APOE and early-onset autosomal dominant Alzheimer disease: For instance, the APOE ɛ4 haplotype is associated with a 2-year earlier onset of symptomatic Alzheimer disease in Down syndrome.78 Further studies should assess the impact of other medical conditions associated with Down syndrome (eg, hypothyroidism, autoimmune disorders, periodontal disease, sleep apnea, epilepsy, vision and hearing problems) as well as the contribution of sociodemographic factors, such as residential status (living with family vs institutionalization), intellectual disability, and economic status of the caregivers.68,79