Shen Defends Dissertation – Center for Health Decision Science

Ye Shen, doctoral student in Health Policy concentrating in Decision Science, successfully defended her thesis, “Insights into the Fragmented US Health System through Simulation Modeling: Childhood Insurance, Care Utilization, and Outcomes.”

The US health system has long been characterized as “fragmented.” However, less is known about the cumulative consequences of growing up in this fragmented system. Through three dissertation papers, Shen examined two features of the fragmentation: the insurance landscape and the medical-dental divide. In each paper, she focused on one domain of cumulative consequences across the full course of childhood: Paper 1 examined health insurance coverage; the remaining chapters expanded this focus to routine care utilization (Paper 2) and dental caries outcomes (Paper 3).

Empirical analyses of insurance, care utilization, and outcomes are often constrained by fragmented health administrative data and limited follow-up in national surveys, yielding only a partial view of these dynamics over time. Therefore, Shen combined strengths of multiple data sources, including national surveys and electronic health records, and developed microsimulation modeling approaches to estimate the cumulative consequences across the full course of childhood.

In Paper 1, Shen created a nationally representative synthetic cohort and developed nonparametric matching algorithms to simulate individual-level trajectories from birth until reaching their 18th birthday across five health insurance types: 1) Medicaid or Children’s Health Insurance Program (CHIP); 2) uninsured; 3) employment-based private; 4) Marketplace; 5) other. Her findings demonstrate the broad reach of Medicaid and CHIP, the common experience of coverage gaps, and substantial state-level variation by Medicaid policy restrictiveness over childhood.

In Paper 2, Shen developed nonparametric matching algorithms and simulated individual trajectories of pediatric routine care utilization across primary care and dental settings. In addition, Shen estimated how medical-dental integration under perfect implementation affects continuity of routine care under two integration scenarios: 1) delivering dental services in primary care; 2) delivering primary care services in dental care. Her findings demonstrate sizable unmet routine care needs in both settings, particularly for dental care. Children with stable coverage predominately in Medicaid/CHIP had high unmet needs, comparable to children who lacked health insurance for more than 10% of childhood (high health insurance gap). While integration improves routine care continuity across insurance groups, Shen estimated the largest reduction in long gaps for the insurance group with the lowest unmet needs (stable coverage predominantly in employment-based health and dental insurance).

Finally in Paper 3, Shen estimated cumulative dental caries outcomes and examined disparities by childhood insurance experience. As children’s dentition evolves, primary and permanent tooth surfaces become susceptible to dental caries, the most common chronic disease of childhood in the United States. Shen developed, calibrated, and validated a dental caries microsimulation model that incorporates changes in dentition, insurance, and dental utilization over childhood. Shen estimated that 72% of US children develop any caries by their 18th birthday, with an average of 5.5 affected tooth surfaces. Children with high health insurance gaps and those with stable coverage predominantly in Medicaid/CHIP experience the highest cumulative burden of caries, whereas those with stable coverage in predominantly employment-based health and dental insurance have the lowest burden.

Learn more: Read Shen’s first dissertation chapter published in JAMA, Insurance Dynamics During Childhood in the Fragmented US Health System
Learn more: Read research by Shen and colleagues in the International Journal of Eating Disorders, Development of Disordered Weight Control Behaviors and Its Progression to Eating Disorders in Canada: A Nationally Representative Microsimulation