Pathways to Disability and Death Before Disability in middle ages: Estimates from the Health and Retirement Study Data

Abstract

This paper studies factors that affect enrollment onto a public insurance program such as the Social Security’s DI (Disability Insurance) program and SSI (Supplemental Security Income) program, and the competing risk of death before disability enrollment by age 65. As individuals age, or misuse drugs, alcohols or intake less nutrient foods, the homeostatic regulatory mechanism that controls physiological body systems such as respiratory, cardiovascular, neuroendocrine, immune, and metabolic becomes more and more frail in its ability to face internal and external stressors. This leads to one-or-comorbid chronic diseases (such as diabetes, cancer, vascular, musculoskeletal, cognitive and mental disorders), DI-qualifying disabilities or death. The speed of progression through these health states depends on the rate of depletion of one’s homeostatic health and frailty levels. Genetic and epigenetic factors comprised of internal and external environments, health care use, health related behavior and cognitive endowments modulate the depletion rate of homeostatic health over life cycle. These, in turn, determine the likelihood of various pathways through the health states. I use the Health and Retirement Study (HRS) data to estimate a multi-state time-to-event model of pathways through these health states. I use data on childhood factors such as childhood SES, health and education, bio-markers such as BMI, CES-D, measures of cognitive health, and indicators of health related behaviors such as smoking, drinking, exercising and use of preventative care along the life-course as determinants of the risks of following various pathways to disability and death before reaching age 65.