APOE and Mental deterioration: However, a limitation common in the existing literature is the use of multi-level linear modelling for non-Gaussian discrete cognitive scores (Kanai et al., 1999; West et al., 2008; Whitehair et al., 2010; Lo et al., 2011; Mielke et al., 2011; Vemuri et al., 2014; Kim et al., 2017; Rawle et al., 2018), therefore, this study, with 744 individuals with at least one ApoE4 gene, investigating both ADAS and MMSE measures of cognitive decline and applying discrete distribution GLMM analyses with the negative binomial models, represents a robust and important contribution to the field.