Observational studies have found positive associations between GPx3 activity and Alzheimer disease (AD, the main form of dementia) likely due to higher concentrations of oxidative stress that can contribute to amyloid aggregation in extracellular space [11,12] leading to GPx3 upregulation [9,[13], [14], [15], [16], [17]]. This evidence concerns the gene GPX3 and early-onset autosomal dominant Alzheimer disease.