Measurement and Structure of Cognition in the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia

Development and assessment of analytic methods to improve the measurement of cognition in longitudinal studies of aging through the use of substudies with comprehensive neuropsychological testing

INTRODUCTION

The Health and Retirement Study International Partner Surveys (HRS IPS) have rich longitudinal data, but the brevity of cognitive batteries is a limitation.

METHODS

We used data from a substudy of the English Longitudinal Study of Ageing (ELSA) administering detailed cognitive assessments with the Harmonized Cognitive Assessment Protocol (ELSA-HCAP) (N = 1273) to inform approaches for estimating cognition in ELSA (N = 11,213). We compared two novel approaches: confirmatory factor analysis (CFA)- and regression-based prediction.

RESULTS

Compared to estimates from the full HCAP battery, estimated cognitive functioning derived using regression models or CFA had high correlations (regression: r = 0.85 [95% confidence interval [CI]: 0.83 to 0.87]; CFA: r = 0.83 [95% CI: 0.81 to 0.85]) and reasonable mean squared error (regression: 0.25 [0.22 to 0.27]; CFA: 0.29 [0.26 to 0.32]) in held-out data. The use of additional items from waves 7 to 9 improved performance.

DISCUSSION

Both approaches are recommended for future research; the similarity in approaches may be due to the brevity of available cognitive assessments in ELSA.

HIGHLIGHTS

Estimates of cognitive functioning informed by English Longitudinal Study of Ageing-Harmonized Cognitive Assessment Protocol (ELSA-HCAP) data had an adequate performance. Standard errors were smaller for associations with example risks when using measures informed by ELSA-HCAP. Performance was better when including additional cognitive measures available in waves 7 to 9. Conceptual advantages to the confirmatory factor analysis (CFA) approach were not important in practice due to the brevity of the ELSA cognitive battery.

Effect of apolipoprotein E ε4 and its modification by sociodemographic characteristics on cognitive measures in South Asians from LASI-DAD

BACKGROUND

We investigated the effects of apolipoprotein E (APOE) ε4 and its interactions with sociodemographic characteristics on cognitive measures in South Asians from the Diagnostic Assessment of Dementia for the Longitudinal Aging Study of India (LASI-DAD).

METHODS

Linear regression was used to assess the association between APOE ε4 and global- and domain-specific cognitive function in 2563 participants (mean age 69.6 ± 7.3 years; 53% female). Effect modification by age, sex, and education were explored using interaction terms and subgroup analyses.

RESULTS

APOE ε4 was inversely associated with most cognitive measures (p < 0.05). This association was stronger with advancing age for the Hindi Mental State Examination (HMSE) score (βε4×age = -0.44, p = 0.03), orientation (βε4×age = -0.07, p = 0.01), and language/fluency (βε4×age = -0.07, p = 0.01), as well as in females for memory (βε4×male = 0.17, p = 0.02) and language/fluency (βε4×male = 0.12, p = 0.03).

DISCUSSION

APOE ε4 is associated with lower cognitive function in South Asians from India, with a more pronounced impact observed in females and older individuals.

HIGHLIGHTS

APOE ε4 carriers had lower global and domain-specific cognitive performance. Females and older individuals may be more susceptible to ε4 effects. For most cognitive measures, there was no interaction between ε4 and education.

Mental Health Impacts of COVID-19: Does Prepandemic Cognition and Dementia Status Matter?

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic disrupted daily life and led to sharp shocks in trends for various health outcomes. Although substantial evidence exists linking the pandemic and mental health outcomes and linking dementia and mental health outcomes, little evidence exists on how cognitive status may alter the impact of COVID-19 on mental health.

METHODS

We used prepandemic data from the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia study and 9 waves of data from the Real-Time Insights of COVID-19 in India study (N = 1 182). We estimated associations between measures of prepandemic cognition (continuous cognition based on 22 cognitive tests, dementia status) and mental health measures during the pandemic (Patient Health Questionnaire [PHQ]-4 [9 time points], PHQ-9 [2 time points], Beck Anxiety Inventory [3 time points]), adjusting for age, gender, rural/urban residence, state, education, and prepandemic mental health.

RESULTS

Summarizing across time points, PHQ-9 score was marginally or significantly associated with prepandemic cognition (PHQ-9 difference: -0.38 [-0.78 to 0.14] points per SD higher cognition; p = .06), and prepandemic dementia (PHQ-9 difference: 0.61 [0.11-1.13] points for those with dementia compared to no dementia; p = .02). Associations with BAI were null, whereas associations with PHQ-4 varied over time (p value for interaction = .02) and were strongest during the delta wave, when pandemic burden was highest.

CONCLUSIONS

We present initial evidence that mental health impacts of COVID-19 or other acute stressors may be unequally distributed across strata of cognitive outcomes. In dynamically changing environments, those with cognitive impairment or dementia may be more vulnerable to adverse mental health outcomes.

Performance of the Informant Questionnaire on Cognitive Decline for the Elderly (IQCODE) in a nationally representative study in India: the LASI-DAD study

BACKGROUND

Low and middle-income countries like India anticipate rapid population aging and increases in dementia burden. In India, dementia screening scales originally developed in other contexts need to be assessed for feasibility and validity, given the number of different languages and varying levels of literacy and education.

METHOD

Using data from the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (N = 4,028), we characterize the performance of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). We described patterns and correlates of missingness, evaluated the psychometric properties of the scale, and assessed criterion validity against the Hindi Mental State Examination (HMSE) using linear regression.

RESULTS

Several IQCODE items had high levels of missingness, which was associated with urbanicity, respondent's gender, and informant's generation (same vs. younger generation). Full IQCODE scores showed strong criterion validity against the HMSE; each 1-point increase in IQCODE score was associated with a 3.03-point lower score on the HMSE, controlling for age, gender, and urbanicity. The statistically significant association between IQCODE and HMSE was stronger in urban than rural settings (p-value for interaction = 0.04). Associations between IQCODE and HMSE remained unchanged after removing the three items with the highest levels of differential missingness (remembering addresses and telephone numbers, ability to work with familiar machines, ability to learn to use new gadget or machine).

CONCLUSION

Findings raise questions about the value of including items with high proportions of missingness, which may signal cultural irrelevance, while removing them did not affect criterion validity.

Anemia, hemoglobin concentration and cognitive function in the Longitudinal Ageing Study in India-Harmonized Diagnostic Assessment of Dementia (LASI-DAD) and the Health and Retirement Study

Background

In India, anemia is widely researched in children and women of reproductive age, however, studies in older populations are lacking. Given the adverse effect of anemia on cognitive function and dementia this older population group warrants further study. The Longitudinal Ageing Study in India - Harmonized Diagnostic Assessment of Dementia (LASI-DAD) dataset contains detailed measures to allow a better understanding of anaemia as a potential risk factor for dementia.

Method

2,758 respondents from the LASI-DAD cohort, aged 60 or older, had a complete blood count measured from venous blood as well as cognitive function tests including episodic memory, executive function and verbal fluency. Linear regression was used to test the associations between blood measures (including anemia and hemoglobin concentration (g/dL)) with 11 cognitive domains. All models were adjusted for age and gender with the full model containing adjustments for rural location, years of education, smoking, region, BMI and population weights.Results from LASI-DAD were validated using the USA-based Health and Retirement Study (HRS) cohort (n=5720) to replicate associations between blood cell measures and global cognition.

Results

In LASI-DAD, we showed an association between anemia and poor memory (p=0.0054). We found a positive association between hemoglobin concentration and ten cognitive domains tested (β=0.041-0.071, p<0.05). The strongest association with hemoglobin was identified for memory-based tests (immediate episodic, delayed episodic and broad domain memory, β=0.061-0.071, p<0.005). Positive associations were also shown between the general cognitive score and the other red blood count tests including mean corpuscular hemoglobin concentration (MCHC, β=0.06, p=0.0001) and red cell distribution width (RDW, β =-0.11, p<0.0001). In the HRS cohort, positive associations were replicated between general cognitive score and other blood count tests (Red Blood Cell, MCHC and RDW, p<0.05).

Conclusion

We have established in a large South Asian population that low hemoglobin and anaemia are associated with low cognitive function, therefore indicating that anaemia could be an important modifiable risk factor. We have validated this result in an external cohort demonstrating both the variability of this risk factor cross-nationally and its generalizable association with cognitive outcomes.

Memory and language cognitive data harmonization across the United States and Mexico

INTRODUCTION

We used cultural neuropsychology-informed procedures to derive and validate harmonized scores representing memory and language across population-based studies in the United States and Mexico.

METHODS

Data were from the Health and Retirement Study Harmonized Cognitive Assessment Protocol (HRS-HCAP) and the Mexican Health and Aging Study (MHAS) Ancillary Study on Cognitive Aging (Mex-Cog). We statistically co-calibrated memory and language domains and performed differential item functioning (DIF) analysis using a cultural neuropsychological approach. We examined relationships among harmonized scores, age, and education.

RESULTS

We included 3170 participants from the HRS-HCAP (Mage = 76.6 [standard deviation (SD): 7.5], 60% female) and 2042 participants from the Mex-Cog (Mage = 68.1 [SD: 9.0], 59% female). Five of seven memory items and one of twelve language items demonstrated DIF by study. Harmonized memory and language scores showed expected associations with age and education.

DISCUSSION

A cultural neuropsychological approach to harmonization facilitates the generation of harmonized measures of memory and language function in cross-national studies.

HIGHLIGHTS

We harmonized memory and language scores across studies in the United States and Mexico.A cultural neuropsychological approach to data harmonization was used.Harmonized scores showed minimal measurement differences between cohorts.Future work can use these harmonized scores for cross-national studies of Alzheimer's disease and related dementias.

Harmonization of Later-Life Cognitive Function Across National Contexts: Results from the Harmonized Cognitive Assessment Protocols (HCAPs)

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 harmonize general and domain-specific cognitive scores from HCAPs across six countries, and evaluate precision and criterion validity of the resulting harmonized scores.

Methods

We statistically harmonized general and domain-specific cognitive function across the six publicly available HCAP partner studies in the United States, England, India, Mexico, China, and South Africa (N=21,141). We used an item banking approach that leveraged common cognitive test items across studies and tests that were unique to studies, as identified by a multidisciplinary expert panel. We generated harmonized factor scores for general and domain- specific cognitive function using serially estimated graded-response item response theory (IRT) models. We evaluated precision of the factor scores using test information plots and criterion validity using age, gender, and educational attainment.

Findings

IRT models of cognitive function in each country fit well. We compared measurement reliability of the harmonized general cognitive function factor across each cohort using test information plots; marginal reliability was high (r> 0·90) for 93% of respondents across six countries. In each country, general cognitive function scores were lower with older ages and higher with greater levels of educational attainment.

Interpretation

We statistically harmonized cognitive function measures across six large, population-based studies of cognitive aging in the US, England, India, Mexico, China, and South Africa. Precision of the estimated scores was excellent. This work provides a foundation for international networks of researchers to make stronger inferences and direct comparisons of cross-national associations of risk factors for cognitive outcomes.

Funding

National Institute on Aging (R01 AG070953, R01 AG030153, R01 AG051125, U01 AG058499; U24 AG065182; R01AG051158).

Polygenic Risk Scores for Alzheimer's Disease and General Cognitive Function Are Associated With Measures of Cognition in Older South Asians

Genome-wide association studies (GWAS) conducted in European ancestry (EA) have identified hundreds of single-nucleotide polymorphisms (SNPs) associated with general cognitive function and/or Alzheimer's disease (AD). The association between these SNPs and cognitive function has not been fully evaluated in populations with complex genetic substructure such as South Asians. This study investigated whether SNPs identified in EA GWAS, either individually or as polygenic risk scores (PRSs), were associated with general cognitive function and 5 broad cognitive domains in 932 South Asians from the Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (LASI-DAD). We found that SNPs identified from AD GWAS were more strongly associated with cognitive function in LASI-DAD than those from a GWAS of general cognitive function. PRSs for general cognitive function and AD explained up to 1.1% of the variability in LASI-DAD cognitive domain scores. Our study represents an important stepping stone toward better characterization of the genetic architecture of cognitive aging in the Indian/South Asian population and highlights the need for further research that may lead to the identification of new variants unique to this population.

A cultural neuropsychological approach to harmonization of cognitive data across culturally and linguistically diverse older adult populations

OBJECTIVE

To describe a cultural neuropsychological approach to prestatistical harmonization of cognitive data across the United States (U.S.) and Mexico with the Harmonized Cognitive Assessment Protocol (HCAP).

METHOD

We performed a comprehensive review of the administration, scoring, and coding procedures for each cognitive test item administered across the English and Spanish versions of the HCAP in the Health and Retirement Study (HRS) in the U.S. and the Ancillary Study on Cognitive Aging in Mexico (Mex-Cog). For items that were potentially equivalent across studies, we compared each cognitive test item for linguistic and cultural equivalence and classified items as confident or tentative linking items, based on the degree of confidence in their comparability across cohorts and language groups. We evaluated these classifications using differential item functioning techniques.

RESULTS

We evaluated 132 test items among 21 cognitive instruments in the HCAP across the HRS and Mex-Cog. We identified 72 confident linking items, 46 tentative linking items, and 14 items that were not comparable across cohorts. Measurement invariance analysis revealed that 64% of the confident linking items and 83% of the tentative linking items showed statistical evidence of measurement differences across cohorts.

CONCLUSIONS

Prestatistical harmonization of cognitive data, performed by a multidisciplinary and multilingual team including cultural neuropsychologists, can identify differences in cognitive construct measurement across languages and cultures that may not be identified by statistical procedures alone. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Identifying Cognitive Impairment Among Older Participants in a Nationally Representative Internet Panel

OBJECTIVES

The Health and Retirement Study Telephone Interview for Cognitive Status (HRS TICS) score and its associated Langa-Weir cutoffs are widely used as indicators of cognitive status for research purposes in population-based studies. The classification is based on in-person and phone interviews of older individuals. Our purpose was to develop a corresponding classification for web-based self-administered assessments.

METHODS

Participants were 925 members of a nationally representative internet panel, all aged 50 and older. We conducted (a) a phone interview comprised of cognitive items used to construct the HRS TICS score, and (b) a web counterpart with self-administered cognitive items, while also considering (c) other already administered web-based cognitive tests and instrumental activities of daily living survey questions, all from the same respondents.

RESULTS

The web-administered HRS TICS items have only modest correlations with the same phone items, although neither mode showed universally higher scores than the other. Using latent variable modeling, we created a probability of cognitive impairment score for the web-based battery that achieved good correspondence to the phone Langa-Weir classification.

DISCUSSION

The results permit analyses of predictors, correlates, and consequences of cognitive impairment in web surveys where relevant cognitive test and functional abilities items are available. We discuss challenges and caveats that may affect the findings.

Deep phenotyping and genomic data from a nationally representative study on dementia in India

The Harmonized Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (LASI-DAD) is a nationally representative in-depth study of cognitive aging and dementia. We present a publicly available dataset of harmonized cognitive measures of 4,096 adults 60 years of age and older in India, collected across 18 states and union territories. Blood samples were obtained to carry out whole blood and serum-based assays. Results are included in a venous blood specimen datafile that can be linked to the Harmonized LASI-DAD dataset. A global screening array of 960 LASI-DAD respondents is also publicly available for download, in addition to neuroimaging data on 137 LASI-DAD participants. Altogether, these datasets provide comprehensive information on older adults in India that allow researchers to further understand risk factors associated with cognitive impairment and dementia.

Neuropsychological Assessment of Older Adults in Nepal for Population-Based Dementia Ascertainment: Needs, Challenges, and Opportunities

The population of Nepal is rapidly aging, as in other low and middle-income countries, and the number of individuals living with Alzheimer's Disease and related dementias (ADRD) is expected to increase. However, information about the neuropsychological assessment of ADRD in Nepal is lacking. We first aimed to examine the needs, challenges, and opportunities associated with the neuropsychological assessment of older adults in Nepal for population-based ADRD ascertainment. Second, we introduce the Chitwan Valley Family Study-Study of Cognition and Aging in Nepal (CVFS-SCAN), which is poised to address these needs, and its collaboration with the Harmonized Cognitive Assessment Protocol (HCAP) international network. We reviewed the existing literature on the prevalence, risk factors, available neuropsychological assessment instruments, and sociocultural factors that may influence the neuropsychological assessment of older adults for ADRD ascertainment in Nepal. Our review revealed no existing population-based data on the prevalence of ADRD in Nepal. Very few studies have utilized formal cognitive assessment instruments for ADRD assessment, and there have been no comprehensive neuropsychological assessment instruments that have been validated for the assessment of ADRD in Nepal. We describe how the CVFS-SCAN study will address this need through careful adaptation of the HCAP instrument. We conclude that the development of culturally appropriate neuropsychological assessment instruments is urgently needed for the population-based assessment of ADRD in Nepal. The CVFS-SCAN is designed to address this need and will contribute to the growth of global and equitable neuropsychology and to the science of ADRD in low- and middle-income countries.

Linear linking for related traits (LLRT): A novel method for the harmonization of cognitive domains with no or few common items

Harmonization means to make data comparable. Recent efforts to generate comparable data on cognitive performance of older adults from many different countries around the world have presented challenges for direct comparison. Neuropsychological instruments vary in many respects, including language, administration techniques and cultural differences, which all present important obstacles to assumptions regarding the presence of linking items. Item response theory (IRT) methods have been previously used to harmonize cross-national data on cognition, but these methods rely on linking items to establish the shared metric. We introduce an alternative approach for linking cognitive performance across two (or more) groups when the fielded assessments contain no items that can be reasonably considered linking items: Linear Linking for Related Traits (LLRT). We demonstrate this methodological approach in a sample from a single United States study split by educational attainment, and in two sets of cross-national comparisons (United States to England, and United States to India). All data were collected as part of the Harmonized Cognitive Assessment Protocol (HCAP) and are publicly available. Our method relies upon strong assumptions, and we offer suggestions for how the method can be extended to relax those assumptions in future work.

How much of the female disadvantage in late-life cognition in India can be explained by education and gender inequality

In social environments characterized by high levels of gender inequality, women fare worse than men in human capital accumulation and health. We examine the association of gender inequality with female disadvantage in late-life cognitive function, using newly available data from Wave 1 (2017-2019) of the Longitudinal Aging Study in India (LASI), representative of the Indian population over the age of 45. We find a substantial female gap in cognition among mid-aged and older adults in India; early life socioeconomic conditions and education explain up to 74 percent of the female disadvantage in cognition, and model predictions suggest that it takes nine years of education on average to overcome this deficit. However, further contextualizing the environment, we find that the level of education at which differences in late-life cognition between women and men become negligible increases with the degree of gender inequality.

Cross-national harmonization of cognitive measures across HRS HCAP (USA) and LASI-DAD (India)

BACKGROUND

As global populations age, cross-national comparisons of cognitive health and dementia risk are increasingly valuable. It remains unclear, however, whether country-level differences in cognitive function are attributable to population differences or bias due to incommensurate measurement. To demonstrate an effective method for cross-national comparison studies, we aimed to statistically harmonize measures of episodic memory and language function across two population-based cohorts of older adults in the United States (HRS HCAP) and India (LASI-DAD).

METHODS

Data for 3,496 HRS HCAP (≥65 years) and 3,152 LASI-DAD (≥60 years) participants were statistically harmonized for episodic memory and language performance using confirmatory factor analysis (CFA) methods. Episodic memory and language factor variables were investigated for differential item functioning (DIF) and precision.

RESULTS

CFA models estimating episodic memory and language domains based on a priori adjudication of comparable items fit the data well. DIF analyses revealed that four out of ten episodic memory items and five out of twelve language items measured the underlying construct comparably across samples. DIF-modified episodic memory and language factor scores showed comparable patterns of precision across the range of the latent trait for each sample.

CONCLUSIONS

Harmonization of cognitive measures will facilitate future investigation of cross-national differences in cognitive performance and differential effects of risk factors, policies, and treatments, reducing study-level measurement and administrative influences. As international aging studies become more widely available, advanced statistical methods such as those described in this study will become increasingly central to making universal generalizations and drawing valid conclusions about cognitive aging of the global population.

Sex Differences in Cognitive Health Among Older Adults in India

OBJECTIVES

To document sex differences in late-life cognitive function and identify their early-life determinants among older Indian adults.

DESIGN

Harmonized Diagnostic Assessment of Dementia for Longitudinal Aging Study in India (LASI-DAD).

SETTING

Individual cognitive testing in hospital or household setting across 14 states of India.

PARTICIPANTS

Individuals aged 60 years and older from LASI-DAD (2017-2019) (N = 2,704; 53.5% female).

MEASUREMENTS

Given the low levels of literacy and numeracy among older Indian adults, we consider two composite cognitive scores as outcome variables. Score I is based on tests that do not require literacy or numeracy, whereas score II is based on tests that require such skills. Ordinary least squares is used to estimate models featuring a progressively increasing number of covariates. We add to the baseline specification, including a sex dummy, age, and state indicators, measures of early-life socioeconomic status (SES), early-life nutrition, as proxied by knee height, and education.

RESULTS

Across most cognitive domains, women perform significantly worse than for men: -0.4 standard deviations (SD) for score I and -0.8 SD for score II. Early-life SES, health, and education explain 90% of the gap for score I and 55% for score II. Results are similar across hospital-based and home testing.

CONCLUSION

In India, lower levels of early-life human capital investments in nutrition and education among women compared with men are associated with a female disadvantage in late-life cognitive health. This has important implications for public health policy, aiming at reducing the risk of cognitive decline and dementia-a nascent concern in India. J Am Geriatr Soc 68:S20-S28, 2020.

Cognitive Function and Cardiometabolic-Inflammatory Risk Factors Among Older Indians and Americans

OBJECTIVES

To investigate how cardiometabolic-inflammatory risk factors are related to cognition among older adults in India and the United States.

DESIGN

The Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (LASI-DAD) and the Harmonized Cognitive Assessment Protocol of the Health and Retirement Study (HRS-HCAP) in the United States conducted an in-depth assessment of cognition, using protocols designed for international comparison.

SETTING

Cognitive tests were conducted in hospital or household settings in India and in household settings in the United States.

PARTICIPANTS

Respondents aged 60 years and older from LASI-DAD (N = 1,865) and respondents aged 65 years and older from HRS-HCAP (N = 2,111) who provided venous blood specimen.

MEASUREMENTS

We used total composite scores from the common cognitive tests administered. Cardiovascular risk was indicated by systolic and diastolic blood pressure, pulse rate, pro-B-type natriuretic peptide (proBNP), and homocysteine. Metabolic risk was measured by body mass index, glycosylated hemoglobin (HbA1c), high-density lipoprotein cholesterol, and lipoprotein (a) (only in India). Inflammatory risk was indicted by white blood cell count, C-reactive protein, albumin, and uric acid (only in India).

RESULTS

The distribution of both total cognition scores and of cardiometabolic risk factors differed significantly between India and the United States. In both countries, lower cognition was associated with older age, lower education, elevated homocysteine, elevated proBNP, and lower albumin levels. The associations between HbA1c levels and cognitive measures were statistically significant in both countries, but in the opposite direction, with a coefficient of 1.5 (P < .001) in India and -2.4 (P < .001) in the United States for one percentage increase in absolute HbA1c value.

CONCLUSION

Cardiometabolic-inflammatory biomarkers are associated with cognitive functional levels in each country, but the relationships may vary across countries. J Am Geriatr Soc 68:S36-S44, 2020.

Learning From Clinical Consensus Diagnosis in India to Facilitate Automatic Classification of Dementia: Machine Learning Study

BACKGROUND

The Harmonized Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (LASI-DAD) is the first and only nationally representative study on late-life cognition and dementia in India (n=4096). LASI-DAD obtained clinical consensus diagnosis of dementia for a subsample of 2528 respondents.

OBJECTIVE

This study develops a machine learning model that uses data from the clinical consensus diagnosis in LASI-DAD to support the classification of dementia status.

METHODS

Clinicians were presented with the extensive data collected from LASI-DAD, including sociodemographic information and health history of respondents, results from the screening tests of cognitive status, and information obtained from informant interviews. Based on the Clinical Dementia Rating (CDR) and using an online platform, clinicians individually evaluated each case and then reached a consensus diagnosis. A 2-step procedure was implemented to train several candidate machine learning models, which were evaluated using a separate test set for predictive accuracy measurement, including the area under receiver operating curve (AUROC), accuracy, sensitivity, specificity, precision, F1 score, and kappa statistic. The ultimate model was selected based on overall agreement as measured by kappa. We further examined the overall accuracy and agreement with the final consensus diagnoses between the selected machine learning model and individual clinicians who participated in the clinical consensus diagnostic process. Finally, we applied the selected model to a subgroup of LASI-DAD participants for whom the clinical consensus diagnosis was not obtained to predict their dementia status.

RESULTS

Among the 2528 individuals who received clinical consensus diagnosis, 192 (6.7% after adjusting for sampling weight) were diagnosed with dementia. All candidate machine learning models achieved outstanding discriminative ability, as indicated by AUROC >.90, and had similar accuracy and specificity (both around 0.95). The support vector machine model outperformed other models with the highest sensitivity (0.81), F1 score (0.72), and kappa (.70, indicating substantial agreement) and the second highest precision (0.65). As a result, the support vector machine was selected as the ultimate model. Further examination revealed that overall accuracy and agreement were similar between the selected model and individual clinicians. Application of the prediction model on 1568 individuals without clinical consensus diagnosis classified 127 individuals as living with dementia. After applying sampling weight, we can estimate the prevalence of dementia in the population as 7.4%.

CONCLUSIONS

The selected machine learning model has outstanding discriminative ability and substantial agreement with a clinical consensus diagnosis of dementia. The model can serve as a computer model of the clinical knowledge and experience encoded in the clinical consensus diagnostic process and has many potential applications, including predicting missed dementia diagnoses and serving as a clinical decision support tool or virtual rater to assist diagnosis of dementia.

The Association of Cognitive and Visual Function in a Nationally Representative Study of Older Adults in India

INTRODUCTION

Due to population aging, India is poised to experience a large increase in the burden of both dementia and vision impairment (VI). Prior studies from other settings suggest that VI may be a modifiable risk factor for cognitive decline and dementia. However, to date, no studies have examined the association of impaired visual acuity and cognition in India.

METHODS

A total of 3,784 participants in wave 1 of the population-based Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India underwent visual acuity testing and a cognitive test battery. Multivariable linear regression was used to model the cross-sectional associations of mild (<6/12-6/16), moderate (<6/18-6/60), and severe visual acuity impairment/blindness (<6/60) with cognitive performance scores corresponding to total cognition, orientation, memory, language/fluency, executive function, and informant-reported cognitive status. Models were adjusted for demographic, socioeconomic, and health characteristics.

RESULTS

The weighted percentage of participants with any VI was 52.6%. VI was independently associated with lower cognitive scores across all domains, even after adjustment for known dementia risk factors. In fully adjusted models of total cognition (mean score: 130.7), mild, moderate, and severe VI/blindness were associated with a significant change of -3.5 (95% CI: -6.3, -0.6), -8.2 (95% CI -10.5, -5.6), and -16.8 (95% CI -22.3, -11.3) units, respectively. A dose-response association between level of VI and cognitive function was observed for all cognitive outcomes except for language/fluency domain scores. Associations were robust when cognitive tests dependent on visual function were excluded. Across each fully adjusted model of total, domain-specific, and informant-reported cognitive performance, moderate VI was equivalent to 5-9 years of cognitive aging.

DISCUSSION/CONCLUSION

This study illustrates that VI is cross-sectionally associated with lower cognitive performance, largely in a dose-response pattern, across various cognitive domains in the Indian population. These findings are important for informing future longitudinal and interventional studies.

Design and Methodology of the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (LASI-DAD)

BACKGROUND/OBJECTIVES

To provide high-quality data on older adults in India that will enable an in-depth study of late-life cognition and dementia in India and cross-country analysis of risk factors for cognitive aging and dementia.

DESIGN

The Longitudinal Aging Study in India (LASI) is a nationally representative survey of health, economic, and social well-being of the Indian population aged 45 and older. Its large sample of more than 70,000 older adults represents not only the country as a whole but also each state. LASI-Diagnostic Assessment of Dementia (DAD) is an in-depth study of late-life cognition and dementia, drawing a subsample of over 3,000 LASI respondents aged 60 and older.

SETTING

Participants were interviewed at home or in a participating hospital according to their preferences.

PARTICIPANTS

Adults aged 60 and older (N = 3,224), along with 3,191 informants.

MEASUREMENTS

Respondents underwent a battery of cognitive tests, and informants were interviewed about their cognitive and health conditions. A common set of cognitive tests was selected to enable international comparisons, and additional cognitive tests suitable for illiterate and innumerate populations were also selected. Rich data on risk factors of dementia were collected through health examination, venous blood assays, and genotyping.

RESULTS

The response rate was 82.9%, varying across sex, education, and urbanicity. Data are available to other researchers.

CONCLUSION

LASI-DAD provides an opportunity to study late-life cognition and dementia and their risk factors in the older population in India and to gain further insights through cross-country analysis by pooling data from its international sister studies. J Am Geriatr Soc 68:S5-S10, 2020.