CDKN2A and Alzheimer disease: The expression of Cdkn1a and Cdkn2a is highly variable in neurodegeneration, with the specific upregulation of Cdkn1a in neurons being associated with aging and PD (Hudson et al. 2024; Jurk et al. 2012; Riessland et al. 2019) and the upregulation of Cdkn2a being more closely associated with AD (Rödel et al. 1996; Vazquez‐Villaseñor et al. 2020).