Apolipoprotein E polymorphism and stroke in a population sample aged 75 years or more

We investigated apolipoprotein E polymorphism stroke risk in a population sample of 1810 persons aged 75 years or more in Stockholm (the Kungsholmen Project). Information on cognition at cohort inception (from 1987 to 1989) and on stroke occurrence (from 1969 to 1994) is available for the cohort. In the cohort, cognitive impairment is associated with the epsilon 4 allele, and longer survival in subjects aged > or = 85 years with good cognition is associated with the epsilon 2 allele and the absence of epsilon 4.

We compared stroke incidence in the 1077 of 1124 genotyped subjects who carried epsilon 2/3, epsilon 3/3, or epsilon 3/4 and estimated the proportion of cognitive impairment attributable to stroke.

Risk of stroke did not vary with apolipoprotein E polymorphism (P = .82): 24% of 87 incident stroke patients during follow-up compared with 25% of 827 subjects with normal cognition and no stroke diagnosis at baseline carried the epsilon 3/4 genotype. An estimated 9% of cognitive impairment was attributable to stroke. Notably, a reduced epsilon 3/4 frequency of 20% was found in subjects who survived a prior stroke and were included in the cohort, and risk of hemorrhagic stroke tended to be associated with the presence of the epsilon 3/4 genotype and the absence of epsilon 2/3.

This population-based study indicates that apolipoprotein E polymorphism is not a risk factor for ischemic stroke in subjects aged > or = 75 years (although it might possibly influence survival after stroke occurrence and be a risk factor for infrequent hemorrhagic stroke) and that approximately 10% of cognitive impairment in this age group is attributable to stroke.