Introduction:
Patients with pneumothorax frequently experience respiratory distress. High-intensity physical exertion and varying degrees of weakness can exacerbate respiratory difficulties, potentially precipitating pneumothorax. The aim of this study was to investigate the causal relationship between physical activity and frailty and pneumothorax using Two-Sample Mendelian randomization (TSMR).

Material and methods:
Using Mendelian randomization (MR) analyses, we examined the potential causal relationship between physical activity, frailty and the risk of pneumothorax. The study was analysed using five different methods, mainly using inverse variance weighted (IVW) to draw causal inferences. In addition, sensitivity analyses were used to assess potential horizontal pleiotropy and heterogeneity in the results, indicating the robustness of the results.

Results:
Our analyses found that light DIY reduced the risk of pneumothorax, but did not find a causal association between other levels of physical activity and pneumothorax. In addition, frailty index (FI) showed a positive association with the risk of developing spontaneous pneumothorax, and this causal relationship persisted after adjustment for body mass index (BMI) and light DIY. Sensitivity analyses further validate the robustness of our findings.

Conclusions:
Our findings support the ability of light DIY to reduce the risk of pneumothorax development. It also emphasises the need for frail individuals to be more aware of the need to protect against pneumothorax in their daily lives. We encourage appropriate exercise to improve fitness and reduce the risk of pneumothorax.