In most states, Medicaid eligibility rules shift at age 19, when individuals transition from child to adult classification. A new study led by the University of Chicago finds that this policy threshold coincides with a sharp spike in Medicaid disenrollment, exposing millions of young adults — including those with significant health needs — to potential gaps in insurance coverage.
In the study, published February 16 in JAMA Pediatrics , researchers observed that 13.4% of young adults with complex medical conditions were disenrolled at age 19, compared with 35.6% of those without complex conditions. Disenrollment was defined as two or more months without comprehensive Medicaid coverage.
While young adults without complex conditions were more likely to lose coverage, researchers emphasized that disruptions among medically complex patients remain clinically significant. Over a three-year window between ages 19 and 21, the cumulative probability of disenrollment reached 37.9% for individuals with complex medical conditions and 74.2% for those without.
"It was known within health policy that there was increased disenrollment around age 19," said Betsy Q. Cliff, PhD , Assistant Professor of Public Health Sciences at UChicago and lead author of the study. "But we're the first we know of to estimate the precise risk across this transition from childhood to adulthood for a national Medicaid population."
The study also found dramatic differences in disenrollment rates based on geography. The probability of disenrollment at age 19 varied widely by state, reflecting substantial differences in Medicaid policies and administrative processes across the country. Among young adults with complex medical conditions, disenrollment rates ranged from 2.6% to 37%. For those without complex conditions, the range was even broader — from 7.3% to 83.9%.
"I was really surprised at the variation among states," said Cliff. "Two equally sick people living in different places can have a very different probability of losing health insurance."
Researchers also identified other factors associated with higher disenrollment risk, including being male, qualifying through income-based eligibility pathways rather than disability-based pathways, living in states that have not expanded Medicaid to all individuals with low incomes, and residing in states where managed care dominates the market. Among individuals with complex medical conditions, those with mental health and cardiac conditions had the highest probability of disenrollment.
Why disruption matters
Although individuals with complex medical conditions, including those with multiple chronic conditions or progressive diseases such as cystic fibrosis or sickle cell disease, represent a small share of Medicaid enrollees, Cliff noted that coverage gaps can carry outsized consequences.
"This is a population that has continuous high healthcare needs," she said. "They're very attached to their healthcare providers and seeing multiple specialists regularly."
Even temporary interruptions in insurance coverage can disrupt treatment plans, delay appointments, and limit access to medications. In some cases, Cliff explained, these disruptions may contribute to worsening health outcomes.
"They could have an exacerbation of the condition," Cliff said. In related work, she said, "We talked to people who ended up in emergency departments because they weren't able to get maintenance medications."
Researchers cautioned that disenrollment does not necessarily mean permanent loss of coverage. Some individuals re-enroll after temporary gaps. In the sample of Medicaid enrollees, 37.9% of disenrolled individuals with complex medical conditions and 29.1% without returned to Medicaid within 12 months.
Additionally, the data did not show whether individuals got other insurance coverage when they lost Medicaid.
"They could be getting private insurance," Cliff said, "but previous studies suggest many become uninsured."
Policy implications for a fragmented system
Since the structure of Medicaid allows coverage policies to vary widely from state to state, it may contribute to health disparities in the U.S., with individuals in states with higher rates of disenrollment at an increased risk of illness or even death.
While sweeping eligibility reforms would require broad policy action, individual states may have opportunities to reduce coverage disruptions.
"For instance, they could think about offering more care navigators," said Cliff. "People specifically helping young adults make a seamless transition from being a child to being an adult in the eyes of Medicaid."
More broadly, Cliff said the results underscore the instability many young adults experience during this period.
"Individuals face so many changes when they turn 19. Many age out of school systems or pediatric care that may have supported enrollment," Cliff said. "If that individual also happens to live in a state that does little to support the transition from child to adult care or has very different eligibility criteria between childhood and adulthood, it could have a significant impact on their health. It's a very stark example of how arbitrary the health insurance system can be."
Further research will examine where disenrolled individuals go and how coverage disruptions shape long-term health outcomes.
