Patterns of sleep disturbances across stages of cognitive decline.

OBJECTIVES: The purpose of this study was to investigate insomnia symptoms and excessive sleep/sluggishness across stages of cognitive decline (cognitively normal [CN], Cognitively Impairment, Not Demented [CIND], dementia) in a large, racially/ethnically diverse sample of older adults (70+) in the US. We also examined whether sleep disturbances at baseline predicted conversion to CIND or dementia at follow-up. METHODS: In this secondary analysis of the Aging, Demographics, and Memory Study (ADAMS) supplement of the Health Retirement Study, we analyzed patterns of informant-reported insomnia and excessive sleep symptoms among three groups of older adults (n = 846): CN, CIND, and dementia. RESULTS: CIND adults were significantly more likely to have informant-reported insomnia symptoms than those in the CN group (p = 0.013). This was driven by a significant race/ethnicity-by-insomnia interaction with diagnostic status (p = 0.029), such that CIND Black and Hispanic older adults had increased insomnia symptom rates compared to CN, whereas White adults had similar insomnia symptoms across diagnostic status. Across all racial/ethnic groups, the prevalence of excessive sleep symptoms increased stepwise from CN to CIND to dementia (p < 0.001). Overall, insomnia symptoms at baseline predicted conversion from CN to CIND (p < 0.001, OR = 0.288; 95% CI: 0.143-0.580) at 4-year (approximate) follow-up; there was no relationship between baseline insomnia or excessive sleep/sluggishness symptoms and conversion from CIND to dementia. DISCUSSION/CONCLUSION: This study provides evidence for the increased risk of insomnia symptoms among Hispanic and Black older adults with CIND, and indicates that insomnia symptoms may be associated with increased risk for development of cognitive impairment.