Insurance Dynamics During Childhood in the Fragmented US Health System

Importance US children’s health insurance is fragmented across public and private sources, with wide state variation. However, the extent of children’s interactions with Medicaid and Children’s Health Insurance Program (CHIP) and their experience of uninsurance over 18 years of childhood remains unclear. Such estimates can provide a baseline for gauging the potential impact of upcoming Medicaid policy changes. Objective To estimate insurance dynamics in relation to Medicaid or CHIP and uninsurance over childhood under post–Affordable Care Act (ACA) prepandemic policy conditions. Design, Setting, and Participants Using a microsimulation model, we projected individual-level monthly insurance coverage (Medicaid or CHIP, Marketplace, employment-based, other, or uninsured) from birth until the 18th birthday for a simulated nationally representative cohort of 100 000 US children. National data were synthesized (2015-2019), including natality records, Medical Expenditure Panel Survey pooled 2-year panels, and 1 Survey of Income and Program Participation (SIPP) 3-year panel. Monthly insurance status was simulated by matching dynamically updated predictors to SIPP samples every 12 months. Predictors included annual family income as a percentage of the federal poverty level, insurance history, state, and age. The analysis was bootstrapped 1000 times to generate 95% uncertainty intervals (95% UI). Exposures Insurance status and state of residence at birth. Main Outcomes and Measures Cumulative insurance experience, overall and by subgroup. Results It was estimated that, by their 18th birthday, 61% (95% UI, 58%-63%) of US children were ever enrolled in Medicaid or CHIP and 42% (95% UI, 38%-46%) were ever uninsured. An estimated 26% (95% UI, 24%-29%) of children were continuously enrolled in employment-based or other insurance excluding Medicaid, CHIP, or Marketplace. Among children born with Medicaid or CHIP, the share ever uninsured was 59% (95% UI, 48%-66%) in ACA nonexpansion states vs 36% (95% UI, 30%-41%) in expansion states. Across alternative categorizations of policy restrictiveness, the highest share of ever uninsured among children born with Medicaid or CHIP was consistently estimated in states with the most restrictive Medicaid and CHIP eligibility criteria. Conclusions and Relevance An estimated 3 of 4 US children relied on publicly subsidized insurance (Medicaid, CHIP, or Marketplace) or experienced a period without any insurance by their 18th birthday in the post-ACA, prepandemic policy environment. Substantial state heterogeneity in childhood uninsurance underscores the critical role of Medicaid policies.