Dynamic Relationship Between Sleep Patterns and Behavioral and Psychological Symptoms of Dementia: Longitudinal Observational Study (Preprint)

BACKGROUND A higher prevalence of behavioral and psychological symptoms of dementia is associated with a greater caregiver burden and increased mortality in people with dementia. Considering the possibility of a reciprocal relationship between sleep disturbances and these symptoms, time series analyses are necessary to explore the associated temporal dynamics. OBJECTIVE This study aimed to examine dynamic interdependencies between sleep disturbances and behavioral and psychological symptoms of dementia in older adults. METHODS Daily interactions between sleep patterns and behavioral and psychological symptoms of dementia were analyzed over a 14-day period using a panel vector autoregressive model. Data were collected from June 2018 to June 2020 in community and institutional settings. A total of 154 older adults with dementia wore wrist actigraphy devices continuously for 2 weeks for sleep data, and caregivers recorded behavioral and psychological symptoms of dementia in a daily symptom diary. RESULTS Using a panel vector autoregressive model, we analyzed data from 154 older adults living with dementia and their caregivers. The results showed unidirectional Granger causality running from the number of awakenings on the previous day to irritability (<i>P</i>=.03) and appetite or eating disorders (<i>P</i>=.04) on the following day. Conversely, some of the previous day’s behavioral and psychological symptoms of dementia temporally preceded subsequent changes in sleep patterns. Specifically, delusions had a Granger-causality effect on total sleep time (<i>P</i>&lt;.001), wake after sleep onset (<i>P</i>=.01), and the number of awakenings (<i>P</i>=.006), while irritability had a Granger causality effect on the number of awakenings (<i>P</i>=.007). Notably, bidirectional Granger causality was observed between irritability and the number of awakenings. CONCLUSIONS This study demonstrates that the relationship between the behavioral and psychological symptoms of dementia and sleep patterns is dynamic and forms a vicious cycle. Consequently, early intervention to alleviate symptoms is imperative, and strategies to enhance sleep quality and address sleep disturbances should be prioritized.