Anti-HSV IgM positivity was not associated with the risk of developing AD (HR = 1.00, 95% CI 0.30–3.29, p = 0.997 and HR = 0.62, 95% CI 0.15–2.59, p = 0.508, respectively) or dementia (fully adjusted model: HR = 0.95, 95% CI 0.38–2.38, p = 0.912 and HR = 0.72, 95% CI 0.26–2.00, p = 0.530, respectively). This evidence concerns the gene CD40LG and Alzheimer disease.