High rate of conversion to Alzheimer's disease in a cohort of amnestic MCI patients

Background: A large proportion of patients with amnestic mild cognitive impairment (MCI) progress to Alzheimer's disease (AD), but the rate of conversion is highly variable, depending on selection and inclusion criteria. In the present prospective study, amnestic MCI criteria were applied in order to enrich the study population with prodromal AD patients. Methods: A composite CERAD word list learning z-score of -1 was applied as a cut-off for memory performance at baseline. Competing causes of memory impairment other than prodromal AD were actively excluded. A cohort of 88 amnestic MCI patients was included; 75 were available for follow-up. Results: After a mean delay of 19 months, 44% were found to have converted to AD, corresponding to an annualized conversion rate of 28%. The rate of new diagnoses other than stable MCI or AD was 6%. Baseline neuropsychological variables were not instrumental to predict progression. Conclusion: Amnestic MCI patients, as identified by the present set of criteria, carry a high risk of median-term progression to AD.