Article

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

ABSTRACT

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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    • "Alzheimer's disease (AD) accounts for approximately half of all dementia diagnoses and vascular dementia accounts for a further 25% (Jia et al., 2014), which is similar to internationally reported proportions (Ott et al., 1995). Mild cognitive impairment (MCI), a less severe cognitive impairment that may progress to dementia, affects up to 42% of people aged over 60 (Ward et al., 2012). In an elderly Chinese sample 10.6% met the criteria for MCI (Jia et al., 2014).Correspondence: Matthew Lewis, Deakin University, Centre for Mental Health and Wellbeing Research, School of Psychology, 221 Burwood Highway, Burwood, 3125, Australia. "
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    ABSTRACT: Background: China's ageing population will lead to increased neurodegenerative illness and age-related mental health problems. Aims: The Chinese Longitudinal Ageing Study has been developed to better understand the impact of ageing on cognition and mental health. An overview of the sample, major diagnoses and results of the first wave of data collection is presented. Method: One thousand and sixty-eight elderly Chinese (42.2% male), mean age of 72.8 years (SD = 8.5) completed a comprehensive cognitive, psychosocial and mental health assessment. Results: Mean MMSE score was 24.73 (SD = 6.17). Primary generalised anxiety was detected in 0.4% of the sample. Sub-clinical depression and depressive disorder were diagnosed in 1.7% and 2.4% of the sample, respectively. Most (84.5%) reported subjective memory decline, however 66.5% had no cognitive impairment. Mild Cognitive Impairment (MCI) was detected in 25%, Alzheimer's disease (AD) in 4.7%, vascular dementia in 2.5%, and mixed dementia in 1.3%. Cognition was worse in those 85+ years, but affective disorder rates were not. Conclusion: Higher rates of dementia were detected than previously reported in China. Normative data is presented for common cognitive and mental health assessment and screening tasks in a Chinese population. This suggests that the true incidence of dementia has been underestimated, and requires further investigation.
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    • "When this memory decline has no underlying medical cause, it is known as age-associated memory impairment (AAMI), which has been considered as a non-progressive normal decline due to aging (Crook et al., 1986; Youngjohn and Crook, 1993; Hänninen et al., 1995). Information on the prevalence rates of AAMI is scantly and varies greatly because of different definitions and unstandardized methodology, but in general prevalence has been estimated to range from 3.6 to 38.4% (see Ward et al., 2012, for a recent review). "
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    ABSTRACT: Previous studies have suggested that older adults with age-associated memory impairment (AAMI) may show a significant decline in attentional resource capacity and inhibitory processes in addition to memory impairment. In the present paper, the potential attentional capture by task-irrelevant stimuli was examined in older adults with AAMI compared to healthy older adults using scalp-recorded event-related brain potentials (ERPs). ERPs were recorded during the execution of a visual search task, in which the participants had to detect the presence of a target stimulus that differed from distractors by orientation. To explore the automatic attentional capture phenomenon, an irrelevant distractor stimulus defined by a different feature (color) was also presented without previous knowledge of the participants. A consistent N2pc, an electrophysiological indicator of attentional deployment, was present for target stimuli but not for task-irrelevant color stimuli, suggesting that these irrelevant distractors did not attract attention in AAMI older adults. Furthermore, the N2pc for targets was significantly delayed in AAMI patients compared to healthy older controls. Together, these findings suggest a specific impairment of the attentional selection process of relevant target stimuli in these individuals and indicate that the mechanism of top-down suppression of entirely task-irrelevant stimuli is preserved, at least when the target and the irrelevant stimuli are perceptually very different.
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    • ", 10 participants for 20s ~ 40s and 20 participants for 50s ~ 70s were separately recruited and gender ratio was balanced. Considering that the prevalence of brain disorders under 50s is relatively small (< 5%) compared to that over 50s (< 45.7%) (Ward et al., 2012), the participant aged 50s ~ 70s was recruited by two times than that aged 20s ~ 40s in the present study. "
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