Light intervention effects on circadian activity rhythm parameters and nighttime sleep in dementia assessed by wrist actigraphy: a systematic review and meta-analysis

Persons with dementia often show circadian rhythm disturbances and sleep problems. Timed light exposure seems to be a promising non-pharmacological treatment option. In this review, meta-analyses were run on light effects on circadian activity rhythm parameters in persons with dementia measured with wrist actimetry. Further, we update a Cochrane review, published in 2014, on actigraphically measured light effects in nighttime sleep parameters in persons with dementia. Four electronic databases were searched for randomized controlled trials. Effects in meta-analyses were summarized by using mean differences and 95% confidence intervals. We followed PRISMA guidelines to assess the risk of bias and registered the review protocol (PROSPERO: CRD42020149001). Thirteen trials met inclusion criteria, and either utilized light therapy devices, ambient room lighting systems, or dawn-dusk interventions. Eleven of these studies were subjected to meta-analyses. They did not reveal significant light effects on circadian activity parameters: amplitude (p=.62; n=313), acrophase (p=.34; n=313), intradaily variability (p=.51; n=354), and interdaily stability (p=.38; n=354). Furthermore, no light effects were found on sleep parameters: total sleep duration (p=.53; n=594), sleep efficiency (p=.63; n=333), wake after sleep onset (p=.95; n=212), and sleep onset latency (p=.26; n=156). Subgroup analyses, pooling data from three studies including persons with Alzheimer's dementia, also did not show light effects on circadian activity and sleep parameters. The overall risk of bias of included studies was high. There is insufficient evidence for actigraphically measured circadian light effects in persons with dementia. More high-quality research is needed to recommend the application of adjunctive light.