Use of an IRT-based latent variable model to link different forms of the CES-D from the Health and Retirement Study.

BACKGROUND: The goal of this study was to calibrate depressive symptoms collected using different versions of the Centers for Epidemiologic Studies - Depression (CES-D) instrument in different waves of the Health and Retirement Study (HRS).
METHOD: The HRS is a prospective and nationally representative cohort study. This analysis included a sample of HRS participants, adults aged 23-85 years in 1992 who had complete data on depressive symptoms at initial 2- and 4-year follow-up interviews (N= 5,734). Depressive symptoms were assessed with the CES-D. Symptom coverage and response categories varied across study wave. The first wave (1992) used a four-category response, whereas subsequent waves (1994 and 1996) used a two-category response. A structural equations model (SEM) based in Item Response Theory (IRT) was used to calibrate symptoms and generate linked depressive symptom burden scores.
RESULTS: Linked depressive symptom burden scores, derived from calibrated symptoms, were distributed similarly across HRS wave.
CONCLUSION: Our results demonstrate the applicability of an IRT-based SEM to address a common challenge in prospective studies: changes in the content and context of symptom assessment. Future investigations may make use of our linked syndrome scores to further explore other aspects of depression from a longitudinal perspective.