Indeed, in a recent genetic epidemiological study we evaluated the relationship between the population frequency of DRB1*13:02 and dementia prevalence in 14 CWE countries and found that dementia prevalence decreased exponentially with increasing frequency of DRB1*13:02, even after adjusting for the prevalence of apoE4.3 Remarkably, the population frequency of DRB1*13:02 accounted for 45% of the variance in dementia prevalence. The gene discussed is APOE; the disease is dementia.