Background/Purpose:

Gout is an inflammatory disorder related to hyperuricemia and abnormal deposition of monosodium urate crystals in joints or other tissues. The relationship between serum uric acid and asthma is controversial in the literature. While some studies found it an initiator and amplifier of asthma, others had the opposite results. Most previous studies involved either animal models or small patient samples. In our study, we analyzed the association of asthma and gout in hospitalized patients

Methods:

We conducted a cross-sectional study using data from National Inpatient Sample (NIS) for the year of 2014. Diagnosis for asthma, subtypes of asthma (i.e. allergic asthma, non-allergic asthma, exercise-induced bronchospasm and cough variant asthma) and gout were identified using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. STATA software package was used for statistical analyses. Multivariate logistic regression models were created to adjust for potential confounders such as age, gender, race, insurance type, current tobacco abuse and obesity. Patients younger than 18 years old were excluded from the study. For asthma exacerbations, we also studied exacerbations related to acute respiratory infections (ARI) and status asthmaticus.

Results:

A total of 858,750 hospitalizations with a diagnosis of gout and 2,331,616 hospitalizations with a diagnosis of asthma were included in the study. Compared with those without gout, asthma patients with gout are more likely to be older (mean age 67.6 vs 54.9), male (50.5% vs 29.2%), more African American and less Hispanic (26.8% and 5.0% vs 21.3% and 10.2%), less smoker (10.3% vs 19.1%) and more obesity (33.8% vs 23.7%). The adjusted OR for all types of asthma and gout was 1.15 (95% CI 1.13 – 1.17, p < 0.001). For asthma subtypes, the adjusted OR was statistically significant only for allergic asthma (OR 1.16, 95% CI 1.01 – 1.35, p = 0.035). There was no difference for non-allergic asthma (OR 0.78, 95% CI 0.47 – 1.32, p = 0.363), exercise-induced bronchospasm (OR 0.93, 95% CI 0.55 – 1.56 p = 0.776), and cough variant asthma (OR 1.43, 95% CI 0.89 – 2.29, p = 0.136) in patients with gout. For patients with asthma exacerbations, gout was associated with a lower risk of overall exacerbations (OR 0.87, 95% CI 0.83 – 0.91, p < 0.001), ARI-related exacerbations (OR 0.78, 95% CI 0.66 – 0.92, p = 0.003) and status asthmaticus (OR 0.59, 95% CI 0.46 – 0.77, p<0.001). There was no difference for exacerbations from allergic asthma (OR 0.76, 95％ CI 0.52 – 1.10, p = 0.142) in patients with gout.

Conclusion:

Our study suggested that gout is a risk factor only for allergic subtypes of asthma, and that it may be a protective factor for asthma exacerbations except for the allergic subtype. This unexpected finding may be due to the unique biochemical properties of uric acid, being both pro-inflammatory and anti-oxidant and also the heterogeneity for different subtypes of asthma. However, we also cannot rule out the effects of systemic steroid, which is one of the short-term treatment for acute gouty arthritis, as a possible confounder. Whether a target level of uric acid in gout patients with allergic and non-allergic asthma needs to be individualized warrants further investigations.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationship-between-gout-and-asthma-a-national-database-analysis/