Date of Graduation

2017

Document Type

Dissertation

Degree Type

PhD

College

School of Pharmacy

Department

Pharmaceutical Sciences

Committee Chair

Nilanjana Dwibedi

Committee Co-Chair

Usha Sambamoorthi

Committee Member

Kim Innes

Committee Member

Sophie Mitra

Committee Member

Xi Tan

Abstract

The relationship between economic status and health has been documented in the previous literature. Economic, sociological and epidemiological studies have indicated that higher economic status is associated with better physical and mental health. While these studies have made significant contributions in this area, a comprehensive evaluation of the relationships between economic indicators and health is still lacking. Most studies focused on a single measure of economic status or health. Further, most studies have focused on one-direction -- economic indicators affecting health; little is known about the effect of health improvement on gain in economic status. Furthermore, only a few studies have conducted comparative analysis of whites and racial minorities. To fill the knowledge gap, the three related aims of this dissertation were to: (1) examine the dynamic relationships between economic status (family income, labor income and net wealth) and physical health measures (self-rated health and functional limitations due to chronic conditions) among working-age adults in the United States US; (2) evaluate the dynamic relationships between economic indicators (family income, labor income and net wealth) and mental health (psychological distress and mental illnesses) among working-age adults in the US; (3) evaluate the heterogeneous relationships between labor income and physical and mental health by racial groups. The study utilized a retrospective observational longitudinal design with repeated measures of economic indicators and health for a period of 14 years using 8 waves of the Panel Study of Income Dynamics: 1999 through 2013. In first aim, System-Generalized Method of Moment (system-GMM) models were used to evaluate the dynamic relationships between economic indicators and physical health measures. Additionally, first-difference estimators were used to examine the associations between changes in economic status and changes in physical health. System-GMM revealed a significant positive relationships between all economic indicators and self-rated health. Nevertheless, only labor income and net wealth were associated with functional limitations. Self-rated health declined due to losses in family income and labor income; decreases in self-rated health resulted in losses in family income, labor income and net wealth. In the second aim, Probit and instrumental variable (IV) probit models were used to evaluate the relationships between economic indicators and mental illnesses. Further, ordinary least squares regression (OLS) and IV OLS were used to examine the relationships between economic indicators and psychological distress scores. First-difference estimators were used to assess the associations between changes in economic status and changes in mental health. After controlling for the endogeneity between economic status and mental health, we observed a significant inverse relationship between net wealth and the presence of a mental illness. On the other hand, adjusted IV OLS revealed significant inverse relationships between family income, net wealth and psychological distress. First-difference estimators indicated that a decline in economic status resulted in a decline in mental health. Similarly, a decline in mental health resulted in losses to net wealth, family and labor income. In the third aim, System-GMM and heteroscedasticity-based instrument regressions were used to examine the relationships between labor income and physical and mental health measures by racial groups. First-difference and lagged fixed effects models were used to examine the effect of loss in income on physical and mental health. We found that adults in higher labor income quartiles had better self-rated health than those in the lowest quartile regardless of racial group. However, the relationship between labor income and psychological distress varied by race group; whites and African Americans in higher labor income quartiles had lower psychological distress scores than their counterparts in the lowest quartile. This was not the case with Hispanics. Reductions in labor income were associated with increases in psychological distress among whites only. In summary, this dissertation revealed that not adjusting for the endogeneity between economic status and health overestimates the relationship between the two. The results of this dissertation suggest that the relationship between economic indicators and health is dependent on the health measures that used to examine the relationship. Health is a multidimensional concept and economic indicators seem to have different dynamic relationships with different components of health. Findings of this dissertation study suggest a strong, bidirectional relationship between economic status and physical health. Finally, the findings suggest heterogeneous relationships between labor income and physical and mental health across racial groups.

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