Incidence of Dementia in Relation to Stroke and the Apolipoprotein E e4 Allele in the Very Old Findings From a Population-Based Longitudinal Study

Background and Purpose—Both stroke and the apolipoprotein E (APOE) e4 allele increase the risk of dementia. However, the interaction between stroke and APOE on dementia is still unclear. We addressed this topic by using a longitudinal design. Methods—We followed up a community cohort of 1301 subjects aged $75 years, who did not have dementia at baseline. Among them, 92 subjects had a history of stroke (from 3 months to 16 years before baseline interview). After the 3-year follow-up, 224 dementia cases had been diagnosed. During the period of follow-up, 91 subjects had a first occurrence of stroke (incident stroke). The APOE genotype was known for 985 subjects. Cox proportional hazards regression models were constructed to estimate the risk for dementia in terms of relative risks (RRs) for stroke and the APOE e4 allele, with adjustment for age, sex, education, systolic blood pressure, antihypertensive medication use, and heart disease. Results—In the entire study population, RRs for dementia related to history of stroke and incident stroke were 1.7 (95% CI, 1.1 to 2.6) and 2.4 (95 % CI, 1.6 to 3.5), respectively, after adjustment for all potential confounders. Subjects with stroke that occurred within 3 years before baseline had RR of 2.4 (95 % CI, 1.4 to 4.2), whereas those with stroke occurring.3 years before baseline had RR of dementia of 1.1 (95 % CI, 0.6 to 2.3). Among those with APOE information, individuals with only history of stroke (that occurred within 3 years before baseline) had RR of 3.1 (95