Public Health

Area of Science:

• Neurology
• Gerontology
• Public Health

Background:

• Alzheimer disease (AD) and vascular dementia (VaD) are leading causes of cognitive impairment worldwide, particularly in aging populations.
• Both conditions are multifactorial, influenced by genetic and environmental factors, with increasing prevalence in low- and middle-income countries (LMICs).
• Post-mortem studies reveal significant vascular pathology in a majority of probable AD cases, suggesting a strong link between vascular and neurodegenerative processes.

Purpose of the Study:

• To explore the interplay between vascular pathology and neurodegenerative changes in Alzheimer disease.
• To highlight the disproportionately high burden of vascular cognitive impairment in Africa due to factors like hypertension and diabetes.
• To investigate the potential for reducing the global dementia burden by managing vascular risk factors.

Main Methods:

• Review of post-mortem findings in Alzheimer disease cases, noting the prevalence of vascular pathology.
• Analysis of epidemiological data, including INTERSTROKE studies, to compare vascular disease markers in LMICs versus high-income countries (HICs).
• Examination of the pathological mechanisms linking vascular factors (e.g., arteriolosclerosis) and neurodegenerative hallmarks (e.g., amyloid plaques, neurofibrillary tangles).

Main Results:

• Over 80% of probable AD cases exhibit variable vascular pathology.
• Vascular factors, particularly hypertension and diabetes, significantly contribute to cognitive impairment, with higher incidence in LMICs.
• Cerebrovascular changes like arteriolosclerosis appear early, while neurodegenerative changes like synaptic loss correlate with cognitive decline progression.
• The combination of vascular and neurodegenerative pathologies is additive, lowering the threshold for AD dementia.

Conclusions:

• Vascular disease is a major contributor to dementia, including Alzheimer disease.
• Managing modifiable vascular risk factors offers a critical strategy for reducing the global burden of dementia.
• Targeting vascular health at individual, community, and population levels in Africa is essential for mitigating cognitive impairment.