High cognitive reserve may reduce the risk for cognitive decline as a study published in Neurology reported the positive effect of cognitive reserve on global cognitive function, episodic memory, and working memory, even after taking brain pathologies into account.
As limited data are available on the effect of cognitive reserve on the cognitive trajectories, such as global cognitive function, episodic memory, and working memory, the objective of the current study was to explore the association between cognitive reserve indicator with global cognitive function, episodic memory, and working memory over time, and to determine the role of brain pathologies in such associations.
The study sample included 1697 patients (mean age, 79.6 years; 75.7% women) without dementia, including 648 patients with brain pathologies. The participants were classified into 3 groups, according to cognitive reserve, with 560 patients in the lowest cognitive reserve group, 560 in the middle cognitive reserve group, and 577 in the highest cognitive reserve group.
Using personal interviews at baseline, information on cognitive reserve-related factors was collected, including data on education, physical activity, mid-life and late-life cognitive activities, late-life social activity and social network. A battery of 21 cognitive performance tests at baseline and annually were used to assess cognitive function, including episodic memory, working memory, semantic memory, perceptual speed, and visuospatial ability.
The cognitive reserve score ranged from -8.002 to 5.378, with a higher score indicating a greater level of cognitive reserve: lowest group, -8.002 to -0.826; middle group, -0.827 to 1.062; highest group, 1.063 to 5.738.
During up to 21 years of follow-up (median 5.31 years), 795 patients died, including 648 patients that underwent autopsies to evaluate brain pathologies.
In multi-adjusted mixed-effect models there was an association between the cognitive reserve indicator with a slower rate of decline in global cognition, episodic memory, semantic memory, working memory, and perceptual speed over time. The highest cognitive reserve was associated with a slower decline in global cognition, episodic memory, and working memory over the follow-up, compared with the lowest cognitive reserve. No significant association was reported for middle cognitive reserve with cognitive function decline.
In brain pathologic data analysis, the highest cognitive reserve was associated with lower burden of global Alzheimer disease pathology (odds ratio, 0.66; 95% CI, 0.45-0.98), neuritic plaque (odds ratio, 0.75; 95% CI, 0.57-1.00), and gross infarcts (odds ratio, 0.47; 95% CI, 0.29-0.76).
After additional adjustment for brain pathologies, the association between the highest cognitive reserve and slower decline in global cognitive function, episodic memory, working memory, or visuospatial ability remained significant.
The study had several limitations, including using retrospective self-reported information to collect data on cognitive reserve, lack of nutritional data, and limited generalizability to younger population or to adults living in rural areas.
“Our findings underscore the importance of educational and mentally stimulating activities throughout the lifespan for preserved cognitive function in late life,” concluded the researchers.
Li X, Song R, Qi X, et al. Influence of cognitive reserve on cognitive trajectories: role of brain pathologies. Neurology. Published online September 7, 2021. doi: 10.1212/WNL.0000000000012728