Association of cognitive reserve indicator with cognitive decline and structural brain differences in mid‐ and late life: a large population‐based cohort study

Abstract

AbstractBackgroundCognitive reserve (CR) contributes to preserving cognition when facing brain aging and damage. CR has been linked to reduced dementia risk in late life. However, the association between CR and brain imaging measures, especially in mid‐life, is unclear. We aimed to explore the association of CR with cognitive decline and structural brain differences in mid‐ and late life.MethodWithin the UK Biobank, 42,301 dementia‐free participants aged 40‐70 were followed for a median of 9 (interquartile range: 8 to 10) years. Latent class analysis was used to generate an indicator of CR (categorized as high, moderate, and low) based on education, occupation, and multiple cognitively stimulating activities at baseline. Cognitive tests for global and domain‐specific cognitive function were administrated at baseline and follow‐up. A subsample (n = 34,041) underwent brain magnetic resonance imaging (MRI) scans at the follow‐up examination. Volumes of total brain, white matter, grey matter, hippocampus, and white matter hyperintensities (TBV, WMV, GMV, HV, and WMHV) were assessed. Data were analyzed using mixed‐effects models and linear regression.ResultAt baseline, 16,032 (37.90%), 10,709 (25.32%), and 15,560 (36.78%) participants had low, moderate, and high levels of CR, respectively. In multi‐adjusted mixed‐effects models, compared to low CR, high CR was associated with a slower decline in global cognitive function (β [95% confidence interval, CI]: 0.10 [0.08, 0.11]), prospective memory (0.10 [0.06, 0.15]), fluid intelligence (0.07 [0.04, 0.10]), and reaction time (0.04 [0.02, 0.06]). In MRI data analysis, high CR was related to lesser TBV (‐0.03 [‐0.04, ‐0.02]), WMV (‐0.03 [‐0.04, ‐0.02], GMV (‐0.02 [‐0.04, ‐0.01]), and WMHV (‐0.03 [‐0.05, ‐0.002]), but greater HV (0.04 [0.02, 0.06]) compared to low CR. In analyses stratified by baseline age, the significant associations between high CR and global cognition and TBV were present among both mid‐life (<60 years) and late‐life (≥60 years) participants. The CR‐cognitive decline association remained significant after additional adjustment for MRI measures.ConclusionHigher CR is associated with slower cognitive decline, lesser TBV, greater HV, and lower microvascular burden, especially in mid‐life. The protective role of high CR on cognition is independent of structural brain differences.