Association between physical activity and imaging biomarker in asthma: An analysis of distributional differences.

<bold>Introduction:</bold> We previously examined physical activity (PA) levels in asthmatic patients and found that those who remained active had better asthma control and preserved respiratory function (Iwamoto et al. JACI in practice, 2023). However, the pathophysiology remains unclear. We aimed to explore the association between PA and chest CT-based imaging in asthmatics. <bold>Methods:</bold> Two groups (cohort 1 and 2) with different enrolment periods were included. We analyzed Parametric Response Mapping (PRM) using inspiratory and expiratory chest CT. This allows the lungs to be classified as normal, emphysema, and functional peripheral airway disease (fSAD). They fitted a physical activity meter for 2 weeks. We examined the relationship between PA and PRM analysis. <bold>Results:</bold> In cohort 1, asthmatics (n=31) were significantly less active than healthy (n=13) at > 2, 3, and 4 METs. Particularly, lower normal, higher emphysema, and higher fSAD in asthmatics were significantly associated with lower PA at high intensity (>4 METs). In cohort 2, asthmatics (n=90) were also significantly less active than healthy (n=43) (>2, 3, and 4 METs: p <0.01, respectively). Similarly, lower normal, higher emphysema, and higher fSAD in asthmatics were significantly associated with lower PA at >4 METs (p<0.001, p<0.01, p<0.05, respectively). When adjusted for age and BMI, the results remained significant except for emphysema. Interestingly, when each lung lobe was examined, the correlation between PA and fSAD was strongest in the left upper lobe (r=0.28; p<0.01). <bold>Conclusion:</bold> In asthmatic patients, fSAD is associated with high-intensity PA. Furthermore, anatomical differences in their distributions are relevant.