Structural brain ageing in Kenya

Establishing normative brain-ageing reference standards is essential for distinguishing healthy ageing from the emergence and progression of neurodegenerative disease. However, most normative references have been derived from cohorts in high-income countries (HICs), representing only ~ 20% of the world’s population. Their generalisability to low- and middle-income countries (LMICs) with varying social and environmental exposures remains uncertain. Here, we present the first and largest Kenyan normative brain ageing model, based on structural MRI from 273 neurologically healthy adults aged 35–81 years. Age-related differences were most robust for cortical thickness and cortical volume, predominantly in association cortices, broadly mirroring patterns reported in European and North American samples. Critically, socio-environmental deprivations moderated the association with age for some brain measures, underscoring the impact of life-course exposures for brain health. These results enhance the global representativeness of brain ageing models and call for the development of LMIC-specific frameworks to support equitable brain health policy.