Article

Incidence of mild cognitive impairment in the Pittsburgh Cardiovascular Health Study-Cognition Study

and Department of Neurology (O.T.C.), University of California Davis, Davis.
Neurology (Impact Factor: 8.3). 10/2012; 79(15). DOI: 10.1212/WNL.0b013e31826e25f0

ABSTRACT OBJECTIVES AND METHODS: The purpose of this study was to examine the incidence of mild cognitive impairment (MCI) and patterns of progression from incident MCI to dementia in 285 cognitively normal subjects (mean age, 78.9 years) in the Cardiovascular Health Study-Cognition Study from 1998-1999 to 2010-2011. RESULTS: Two hundred (70%) of the participants progressed to MCI; the age-adjusted incidence of MCI was 111.09 (95% confidence interval, 88.13-142.95) per 1,000 person-years. A total of 107 (53.5%) of the incident MCI subjects progressed to dementia. The mean time from MCI to dementia was 2.8 +/- 1.8 years. Forty (20%) of the incident MCI cases had an "unstable" course: 19 (9.5%) converted to MCI and later returned to normal; 10 (5%) converted to MCI, to normal, and later back to MCI; 7 (3.5%) converted to MCI, to normal, to MCI, and later to dementia; and 4 (2%) converted to MCI, to normal, and later to dementia. There was an increased mortality rate among the cognitively normal group (110.10 per 1,000 person-years) compared to those with incident MCI who converted to dementia (41.32 per 1,000 person-years). CONCLUSIONS: The majority of the subjects aged >80 years developed an MCI syndrome, and half of them progressed to dementia. Once the MCI syndrome was present, the symptoms of dementia appeared within 2 to 3 years. Progression from normal to MCI or from normal to MCI to dementia is not always linear; subjects who developed MCI and later returned to normal can subsequently progress to dementia. Competing mortality and morbidity influence the study of incident MCI and dementia in population cohorts.

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    • "Others have noted that impairments in executive functions (i.e., Trail Making B [6] [32]), language (i.e., Semantic Fluency [6] [26] [34]), or even a summary measure of mental state (i.e., Mini-Mental State Examination (MMSE) [6] [35], Clock test [26]) are better predictors of dementia than memory function alone. However, it should be noted that even among the longitudinal studies, follow-up is generally limited to two years or fewer and most of the conversions from MCI to dementia occur relatively early in the longitudinal follow-up suggesting that these patients were on the cusp of clinical dementia (for discussion, see [36]). Brain functional imaging studies with SPECT have found that those patients who develop dementia from MCI showed reduced cerebral blood flow in a variety of brain regions including the medial temporal lobe, the temporal/parietal cortex, the posterior cingulate gyrus, the precuneus, and the prefrontal cortex [35, 37–43]. "
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