text: Dyspnea regressed on spirometry disease group, after removing contri- 
  butions from subject-speciﬁc factors in Table 4 (12.4% of variability 
  explained). Boldface indicates statitistical signiﬁcance. NA ¼ not appli- 
  cable; PRISm ¼ preserved ratio impaired spirometry. 
  aNormal spirometry group is the reference category. 