Impact of Environmental and Seasonal Factors on Spontaneous Pneumomediastinum With and Without Pneumorrhachis.

Spontaneous pneumomediastinum (SPM) with pneumorrhachis is rare but generally benign and self-limiting. However, the impact of environmental and seasonal factors on SPM remains unclear. This study investigated their association with SPM onset and clinical outcomes. We conducted a 12-year retrospective review of SPM cases, comparing clinical characteristics and outcomes between patients with and without pneumorrhachis. A case-crossover design was used to assess short-term associations between environmental exposures and SPM incidence, analyzed via conditional logistic regression. A total of 70 consecutive patients were identified, with 9 classified as SPM with pneumorrhachis and 61 as SPM without pneumorrhachis. While both groups were predominantly managed with hospitalization, those with pneumorrhachis had longer hospital stays (median: 7 vs. 3 days, p = 0.002) and were more often associated with severe-grade SPM and identifiable triggers (p < 0.001 and p = 0.009, respectively). No significant environmental exposure differences were observed between groups. Seasonally, SPM incidence was significantly higher in autumn and winter (p < 0.001), consistent with elevated air pollutant levels. Linear regression showed that standardized β coefficients for PM_2.5 were higher in autumn and winter (β = 1.15 and β = 1.18), indicating a seasonal association between PM_2.5 and SPM onset. Despite experiencing more triggers and longer hospitalization, patients with pneumorrhachis had similarly favorable clinical courses. The seasonal clustering of SPM and its association with elevated PM_2.5 levels suggest that air pollution may be a contributing factor, warranting further investigation.