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Prevalence of mild cognitive impairment: a population-based study in elderly subjects
T Hänninen1, M Hallikainen, S Tuomainen
1Department of Neuroscience and Neurology, University of Kuopio, Finland. tuomo.hanninen@kuh.fi
Objectives:
Mild cognitive impairment (MCI) has been suggested as a term for a boundary area between normal aging and dementia, especially Alzheimer's disease (AD). In follow-up studies, more than 50% of MCI subjects have been converted to dementia in 3-4 years. However, the epidemiology of MCI is not well known. This study was designed to determine the prevalence of MCI in an elderly population.
Methods:
A total of 806 subjects (60-76 years of age) from a population-based random sample of 1150 subjects living in the city of Kuopio in eastern Finland were evaluated. Neuropsychological tests and a structured interview including the modified Clinical Dementia Rating (CDR) were used to apply the diagnostic criteria of MCI as proposed by Mayo Clinic Alzheimer's Disease Research Centre. Thus, subjects having a test score more than 1.5 SDs below the age appropriate mean in memory tests and a CDR score of 0.5 but no dementia, were diagnosed as having MCI.
Results:
A total of 43 subjects, 5.3%, met the MCI criteria. MCI was more prevalent in older and less-educated subjects, but no difference was found between men and women. The CDR appeared to be the most important part of the criteria. The memory tests had less impact on prevalence variables.
Conclusions:
The low prevalence of MCI indicate that in a population-based study design its criteria may identify a more homogeneous group of subjects at the lower end of the cognitive continuum as contrasted with various other criteria of cognitive impairment in the elderly population. This is compatible with follow-up studies showing a high probability of dementia in the MCI group. Thus, probable candidates for trials of preventive intervention for dementia can be screened from the elderly population using these diagnostic criteria.
Insights
This study found that 5.3% of elderly individuals met the criteria for mild cognitive impairment (MCI). The prevalence of MCI was higher in older, less-educated individuals, suggesting a specific group for dementia prevention trials.
Area of Science:
- Neurology
- Gerontology
- Epidemiology
Background:
- Mild cognitive impairment (MCI) is a transitional stage between normal aging and dementia, particularly Alzheimer's disease (AD).
- Over 50% of individuals with MCI progress to dementia within 3-4 years.
- The epidemiology of MCI remains poorly understood.
Purpose of the Study:
- To determine the prevalence of MCI in an elderly population.
- To identify demographic factors associated with MCI.
- To assess the utility of specific diagnostic criteria for MCI.
Main Methods:
- A population-based random sample of 806 Finnish adults aged 60-76 years was evaluated.
- Diagnostic criteria included memory test scores more than 1.5 SDs below the age-appropriate mean and a Clinical Dementia Rating (CDR) score of 0.5.
- Neuropsychological tests and a structured interview with the modified CDR were employed.
Main Results:
- The prevalence of MCI was 5.3% (43 subjects).
- MCI was more common in older and less-educated individuals.
- The CDR score was a critical factor in diagnosis, with memory tests having less impact on prevalence.
Conclusions:
- The specific MCI criteria used identified a homogeneous group at the lower end of the cognitive spectrum.
- This group exhibits a high probability of progressing to dementia.
- These criteria can effectively screen elderly individuals for preventive dementia intervention trials.