Little is known about the impact of the Affordable Care Act (ACA) on insurance attainment among complex, high-cost populations such as those with multimorbidity. Our objective was to evaluate the impact of the ACA on insurance status in nonelderly adults with moderate versus complex multimorbidity.

We identified adults, 18-64 years, from the 2010 and 2015 Medical Expenditures Panel Survey (MEPS) Household Component. Chronic conditions (185 conditions) were defined as those lasting 12 or more months, and resulting in functional limitations or ongoing care. Multimorbidity was defined as the presence of 2 or more chronic conditions, and categorized as moderate (2-4 conditions) or complex (5 or more). We compared pre- and post-ACA (2010 vs. 2015) prevalence of multimorbidity, and examined proportion of insurance coverage by multimorbidity category. Logistic regression was used to estimate the association between complex multimorbidity and insurance status, adjusted for race, age categorical, sex, and level of individual yearly income. Estimates are weighted to represent the non-institutionalized U.S population.

In 2015, among those with at least one chronic condition, 47.74% (n=49,381,262) of the population had moderate and 9.90% (n=10,237,728) had complex multimorbidity, with similar prevalence estimates in 2010. The proportion of uninsured individuals decreased by 4.8% and 5.2% among those with moderate and complex multimorbidity respectively, from 2010 to 2015. Pre-ACA, the odds of being insured were higher among those with complex versus those with moderate multimorbidity [2010 OR=1.44; 95% CI (1.05, 1.96)], and remained high post-ACA [2015 OR=1.89; 95% CI (1.09, 3.27)].

The ACA had a differential impact on access to health insurance among those with moderate versus complex multimorbidity. Changes in cost sharing and coverage restrictions can have a differential impact on vulnerable populations. Better characterization of determinants of attainment of health insurance among high risk populations is needed.