OBJECTIVES: Asthma is sometimes considered as an autoimmune disorder, however, burden of autoimmune disorders among patients with asthma is not well understood. This study aims to provide evidence regarding the prevalence and economic burden of autoimmune disorders among patients with asthma in the US.

METHODS: A cross-sectional, retrospective study design using data from alternate multiple years (2008/2010/2012/2014) of the Medical Expenditure Panel Survey was conducted. Adults with asthma were identified using the ICD-9-CM code for asthma (493.xx). Patients with Ankylosing spondylitis, Crohn’s disease, Lupus, Psoriasis, and Rheumatoid arthritis were considered as having autoimmune disorders. Annual healthcare expenditures for hospitalizations, emergency room and outpatient visits, prescription drugs, and other services were assessed. Unadjusted differences in average annual healthcare expenditures between patients with and without autoimmune disorders were determined using t-tests. Adjusted ordinary least squares (OLS) regression on log-transformed healthcare expenditures were conducted to estimate the magnitude of excess healthcare expenditures associated with autoimmune disorders. All analyses were weighted to control for the complex sample design of MEPS.

RESULTS: A total of 5,139 adults with asthma (weighted n=36.8 million) were identified; of these, 5.8% had comorbid autoimmune disorders. Unadjusted comparison of total annual expenditures showed that expenditures were significantly higher among those with autoimmune disorders compared to those without them ($18,068 vs $10,162 [P<0.05]). Prescription drugs and outpatient services were major contributors of the increased healthcare expenditures. Adjusted OLS regression revealed that patients with comorbid autoimmune disorders had 19% (β=0.182; exp[β]=1.19; P<0.05) higher expenditures than patients without autoimmune disorders.

CONCLUSIONS: The study found that presence of autoimmune disorders was associated with increased economic burden among patients with asthma. Further research is required to understand potential drivers for the increased economic burden associated with asthma and comorbid autoimmune disorders.