Incidence of mild cognitive impairment and Alzheimer disease in Southern Brazil

The objective of the study was to evaluate incident cases of Alzheimer disease (AD) and mild cognitive impairment (MCI) in an elderly community cohort in a major city of southern Brazil and to determine the variables associated with the development of cognitive dysfunction. Data were drawn from a cohort to investigate healthy aging among community elderly (N = 345) and were derived from the follow-up for a maximum of 8 years. Sociodemographic, psychiatric and medical information, the Mini-Mental State Examination (MMSE), and the Clinical Dementia Rating scale were obtained in each assessment. The Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition; DSM-IV), NINCDS-ADRDA (National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and related Disorders Association), and the Mayo Clinic criteria were applied to ascertain diagnoses of AD and MCI. The incidence rate per 1000 persons-year for MCI was 13.2 (95% confidence interval [CI] 7.79-20.91) and for AD was 14.8 (95% CI 9.04-22.94). Cognitive dysfunction was associated with education (odds ratio [OR] = 0.86; confidence limit [CL] 0.76-0.97 95%) and baseline MMSE (OR = 0.81; CL 0.70-0.94 95%). The AD incidence in this sample was higher than those reported in a previous Brazilian study. The study filled the epidemiological gap in the evaluation of MCI in Brazil.