TABLE 1

Characteristics of the study population by asthma diagnosis (N=1 174 424)

CharacteristicAsthma cases#Nonasthma controls#Standardised difference
Age group at baseline years
 5–9115 189 (19.6%)115 189 (19.6%)0.000
 10–14147 737 (25.2%)147 737 (25.2%)0.000
 15–19171 356 (29.2%)171 356 (29.2%)0.000
 20–24152 930 (26.0%)152 930 (26.0%)0.000
Sex
 Female243 969 (41.5%)243 969 (41.5%)0.000
 Male343 243 (58.5%)343 243 (58.5%)0.000
Asthma duration years mean±sd11.6±6.0
Ontario Marginalization Index
 Deprivation quintile
  1, lowest133 636 (22.8%)131 345 (22.4%)0.009
  2128 432 (21.9%)126 630 (21.6%)0.007
  3111 763 (19.0%)111 344 (19.0%)0.002
  4101 696 (17.3%)103 949 (17.7%)0.010
  5, highest111 685 (19.0%)113 944 (19.4%)0.010
 Dependency quintile
  1, lowest194 920 (33.2%)192 883 (32.8%)0.007
  2129 077 (22.0%)128 180 (21.8%)0.004
  3100 243 (17.1%)100 692 (17.1%)0.002
  488 636 (15.1%)89 773 (15.3%)0.005
  5, highest74 336 (12.7%)75 684 (12.9%)0.007
 Ethnic Concentration Quintile
  1, lowest66 831 (11.4%)68 204 (11.6%)0.007
  283 814 (14.3%)81 572 (13.9%)0.011
  3101 785 (17.3%)97 088 (16.5%)0.021
  4132 846 (22.6%)127 439 (21.7%)0.022
  5, highest201 936 (34.4%)212 909 (36.3%)0.039
 Residential Instability Quintile
  1, lowest172 074 (29.3%)162 727 (27.7%)0.035
  2117 815 (20.1%)115 345 (19.6%)0.011
  3101 220 (17.2%)101 141 (17.2%)0.000
  498 530 (16.8%)97 822 (16.7%)0.003
  5, highest97 573 (16.6%)110 177 (18.8%)0.056
Rurality
 Urban545 302 (92.9%)539 000 (91.8%)0.040
 Rural41 910 (7.1%)48 212 (8.2%)0.040
Presence of common infections and allergic conditions
 Bronchitis30 447 (5.2%)17 859 (3.0%)0.108
 Influenza8217 (1.4%)5835 (1.0%)0.037
 Pneumonia8564 (1.5%)4542 (0.8%)0.065
 Allergic rhinitis30 684 (5.2%)17 525 (3.0%)0.113
 Eczema41 825 (7.1%)30 477 (5.2%)0.080
 Tonsillitis and adenoiditis21 561 (3.7%)15 831 (2.7%)0.056
 Ear infection39 570 (6.7%)28 824 (4.9%)0.078
 Appendicitis1837 (0.3%)1482 (0.3%)0.011
Presence of any complex chronic condition
 Yes1465 (0.2%)924 (0.2%)0.020
 No585 747 (99.8%)586 288 (99.8%)0.020

#: n=587 212; : standardised difference >0.1 generally considered different (shown in bold).