We used NHANES, a population-based survey of U.S. households conducted by the National Center for Health Statistics. NHANES uses a complex, multistage probability sample of the U.S. civilian, non-institutionalized population. We used the following questionnaire components: 1) Respiratory Health and Disease, 2) Medical Conditions, 3) Hospital Utilization and Access to Care, 4) Prescription Medications, and 5) Demographics. Data from surveys in 2003–2004, 2005–2006, and 2007–2008 were aggregated for our analysis. For children <16, data are reported by an adult in the household, usually a parent or guardian. Our analysis is restricted to 11,719 children ages 1–17.

Insured children with intermittent asthma symptoms have a greater likelihood of being diagnosed with asthma and receiving long-term inhaled corticosteroid treatment than those without insurance. Further, insured children with intermittent symptoms are also more likely to make acute outpatient and ED visits for asthma attacks. These differences in asthma diagnosis, treatment, and utilization by health insurance were not observed for those with persistent symptoms.

Our findings suggest that, although health insurance may be an important factor in asthma diagnosis among children with intermittent symptoms, it may play a much smaller role in asthma diagnosis among children with persistent symptoms. Insured children with persistent symptoms are about as likely to have a diagnosis of asthma as uninsured children with similar symptoms. One likely explanation is that, because children with persistent symptoms have a higher level of need for acute asthma care, they tend to present to clinics, urgent care centers, and EDs regardless of their insurance status, thus creating similar opportunities for diagnosis.

Among children with intermittent asthma symptoms, insured children were more likely than uninsured children not only to take an inhaled corticosteroid, but also to have had a recent acute care visit or ED visit for “wheezing attacks.” This finding is somewhat counterintuitive, given that inhaled corticosteroids have been shown to reduce acute care utilization. There are at least three plausible explanations for this observation. First, some uninsured children may have a similar need for acute care as insured children but may be unable to receive it consistently because they do not have insurance (Hoffman, and Paradise 2008; Kenney 2007; Stoddard, St. Peter, and Newacheck 1994). Alternatively, some children with intermittent symptoms may over-utilize acute care services once they are provided with both insurance and a diagnosis; for instance, a diagnosis of asthma may sensitize parents and heighten their anxiety about minor symptoms. Third, the increased acute care utilization may have occurred before the patient began using the inhaled corticosteroid.

Our findings suggest that there may be a significant “reservoir” of undiagnosed asthmatic children, especially among those who lack health insurance. The benefits of identifying these children, however, are unclear—they are more likely to have intermittent symptoms, which may not benefit greatly from control therapy. As access to insurance expands through health care reform, asthma diagnoses may increase from their current plateau, and we may see additional increases in inhaled corticosteroid use. Such increases, however, may incur a cost that might not greatly improve societal health.

This study has several important limitations. First, based on the age of the participant (1–15 years versus 16–17 years), the data were collected via parent-report or self-report. We do not have data on differences in the accuracy of the reporting methods based on these age groups for reporting asthma-related symptoms, medication, and utilization. Second, our findings are based on cross-sectional data, and we are unable to determine the temporal ordering of events. For example, some children with no or intermittent symptoms were taking inhaled corticosteroids, and possibly had persistent asthma that was now well-controlled on inhaled corticosteroids. However, our sensitivity analysis suggested that our findings were similar when restricted to children not currently on a control medication. Next, our analysis used a limited number of covariates that could have missed important confounders. For example, our study confirms previous studies showing that asthma diagnosis and symptoms vary by race/ethnicity (Akinbami, Rhodes, and Lara 2005; Crocker et al. 2009; Flores, and The Committee on Pediatric Resarch 2010; Gold, and Wright 2005; Quinn et al. 2006). Some evidence suggests that much of this disparity can be attributed to socioeconomic factors (Litonjua et al. 1999; Smith et al. 2005); however, other factors related to race/ethnicity, such as stress, also appear to be critical (Gold, and Wright 2005; Williams, Sternthal, and Wright 2009). Finally, we were unable to use NHLBI guidelines to categorize asthma severity. Some of the indicators of symptom severity that we used are also in the NHLBI classification, but there are also some indicators from NHLBI that were not available in the NHANES dataset. A side-by-side comparison of the criteria used in this study compared with the criteria used in the NHLBI 2007 guidelines is available as a supplementary table.

In conclusion, we found that having health insurance is associated with an increased likelihood that a child with intermittent asthma symptoms will receive an asthma diagnosis and asthma control medication, but is not associated with improvements in asthma-related acute care utilization. We also found that, for children with persistent symptoms, having health insurance is not associated with diagnosis, treatment, or utilization. These findings suggest that while increasing access to insurance could lead to the identification of more children with intermittent asthma symptoms, benefits with respect to acute care utilization remain unclear. CHIPRA and expanded Medicaid coverage of parents under the ACA may lead to many previously uninsured children in the U.S. becoming insured (Kaiser Family Foundation 2010; Sebelius 2010). This increase in the proportion of insured children may reduce the number of undiagnosed children with intermittent asthma symptoms and ensure that they receive more appropriate treatment; large cost savings from reduced acute care utilization, however, may not be a realistic expectation. Potential long-term benefits and costs of detecting and treating undiagnosed asthma in these newly insured children should be explored.