Dementia is a devastating disease with a global impact, and there is an urgent need for effective interventions to alleviate the accompanying disturbances in behavior, mood, sleep, and circadian rhythms. Bright light treatment (BLT) is a promising non-pharmacological intervention; however, studies have yielded conflicting results. This systematic review provides a comprehensive overview of the effect of BLT in dementia, with a specific focus on how study characteristics might have affected the available results. The included studies were small and comprised time-limited interventions and follow-ups. Light values, adherence to treatment, and time of year were not consistently reported. Varying designs, methods, and population characteristics such as age, gender, dementia diagnosis, circadian phase, and baseline symptoms may have moderated the outcomes and affected review results. The use of crossover designs and too high illumination as placebo lights might have nullified positive effects of BLT. Because some studies had negative outcomes after ambient BLT with high amounts of short wavelengths, more modest light levels should be further investigated. Employing rigorous designs and detailed reporting of intervention characteristics, i.e., the illumination, correlated color temperature, timing, and duration of light utilized, are of utmost importance to establish the optimal treatment approach in this population.

Systematic review registration number: PROSPERO CRD42017051004.

痴呆症是一种具有全球影响的毁灭性疾病，迫切需要有效的干预措施来减轻随之而来的行为、情绪、睡眠和昼夜节律紊乱。亮光治疗（BLT）是一种很有前景的非药物干预措施；然而，研究得出了相互矛盾的结果。本系统综述全面概述了 BLT 对痴呆症的影响，特别关注研究特征如何影响现有结果。纳入的研究规模较小，且包含有时间限制的干预措施和随访。光值、治疗依从性和一年中的时间的报告并不一致。不同的设计、方法和人群特征（例如年龄、性别、痴呆诊断、昼夜节律阶段和基线症状）可能会调节结果并影响审查结果。使用交叉设计和过高的照明作为安慰剂灯可能会抵消 BLT 的积极作用。由于一些研究在使用大量短波长的环境 BLT 后产生了负面结果，因此应进一步研究更温和的光照水平。采用严格的设计和详细报告干预特征，即照明、相关色温、时间和光的持续时间，对于在该人群中建立最佳治疗方法至关重要。

系统审评注册号：PROSPERO CRD42017051004。