APOE-ε4 is associated with memory decline in cognitively impaired elderly

Objective: To investigate whether the association between APOE-ε4 and memory decline is modified by baseline cognition and age in a population- based elderly sample. Methods: The study sample consisted of 1,242 subjects, 62 to 85 years old, with a Mini-Mental State Examination (MMSE) score between 21 and 30 and known APOE phenotypes. Memory performance was measured with an abbreviated Auditory Verbal Learning Test (AVLT) at baseline and repeated after 3 years (n = 854). Memory decline was defined as a decrease of at least 1 SD from the mean change score on immediate recall (IR), delayed recall (DR), and retention, based on the AVLT. Results: Multivariate logistic regression analyses showed that APOE-ε4 is associated with memory decline in cognitively impaired subjects (MMSE score, 21 to 26) (OR for decline on IR adjusted for age, sex, education, and baseline recall score, 3.8; 95% CI, 1,4 to 10.0; adjusted OR for decline on DR, 2.9; 95% CI, 1.2 to 7.0; adjusted OR for decline on retention, 3.3; 95% CI, 1.1 to 10.1), but not in cognitively normal subjects (MMSE score, 27 to 30) (adjusted OR for decline on IR, 1.1; 95% CI, 0.6 to 2.0; adjusted OR for decline on DR, 1.0; 95% CI, 0.6 to 1.8; adjusted OR for decline on retention, 1.5; 95% CI, 0.7 to 3.0). In particular, cognitively impaired ε4 carriers older than 75 years were at high risk of memory decline (adjusted OR for decline on IR, 4.5; 95% CI, 1.4 to 13.8; adjusted OR for decline on DR, 3.6; 95% CI, 1.2 to 10.8; adjusted OR for decline on retention, 6.6; 95% CI, 1.5 to 29.7). Conclusions: APOE-ε4 was associated with memory decline in subjects with cognitive impairment, but not in normally functioning subjects. Contrary to AD studies, our study suggests that the risk of APOE-ε4 on memory decline does not decrease at higher ages.