Socioeconomic and Cardiovascular Sources of Cross-National Variation in Cognitive Health Among Older Adults

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PROJECT SUMMARY Although nearly 75% of global Alzheimer’s disease and related dementias (ADRD) cases will occur in lower- and middle-income countries (LMICs) by 2050, little ADRD research includes data from these regions. This is a major missed opportunity to identify individual-level and contextual influences on later-life cognitive function. Evidence from high-income countries suggests ADRD is partly attributable to socioeconomic factors, such as education, and cardiovascular factors, such as hypertension. Whether these same factors contribute to cognitive health outcomes to a similar degree in LMICs with rapidly aging populations is unknown. Comparative research across LMICs and high-income countries could help to unlock important drivers of ADRD and identify key differences between countries that could be leveraged for prevention strategies to reduce the global ADRD burden. The NIA-funded Harmonized Cognitive Assessment Protocol (HCAP) was recently introduced into the US Health and Retirement Study (HRS) and its International Partner Studies (IPS) as a comparable cross-national cognitive assessment. Critically, no work has demonstrated that HCAP data from the various countries are in fact directly comparable. Any observation of country-level differences may thus be an unknown mixture of actual differences in the distribution of cognitive function and bias attributable to incommensurate measurement. Our overarching goal is to estimate the contributions of key socioeconomic and cardiovascular ADRD risk factors to later-life cognitive function between individuals and between countries in the US HRS and IPS in South Africa, Mexico, India, and England. We have assembled HCAP and main HRS/IPS survey data on N=10,642 older adults from these five countries. To accomplish our goal, we aim to: 1) statistically harmonize HCAP measures across HRS/IPS countries using modern psychometrics to enable us to identify and address any differential item functioning of HCAP measures across countries in order to facilitate valid cross-national comparisons; 2) investigate and quantify the contributions of life course socioeconomic factors to variation in later-life cognitive function between individuals and between countries; and, 3) investigate and quantify the contributions of cardiovascular factors to variation in later-life cognitive function between individuals and between countries. Key innovations are: 1) adaptation of sophisticated psychometric methods to harmonize HCAP data across economically, socially, and culturally diverse country contexts; 2) inclusion of cross-national data to diversify and expand representation of global populations in the ADRD evidence base; and, 3) use of multi-level models to partition variance in later-life cognitive function to differences between individuals and differences between countries. We will make our harmonized data available through the established Gateway to Global Aging Data website. Our results will set the stage to identify intervention targets for high-risk individuals as well as whole populations, with the ultimate goal of preventing and/or delaying the onset of ADRD from a global perspective.