Structural Basis of Cognitive Reserve in Ageing Nigerians: A Cortical Morphometry and Synaptic Density Study

Cognitive reserve, the brain's capacity to maintain function in the presence of neurodegeneration, is influenced by education, social engagement, and structural neuroanatomical factors including cortical thickness, gyrification, and synaptic density. Understanding the structural anatomical basis of cognitive reserve in Nigerian older adults is of considerable public health importance given the expected surge in dementia prevalence in West Africa over the coming decades. This study aims to characterise the cortical morphometric and synaptic density correlates of cognitive reserve in community-dwelling older Nigerians across three geopolitical zones. Three hundred individuals aged 60 years and above will be recruited from community cohort studies in Lagos, Kano, and Enugu. Structural MRI will provide cortical thickness and gyrification index measures. A subsample undergoing neurological evaluation and post-mortem brain donation will enable synaptic density quantification using synaptophysin immunohistochemistry in prefrontal and hippocampal regions. Cognitive reserve index will be estimated using a validated composite of education, occupational complexity, and social activities. Multivariate analyses will identify which structural neuroanatomical features best predict cognitive reserve after controlling for age and vascular risk factors. This study will produce the first evidence base on the anatomical structure of cognitive reserve in Nigerian older adults, providing a platform for dementia prevention neuroimaging research.

Keywords: cognitive reserve, cortical morphometry, ageing, dementia, Nigeria