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Background: The longitudinal associations of sleep timing and time in bed (TIB) with dementia and cognitive decline in older adults are unclear. Methods: This population‐based cohort study used data from 1982 participants who were aged ≥60 years, free of dementia, and living in rural communities in western Shandong, China. At the baseline (2014) and follow‐up (2018) examinations, sleep parameters were assessed using standard questionnaires. Cognitive function was measured using the Mini‐Mental State Examination (MMSE). Dementia was diagnosed following the DSM‐IV criteria, and the NIA‐AA criteria for Alzheimer disease (AD). Data were analyzed using restricted cubic splines, Cox proportional‐hazards models, and general linear models. Results: During the mean follow‐up of 3.7 years, dementia was diagnosed in 97 participants (68 with AD). Restricted cubic spline curves showed J‐shaped associations of sleep duration, TIB, and rise time with dementia risk, and a reverse J‐shaped association with mid‐sleep time. When sleep parameters were categorized into tertiles, the multivariable‐adjusted hazard ratio (HR) of incident dementia was 1.69 (95%CI 1.01–2.83) for baseline sleep duration >8 hours (vs. 7–8 h), 2.17 (1.22–3.87) for bedtime before 9 p.m. (vs. 10 p.m. or later), and 2.00 (1.23–3.24) for mid‐sleep time before 1 a.m. (vs. 1–1.5 a.m.). Early bedtime and mid‐sleep time were significantly associated with incident AD (HR range: 2.25–2.51; p < 0.05). Among individuals who were free of dementia at follow‐up, baseline long TIB, early bedtime and mid‐sleep time, early and late rise time, and prolonged TIB and advanced bedtime and mid‐sleep time from baseline to follow‐up were associated with a greater decline in MMSE score (p < 0.05). These associations with cognitive decline were statistically evident mainly among men or participants who were aged 60–74 years. Conclusions: Long TIB and early sleep timing are associated with an increased risk of dementia, and the associations with greater cognitive decline are evident only among older people aged 60–74 years and men. [ABSTRACT FROM AUTHOR]

Background: Olfactory impairment is associated with dementia in clinical settings. We examined the relationship of olfactory identification function with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VaD) and assessed the discriminative ability of the Sniffin' Sticks Identification Test (SSIT), the self-rated Ascertain Dementia 8-item Questionnaire (AD8), and their combination for dementia detection among rural-dwelling older adults in China., Methods: This population-based cross-sectional study included 4481 participants (age ≥ 65 years; 56.8% women; 38.1% illiteracy) living in rural communities. The 16-item SSIT was performed to assess olfactory identification function. The self-rated AD8 was administered to participants for cognitive status. We diagnosed dementia, AD, and VaD following the international criteria. Data were analyzed with logistic regression models and receiver operating characteristic curve., Results: Of the 4481 participants, dementia was diagnosed in 139 persons (3.1%), including 92 with AD and 42 with VaD. The SSIT score (range, 0-16) was associated with multiadjusted odds ratios of 0.83 (95% CI: 0.79-0.88) for dementia, 0.84 (0.79-0.90) for AD, and 0.79 (0.71-0.87) for VaD. The area under the curve for the discrimination between participants with and without dementia was 0.73 (95% CI: 0.69-0.77) for SSIT score ≤ 8 alone, 0.86 (0.82-0.89) for self-rated AD8 score ≥ 3 alone, and 0.89 (0.86-0.92) for their combination using a logistic model., Conclusions: Olfactory impairment is a clinical marker for all-cause dementia, AD, and VaD. The smell identification test, in combination with the brief self-rated cognitive screening tool, is accurate for screening dementia among rural-dwelling Chinese older adults with no or limited education., (© 2021 The American Geriatrics Society.)