Early- and late-life brain reserve proxies and their interactions with education on cognitive outcomes in older adults: A population-based MRI study

BackgroundThe interplay between early- and late-life brain reserve (BR) and early-life education in shaping late-life cognitive function requires further elucidation.ObjectiveWe sought to examine the associations of early- and late-life BR and cognitive function among rural older adults in China, and to assess whether education influenced their relationships.MethodsIn this cross-sectional study (n = 1304), early-life and late-life BR were proxied by total intracranial volume (TIV) and the ratio of total normal brain tissue volume-to-TIV, respectively. Both measures were dichotomized into high and low BR according to their median. Education was classified as high (any formal schooling) and low (no formal schooling). We administered a neuropsychological test battery to assess memory, verbal fluency, executive function, and attention. Mild cognitive impairment (MCI) was diagnosed following Petersen's criteria. Regression analyses were performed.ResultsHigher late-life BR was associated with better performance across all cognitive domains (p < 0.01) and reduced likelihoods of MCI and amnestic MCI (p < 0.001). Joint-exposure analyses suggested that compared to participants with low BR and low education, individuals with both high late-life BR and high education showed best cognitive performance and lowest likelihoods of MCI, followed by those with low BR and high education. Moreover, higher late-life BR was linked to better executive function, attention, and global cognition only in participants with high education (p for interaction<0.05).ConclusionsLate-life BR has a stronger association with cognitive health than early-life BR, even among older adults without formal schooling. Furthermore, formal education may enhance the association between late-life BR and cognitive function.