Demographic and ethnicity effects on neuropsychological test performance : implications for dementia assessment in Caribbean populations

Prevalence rates of dementia are increasing worldwide and more so in developing countries. Early and accurate diagnosis of dementia then assumes critical importance. Cross-cultural neuropsychological assessment of dementia depends on the use of instruments that have been appropriately normed and validated for target populations. While culture and ethnicity have been acknowledged as variables which significantly impact cognitive performance, they are not usually included in normative and validation studies. The main aim of this dissertation was to standardise and identify the role played by ethnicity in performance on a number of instruments used in the assessment of dementia and identify the role and interaction of ethnicity with other common demographic variables on performance for Caribbean populations. Performance on the Mini Mental State Exam (MMSE) was influenced by age, education and ethnicity and a validation of corrected scores yielded a cut-off that resulted in a 35% reduction in false positive rates among non-AD persons. The Alzheimer’s Disease Assessment Scale-cognitive section (ADAS-cog) was influenced by education and was resistant to effects of ethnicity. Cut-off scores were lower than traditionally suggested, perhaps due to higher educational levels, but resulted in very high sensitivity (89%) and specificity (89%) rates. Education influenced scores on most measures: digit span, digit cancellation, logical memory, semantic and phonemic fluency and Raven’s Coloured Progressive Matrices. Ethnicity also influenced scores on digit span backwards, digit cancellation, semantic fluency and Raven’ Matrices. Ethnic differences in performance may be attributed to differences in attention, working memory and also to differences in cognitive styles. Differences in educational attainment across cultures and generations renders earlier norms invalid and highlight the needs for norms to be periodically revised in order to be considered representative of current populations. The provision of culturally relevant and contemporary norms yielded in this study can be regarded as invaluable tools in the assessment and diagnosis of dementia in diverse populations