APOE and early-onset autosomal dominant Alzheimer disease: Environmental influences on Alzheimer's disease (AD) and related dementias (ADRD) are poorly documented.1 Apolipoprotein E (APOE) ɛ4 and other loci identified by large GWAS account for less than 50% of heritable AD risk.2 Thus, attention is drawn to environmental risk factors, including common neurotoxins and their interactions with APOE and other genes.2, 3