Risk factors and age-specific monthly patterns of primary spontaneous pneumothorax: a multicenter study.

Background: Primary spontaneous pneumothorax (PSP) is characterized by sudden lung collapse without external injury or underlying lung disease. However, detailed research on its causes and recurrence patterns is lacking, prompting investigating monthly epidemiology and factors influencing recurrence. Therefore, we aimed to assess the monthly trends in PSP occurrence and identify factors contributing to its recurrence, with a focus on teenagers due to the high incidence rates in this population, while also examining risk factors across other age groups. Methods: We conducted a multicenter retrospective study involving 4,231 cases of PSP from five hospitals in Korea. Patients aged 10-39 years were included, wherein monthly incidence patterns were assessed. Statistical analyses using physical parameters and laboratory data were performed to determine factors influencing recurrence. Results: Our analysis revealed that July was the most common diagnosis month in teenagers, followed by October and March. This month-based pattern differed from that observed in the other age groups. Multivariate analysis revealed body mass index (BMI) at initial diagnosis to be a significant risk factor for first recurrence in male patients aged 16-19 years [hazard ratio (HR), 0.98; 95% confidence interval (CI): 0.97-0.99; P=0.001] and in male patients older than 20 years (HR, 0.99; 95% CI: 0.98-0.99; P<0.001). In male patients aged ≥20 years, the monocyte-lymphocyte ratio (MLR) at initial diagnosis was also a significant factor for first recurrence (HR, 1.20; 95% CI: 1.10-1.32; P<0.001). In female patients aged ≥20 years, MLR at the time of the first pneumothorax was significantly associated with recurrence (HR, 1.41; 95% CI: 1.07-1.87; P=0.01). Conclusions: Our study provided valuable insights into the month-based epidemiology of PSP in Korea, highlighting differences in incidence patterns among teenagers compared with those in the other age groups. Moreover, the reported link between BMI, inflammation, and pneumothorax recurrence might be a basis for future prospective studies aimed to prevent and treat pneumothorax.