The Effects of Light Therapy for Depression in Dementia: A Systematic Review and Meta-Analysis

Background: Depression is one of the most common symptoms in patients with dementia. Objective: This meta-analysis aimed to evaluate the effect of light therapy on depression associated with dementia by using a single scale. Methods: Published studies based on the terms including "Dementia", "depression", and "Phototherapy" were searched. Web of Science, PubMed, Embase, CiNii, CNKI, Wanfang Database, and China Biology Medicine disc were adopted to collect randomized controlled studies or cross-controlled studies using the Cornell Scale for Depression in Dementia (CSDD) until February 2022. GRADE and Review Manager Version 5.4.1 were employed to assess the risk of bias. A meta-analysis was conducted by R 4.0.2 software based on the changes in CSDD scores. Results: A total of 1,055 studies were retrieved from the databases, and six studies were included after screening. Some 406 people with dementia were included with an average age of over 80 years. Forest plot results showed that light intervention improved depression scores of dementia patients (MD = -2.59, 95% CI: -4.46 to -0.71), and light intensity less than 1,000 lux improved depression symptoms of dementia patients (MD = -2.76, 95% CI: -4.55 to -0.97). An intervention that lasted 8 to 12 weeks was the most effective (MD = -3.77, 95% CI: -6.93 to -0.60), and non-stable interventions such as ceiling LED lights exerted more positive effects (MD = -2.12, 95% CI: -3.38 to -0.85). Conclusion: The overall results of the meta-analysis suggested that light intervention can improve the depressive symptoms of older patients with dementia.