Cognitive reserve can impact trajectories in ageing: a longitudinal study.

Trajectories of decline from healthy aging to dementia are not linear; they may range from a more attenuated to a more accelerated cognitive worsening. This longitudinal study investigates the impact of Cognitive Reserve (CR) on task performance in a cohort of 117 individuals (mean age 74.89; SD = 7.43) who experienced difficulties in everyday life and referred to a neuropsychology unit for cognitive assessment. Only participants assessed three times were included in the study. CR was estimated for each participant based on educational level and occupational complexity. Results revealed a general decline in global cognitive performance over time, in particular from the second to the final assessment (mean years = 2.95 ± 2.11). The two groups (high CR vs. low CR) did not differ for sex or age across assessments. Individuals with high CR not only exhibited greater cognitive efficiency at baseline-consistent with Stern's (2009) construct-but also maintained a more stable cognitive state over time compared to those with low CR. Post-hoc analyses confirmed that while the two groups did not differ in task performance between the first and the second assessment, they significantly differed from the second to the third. Individuals with high CR (even those who were diagnosed with a major neurocognitive disorder) preserved their cognitive profile whereas the profile of those with low CR declined significantly. This study demonstrates that cognitive trajectories are shaped by CR and that, despite the plausible progression of brain deterioration, individuals with high CR may not experience an accelerated cognitive deterioration. Instead, they may exhibit a more gradual decline and sustain cognitive functioning for a longer period despite age-related changes.