Insomnia symptoms and stress exposure interact in relation to Alzheimer's disease biomarkers.

BACKGROUND: Several modifiable factors affect Alzheimer's disease (AD) risk. However, evidence on how these factors interact remains scarce, limiting our understanding of their role in AD development. This study aims to assess interactions between chronic stress exposure and insomnia in relation to AD biomarkers beta-amyloid (Aβ42), total tau, and phosphorylated tau. METHODS: The present study included 124 memory clinic patients without dementia from the Cortisol and Stress in Alzheimer's disease (Co-STAR) cohort study. Insomnia symptoms, stressful life events (SLEs) and current perceived stress were self-reported via questionnaires, while AD biomarkers were assessed from the cerebrospinal fluid (CSF). Cross-sectional interactions between stress and insomnia in relation to AD biomarkers were examined using linear regression models. RESULTS: Insomnia and SLEs interacted in relation to Aβ42. Greater stressor exposure was associated with reduced CSF Aβ42 levels, reflecting greater brain amyloid accumulation, only in those with moderate-to-high insomnia scores. No interactions were found for total or phosphorylated tau. CONCLUSIONS: This study suggests that chronic stress and sleep disturbances exhibit an interactive relationship in their associations with AD pathology, and highlights the need for further research into interactive effects of multiple modifiable risk factors in the development of AD.