Table 1 Characteristics of the random sample and asthma cohort in a longitudinal study of respiratory disability
VariableRandom sampleAsthma cohort
Respiratory work disabilityRespiratory work disability
NoYesNoYes
No65887174138
Mean (SD) age (years)43.5 (6.8)41.6 (6.6)42.9 (6.9)43.0 (6.9)
Mean (SD) BMI (kg/m2)25.5 (4.4)25.9 (3.8)25.6 (5.0)25.3 (3.4)
Females, n (%)3327 (50.5)34 (47.9)385 (52.0)26 (68.4)
Smoking at baseline, n (%)
    Never smokers2835 (43.0)34 (47.9)374 (50.5)19 (51.3)
    Former smokers1441 (21.9)14 (19.7)151 (20.4)11 (29.0)
    Current smokers2312 (35.1)23 (32.4)216 (29.2)8 (21.1)
Passive smoking, n (%)1892 (28.7)20 (28.2)196 (26.5)13 (34.2)
Atopy, n (%)*1570 (28.3)20 (37.7)413 (65.9)19 (61.3)
Mean (SD) FEV1 (% predicted)†106.4 (13.3)102.2 (14.9)99.2 (15.5)96.8 (16.6)
Mean (SD) symptom score at baseline0.48 (0.94)1.24 (1.53)2.16 (1.66)2.55 (1.66)
Physician-diagnosed asthma, n (%)382 (5.8)12 (16.9)741 (100)38 (100)
Rhinitis, n (%)1598 (24.3)25 (35.2)473 (63.8)27 (71.1)
  • *n = 5603 (random sample), n = 658 (asthma cohort). †n = 6084 (random sample), n = 709 (asthma cohort).

  • BMI, body mass index; FEV1, forced expiratory volume in 1 s.