The risk of secondary spontaneous pneumothorax in patients with chronic obstructive pulmonary disease in Taiwan

Introduction: Secondary spontaneous pneumothorax (SSP) is often linked to chronic obstructive pulmonary disease (COPD). The frequency of SSP occurrence in COPD patients varies among different research findings. SSPs are more commonly found in the elderly population diagnosed with COPD. Previous studies have reported a pneumothorax rate of 26 per 100,000 COPD patients. There is, however, a notable lack of detailed epidemiological information regarding SSP in Asia. Our study focused on determining the occurrence rate of SSP among COPD patients in Taiwan using an extensive national database. Additionally, this study aimed to identify comorbidities associated with SSP in this patient group. Methods: In this study, we used the Longitudinal Health Insurance Database, which contains records of 2 million people who were randomly chosen from among the beneficiaries of the Taiwan National Health Insurance program. The dataset includes information from 2005 to the end of 2017. Our focus was on individuals diagnosed with COPD, identified through ICD-9-CM codes in at least one hospital admission or two outpatient services, with the COPD diagnosis date as the index date. The exclusion criteria included individuals younger than 40 years, those with incomplete records, or those with a previous diagnosis of pneumothorax before the index date. We conducted a matched comparison by pairing COPD patients with control subjects of similar age, sex, and comorbidities using propensity score matching. The follow-up for all participants started from their index date and continued until they developed pneumothorax, reached the study's end, withdrew from the insurance program, or passed away. The primary objective was to evaluate and compare the incidence of pneumothorax between COPD patients and matched controls. Results: We enrolled 65,063 patients who were diagnosed with COPD. Their mean age (+/- SD) was 66.28 (+/- 12.99) years, and approximately 60 % were male. During the follow-up period, pneumothorax occurred in 607 patients, equivalent to 9.3 % of the cohort. The incidence rate of SSP in COPD patients was 12.10 per 10,000 person-years, whereas it was 6.68 per 10,000 person-years in those without COPD. Furthermore, COPD patients with comorbidities such as atrial fibrillation, congestive heart failure, coronary artery disease, diabetes mellitus, hypertension, and cancer exhibited an increased incidence of SSP compared to COPD patients without such comorbidities. This was observed after conducting a multivariable Cox regression analysis adjusted for age, sex, and other comorbidities. Conclusion: Our study revealed an elevated risk of SSP in patients with COPD. It has also been suggested that COPD patients with comorbidities, such as atrial fibrillation, congestive heart failure, coronary artery disease, diabetes mellitus, hypertension, and cancer, have an increased risk of developing SSP.