Several studies have reported that APOE genotype significantly modifies the association between smoking status and risk of dementia, whereby current smoking was associated with a higher risk of developing dementia amongst people who were not APOE‐ε4 allele carriers, but not in carriers [14, 15, 16], including in Alzheimer's disease specifically [14, 16]. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.