The clinical effect of smoking and environmental factors in spontaneous pneumothorax: a case-crossover study in an Inland province

Background: The factors that trigger spontaneous pneumothorax have not been sufficiently evaluated. The purpose of this study is to analyze the relationship between the development of spontaneous pneumothorax and meteorological parameters, including air pollutants. Methods: This is a retrospective study using the medical records of 379 patients who were admitted for spontaneous pneumothorax (SP) over a period of 4 years. Meteorological and air pollution data were obtained from the National Meteorological Office and the Ministry of Environment. We employed a case-crossover design to evaluate the short-term association between SP and meteorological factors including air pollutants. Conditional logistic regression was used to analyze bi-directional matched data. Results: Increase of relative humidity (RH) and of carbon monoxide (CO) were associated with the risk of pneumothorax, with odds ratio (OR) for RH = 1.18 (1.02–1.36), CO = 1.23 (1.02–1.48). Moreover, as air pressure (AP) decreased, risk of pneumothorax increased, with OR = 1.30 (1.05–1.59) but others did not. In the stratified analysis, the effect of RH was positive in ex-smokers (OR = 3.31) and non-smokers (OR = 1.32), but negative in current smokers (OR = 0.72). The effect of AP was significant in younger patients (OR = 1.33), males (OR = 1.40), and non-smokers (OR = 1.36). CO was related only with non-smokers (OR = 1.35) Conclusion: The triggering factors for spontaneous pneumothorax were relative humidity, carbon monoxide, and air pressure. The effect of the trigger was prominent in patients who were younger (