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Preplanned Studies: Early-Life Circumstances and Cross-Country Disparities in Cognition Among Older Populations — China, the US, and the EU, 2008–2018

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  • Summary

    What is already known about this topic?

    Many health challenges have emerged due to rapid population aging, including declined cognitive ability among older adults.

    What is added by this report?

    Childhood circumstances have significant and lasting impacts on cognition in old age. This study compared cognition data from China with both the United States (U.S.) and the European Union (EU) during 2008–2018, finding that childhood circumstances could respectively explain 65.4% [95% confidence interval (CI): 59.4%, 71.4%] (China vs. the U.S.) and 38.2% (95% CI: 35.1%, 41.2%) (China vs. the EU) of the overall differences in cognition among older adults. Family socioeconomic status explained the largest share of differences among all considered childhood circumstances.

    What are the implications for public health practice?

    Large disparities in cognition should be addressed by mitigating childhood disadvantages.

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  • Funding: Supported by the National Natural Science Foundation of China (71974097); and a Career Development Award (K01AG053408), a major research grant (R01AG077529), the Claude D. Pepper Older Americans Independence Center at Yale School of Medicine (P30AG021342) funded by the National Institute on Aging, Jiangsu Qinglan Project, Jiangsu the Priority Academic Program Development of Jiangsu Higher Education Institute (PAPD)
  • [1] United Nations Department of Economic and Social Affairs Population Division. World population prospects 2022. https://population.un.org/wpp/. [2022-8-30].https://population.un.org/wpp/
    [2] Yan BJ, Chen X, Gill TM. Health inequality among Chinese older adults: the role of childhood circumstances. J Econ Ageing 2020;17:100237. http://dx.doi.org/10.1016/j.jeoa.2020.100237CrossRef
    [3] Wang YN, Song X. Health policy response to population aging: what China can learn from major developed countries. Sci Res Aging 2022;10(5):29 − 43. http://dx.doi.org/10.3969/j.issn.2095-5898.2022.05.004 (In Chinese). CrossRef
    [4] Lin ZE, Chen X. Adverse childhood circumstances and cognitive function in middle-aged and older Chinese adults: lower level or faster decline? SSM Popul Health 2021;14:100767. http://dx.doi.org/10.1016/j.ssmph.2021.100767.http://dx.doi.org/10.1016/j.ssmph.2021.100767
    [5] Barnes LL, Wilson RS, Everson-Rose SA, Hayward MD, Evans DA, De Leon CFM. Effects of early-life adversity on cognitive decline in older African Americans and whites. Neurology 2012;79(24):2321 − 7. http://dx.doi.org/10.1212/WNL.0b013e318278b607CrossRef
    [6] Horvat P, Richards M, Malyutina S, Pajak A, Kubinova R, Tamosiunas A, et al. Life course socioeconomic position and mid-late life cognitive function in Eastern Europe. J Gerontol Ser B Psychol Sci Soc Sci 2014;69(3):470 − 81. http://dx.doi.org/10.1093/geronb/gbu014CrossRef
    [7] Shih RA, Lee J, Das L. Harmonization of cross-national studies of aging to the health and retirement study: cognition. Santa Monica, CA: RAND Corporation; 2012. http://dx.doi.org/10.7249/WR861.7.http://dx.doi.org/10.7249/WR861.7
    [8] Langa KM, Ryan LH, McCammon RJ, Jones RN, Manly JJ, Levine DA, et al. The health and retirement study harmonized cognitive assessment protocol project: study design and methods. Neuroepidemiology 2020;54(1):64 − 74. http://dx.doi.org/10.1159/000503004CrossRef
    [9] Juárez FWC, Soloaga I. Iop: estimating Ex-ante inequality of opportunity. Stata J 2014;14(4):830 − 46. http://dx.doi.org/10.1177/1536867X1401400408CrossRef
    [10] Oaxaca R. Male-female wage differentials in urban labor markets. Int Econom Rev 1973;14(3):693 − 709. http://dx.doi.org/10.2307/2525981CrossRef
    [11] Then FS, Luck T, Angermeyer MC, Riedel-Heller SG. Education as protector against dementia, but what exactly do we mean by education? Age Ageing 2016;45(4):523-8. http://dx.doi.org/10.1093/ageing/afw049.http://dx.doi.org/10.1093/ageing/afw049
    [12] Chen X, Yan BJ, Gill TM. Childhood circumstances and health inequality in old age: comparative evidence from China and the USA. Soc Indic Res 2022;160(2 − 3):689 − 716. http://dx.doi.org/10.1007/s11205-020-02436-2CrossRef
  • FIGURE 1.  Distributions of cognitive score for older adults — China, the United States, and the European Union, 2008–2018.

    Notes: The kernel density plots represent the distributions of assessed cognitive ability for older adults in China, the US, and the EU. This figure is plotted using raw cognitive assessment data without accounting for differences in education across the countries. The MMSE score was calculated based on common items in three dimensions in the CHARLS, HRS and SHARE surveys. Specifically, the cognitive ability score ranges from 0 to 29, and the larger the value, the better the cognitive ability. The three dimensions included functions of orientation to time and attention, episodic memory, and computational ability. There were 4 points for orientation function, i.e., correct answers to the year, month, day, and day of the week; 20 points for episodic memory, i.e., 10 points for immediate memory and 10 points for delayed memory; and 5 points for computational ability, i.e., subtracting 7 from 100 for five consecutive times, and the number of correct answers is the computational ability score.

    Abbreviation: MMSE=Mini-mental State Examination; CHARLS=China Health and Retirement Longitudinal Study; HRS=Health and Retirement Study; SHARE=the Survey of Health, Aging, and Retirement in Europe.

    TABLE 1.  Summary statistics for older adults — China, the US, and the EU, 2008–2018.

    VariablesCountryObsMeanS.D.MinMaxVariable description
    CognitionCN8,8198.96.8028Continuous: include orientation, episodic memory, and calculating ability; possible values 0–29
    US6,10616.54.5129
    EU18,54017.54.3029
    Standardized cognition scoreCN8,819−1.01.1−2.42.1Measured in Z-scores, using mean and standard deviation of cognition scores in all three HRS-family surveys combined
    US6,1060.20.7−2.22.2
    EU18,5400.40.7−2.42.2
    MaleCN8,8190.50.5//Dummy: males were assigned 1, females were assigned 0
    US6,1060.40.5//
    EU18,5400.40.5//
    AgeCN8,81969.37.160102Continuous: selected samples aged ≥60 years
    US6,10676.17.260100
    EU18,54072.67.560100
    Years of educationCN8,8194.54.0016Continuous: years of education the respondents received
    US6,47212.04.5017
    EU15,70911.24.2025
    War or famine experiencesCN8,8190.20.4//Dummy: experienced World War II, the Anti-Japanese War or famine in childhood assigned 1;
    0 otherwise
    US6,1060.00.1//
    EU18,5400.00.2//
    Family SES in childhood
    Father: no schoolCN8,8190.60.5//Dummy: fathers did not attend school were assigned 1; 0 otherwise
    US6,1060.00.2//
    EU18,5400.00.2//
    Father: below primary schoolCN8,8190.20.4//Dummy: fathers did not finish primary school were assigned 1; 0 otherwise
    US6,1060.10.2//
    EU18,5400.10.2//
    Father: primary schoolCN8,8190.10.3//Dummy: fathers finished primary school were assigned 1; 0 otherwise
    US6,1060.10.4//
    EU18,5400.40.5//
    Father: secondary schoolCN8,8190.10.2//Dummy: fathers finished secondary school were assigned 1; 0 otherwise
    US6,1060.60.5//
    EU18,5400.20.4//
    Father: university and aboveCN8,8190.00.1//Dummy: fathers attended university or above were assigned 1; 0 otherwise
    US6,1060.20.4//
    EU18,5400.30.5//
    Mother: no schoolCN8,8190.90.3//Dummy: mothers did not attend school were assigned 1; 0 otherwise
    US6,1060.00.2//
    EU18,5400.00.1//
    Mother: below primary schoolCN8,8190.00.2//Dummy: mothers did not finish primary school were assigned 1; 0 otherwise
    US6,1060.00.3//
    EU18,5400.10.3//
    Mother: primary schoolCN8,8190.00.1//Dummy: mothers finished primary school were assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.50.5//
    Mother: secondary schoolCN8,8190.00.1//Dummy: mothers finished secondary school were assigned 1; 0 otherwise
    US6,1060.70.5//
    EU18,5400.20.4//
    Mother: university and aboveCN8,8190.00.03//Dummy: mothers attended university or above were assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.20.4//
    Parental health
    Father: aliveCN8,8190.10.2//Dummy: fathers still alive assigned 1; 0 otherwise
    US6,1060.00.1//
    EU18,5400.00.1//
    Father: lower lifespan than averageCN8,8190.40.5//Dummy: fathers died at below-average lifespan assigned 1; 0 otherwise
    US6,1060.40.5//
    EU18,5400.50.5//
    Father: higher lifespan than averageCN8,8190.40.5//Dummy: fathers died at above-average lifespan assigned 1; 0 otherwise
    US6,1060.50.5//
    EU18,5400.40.5//
    Mother: aliveCN8,8190.10.4//Dummy: mothers still alive assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.10.3//
    Mother: lower lifespan than averageCN8,8190.40.5//Dummy: mothers died at below-average lifespan assigned 1; 0 otherwise
    US6,1060.40.5//
    EU18,5400.40.5//
    Mother: higher lifespan than averageCN8,8190.30.5//Dummy: mothers died at above-average lifespan assigned 1; 0 otherwise
    US6,1060.50.5//
    EU18,5400.40.5//
    Childhood healthCN8,8192.71.015Continuous: possible values 1–5, higher indicate poorer self-rated health in childhood
    US6,1061.70.915
    EU18,5402.31.115
    Child abuseCN8,8190.30.4//Dummy: beaten by parents during childhood were assigned 1; 0 otherwise
    US6,1060.10.2//
    EU18,5400.30.4//
    Note: This table presents summary statistics for cognitive assessments, demographic, and childhood circumstance variables. The 10th, 25th, 50th, 75th, 90th percentiles of cognitive score (for CN) are 0, 3, 8, 14, 18, respectively.
    Abbreviation: CN=China; US=the United States; EU=the European Union; SD=standard deviation; SES=socioeconomic status; HRS= Health and Retirement Study.
    Download: CSV

    TABLE 2.  Differences in cognitive score between countries explained by childhood circumstances.

    ItemCN and USCN and EU
    Overall gapExplained gapExplained proportion (%)95% confidence interval (%)Overall gapExplained gapExplained proportion (%)95% confidence interval (%)
    Difference (standardized score of cognitive score)1.20.8065.40(59.4, 71.4)1.40.5038.20(35.1, 41.2)
    War / famine experiences0.021.30(0.7, 1.9)0.021.60(1.3, 2.0)
    Parental health0.043.50(2.6, 4.4)0.010.60(0.2, 1.0)
     Father: alive−0.00−0.07(−0.4, 0.2)−0.00−0.20(−0.4, −0.01)
     Father: < average lifespan−0.00−0.20(−0.4, −0.09)−0.00−0.20(−0.3, −0.09)
     Mother: alive−0.01−1.10(−1.0, −0.6)−0.01−0.70(−0.9, −0.6)
     Mother: < average lifespan0.000.01(−0.04, 0.06)−0.00−0.07(−0.1, 0.007)
    Family SES0.7057.60(51.8, 63.4)0.5035.00(31.9, 38.0)
     Father: < primary school−0.30−3.80(−4.4, −3.1)−0.03−2.50(−3.1, −1.9)
     Father: primary school0.100.90(0.6, 1.2)0.053.70(2.8, 4.5)
     Father: secondary school1.4018.40(15.4, 21.5)0.053.70(3.2, 4.3)
     Father: college and above0.505.90(4.9, 6.9)0.108.20(7.2, 9.3)
     Mother: < primary school0.020.20(0.02, 0.4)0.000.20(−0.003, 0.3)
     Mother: primary school0.202.40(1.7, 3.1)0. 109.20(7.7, 10.7)
     Mother: secondary school2.0026.80(21.7, 31.8)0.096.60(5.8, 7.4)
     Mother: college and above0.506.80(5.6, 8.0)0.085.90(5.2, 6.5)
    Childhood health0.304.40(3.2, 5.6)0.011.00(0.8, 1.3)
    Child abuse−0.10−1.40(−2.1, −0.7)−0.00−0.04(−0.08, 0.0007)
    Notes: The reference group for parental health is “Father (Mother): Higher lifespan than average”, and the reference group for family SES in childhood is “Father (Mother): No school”.
    Abbreviation: CN=China, US=the United States; EU=the European Union; SES=Socioeconomic Status.
    Download: CSV

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Early-Life Circumstances and Cross-Country Disparities in Cognition Among Older Populations — China, the US, and the EU, 2008–2018

View author affiliations

Summary

What is already known about this topic?

Many health challenges have emerged due to rapid population aging, including declined cognitive ability among older adults.

What is added by this report?

Childhood circumstances have significant and lasting impacts on cognition in old age. This study compared cognition data from China with both the United States (U.S.) and the European Union (EU) during 2008–2018, finding that childhood circumstances could respectively explain 65.4% [95% confidence interval (CI): 59.4%, 71.4%] (China vs. the U.S.) and 38.2% (95% CI: 35.1%, 41.2%) (China vs. the EU) of the overall differences in cognition among older adults. Family socioeconomic status explained the largest share of differences among all considered childhood circumstances.

What are the implications for public health practice?

Large disparities in cognition should be addressed by mitigating childhood disadvantages.

  • 1. College of Economics and Management, Nanjing Agricultural University, Nanjing City, Jiangsu Province, China
  • 2. Department of Internal Medicine, Yale School of Medicine, New Haven, CT, US
  • 3. Department of Health Policy and Management, Yale School of Public Health, New Haven, CT, US
  • 4. Department of Economics, Yale University, New Haven, CT, US
  • 5. Yale Alzheimer’s Disease Research Center, Yale University, New Haven, CT, US
  • Corresponding author:

    Xi Chen, xi.chen@yale.edu

  • Funding: Supported by the National Natural Science Foundation of China (71974097); and a Career Development Award (K01AG053408), a major research grant (R01AG077529), the Claude D. Pepper Older Americans Independence Center at Yale School of Medicine (P30AG021342) funded by the National Institute on Aging, Jiangsu Qinglan Project, Jiangsu the Priority Academic Program Development of Jiangsu Higher Education Institute (PAPD)
  • Online Date: November 11 2022
    Issue Date: November 11 2022
    doi: 10.46234/ccdcw2022.205
  • With accelerated aging across the globe (1), it is critical to improving health in older populations (2), including aspects relating to cognitive ability (3). Growing scientific evidence found associations between childhood circumstances and cognition in old age (4-6). However, it has yet to be discovered to what extent childhood circumstances may explain cross-country disparities in cognition in older populations, especially between countries in different stages of development. This study applied the Oaxaca-Blinder decomposition to a validated measure of cognition in harmonized global aging surveys to explore the contributions of childhood circumstances to cross-country differences in cognition. Our results demonstrated a large share of cross-country differences in cognition among older adults being explained by childhood circumstances. Specifically, childhood disadvantages contributed 65.4% to the China-US difference in cognition, while childhood disadvantages contributed 38.2% to the China-EU difference in cognition. In both cases, family socioeconomic status explained the largest share of cross-country differences in cognition. The large gap in the cognition of older adults across these countries and their risk factors in childhood stress the urgency of mitigating childhood disadvantages to achieve more equitable, healthy aging.

    This study used three Health and Retirement Study (HRS)-family surveys: the China Health and Retirement Longitudinal Study (CHARLS); the U.S. HRS; and the Survey of Health, Aging, and Retirement in Europe (SHARE). In the past three decades, the U.S. National Institutes of Health and HRS-family survey teams in each country have collected and harmonized data for aging populations to offer an opportunity for cross-national comparisons (7-8). Our analysis was restricted to individuals aged 60 years and older, with no proxy respondents. We matched CHARLS Life History Survey 2014 (9,846 respondents) with CHARLS core survey 2018 (11,096 respondents); HRS Life History Mail Survey 2015/2017 (8,579 respondents) with HRS core survey 2016 (7,744 respondents); and SHARELIFE 2008/2017 (30,706 respondents) with SHARE core survey 2017 (27,173 respondents). For the three HRS-family surveys, the earliest and latest years in which cognition data were collected for this analysis were 2008 and 2018, respectively. To make the cognitive assessments most comparable across China, the U.S., and the EU, we measured cognitive ability using the validated Mini-Mental State Examination (MMSE). Our cognitive score included the typical dimensions and items across the three HRS-family surveys, ranging from 0 to 29. The larger the value, the better the cognitive ability. Considering salient differences in the distribution of cognitive scores between China and the U.S. and between China and the EU, standardized cognitive scores were measured. Z-scores were determined to facilitate cross-country comparisons, using the combined mean and standard deviation of cognition scores in all three HRS-family surveys. We used the Oaxaca-Blinder decomposition to estimate the extent to which various childhood circumstances were explained in the cognitive abilities of older adults across countries (9). Originally proposed in 1973, the Oaxaca-Blinder decomposition offered a regression-based approach to attributing cross-country differences in cognition of older adults to differences in childhood circumstances (composition effect) versus differences in the effects of these circumstances (association effect) (10). A package iop in STATA (version16.0, Stata Corp, College Station, U.S.) was used to perform the analyses (9).

    We measured cognitive abilities among older populations in China, the U.S., and the EU, all of which exhibited rapid aging processes, though at different stages of development. While the cognitive scores of older adults in the U.S. and EU are relatively similar in level and distribution, Figure 1 displays the large differences with their Chinese counterparts who tended to have lower cognitive scores. As shown in Table 1, Chinese older adults in the sample also tended to receive lower education (on average 4.5 years, versus 12.0 years in the U.S. and 11.2 years in the EU). Education has been recognized as a profound, protective factor of cognitive ability (11).

    Figure 1. 

    Distributions of cognitive score for older adults — China, the United States, and the European Union, 2008–2018.

    Notes: The kernel density plots represent the distributions of assessed cognitive ability for older adults in China, the US, and the EU. This figure is plotted using raw cognitive assessment data without accounting for differences in education across the countries. The MMSE score was calculated based on common items in three dimensions in the CHARLS, HRS and SHARE surveys. Specifically, the cognitive ability score ranges from 0 to 29, and the larger the value, the better the cognitive ability. The three dimensions included functions of orientation to time and attention, episodic memory, and computational ability. There were 4 points for orientation function, i.e., correct answers to the year, month, day, and day of the week; 20 points for episodic memory, i.e., 10 points for immediate memory and 10 points for delayed memory; and 5 points for computational ability, i.e., subtracting 7 from 100 for five consecutive times, and the number of correct answers is the computational ability score.

    Abbreviation: MMSE=Mini-mental State Examination; CHARLS=China Health and Retirement Longitudinal Study; HRS=Health and Retirement Study; SHARE=the Survey of Health, Aging, and Retirement in Europe.

    VariablesCountryObsMeanS.D.MinMaxVariable description
    CognitionCN8,8198.96.8028Continuous: include orientation, episodic memory, and calculating ability; possible values 0–29
    US6,10616.54.5129
    EU18,54017.54.3029
    Standardized cognition scoreCN8,819−1.01.1−2.42.1Measured in Z-scores, using mean and standard deviation of cognition scores in all three HRS-family surveys combined
    US6,1060.20.7−2.22.2
    EU18,5400.40.7−2.42.2
    MaleCN8,8190.50.5//Dummy: males were assigned 1, females were assigned 0
    US6,1060.40.5//
    EU18,5400.40.5//
    AgeCN8,81969.37.160102Continuous: selected samples aged ≥60 years
    US6,10676.17.260100
    EU18,54072.67.560100
    Years of educationCN8,8194.54.0016Continuous: years of education the respondents received
    US6,47212.04.5017
    EU15,70911.24.2025
    War or famine experiencesCN8,8190.20.4//Dummy: experienced World War II, the Anti-Japanese War or famine in childhood assigned 1;
    0 otherwise
    US6,1060.00.1//
    EU18,5400.00.2//
    Family SES in childhood
    Father: no schoolCN8,8190.60.5//Dummy: fathers did not attend school were assigned 1; 0 otherwise
    US6,1060.00.2//
    EU18,5400.00.2//
    Father: below primary schoolCN8,8190.20.4//Dummy: fathers did not finish primary school were assigned 1; 0 otherwise
    US6,1060.10.2//
    EU18,5400.10.2//
    Father: primary schoolCN8,8190.10.3//Dummy: fathers finished primary school were assigned 1; 0 otherwise
    US6,1060.10.4//
    EU18,5400.40.5//
    Father: secondary schoolCN8,8190.10.2//Dummy: fathers finished secondary school were assigned 1; 0 otherwise
    US6,1060.60.5//
    EU18,5400.20.4//
    Father: university and aboveCN8,8190.00.1//Dummy: fathers attended university or above were assigned 1; 0 otherwise
    US6,1060.20.4//
    EU18,5400.30.5//
    Mother: no schoolCN8,8190.90.3//Dummy: mothers did not attend school were assigned 1; 0 otherwise
    US6,1060.00.2//
    EU18,5400.00.1//
    Mother: below primary schoolCN8,8190.00.2//Dummy: mothers did not finish primary school were assigned 1; 0 otherwise
    US6,1060.00.3//
    EU18,5400.10.3//
    Mother: primary schoolCN8,8190.00.1//Dummy: mothers finished primary school were assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.50.5//
    Mother: secondary schoolCN8,8190.00.1//Dummy: mothers finished secondary school were assigned 1; 0 otherwise
    US6,1060.70.5//
    EU18,5400.20.4//
    Mother: university and aboveCN8,8190.00.03//Dummy: mothers attended university or above were assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.20.4//
    Parental health
    Father: aliveCN8,8190.10.2//Dummy: fathers still alive assigned 1; 0 otherwise
    US6,1060.00.1//
    EU18,5400.00.1//
    Father: lower lifespan than averageCN8,8190.40.5//Dummy: fathers died at below-average lifespan assigned 1; 0 otherwise
    US6,1060.40.5//
    EU18,5400.50.5//
    Father: higher lifespan than averageCN8,8190.40.5//Dummy: fathers died at above-average lifespan assigned 1; 0 otherwise
    US6,1060.50.5//
    EU18,5400.40.5//
    Mother: aliveCN8,8190.10.4//Dummy: mothers still alive assigned 1; 0 otherwise
    US6,1060.10.3//
    EU18,5400.10.3//
    Mother: lower lifespan than averageCN8,8190.40.5//Dummy: mothers died at below-average lifespan assigned 1; 0 otherwise
    US6,1060.40.5//
    EU18,5400.40.5//
    Mother: higher lifespan than averageCN8,8190.30.5//Dummy: mothers died at above-average lifespan assigned 1; 0 otherwise
    US6,1060.50.5//
    EU18,5400.40.5//
    Childhood healthCN8,8192.71.015Continuous: possible values 1–5, higher indicate poorer self-rated health in childhood
    US6,1061.70.915
    EU18,5402.31.115
    Child abuseCN8,8190.30.4//Dummy: beaten by parents during childhood were assigned 1; 0 otherwise
    US6,1060.10.2//
    EU18,5400.30.4//
    Note: This table presents summary statistics for cognitive assessments, demographic, and childhood circumstance variables. The 10th, 25th, 50th, 75th, 90th percentiles of cognitive score (for CN) are 0, 3, 8, 14, 18, respectively.
    Abbreviation: CN=China; US=the United States; EU=the European Union; SD=standard deviation; SES=socioeconomic status; HRS= Health and Retirement Study.

    Table 1.  Summary statistics for older adults — China, the US, and the EU, 2008–2018.

    In addition to the gaps in educational attainment, a key predictor of cognitive disparities for older populations, other economic and social development aspects may also widen the cross-country cognitive disparities. To better understand these economic and social conditions at an individual level, we considered the role of various childhood circumstances of our study subjects before completing their education. Table 1 shows the summary statistics, a significantly higher proportion of Chinese older adults experienced war or famine compared to those in the U.S. and the EU. Five levels of schooling were created across China, the U.S., and the EU to indicate parental educational attainment to harmonize parental educational data for comparison. There were significant cross-country differences in parental education. Specifically, for older Chinese adults above age 60, about 60% of their fathers and 90% of their mothers received no formal education. By contrast, only 3% of fathers and 3% of mothers of older U.S. adults received no formal education. Similar differences existed when comparing other childhood circumstances, including parental and individual health. Chinese and European older adults experienced more abuse in childhood than their U.S. counterparts. Childhood circumstance variables in Table 1 were defined according to the literature (12).

    Using the three HRS-family surveys and the Oaxaca-Blinder decomposition based on the standardized cognitive scores (Z-scores), Table 2 further illustrates the differences in cognition of the elderly and the contribution of childhood circumstances: 1) Chinese older persons had significantly lower assessed cognition (8.9 out of a total score of 29) than their U.S. and EU counterparts, respectively, at 16.5 and 17.5 (Table 1); 2) comparing China to the U.S. and the EU, overall childhood circumstances respectively explained 65.4% [95% confidence interval (CI): 59.4%, 71.4%] and 38.2% (95% CI: 35.1%, 41.2%) of the China-US and China-EU disparities in cognitive ability; 3) various childhood circumstances significantly contributed to cross-country differences in the cognitive ability of older adults. Of the childhood circumstances considered, family socioeconomic status, measured by parental educational attainment, contributed the largest — 57.6% (95% CI: 51.8%, 63.4%) to the China-US difference and 34.9% (95% CI: 31.9%, 38.0%) to the China-EU difference in cognitive ability. Of the other factors, individual health, parental health, and war or famine experiences respectively explained 4.4% (95% CI: 3.2%, 5.6%), 3.5% (95% CI: 2.6%, 4.4%), and 1.3% (95% CI: 0.7%, 1.9%) of the China-US difference, while war or famine experiences, individual health, and parental health explained 1.6% (95% CI: 1.3%, 2.0%), 1.0% (95% CI: 0.8%, 1.3%), and 0.6% (95% CI: 0.2%, 1.0%) of the China-EU difference.

    ItemCN and USCN and EU
    Overall gapExplained gapExplained proportion (%)95% confidence interval (%)Overall gapExplained gapExplained proportion (%)95% confidence interval (%)
    Difference (standardized score of cognitive score)1.20.8065.40(59.4, 71.4)1.40.5038.20(35.1, 41.2)
    War / famine experiences0.021.30(0.7, 1.9)0.021.60(1.3, 2.0)
    Parental health0.043.50(2.6, 4.4)0.010.60(0.2, 1.0)
     Father: alive−0.00−0.07(−0.4, 0.2)−0.00−0.20(−0.4, −0.01)
     Father: < average lifespan−0.00−0.20(−0.4, −0.09)−0.00−0.20(−0.3, −0.09)
     Mother: alive−0.01−1.10(−1.0, −0.6)−0.01−0.70(−0.9, −0.6)
     Mother: < average lifespan0.000.01(−0.04, 0.06)−0.00−0.07(−0.1, 0.007)
    Family SES0.7057.60(51.8, 63.4)0.5035.00(31.9, 38.0)
     Father: < primary school−0.30−3.80(−4.4, −3.1)−0.03−2.50(−3.1, −1.9)
     Father: primary school0.100.90(0.6, 1.2)0.053.70(2.8, 4.5)
     Father: secondary school1.4018.40(15.4, 21.5)0.053.70(3.2, 4.3)
     Father: college and above0.505.90(4.9, 6.9)0.108.20(7.2, 9.3)
     Mother: < primary school0.020.20(0.02, 0.4)0.000.20(−0.003, 0.3)
     Mother: primary school0.202.40(1.7, 3.1)0. 109.20(7.7, 10.7)
     Mother: secondary school2.0026.80(21.7, 31.8)0.096.60(5.8, 7.4)
     Mother: college and above0.506.80(5.6, 8.0)0.085.90(5.2, 6.5)
    Childhood health0.304.40(3.2, 5.6)0.011.00(0.8, 1.3)
    Child abuse−0.10−1.40(−2.1, −0.7)−0.00−0.04(−0.08, 0.0007)
    Notes: The reference group for parental health is “Father (Mother): Higher lifespan than average”, and the reference group for family SES in childhood is “Father (Mother): No school”.
    Abbreviation: CN=China, US=the United States; EU=the European Union; SES=Socioeconomic Status.

    Table 2.  Differences in cognitive score between countries explained by childhood circumstances.

    • Using harmonized data from HRS-family surveys conducted in China (CHARLS), the U.S. (HRS), and the European Union (SHARE), this study examined cross-country disparities in the cognitive ability of older adults, with a focus on the influences of childhood circumstances. The three countries were chosen due to their high levels of population aging but different stages of socioeconomic development, which provided a clear basis for comparisons. We found that childhood circumstances explained large shares of differences in the cognitive ability of older persons across countries. Further decomposing these cross-country disparities, we specifically showed that the contributions of childhood circumstances amounted to 65.4% of the China-US and 38.2% of the China-EU differences in cognitive ability in older age, respectively.

      Among all domains considered, we identified that family socioeconomic status was the most significant contributor to these differences. Striving for parental educational equity may compensate for cognitive disparities resulting from other childhood disadvantages. Although modest, parental health status during childhood also contributed to disparities in cognitive ability. Relative to mothers’ lifespan, fathers’ lifespan was much more statistically significant but only slightly larger in terms of the size of cross-country differences. In addition to indicating inherited health endowments from parents, men’s health explained slightly more as they often constituted the primary labor force and were expected to bring in substantial resources for their families. Therefore, long-term cognitive ability may be influenced more by the health status of their fathers. Other childhood circumstances, including war or famine experiences and individual health, also had statistically significant but modest contributions.

      Overall, our main finding of childhood circumstances contributing substantially to the cross-country disparities in the cognitive ability of older populations highlights the value of taking a life-course perspective to study health inequalities. In the meantime, the economic theory of equality of opportunity calls for public policies to offer more equitable childhood circumstances and compensate for those who had adverse childhood circumstances to improve cognitive health in older age. These policies can potentially narrow the differences between developing and developed countries that promote global health equity.

      This study had some limitations. First, while we used a comprehensive and harmonized MMSE for cross-country comparisons, the lack of clinical diagnosis data prevented us from directly assessing the link between childhood circumstances and cognitive impairment using validated clinical criteria. Second, the self-reported childhood circumstances data can be subject to recall error. Third, considering the nature of cross-country comparisons, we included early life circumstance indicators that are more consistent across the three surveys, which indicate a lower bound, and therefore a conservative estimate.

    • No conflicts of interest.

    • The teams of CHARLS, HRS, and SHARE.

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