Abstract:
Background: A large volume of studies has explored the role of Mild Cognitive Impairment (MCI) between normal aging and dementia, highlighting the importance of the predementia states. Objectives. To investigate the prevalence of amnestic Subjective Cognitive Decline (a-SCD) and amnestic Early and Late MCI (a-EMCI and a-LMCI) and their progression to incident dementia and Alzheimer’s Disease (AD), in a community cohort from São Paulo, Brazil.
Methods: A representative sample aged ≥ 60 years composed initially of 1563 subjects in dementia baseline study was followed in incidence study. In baseline, subjects with at least one cognitive complaint, without functional impairment and with specific scores in Fuld Object Memory Evaluation were classified as having a-SCD, a-EMCI and a-LMCI. The progression of a-SCD, a-EMCI and a-LMCI to dementia and AD was directly estimated and by calculating the incidence rates and the hazard ratios.
Results: The prevalence rates of a-SCD, a-EMCI and a-LMCI were 58.6% (N=804), 3.9% (N=54) and 4.9% (N=68), respectively. The progression to dementia and AD was 5.8% and 4.9% for a-SCD, respectively, 25% for a-EMCI and 53.8% for a-LMCI. The incidence rates of dementia and AD were 37.0 per 1000 person-years, for a-EMCI, and 93.1 per 1000 person-years, for a-EMCI. The risks of developing dementia and AD were 2.57 (p=0.084) and 3.29 (p=0.034), for a-EMCI, and 12.66 and 17.2 (p<0.001), for a-LMCI, respectively.
Conclusion: The most striking finding was to illustrate the implication of expanding the concept of MCI to an earlier form in research and clinical practice of cognitive decline.