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P2‐116: Is APOE e4 a risk factor for dementia also among the oldest old? Findings from the Gothenburg 95+ Study
Author(s) -
BörjessonHanson Anne,
Blennow Kaj,
Kern Silke,
Zetterberg Henrik,
Skoog Ingmar
Publication year - 2011
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2011.05.1005
Subject(s) - dementia , apolipoprotein e , population , allele , genotyping , risk factor , medicine , longitudinal study , alzheimer's disease , gerontology , disease , pediatrics , demography , psychology , genotype , genetics , biology , pathology , environmental health , sociology , gene
Background:Apolipoprotein E (APOE) exists in three different alleles: e2, e3 and e4. APOE e4 is associated with an increased risk for Alzheimer’s disease. It has been suggested that e4 carriers develop dementia earlier than those without this allele, and that the risk for dementia in e4 carriers diminishes after age 90. The frequency of one or two e4 alleles is approximately 30% in the general population and it has been suggested that this frequency decreases with age. The aim of this study was to examine APOE e4 frequency and its relation to dementia in a population-based sample of individuals aged 99 years. Methods: A representative sample of 263 99-year-olds was examined with comprehensive neuropsychiatric examinations as part of the Gothenburg 95+ Study, a longitudinal population study in Gothenburg, Sweden. Dementia was diagnosed according to the DSM-III-R criteria. Blood samples were collected and APOE genotyping was performed by solid-phase minisequencing. Results were compared with a sample of 85year-olds (N 1⁄4 412) examined with similar methods (H-70 Study in Gothenburg). Results: The prevalence of carrying at least one APOE e4 allele was 16% (n 1⁄4 43) among 99-year-olds and 43% (n 1⁄4 179) among 85year-olds. Only two individuals in the 99-year-old sample (< 1%) were homozygotic for e4 (both had dementia), compared to 19 of the 85-year-olds (5%). Among the 99-year-olds, 77% (n 1⁄4 33) of e4 carriers had dementia, compared to 33% (n 1⁄4 60) of 85-year-olds. The OR for dementia in e4 carriers was 2.51 (95% CI 1.18-5.34 p 1⁄4 0.017) among 99-year-olds, and 1.9 (95% CI 1.2-2.9: p < 0.01) among 85-year-olds. In the 99-year-old sample sample, 21% (n 1⁄4 33) of the demented and 9.5% (n 1⁄4 10) of the non-demented carried at least one e4 allele; while 55% (n 1⁄4 60) of demented and 39% (n 1⁄4 119) of non-demented had at least one e4 allele among the 85 year olds. Conclusions: The frequency of at least one APOE e4 was lower among 99-year-olds than in 85-year-olds, suggesting a survival effect, and APOE e4 was still a risk factor for dementia among the oldest old.