0942 Effects of Timed Light on Mood and Cognition in Alzheimer`s Disease

Circadian disturbances are often associated with cognitive decline in patients with Alzheimer’s disease(AD). Reduced light exposure in addition to the degeneration of circadian clock in AD might lead to depression. Light therapy(LT) has been known to improve depression and cognitive function by stabilizing the circadian rhythm. We aimed to examine the effects of timed LT on mood and cognition in AD patients. We recruited mild to moderate AD patients with Pittsburgh Sleep Quality Index score ≥ 5. They were randomly assigned to treatment group(TG) and control group(CG). The dim light melatonin onset(DLMO) was determined from seven hourly saliva samples obtained before sleep onset measured by actigraphy. Home-based one-hour blue-enriched light was applied between 9to 10h after DLMO for 2 weeks. The CG patinets wore blue-blocked glasses during timed LT. The Cornell Scale for Depression in Dementia(CSDD), Global Vigor(GVS) and Affect Scale(GAS) were administered before and immediately after timed LT. The MMSE in the Korean version of CERAD Packet(MMSE-KC), Trail Making Test-A(TMT-A), Digit Span Forwards(DSF) and Backwards(DSB) tests were also assessed. Changes in the values assessed before and after timed LT were analyzed for 15 patients(76.9±5.5years) of TG and 11 patients(78.3±7.7years) of CG. The effects of group and time were evaluated using two-way repeated measures ANOVA. There were no significant changes in the scores of the GVS and GAS after timed LT in both groups, while the TG showed reduced CSDD scores with an expected trend(7.6±5.7to 5.2±3.8, p=.1). The CG had significantly increased MMSE-KC scores(p<.05) after timed LT, and the MMSE-KC scores yielded a significant time effect(F1, 22=9.94, p<.01) with no significant group effect or interactions. No significant changes in the scores of the TMT-A, DSF and DSB were found after timed LT in both groups. Our finding suggests that timed LT would be beneficial for improving the overall cognitive function in AD patients. And LT might influence reducing their depressive symptoms. Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning(2017R1A2B4003493)