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Geographical variation in dementia: systematic review with meta-analysis
Tom C Russ1, G David Batty, Gena F Hearnshaw
1Scottish Dementia Clinical Research Network, NHS Scotland, UK. tom.russ@nhs.net
International Journal of Epidemiology
|July 17, 2012
Summary
Geographical variations in dementia rates exist, with rural living potentially increasing Alzheimer disease risk, especially from early life exposure. More research is needed in resource-poor settings.
Area of Science:
- Epidemiology
- Neurology
- Environmental Health
Background:
- Geographical variations in dementia prevalence and incidence suggest socio-environmental factors influence dementia aetiology.
- Previous comparative studies were limited by methodological inconsistencies.
- This review systematically synthesizes studies using identical methodologies to examine geographical dementia variation.
Purpose of the Study:
- To systematically review and synthesize studies on geographical variation in dementia prevalence and incidence.
- To compare dementia rates across different geographical scales using consistent methodologies.
- To investigate the association between rural living and dementia risk.
Main Methods:
- Comprehensive electronic database search, reference list review, expert consultation, and known literature re-examination.
- Independent review of identified articles against inclusion/exclusion criteria.
- Meta-analysis of rural/urban comparisons.
Main Results:
- 51 articles were included from 12,580 records, revealing geographical variation in dementia prevalence and incidence across multiple scales.
- Rural living showed a modest association with increased dementia prevalence (OR=1.11) and incidence (OR=1.20).
- This rurality association was stronger for Alzheimer disease, particularly with early life rural exposure (prevalence OR=2.22, incidence OR=1.64).
Conclusions:
- Geographical variation in dementia rates is evident in affluent countries at various scales.
- Rural living is linked to a higher risk of Alzheimer disease, with early life rural exposure potentially exacerbating this risk.
- Limited studies in resource-poor countries restrict broader conclusions on dementia epidemiology.
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