Cross-national statistical harmonization of the Center for Epidemiologic Studies Depression (CES-D) scale among older adults in China, England, India, Mexico, South Africa, and the United States.

OBJECTIVES: We examined differential item functioning (DIF) of the Center for Epidemiologic Studies Depression Scale (CES-D) items by country and statistically harmonized common cross-national factor scores for the CES-D to aid further cross-national research.

STUDY DESIGN AND SETTING: Data were from Harmonized Cognitive Assessment Protocol (HCAP) studies in China (N = 9639), England (N = 1262), India (N = 4048), Mexico (N = 1918), South Africa (N = 631), and the United States (N = 3321). Multiple indicators, multiple causes models were estimated to test DIF in the CES-D items by country. DIF items were defined as having an odds ratio (OR) outside the range of 0.75-1.25 in multiple indicators, multiple causes models. We evaluated DIF impact and identified salient DIF by examining whether the difference between DIF-adjusted factor scores and non-DIF-adjusted factor scores exceeded a threshold of 0.30 standard deviation (SD) units. Confirmatory factor analysis was used to create DIF-adjusted, cross-nationally harmonized CES-D factor scores.

RESULTS: Controlling for underlying depressive symptoms, HCAP participants in India had higher odds of reporting being not hopeful about future (OR = 1.38, 95% confidence interval [CI]: 1.34-1.42), not enjoying life (OR = 1.43, 95% CI: 1.38-1.48), and being unhappy (OR = 1.29, 95% CI: 1.25-1.34), compared to HCAP participants in the United States. These identified DIF items artificially increased mean harmonized CES-D factor scores by 0.48 SD units in the India HCAP, with over 50% of the factor scores increased by over 0.30 SD units, indicating salient DIF in the India HCAP.

CONCLUSION: Our findings demonstrate cross-national heterogeneity in the expression of depressive symptoms. We provide DIF-adjusted CES-D factor scores to improve the quality of cross-national comparisons in aging research.