization in institutionalized elderly patients. Melatonin alone may aggravate negative affect and withdrawn behavior, indicating it should be co-administered with bright light when used for sleep disturbances in dementia.
Limits
The study population was 90% female and restricted to institutionalized residents in Dutch group care facilities, limiting generalizability to men and community-dwelling individuals. Light was cluster-randomized across only 12 facilities. High variance in follow-up duration (mean 15 months, SD 12 months) indicates substantial attrition over time, and the absolute effect sizes across cognitive and behavioral scales were modest.
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