Cognitive differences across ethnoracial category, socioeconomic status across the Alzheimer's disease spectrum: Can an ability discrepancy score level the playing field?

An ability discrepancy (crystallized minus fluid abilities) might be a personally relevant cognitive marker of risk for Alzheimer's disease (AD) and might help reduce measurement bias often present in traditional measures of cognition. In a large national sample of adults aged 60-104 years (N = 14,257), we investigated whether the intersectionality of group characteristics previously shown to pose a risk for AD including ethnoracial category, socioeconomic status, and sex (a) differed in ability discrepancy compared to traditional neuropsychological tests and (b) moderated the relationship between an ability discrepancy and AD symptom severity. In cognitively normal older adults, results indicated that across each decade, fluid and memory composite scores generally exhibited large group differences with sex, education, and ethnoracial category. In contrast, the ability discrepancy score showed much smaller group differences, thus removing much of the biases inherent in the tests. Women with higher education differed in discrepancy performance from other groups, suggesting a subgroup in which this score might reduce bias to a lesser extent. Importantly, a greater ability discrepancy was associated with greater AD symptom severity across the AD continuum. Subgroup analyses suggest that this relationship holds for all groups except for some subgroups of Hispanic Americans. These findings suggest that an ability discrepancy measure might be a better indicator of baseline cognition than traditional measures that show more egregious measurement bias across diverse groups of people.