In contrast, the Uppsala Longitudinal Study found that high levels of serum cystatin C were related to a decreased risk of AD in men aged between 70 and 77 years-old (Sundelöf et al., 2008), and a study also found that MCI patients with higher serum cystatin C levels remained stable, without developing to dementia (Romero-Sevilla et al., 2018). This evidence concerns the gene CST3 and Alzheimer disease.