. 2023 Oct;4(10):e573-e583.

doi: 10.1016/S2666-7568(23)00170-8.

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

Affiliations

¹ Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Center on Aging and Health, Johns Hopkins University, Baltimore, MD, USA. Electronic address: agross14@jhu.edu.
² Center for Social Epidemiology and Population Health, Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI, USA; Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA.
³ Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA.
⁴ Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA.
⁵ Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, RI, USA.
⁶ Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA; Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA; Veterans Affairs Center for Clinical Management Research, Ann Arbor, MI, USA.
⁷ Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Center on Aging and Health, Johns Hopkins University, Baltimore, MD, USA; Center for Economic and Social Research, University of Southern California, Los Angeles, CA, USA.
⁸ Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA.
⁹ School of Public and Population Health, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, USA.
¹⁰ Harvard Center for Population and Development Studies and Department of Social and Behavioral Sciences, Harvard T H Chan School of Public Health, Cambridge, MA, USA.
¹¹ Center for Economic and Social Research, University of Southern California, Los Angeles, CA, USA; Department of Economics, University of Southern California, Los Angeles, CA, USA.

PMID: 37804847
PMCID: PMC10637129
DOI: 10.1016/S2666-7568(23)00170-8

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

Alden L Gross et al. Lancet Healthy Longev. 2023 Oct.

. 2023 Oct;4(10):e573-e583.

doi: 10.1016/S2666-7568(23)00170-8.

Authors

Affiliations

¹ Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Center on Aging and Health, Johns Hopkins University, Baltimore, MD, USA. Electronic address: agross14@jhu.edu.
² Center for Social Epidemiology and Population Health, Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI, USA; Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA.
³ Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA.
⁴ Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA.
⁵ Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, RI, USA.
⁶ Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA; Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA; Veterans Affairs Center for Clinical Management Research, Ann Arbor, MI, USA.
⁷ Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Center on Aging and Health, Johns Hopkins University, Baltimore, MD, USA; Center for Economic and Social Research, University of Southern California, Los Angeles, CA, USA.
⁸ Survey Research Center, University of Michigan Institute for Social Research, Ann Arbor, MI, USA.
⁹ School of Public and Population Health, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, USA.
¹⁰ Harvard Center for Population and Development Studies and Department of Social and Behavioral Sciences, Harvard T H Chan School of Public Health, Cambridge, MA, USA.
¹¹ Center for Economic and Social Research, University of Southern California, Los Angeles, CA, USA; Department of Economics, University of Southern California, Los Angeles, CA, USA.

PMID: 37804847
PMCID: PMC10637129
DOI: 10.1016/S2666-7568(23)00170-8

Abstract

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.

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Conflict of interest statement

Declaration of interests ALG reports payment for lectures from the University of California, Berkeley, and the University of Michigan. KML reports consulting fees on projects funded by the US National Institutes of Health at Harvard University, the University of Pennsylvania, the University of Minnesota, the University of Colorado at Boulder, Dartmouth University, and the University of Southern California. JL reports grants or contracts from Bright Focus, the World Bank, and the UN; honoraria for lectures from the US National Institutes of Health and Southern Illinois University School of Medicine; and support for attending meetings from the University of California, Berkeley, University College London, and the University of Venice. All other authors declare no competing interests.

Figures

**Figure 1:. Heatmap of cognitive test item indicators and their overlap across each HCAP study**
The heatmap shows factor loadings from domain-specific factor analyses. Loadings are standardised to have a range from –1 to 1, and can thus be interpreted as correlations between items and the underlying factor. All loadings presented are positive, indicating that items are positively correlated. The presence of factor loadings for a given test item in each column reflects decisions about the comparability of items made during prestatistical harmonisation and after testing for DIF. Grey cells indicate cognitive test items not administered in the HCAP battery for a given country. CERAD=Consortium to Establish a Registry for Alzheimer’s Disease. CHARLS=China Health and Retirement Longitudinal Study. DIF=differential item functioning. ELSA=English Longitudinal Study on Ageing. HAALSI=Health and Aging in Africa: A Longitudinal Study in South Africa. HCAP=Harmonized Cognitive Assessment Protocol. HRS=US Health and Retirement Study. LASI-DAD=Longitudinal Aging Study in India-Diagnostic Assessment of Dementia. Mex-Cog=Mexican Health and Aging Study Cognitive Aging Ancillary Study. *1 and 2 notation reflects judgements made during prestatistical harmonisation on the similarities of the tests. †110 items, in which participants assign numbers to symbols on the basis of a key. ‡56 items, in which participants assign symbols provided on the basis of a key.

**Figure 2:. Distribution of harmonised general and domain-specific cognitive factor scores in the HCAP studies**
The histograms show general cognitive function (first column) and domain-specific cognitive factors (subsequent columns) by study. Bar heights in each histogram indicate relative frequency of observations with a value along the x-axis. CHARLS=China Health and Retirement Longitudinal Study. ELSA=English Longitudinal Study on Ageing. HAALSI=Health and Aging in Africa: a Longitudinal Study in South Africa. HCAP=Harmonized Cognitive Assessment Protocol. HRS=US Health and Retirement Study. LASI-DAD=Longitudinal Aging Study in India-Diagnostic Assessment of Dementia. Mex-Cog=Mexican Health and Aging Study Cognitive Aging Ancillary Study.

**Figure 3:. Marginal reliability for overall and domain-specific cognitive performance in each HCAP study**
Plots show the marginal reliability of general and domain-specific factor scores for each study. This figure shows differences in the reliability of estimated factor scores as a function of corresponding abilities on the latent trait. Horizontal dashed lines at reliabilities of 0·8 and 0·9 indicate acceptable thresholds of reliability for basic research and high-stakes testing, respectively. CHARLS=China Health and Retirement Longitudinal Study. ELSA=English Longitudinal Study on Ageing. HAALSI=Health and Aging in Africa: a Longitudinal Study in South Africa. HCAP=Harmonized Cognitive Assessment Protocol. HRS=US Health and Retirement Study. LASI-DAD=Longitudinal Aging Study in India-Diagnostic Assessment of Dementia. Mex-Cog=Mexican Health and Aging Study Cognitive Aging Ancillary Study.

See this image and copyright information in PMC

Update of

Harmonization of Later-Life Cognitive Function Across National Contexts: Results from the Harmonized Cognitive Assessment Protocols (HCAPs).
Gross AL, Li C, Briceno EM, Rentería MA, Jones RN, Langa KM, Manly JJ, Nichols EL, Weir D, Wong R, Berkman L, Lee J, Kobayashi LC. Gross AL, et al. medRxiv [Preprint]. 2023 Jun 12:2023.06.09.23291217. doi: 10.1101/2023.06.09.23291217. medRxiv. 2023. Update in: Lancet Healthy Longev. 2023 Oct;4(10):e573-e583. doi: 10.1016/S2666-7568(23)00170-8. PMID: 37398152 Free PMC article. Updated. Preprint.

Comment in

Advances in cross-national comparisons of cognitive ageing.
Nakagawa T. Nakagawa T. Lancet Healthy Longev. 2023 Oct;4(10):e526-e527. doi: 10.1016/S2666-7568(23)00192-7. Lancet Healthy Longev. 2023. PMID: 37804840 No abstract available.

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

Affiliations

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

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

Update of

Comment in

References

Publication types

MeSH terms

Grants and funding

LinkOut - more resources

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