Coorte prospectiva de pacientes com comprometimento cognitivo leve amnéstico: fatores relacionados a conversão para demência de Alzheimer e remissão a normalidade cognitiva em amostra de brasileiros de baixa escolaridade

Abstract

Introduction: Mild cognitive impairment (MCI) is an intermediate condition between a normal cognition and dementia. The conversion rate from MCI to dementia is high, averaging 12% to 15% at a year. However, there has been few studies in the rate of conversion in the Brazilian population and its considered as scientific knowledge gap. Objectives: To determine the amnestic MCI conversion rate to dementia (Alzheimers or other related forms) and remission rate from MCI to normal cognition; evaluate the clinical and demographic factors related to conversion; study the capacity of allele APOE å-4, rs6265 polymorphism of Brain Derived Neurotrophic factor (BNDF) and the latency and amplitude of evoked potential P300 and the latency of N200 potential in predicting the conversion. Methods: Cohort of patients with MCI and controls with normal cognition aged over 60 years were recruited between 2010 and 2015. The elderly were evaluated annually by geriatricians and neuropsychologists trained in cognitive assessment. The categorical dates were analyzed by chi-squared test and Fisher test and means comparison by T student, Anova, Mann Whiney e Kruskal-wallis tests. For evaluation remission from MCI amnestic to normal cognition and conversion from MCI amnestic to dementia, Kaplan-Meier survive curve was performed. Risk factors were evaluated using binary logistic regression analysis or linear regression analysis. Only were selected variables with p value < 0,200. Variables with missing more than 20% or with Pearson or Spearman correlation between than 0.7 or more were excluded. We used the statistical package SPSS version 20.0 ((IBM®). Results: Out of 306 patients initially evaluated for inclusion criteria, only 176 patients were selected. Among the elderly recruited, 51 were in the control group, 112 in amnestic group and 13 in non-amnestic group, with age of 75.51±7.26 years, 69.9% female, all had 4.10±3.41 years of education. At the end of research, 25 patients dropped out mainly due to cancelation of consent form (44%), death (16%) or lost of phone contact (20%). We detected 20 cases of conversion from amnestic MCI to dementia after a mean period of 2.53±1.22 years of followup (annualy mean ratio of 7.08%). Out of 20 cases, 18 (90%) were Alzheimers dementia (AD). The conversion to dementia in the other groups wasnt recorded. Remission occurred in 14.3% of the 112 amnestic MCI patients group and in 30.8% of the 13 non-amnestic MCI group. By means of multivariate analysis, the conversion risk factor from MCI amnestic to dementia was the result of Mattis Dementia Rating Scale, subtopic dementia, [RR: 0.935 (95% CI: 0.907 0.963), p value <0.001]. The associated factors with a remission from MCI amnestic to normal cognition, in multivariate analysis, were age [RR: 0.907 (95% CI: 0.849 0.969), p value: 0.004], Geriatric Depression Scale 15 item version (GDS-15) [RR: 0.733 (95% CI: 0.553 0.972), p value: 0.031], list of words from the Consortium to Establish a Registry for Alzheimers Disease (CERAD) subtopic evocation [RR: 1.492 (95% CI: 1.038 2.144), p value: 0.031] and mini-mental state examination (MMSE) [RR: 1.273 (95% CI: 1.048 1.548), p value: 0.015]. Conclusion: After mean period of 2.5 years, the conversion rate of the studied population was 17.9% (annualy mean ratio of 7.08%). The remission ratio was 14.3%. Risk factors associated with conversion were the result of Mattis Dementia Rating Scale, subtopic dementia, whereas age, GDS-15, list of words from the Consortium to Establish a Registry for Alzheimers Disease (CERAD) subtopic evocation and MMSE were associated with remission from MCI amnestic to normal cognition.