IL-6 levels were significantly higher in subjects with VaD compared to those with AD (SMD: 0.40, 95% CI: 0.18 to 0.62), with low heterogeneity (I2 = 41%, p = 0.13) (Fig. 2B) and no evidence of small study effect at Egger’s test (p = 0.662) (Supplementary Fig. 2). This evidence concerns the gene IL6 and Alzheimer disease.