Harmonisation of later-life cognitive function across national contexts: results from the Harmonized Cognitive Assessment Protocols.

BACKGROUND: The Harmonized Cognitive Assessment Protocol (HCAP) is an innovative instrument for cross-national comparisons of later-life cognitive function, yet its suitability across diverse populations is unknown. We aimed to harmonise general and domain-specific cognitive scores from HCAP studies across six countries, and evaluate reliability and criterion validity of the resulting harmonised scores. METHODS: We statistically harmonised general and domain-specific cognitive function scores across publicly available HCAP partner studies in China, England, India, Mexico, South Africa, and the USA conducted between October, 2015 and January, 2020. Participants missing all cognitive test items in a given HCAP were excluded. We used an item banking approach that leveraged common cognitive test items across studies and tests that were unique to studies. We generated harmonised factor scores to represent a person's relative functioning on the latent factors of general cognitive function, memory, executive function, orientation, and language using confirmatory factor analysis. We evaluated the marginal reliability, or precision, of the factor scores using test information plots. Criterion validity of factor scores was assessed by regressing the scores on age, gender, and educational attainment in a multivariable analysis adjusted for these characteristics. FINDINGS: We included 21 144 participants from the six HCAP studies of interest (11 480 women [54·3%] and 9664 [45·7%] men), with a median age of 69 years (IQR 64-76). Confirmatory factor analysis models of cognitive function in each country fit well: 31 (88·6%) of 35 models had adequate or good fit to the data (comparative fit index ≥0·90, root mean square error of approximation ≤0·08, and standardised root mean residual ≤0·08). Marginal reliability of the harmonised general cognitive function factor was high (>0·9) for 19 044 (90·1%) of 21 144 participant scores across the six countries. Marginal reliability of the harmonised factor was above 0·85 for 19 281 (91·2%) of 21 142 participant factor scores for memory, 7805 (41·0%) of 19 015 scores for executive function, 3446 (16·3%) of 21 103 scores for orientation, and 4329 (20·5%) of 21 113 scores for language. In each country, general cognitive function scores were lower with older age and higher with greater levels of educational attainment. INTERPRETATION: We statistically harmonised cognitive function measures across six large population-based studies of cognitive ageing. These harmonised cognitive function scores empirically reflect comparable domains of cognitive function among older adults across the six countries, have high reliability, and are useful for population-based research. This work provides a foundation for international networks of researchers to make improved inferences and direct comparisons of cross-national associations of risk factors for cognitive outcomes in pooled analyses. FUNDING: US National Institute on Aging.

The (in)visible Brazilians: A perspective review on the need for brain health and dementia research with Brazilian immigrants in the United States.

Introduction: The Brazilian population in the United States (U.S.), a Latinx subgroup, is rapidly growing and aging but remains underrepresented in U.S. health research. In addition to group-specific genetic and environmental risks, Brazilian immigrants and their offspring in the U.S. likely have cumulative risks for health inequities.It is estimated that 71% of Brazilian immigrants in the U.S. are undocumented, which may limit healthcare access/utilization. Furthermore, mental health is reported as a health priority by Brazilian immigrants in the U.S., and there is a lack of research on Alzheimer's disease and related dementia (AD/ADRD) in this population. Methods: We reviewed the scientific literature using traditional (e.g., PubMed) sources and databases generated by U.S. and Brazilian governments, as well as international organizations, and press articles. Results: This perspective review lists recommendations for researchers, health providers, and policymakers to promote greater inclusion of U.S. Brazilian populations in health research and care. The review identifies research areas in need of attention to address health inequities and promote mental/brain health in Brazilian immigrants and their offspring living in the U.S. These research areas are: 1) epidemiological studies to map the prevalence and incidence of mental/brain health conditions; 2) research on aging and AD/ADRD risk factors among Brazilian populations in the U.S.; and 3) the need for greater representation of U.S-residing Brazilian population in other relevant research areas involving genetics, neuropathology, and clinical trials. Conclusions: The recommendation and research efforts proposed should help to pave the way for the development of community-engagement research and to promote mental/brain health education, improvement of mental/brain health and AD/ADRD services, and the development of culturally-informed intervention to the U.S.-residing Brazilian communities. HIGHLIGHTS: The Brazilian population in the United States is growing but is underrepresented in U.S. health research.Approximately 71% of Brazilian immigrants in the United States are undocumented, with an increased risk for health inequities.Mental health is reported as a central health priority by Brazilian immigrants in the United States.There is a lack of research on Alzheimer's disease and other dementias (ADRD) in Brazilian immigrants in the United States.Epidemiological research is needed to map the prevalence/incidence of mental health conditions and ADRD risk factors among Brazilian immigrants in the United States.

Psychological predictors of memory decline in a racially and ethnically diverse longitudinal sample of older adults in the United States.

OBJECTIVES: In the United States, racial and ethnic disparities in memory dysfunction and Alzheimer disease are evident even after accounting for many risk factors. Psychological factors, such as psychological well-being, perceived control, depressive symptoms, and negative affect, may influence memory dysfunction, and associations may differ by race and ethnicity. This study examined whether psychological factors are differentially associated with episodic memory trajectories across racial and ethnic groups in the United States. METHODS/DESIGN: The National Health and Aging Trends Study (NHATS), is a US-representative, longitudinal study of Medicare-eligible adults 65+ years old. Analyses of 5 years of data, included a total of 9411 participants without dementia at baseline. Adjusting for relevant covariates, a linear mixed model estimated the associations between psychological predictors and a composite of immediate and delayed trials from a word list memory test. RESULTS: More depressive symptoms (B = -0.02), lower psychological well-being (B = 0.03), and lower perceived control (B = 0.05) were independently associated with lower initial memory. Depressive symptoms were associated with faster rate of memory decline (B = -0.01). Black (B = -0.34) and Hispanic (B = -0.28) participants evidenced lower initial memory level than whites, but only Hispanic (B = -0.04) participants evidenced faster memory decline than whites. There were no significant interactions between the psychological variables and race and ethnicity. CONCLUSIONS: Results extend previous studies showing racial and ethnic disparities in episodic memory trajectories, and the longitudinal effects of depressive symptoms on episodic memory in US samples. Epidemiological studies of cognitive aging should incorporate more psychological factors clarify cognitive decline and disparities.

Education Moderates the Relation Between APOE ɛ4 and Memory in Nondemented Non-Hispanic Black Older Adults.

BACKGROUND: The APOEɛ4 allele is a well-known risk factor for Alzheimer's disease (AD). Previous research argues that higher education helps to preserve cognition in older adults with AD pathology because of its key role in cognitive reserve and resilience. OBJECTIVE: To test if higher educational level buffers the effect of APOEɛ4 on cognition among older non-Hispanic Blacks. METHODS: Participants were 849 non-demented older non-Hispanic Blacks (38.3% APOEɛ4+), who underwent a comprehensive neuropsychological evaluation. Multiple linear regression models tested the relationship between APOEɛ4 status and twelve cognitive measures with education (up to high school and beyond high school) as a moderator. RESULTS: Education buffered the effects of the APOEɛ4 allele, such that there was no impact of APOEɛ4 status on word-list memory retention and working memory among participants with more than a high school degree. This pattern was not observed for ten other cognitive measures of verbal and visual episodic memory, semantic memory, executive function, and processing speed-although a similar trend was observed for switching ability in executive functioning. The buffering effect of education was stronger among women than men. CONCLUSION: Our findings suggest that genetic effects on late-life cognition may be modified by environmental factors such as educational attainment. These results are consistent with the framework of cognitive reserve such that engaging in cognitively enriching activities and acquiring skills and knowledge with more years of education may increase the capacity to maintain cognitive function despite high genetic risk for impairment.