It has been assumed that each MCI subtype is associated with an increased risk for a particular type of dementia. We can only partially agree with this.
As there is no construct to date that pools all efforts of defining mild cognitive impairment, the review provides suggestions for an agreement on constructive terminology and research practice.
Modified criteria should be applied if a concept for MCI with a high sensitivity is required and the original criteria (including subjective cognitive complaint) if a concept with high specificity and high PPP is required.
BackgroundBackground Although mild cognitive Although mild cognitive impairmentis associated with anincreased impairmentis associated with anincreased risk of developing dementia, there has risk of developing dementia, there has been little work on its incidence and been little work on its incidence and prevalence. prevalence.
AimsAims To report age-specificTo report age-specific prevalence, incidence and predictive prevalence, incidence and predictive validities for four diagnostic concepts of validities for four diagnostic concepts of mild cognitive impairment. mild cognitive impairment.
Method Method A community sample of1045A community sample of1045 dementia-free individuals aged 75 years dementia-free individuals aged 75 years and over was examined by and over was examined by neuropsychological testing in a threeneuropsychological testing in a threewave longitudinal study. wave longitudinal study.
Results
Results Prevalence rates ranged fromPrevalence rates ranged from 3% to 20%, depending on the concept 3% to 20 %, depending on the concept applied.The annual incidence rates applied.The annual incidence rates applying different case definitions varied applying different case definitions varied from 8 to 77 per1000 person-years.Rates from 8 to 77 per1000 person-years.Rates of conversion to dementia over 2.6 years of conversion to dementia over 2.6 years ranged from 23% to 47%. ranged from 23% to 47%.
Conclusions Conclusions Mild cognitiveMild cognitive impairment is frequent in older people. impairment is frequent in older people. Prevalence, incidence and predictive Prevalence, incidence and predictive validities are highly dependent on the validities are highly dependent on the diagnostic criteria applied. diagnostic criteria applied.
Further long-term studies are needed to examine the time-dependent evolution from mild cognitive impairment to dementia and to establish age-specific conversion rates during lifetime.
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