Demographic information for all patients and for those with full lung function tests stratified by degree of impairment of FEV1
1-a Data are median with interquartile range in parentheses.
1-b The total number of patients with co-morbidity is shown (see text for details).
1-150 p = 0.02,
1-160 p = 0.0035,
1-165 p<0.0005 compared with other groups.