CD40LG and Brain atrophy: When we stratified by APOE4 allele status in our specialised population, results were inconsistent: high HSV‐1 IgG titres/IgM were associated with a more rapid decline in MMSE score only among APOE4‐negative participants; in contrast, being seronegative for HSV‐1 was associated with a higher whole brain atrophy rate among APOE4 carriers.