A longitudinal study of patients with mild cognitive impairment (MCI) showed that serum levels of IFNγ, IL−1β, IL−2, IL−4, IL−6, and IL−10 decreased over time, and these decreases were highly correlated with decreased cognition (Thomas et al., 2020), and a study of post-mortem samples reported that relative to non-demented controls, AD brains and serum had decreased levels of IL-1b, IL-6, IL-7, IL-8, and IL-16 (Chen et al., 2016). This evidence concerns the gene IL6 and Alzheimer disease.