Prevalence of apolipoprotein E4 genotype and homozygotes (APOE e4/4) among patients diagnosed with Alzheimer's disease: a systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of observational prevalence studies (by design analogy)
PubMed 22179327 · doi:10.1159/000334607
What was done
Systematic review and meta-analysis of English-language publications from January 1, 1985, to May 31, 2010, reporting APOE e4 status in patients diagnosed with Alzheimer's disease (AD). Clinical trials and autopsy-based studies were excluded. APOE e4 carrier and e4/4 homozygote prevalence data were pooled with 95% confidence intervals (CIs) globally and by geographic region and country.
What was found
Pooled APOE e4 carrier prevalence across 142 independent samples was 48.7% (95% CI: 46.5-51.0). Pooled e4/4 homozygote prevalence across 73 samples was 9.6% (95% CI: 8.4-10.8). The highest estimates were found in Northern Europe: 61.3% (95% CI: 55.9-66.7) for e4 carriers and 14.1% (95% CI: 12.2-16.0) for e4/4 homozygotes. The lowest estimates were in Asia and Southern Europe (no specific numbers reported in abstract). Substantial heterogeneity across prevalence estimates was observed.
Why it matters
It establishes global baseline prevalence estimates for the APOE e4 risk allele among clinically diagnosed Alzheimer's patients, confirming that while e4 is a major risk factor, more than half of global AD cases are non-carriers and prevalence varies substantially across geographic populations.
Limits
The review was restricted to English-language publications. Autopsy-confirmed cases and clinical trials were excluded, potentially introducing diagnostic inaccuracy. Total participant count and exact numerical estimates for Asia and Southern Europe are omitted in the abstract, and substantial heterogeneity across included studies remained unexplained.
Cited by
- contradicts Between 65% and 80% of individuals diagnosed with Alzheimer's disease carry at least one APOE4 allele.