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There is a need to elucidate the combined influence of neurodegeneration and cerebrovascular disease (CeVD) on cognitive impairment, especially in diverse populations. Here, we evaluated 840 multiethnic individuals (mean age = 70.18) across the disease spectrum from the Epidemiology of Dementia in Singapore study. First, we determined whether a validated quantitative MRI score of mixed pathology is associated with clinical diagnosis and whether the score differed between ethnicities (Chinese, Malays, and Indians). We then evaluated whether the score was associated with multidomain cognitive impairment and if additional measures of CeVD were further associated with cognitive impairment. We found that lower quantitative MRI scores were associated with severity of clinical diagnosis and Chinese individuals had the highest quantitative MRI scores, followed by Indians and Malays. Lower quantitative MRI scores were also associated with lower performance in attention, language, visuoconstruction, visuomotor, visual, and verbal memory domains. Lastly, the presence of intracranial stenosis and cortical cerebral microinfarcts, but not cerebral microbleeds, were associated with memory performance beyond quantitative MRI scores. Taken together, our results demonstrate the utility of using multiple MRI markers of neurodegeneration and CeVD for identifying multiethnic Asians with the greatest cognitive impairment due to mixed pathology. [ABSTRACT FROM AUTHOR]

Background: Dementia is the leading cause of dependency and disability among older persons worldwide. There remains, however, limited studies on dementia rates within the Asia-Pacific region, with little data on differences across major Asian ethnic groups., Objective: To study the prevalence of cognitive impairment (CI) and dementia in community-dwelling Indians from Singapore and to examine interethnic differences among Chinese, Malays, and Indians., Methods: Participants (>60 years) drawn from the Indian component of the multiethnic Epidemiology of Dementia in Singapore (EDIS) study were screened using the locally validated Abbreviated Mental Test and Progressive Forgetfulness Questionnaire. Screen-positive participants underwent further detailed neuropsychological assessments. CI was classified into Cognitive impairment no dementia (CIND)-mild, CIND-moderate, and dementia., Results: Of 961 Indian adults, 120 (12.5%) had CIND-mild, 101 (10.5%) CIND-moderate, and 12 (1.2%) dementia. The overall age-standardized prevalence of any CI was 24.6%. The prevalence of any CI increased with age (15.7% in ages 60-64 years to 30.1% in ages≥80 years), and was higher in women than men. Multivariate analysis showed that age, lower education, and hypertension were independently associated with CI. Even after demographic and cardiovascular risk factor adjustment, Indians were more likely to be cognitively impaired compared to Chinese (odds ratio [OR], 95% CI:1.37 [1.01-1.86]) but not Malays (0.89 [0.72-1.10])., Conclusions: Among elderly Indians, the overall prevalence of any CI was 24.6%. Despite similar assessment protocols and risk factor adjustments, the prevalence of CI was higher in Indians compared to Chinese but similar to Malays. Further research is needed to unravel other factors that may underlie these ethnic differences.