Associations of lifespan cognitive reserve with mild cognitive impairment and dementia among older adults with low literacy: A population‐based cohort study

Abstract

AbstractBackgroundEducational attainment in early life represents a major contributor to cognitive reserve (CR). High CR capacity derived from lifespan enriching factors could delay cognitive decline. We sought to investigate the longitudinal associations of CR capacity with mild cognitive impairment (MCI) and dementia among older adults with no or low literacy.MethodThis population‐based cohort study included 2141 rural participants (age≥60 years; 59.5% women; 84.8% illiteracy or elementary school) in the Shandong Yanggu Study of Aging and Dementia who were free of dementia at baseline (August‐December 2014) and who undertook follow‐up examinations in March‐September 2018. CR capacity was estimated by integrating early‐life education attainment, adulthood occupation and marital status, and late‐life physical activity and social support, and categorized into low, intermediate, and high levels using tertiles. MCI and amnestic MCI were defined according to the Petersen’s criteria that integrated clinical assessment with neuropsychological tests. Dementia and Alzheimer’s disease (AD) were diagnosed according to the DSM‐IV and NIA‐AA criteria, respectively. Data were analyzed using the structural equation and Cox proportional‐hazards models.ResultDuring an average of 3.7 (SD = 0.4) years of follow‐up, 102 of the 2141 dementia‐free participants were diagnosed with dementia, including 75 with AD. Compared to the low CR level, intermediate and high CR levels were associated with multi‐adjusted hazards ratios (HRs) (95% confidence intervals [CIs]) of 0.59 (0.37–0.94) and 0.47 (0.26–0.85) for dementia and 0.53 (0.31–0.92) and 0.38 (0.17–0.83) for AD, respectively. In addition, out of the 1727 MCI‐free participants at baseline, 330 developed MCI at follow‐up, including 270 with aMCI. Intermediate and high CR levels (vs. low) were associated with multi‐adjusted HRs (95% CIs) of 0.70 (0.53–0.92) and 0.60 (0.45–0.81) for MCI and 0.65 (0.48–0.87) and 0.58 (0.42–0.79) for amnestic MCI, respectively.ConclusionIn Chinese rural elderly, high CR capacity is associated with reduced risks of MCI, amnestic MCI, dementia, and AD. This suggests that the effect of CR capacity in delaying the onset of MCI and dementia exists even among rural older adults with no or very low literacy.