Pathways to Educational Disparities in Disability Incidence: The Contributions of Excess Body Mass Index, Smoking, and Manual Labor Involvement

Objectives: In the United States, educational disparities in disability are large and increasing, but the mechanisms underlying them are not well understood. We estimate the proportion of population-level educational disparities in disability incidence explained by excess body mass index (BMI), smoking, and manual labor. Method: We use waves 2003-2015 of the nationally representative Panel Study of Income Dynamics to calculate observed disability incidence and counterfactual incidence absent the key mediators (3,129 individuals; 13,168 observations). We take advantage of earlier-life measures, including childhood socioeconomic status, 1986 BMI, and occupational history between 1968 and 2001. To account for distinct processes in women and men at middle versus older ages, we stratify by gender and at age 65. Results: Educational disparities in disability incidence were evident in women and men at younger and older ages, and were largest among older women. Together, the mediators of interest were estimated to explain roughly 60% of disparities in younger women, 65%-70% in younger men, 40% in older women, and 20%-60% in older men. The main contributors to disparities appeared to be excess BMI and smoking in younger women; manual labor and smoking in younger men; excess BMI in older women; and smoking in older men. Discussion: These mediators explain much of disparities in earlier-age disability; successful interventions to address these factors may substantially reduce them. However, a considerable proportion of disparities remained unexplained, particularly at older ages, reflecting the myriad pathways by which educational attainment can influence disability status.