The prevalence of COPD and asthma is increasing all over the world; however, their morbidities are thought to be greatly underestimated because of unawareness of patients' conditions and respiratory symptoms. Spirometry is useful for the early detection of COPD and asthma with airflow limitation (AL), although it is not yet widely used for screening in epidemiological and primary care settings. A simple predictive marker used in combination with spirometry for AL is expected to be established. In medical health check-ups, serum uric acid (s-UA) is measured when screening for gout and has recently been suggested to have an association with several respiratory disorders, including asthma and COPD. However, whether s-UA influences the development of AL remains unclear. Therefore, the aims of this study were to examine the relationship between AL and s-UA and to investigate s-UA as a potential auxiliary marker for predicting AL risk in medical health check-ups. A total of 8,662 subjects aged >40 years were included. They were administered a simple questionnaire and assessed using pulmonary function tests, blood pressure (BP) measurements, and blood samplings. One hundred and fifty-six subjects (1.8%) had AL, just 29% of whom had experienced respiratory symptoms. The subjects with AL had significantly higher s-UA levels compared with never-smoking subjects without AL. Forced expiratory volume in 1 second (FEV1) %predicted showed significant correlations with age, smoking index, body mass index (BMI), mean BP, white blood cells, hemoglobin A1c, s-UA, and high-density lipoprotein cholesterol. In multiple logistic regression analysis, s-UA, in addition to age, smoking index, respiratory symptoms, and BMI, was independently associated with AL. In conclusion, elevated s-UA levels, together with respiratory symptoms, high smoking index, and weight loss, may epidemiologically predict the development of AL risk.
Keywords: COPD; airflow limitation; asthma; health check-up; uric acid.