Background/Purpose:  Smoking has been found to be negatively correlated with serum uric acid levels by virtue of reduced production and increased consumption of endogenous anti-oxidant uric acid among smokers and has been reported to decrease incidence of gout. We looked at the question of association between active smoking and acute gout by examining this association using a large inpatient US database.

Methods: We used the Nationwide Inpatient Sample (NIS) database (largest publicly available all-payer inpatient care database in the United States) from the years 2009-2011 to identify patients aged ³ 18 years without missing information for gender and age. Current smokers among them were selected using previously validated ICD-9 code 305.1. Hospitalizations with history of smoking but not active smoker were. Patients who developed acute gout during hospitalization were identified based on ICD-9 code 274.01 marked as a secondary diagnosis. Patients with acute gout as a primary diagnosis were excluded to prevent confounding from a group that may still have been actively smoking at the time of their flare. Univariate logistic regression was used to examine the previously reported confounding factors including age, sex, diabetes, hyperlipidemia, hypertension, chronic kidney disease (CKD), early menopause/post menopause, major organ transplant, obesity and alcohol. We then constructed a multivariable logistic regression using all factors with significant associations during univariate analysis (defined as p<0.10). STATA version 13.0 (College Station, TX) was used for analysis to accommodate for the complex design of survey sample data (NIS).

Results: A total of 17,847,045 discharge records were used in the analysis. Both univariate (OR 0.59, CI 0.54-0.63, p<0.0001) and multivariate (OR 0.64, CI 0.59-0.68, p<0.0001) regressions showed statistically significant reduction of acute gout incidence among hospitalized patients who were current smokers but were assumed to have ceased smoking during hospital stay.

Conclusion: Active tobacco use was associated with a lower risk of acute inpatient gouty arthritis, even when controlling for conventional risk factors. More study is needed to correlate this finding with uric acid levels, and a better understanding of the mechanisms that explain this finding are necessary. Figure 1: Selection process for discharges included in analysis

Table 1: Univariate analysis (logistic regression) of incident acute gout in current smokers among hospitalized patients.

Table 2: Multivariate logistic regression of incident acute gout among hospitalized patients.