Study of Ancestry, Health, Environment, and Late-Life Neurodegeneration (SAHEL)

Technical Summary: Study of Ancestry, Health, Environment, and Late-Life Neurodegeneration (SAHEL)

Problem Statement
Dementia research within sub-Saharan Africa faces significant limitations, characterized by a scarcity of data despite the region undergoing rapid population aging. This gap is particularly critical given the substantial diversity in ancestry, environmental exposures, and vascular risk factors present across the continent. There is a pressing need to characterize late-life cognitive decline and neurodegeneration within these underrepresented populations to understand disease mechanisms specific to African contexts.

Methodology
The Study of Ancestry, Health, Environment, and Late-Life Neurodegeneration (SAHEL) addresses this gap by establishing a comprehensive research platform in north-eastern Nigeria, specifically within Yobe and Borno States. The study employs a dual-cohort design:

• Community Cohort: Adults aged 55 years or older recruited from the general population.
• Hospital Cohort: Adults aged 55 years or older recruited from clinical settings, including individuals with diagnosed Alzheimer's disease, vascular dementia, mixed dementia, and mild cognitive impairment (MCI).

Participants undergo a rigorous, multi-modal assessment protocol including:

• Clinical Evaluations: Cognitive, functional, neuropsychiatric, and neurological assessments.
• Systemic Profiling: Cardiovascular and metabolic evaluations, alongside environmental exposure assessments.
• Biological Sampling: Blood collection for clinical profiling and biobanking. Consenting hospital participants provide skin biopsies for the generation of induced pluripotent stem cells (iPSCs).
• Planned Integrative Analyses: The study design incorporates future investigations into gut microbiota profiling, retinal imaging, and brain magnetic resonance imaging (MRI) to map biological pathways and markers associated with healthy aging and cognitive outcomes.

Key Results
The paper reports the initial enrollment and characterization of the SAHEL cohorts from August 2025 through February 2026:

• Community Screening: 1,044 participants were screened, with a mean age of 69.4 years and a female representation of 56.4%. Of these, 379 participants (36.3%) screened positive for cognitive concerns and were entered into longitudinal follow-up.
• Hospital Enrollment: 102 participants were enrolled, with a mean age of 73.5 years and a male representation of 57.8%. This cohort includes confirmed cases of various dementia subtypes and MCI.
• Biological Resources: Blood samples were successfully collected from 809 community participants and all 102 hospital participants.
• Ancestral Diversity: The cohort represents a diverse genetic landscape, including participants of Kanuri, Fulani, Hausa, Babur/Bura, and Shuwa Arab ancestry.

Significance and Claims
The paper positions SAHEL as a foundational platform for dementia research in north-eastern Nigeria. Its primary significance lies in the establishment of a deeply characterized resource that links clinical data with environmental, biomarker, genomic, imaging, microbiome, and cellular resources. The authors claim that this integrated approach will enable the investigation of population-specific mechanisms of risk and resilience. Ultimately, the study aims to strengthen the broader landscape of dementia research and advance precision medicine specifically for African populations, addressing the historical lack of data in the region.