Mild cognitive impairment: Disparity of incidence and prevalence estimates

United BioSource Corporation, Center for Epidemiology and Database Analytics, Lexington, MA, USA.
Alzheimer's & dementia: the journal of the Alzheimer's Association (Impact Factor: 12.41). 01/2012; 8(1):14-21. DOI: 10.1016/j.jalz.2011.01.002
Source: PubMed


The purpose of conducting this study was to identify areas of concordance and sources of variation for the published rates of prevalence and incidence associated with various definitions for mild cognitive impairment (MCI).
The study used systematic review of studies published in English since 1984. Studies were identified by searching MEDLINE and EMBASE databases. Population-based observational studies of incidence or prevalence of MCI and related terms were eligible for inclusion.
A total of 3,705 citations were identified, and 42 were accepted for inclusion; 35 included data on prevalence and 13 on incidence. The following four terms predominated: age-associated memory impairment (AAMI); cognitive impairment no dementia (CIND); MCI; and amnestic MCI (aMCI). Within each term, the operational definition varied. Substantial variation was observed for both incidence (MCI: 21.5-71.3; aMCI: 8.5-25.9 per 1,000 person-years) and prevalence of each definition of cognitive impairment (AAMI 3.6%-38.4%; CIND 5.1%-35.9%; MCI 3%-42%; aMCI 0.5%-31.9%). CIND and MCI showed increasing prevalence among older age groups, whereas age-specific rates of aMCI were lower and without any apparent age relationship.
Prevalence and incidence estimates associated with MCI vary greatly both between definitions and within a definition across the 42 publications. These wide differences pose a significant challenge to our understanding of the social burden of this disease. Enhancement and standardization of operational definitions of the subtypes of cognitive impairment could improve estimates of disease burden and provide a mechanism to assist in the identification of individuals at risk for future Alzheimer's disease and other dementias.

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    • "It has been shown, for example, that HIV+ individuals showed a similar pattern and level of cognitive performance as much older seronegatives (Van Gorp et al. 1989). Indeed, the present sample of HIV+ individuals in their 60s had prevalence rates of MCI that were similar to those typically observed in seronegative adults aged 70 and over (Ward et al. 2012). These cognitive deficits in the cART era appear to be driven by a rise in the prevalence of impairment in memory and executive functions among HIV+ individuals who are medically asymptomatic (Heaton et al. 2011). "
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    ABSTRACT: With the rising number of individuals in their 50s and 60s who are infected with HIV, concerns have emerged about possible increases in the rates of non-HIV-associated dementias. The current study examined the prevalence of mild cognitive impairment (MCI) in older HIV-infected adults, since MCI is an intermediate state between typical cognitive aging and dementia that emerges in this age range. Participants included 75 adults with HIV disease aged 50 years and older who were on combination antiretroviral therapy (cART) and had undetectable plasma viral loads and 80 demographically similar HIV-seronegative comparison subjects. Participants completed a research neuropsychological evaluation that was used to classify MCI according to the comprehensive diagnostic scheme described by Bondi et al. (J Alzheimers Dis 42:275-289, 2014). HIV-infected persons were over seven times more likely to have an MCI designation (16 %) than their seronegative counterparts (2.5 %). Within the HIV+ cohort, MCI had minimal overlap with diagnoses of asymptomatic neurocognitive impairment and was significantly associated with older age, lower Karnofsky Scale of Performance Scores, and mild difficulties performing instrumental activities of daily living (iADLs). HIV infection in older adults is associated with a notably elevated concurrent risk of MCI, which may increase the likelihood of developing non-HIV-associated dementias as this population ages further.
    Journal of NeuroVirology 07/2015; DOI:10.1007/s13365-015-0366-7 · 2.60 Impact Factor
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    • ". Though this work is specific to AD and not dementia, as AD is considered to be the most common type of dementia [20], similar age-specific trends and magnitude between the Europe and the United States is not unexpected. Sources of variability for prevalence of MCI and dementia have been previously described and potential causes include age and gender characteristics of study, diagnosis implementation, country, and year of study [16] [17]. For MCI in particular, a lack of consensus in criteria choice and implementation remains an important factor of heterogeneity: overall prevalence was more than doubled using DSM-IV versus Petersen criteria in the same population sample [8]. "
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    ABSTRACT: Abstract: The prevalence of mild cognitive impairment (MCI) and dementia according to age remain uncertain. We systematically extracted age-stratified estimates of MCI and dementia prevalence reported in European studies since 1995, and performed meta-analyses for dementia. We identified 10 relevant studies on MCI and 26 studies on dementia. Studies on MCI presented visually substantial heterogeneity preventing a meta-analysis, a majority reporting an increase in prevalence at ≥75 years old. Prevalence of dementia rose continuously from 55 years of age, reaching 44.7% (39.8; 49.6) in those ≥95 years of age. Homogenization of MCI criteria, and additional studies in Northern European population would be warranted.
    Journal of Alzheimer's disease: JAD 01/2015; 48(2). · 4.15 Impact Factor
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    • "Using the current definitions—averaged across the major population-based studies—worldwide prevalence of MCI and a-MCI among adults over 65 years is 18.9% (Petersen et al., 2014) and 7% (Ward et al., 2012a), respectively. That being said, prevalence estimates vary greatly across studies highlighting the need for enhanced standardization of operational definitions of MCI and its various subtypes (Ward et al., 2012a). With respect to risk factors, MCI is much the same as dementia: age, education, APOE genotype, vascular disease, and diabetes have all been identified (reviewed in Petersen et al., 2014). "
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    ABSTRACT: As of 2010, the worldwide economic impact of dementia was estimated at $604 billion USD; and without discovery of a cure or effective interventions to delay disease progression, dementia’s annual global economic impact is expected to surpass $1 trillion USD as early as 2030. Alzheimer’s disease (AD) is the leading cause of dementia accounting for over 75% of all cases. Toxic accumulation of amyloid beta (Aβ), either by overproduction or some clearance failure, is thought to be an underlying mechanism of the neuronal cell death characteristic of AD—though this amyloid hypothesis has been increasingly challenged in recent years. A compelling alternative hypothesis points to chronic neuroinflammation as a common root in late-life degenerative diseases including AD. Apolipoprotein-E (APOE) genotype is the strongest genetic risk factor for AD: APOE-ε4 is proinflammatory and individuals with this genotype accumulate more Aβ, are at high risk of developing AD, and almost half of all AD patients have at least one ε4 allele. Recent studies suggest a bidirectional relationship exists between sleep and AD pathology. Sleep may play an important role in Aβ clearance, and getting good quality sleep vs. poor quality sleep might reduce the AD risk associated with neuroinflammation and the ε4 allele. Taken together, these findings are particularly important given the sleep disruptions commonly associated with AD and the increased burden disrupted sleep poses for AD caregivers. The current review aims to: (1) identify individuals at high risk for dementia who may benefit most from sleep interventions; (2) explore the role poor sleep quality plays in exacerbating AD type dementia; (3) examine the science of sleep interventions to date; and (4) provide a road map in pursuit of comprehensive sleep interventions, specifically targeted to promote cognitive function and delay progression of dementia.
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