Association of Serum Uric Acid with Lung Function in the National Health and Nutrition Examination Survey (NHANES), 2007-2012: A Cross-Sectional Study.

Abstract Background Evidence regarding the relationship between serum uric acid and lung function was controversial. Therefore, this study is designed to investigate whether serum uric acid was independently related to lung function in the National Health and Nutrition Examination Survey (NHANES) (2007-2012) after adjusting for other covariates. Methods The present study was a cross-sectional study. The total participants from NHANES (2007-2012) were 30442. After exclusion of subjects, 9474 subjects remained for the final analysis. The target independent variable and the dependent variable were serum uric acid measured at baseline and lung function respectively. Covariates involved in this study included age, sex, race, income-poverty ratio, body mass index, systolic blood pressure, diastolic blood pressure, blood urea nitrogen, cholesterol, creatinine, total protein, FeNO, calcium, alcohol drinking, smoke, phosphorus and total bilirubin. Results The average age of 9626 selected participants was 37.12 ± 16.03 years old, and about 49.19% of them were male. Result of fully adjusted linear regression showed serum uric acid was negatively associated with FEV1, FEV and PEF after adjusting confounders (Odds ratio (OR)= for FEV1 [-21.28 (-32.26, -10.30)], for FVC [-26.79 (-40.56, -13.01)] and for PEF [-72.19 (-101.93, -42.46)]). FEV1 and PEF were found a non-linear relationship with serum uric acid and the inflection points was 6.5mg/dl and 7.3 mg/dl respectively. The effect sizes and the confidence intervals in FEV1 and PEF of the left and right sides of inflection point were -11.50 (-25.55, 2.54) and -48.07 (-74.49, -21.66), -38.17 (-71.91, -4.43) and -311.11 (-427.28, -194.94) respectively. Conclusions We find serum uric acid was negatively associated with FEV1, FVC and PEF in a general population. Besides, there is a threshold effect on the independent association between serum uric acid and FEV1 and PEF. Those results are only found in the general population. Further epidemiologic studies will still be required to confirm this reverse association between serum uric acid and lung function.