ABSTRACT
OBJECTIVES: To estimate the incidence of cognitive impairment (CI) among cognitively healthy, Mexican subjects, and to evaluate the impact of demographic and vascular factors on the conversion to CI and mortality. METHODS: 734 eligible subjects (aged 55 to >90 years) from a population-based sample were examined. The cognitive function of participants was assessed using the Mini-Mental State Examination (MMSE) every 2 years. The subjects were followed for an average of 3.2 years. The CI was defined using two sets of criteria: (i) moderate CI, as a drop to 25-21 on the MMSE at 2-year follow-up or a decrease of at least four points and (ii) severe CI, defined as a drop of 21 or less in MMES at follow-up. The incidence density and period prevalence were determined as epidemiological measures as well as the cumulative incidence as a risk measure. Kaplan-Meier survival curves were used to analyse the main points of interest: CI, dementia and mortality. RESULTS: The period prevalence of moderate CI was 20%, and 10% for severe CI. During 1959 person-years of follow-up, severe CI developed in 33 of the 361 participants. While during 2096 person-years of follow-up; 80 of 361 participants developed moderate CI. The rate of progression to severe CI in moderate CI subjects gradually increases with follow-up. Both, moderate and severe CI were associated with low educational level, higher age and higher mortality. CONCLUSIONS: Elderly people with moderate CI have an increased risk of severe CI. Moderate and severe CI are both predictive of higher mortality in Mexican subjects.
