OBJECTIVES-To test whether the addition of melatonin to bright-light therapy enhances the efficacy in treating rest-activity (circadian) disruption in institutionalized patients with Alzheimer's disease (AD). DESIGN-Randomized, controlled trial. SETTING-Two nursing homes in San Francisco, California.PARTICIPANTS-Fifty subjects (mean age 86) with AD.INTERVENTION-Experimental subjects received 1 hour of morning light exposure (≥2,500 lux in gaze direction) Monday to Friday for 10 weeks and 5 mg melatonin (LM, n = 16) or placebo (LP, n = 17) in the evening. Control subjects (n = 17) received usual indoor light (150-200 lux).MEASUREMENTS-Nighttime sleep variables, day sleep time, day activity, day:night sleep ratio, and rest-activity parameters were determined using actigraphy.RESULTS-Linear mixed models were employed to test the primary study hypotheses. No significant differences in nighttime sleep variables were found between groups. At the end of the intervention, the LM group showed significant improvement in daytime somnolence as indicated by a reduction in the duration of daytime sleep, an increase in daytime activity, and an improvement in day:night sleep ratio. The LM group also evidenced a significant increase in rest-activity rhythm amplitude and goodness of fit to the cosinor model. CONCLUSION-Light treatment alone did not improve nighttime sleep, daytime wake, or restactivity rhythm. Light treatment plus melatonin increased daytime wake time and activity levels and strengthened the rest-activity rhythm. Future studies should resolve the question of whether these Address correspondence to Glenna A. Dowling, PhD, Department of Physiological Nursing, University of California, San Francisco, 2 Koret Way, Room N631, San Francisco, CA 94143. E-mail: glenna.dowling@nursing.ucsf.edu. Conflict of Interest:The editor in chief has reviewed the personal and financial checklist provided by the authors and has determined that none of the authors have any conflicts related to this manuscript.Author Contributions: Glenna A. Dowling, principal investigator, and Jay S. Luxenberg, co-investigator: study concept and design, acquisition of subjects and data, analysis and interpretation of data, and preparation of manuscript. Erin M. Hubbard: acquisition of subjects and data, analysis and interpretation of data, and preparation of manuscript. Robert L. Burr, Eus J. W. Van Someren, Judy Mastick, and Bruce A. Cooper: analysis and interpretation of data and preparation of manuscript. Exposure of the eyes to light of sufficient intensity and duration at the appropriate time of day can have profound effects on the quality, duration, and timing of sleep. The retinohypothalamic tract mediates the effect of light on the brain, and the daily light-dark cycle is the primary synchronizer responsible for entrainment of circadian rhythms to the 24-hour day. In an institutional environment, where light levels tend to be low, residents may not be exposed to sufficient bright light to entrain to the 24-hour day. 6 NIH Public AccessT...

Although significant improvements were found in subjects with aberrant timing of their rest-activity rhythm, morning bright light exposure did not induce an overall improvement in measures of sleep or the rest-activity in all treated as compared to control subjects. The results indicate that only subjects with the most impaired rest-activity rhythm respond significantly and positively to a brief (one hour) light intervention.