Neuropsychological and genetic differences between age-associated memory impairment and mild cognitive impairment entities

OBJECTIVE: To neuropsychologically and genetically compare age-associated m emory impairment (AAMI) and mild cognitive impairment (MCI) entities and to determine what proportion of AAMI diagnosed individuals could also receive a MCI diagnosis. To compare the distribution of a previously known genetic risk factor for Alzheimer's disease (apolipoprotein E common polymorphism) associated with these two conditions with a sample of the normal aging. DESIGN: Neuropsychological and genetic assessments in AAMI and MCI individu als. Genetic assessment in AAMI, MCI, and control subjects. SETTING: General health centers and geriatric homes from northeastern Spain (Catalunya). PARTICIPANTS: One hundred and four subjects presenting subjective memory co mplaints were selected and the AAMI and MCI criteria were applied. One hund red and twenty-four healthy Spanish subjects age 50 and older were defined as controls. MEASUREMENTS: Memory, language, and frontal lobe functions were assessed us ing standard neuropsychological tests. The apolipoprotein E (apo E) polymor phism was obtained by using polymerase chain reaction (PCR) and Hbal restri ction endonuclease. RESULTS: Sixty-seven percent of previously diagnosed AAMI individuals could also be identified as MCI subjects. These MCI cases differed from those on ly-AAMI individuals both in neuropsychological and genetic analyses, perfor ming worse not only on memory but also on language and frontal lobe tests a nd presenting high and low prevalences of the apo E epsilon3/epsilon4 and e psilon3/epsilon3 genotypes, respectively. The general AAMI sample of 93 ind ividuals also differed from controls in the apo E genotype and allele distr ibutions but these differences were no longer present after subtracting the MCI cases (63 subjects). These findings reflect that the differences betwe en the memory impaired sample and the control sample regarding the apo E po lymorphism were mainly attributable to MCI individuals and not to those who received only a diagnosis of AAMI alone. CONCLUSIONS: Our findings suggest that among AAMI subjects, those who also fulfill the MCI criteria present a neuropsychological and genetic profile c loser to that previously related to Alzheimer's disease than those individu als only eligible for a diagnosis of AAMI. However, our findings also sugge st that using only the AAMI criteria still appears to select a population t hat differs genetically from the normal older population.