TABLE 1

Characteristics of the study population and baseline medication use by number of short-acting β2-agonist (SABA) canisters (n=59 533)

CovariatesNumber of SABA canistersTotalp-value#
01–23–5≥6
Subjects n33 33217 7365332313359 533
Participant factors
 Sex n (%)
  Female21 898 (65.7)12 561 (70.8)3645 (68.4)1982 (63.3)40 086 (67.3)<0.001
  Male11 434 (34.3)5175 (29.2)1687 (31.6)1151 (36.7)19 447 (32.7)
 Age at index date years
  Mean±sd69.80±6.1269.55±5.8269.38±6.0869.35±6.2669.67±6.04<0.001
  Median (IQR)67.00 (65.00–73.00)67.00 (65.00–72.00)66.00 (65.00–72.00)66.00 (65.00–72.00)67.00 (65.00–72.00)<0.001
 Age group at index
 date years, n (%)
  65–6921 254 (63.8)11 551 (65.1)3536 (66.3)2080 (66.4)38 421 (64.5)<0.001
  70–745533 (16.6)3044 (17.2)841 (15.8)476 (15.2)9894 (16.6)
  75–793415 (10.2)1727 (9.7)498 (9.3)300 (9.6)5940 (10.0)
  80–893130 (9.4)1414 (8.0)457 (8.6)277 (8.8)5278 (8.9)
 Age at asthma
 prevalence
 years
  Mean±sd59.73±9.7459.40±9.5959.98±10.4759.62±10.8559.64±9.83<0.001
  Median (IQR)59.00 (52.00–66.00)59.00 (52.00–66.00)60.00 (51.00–67.00)59.00 (50.00–67.00)59.00 (52.00–66.00)0.004
 Years of asthma at index
 date
  Mean±sd10.03±6.6110.12±6.859.32±7.079.60±7.099.97±6.76<0.001
  Median (IQR)10.63 (4.14–15.16)10.68 (3.65–15.53)9.78 (1.72–14.99)10.19 (2.25–14.95)10.57 (3.68–15.23)<0.001
Baseline asthma medication use, n (%)
 No asthma medication20 672 (62.0)0 (0.0)0 (0.0)0 (0.0)20 672 (34.7)<0.001
 ICS only or ICS-LABA11 653 (35.0)3988 (22.5)1742 (32.7)1134 (36.2)18 517 (31.1)
 SABA only0 (0.0)6292 (35.5)1100 (20.6)491 (15.7)7883 (13.2)
 Other asthma
 medication
1007 (3.0)7456 (42.0)2490 (46.7)1508 (48.1)12 461 (20.9)
Socio-demographic factors
 Neighbourhood income
 quintile, n (%)
  1 (lowest)5639 (16.9)2972 (16.8)1051 (19.7)704 (22.5)10 366 (17.4)<0.001
  26648 (19.9)3562 (20.1)1133 (21.2)726 (23.2)12 069 (20.3)
  36445 (19.3)3563 (20.1)1073 (20.1)642 (20.5)11 723 (19.7)
  46911 (20.7)3763 (21.2)1048 (19.7)522 (16.7)12 244 (20.6)
  5 (highest)7604 (22.8)3843 (21.7)1010 (18.9)527 (16.8)12 984 (21.8)
  Missing85 (0.3)33 (0.2)17 (0.3)12 (0.4)147 (0.2)
Ontario Marginalization Indices (lowest quintile is the least marginalised)
 Deprivation quintile,
 n (%)
  1 (least)6953 (20.9)3735 (21.1)1000 (18.8)516 (16.5)12 204 (20.5)<0.001
  26752 (20.3)3517 (19.8)978 (18.3)505 (16.1)11 752 (19.7)
  36606 (19.8)3506 (19.8)989 (18.5)616 (19.7)11 717 (19.7)
  46652 (20.0)3532 (19.9)1190 (22.3)710 (22.7)12 084 (20.3)
  5 (most)6185 (18.6)3354 (18.9)1135 (21.3)766 (24.4)11 440 (19.2)
  Missing184 (0.6)92 (0.5)40 (0.8)20 (0.6)336 (0.6)
 Dependency quintile,
 n (%)
  1 (least)5449 (16.3)3186 (18.0)1044 (19.6)678 (21.6)10 357 (17.4)<0.001
  25981 (17.9)3322 (18.7)1040 (19.5)620 (19.8)10 963 (18.4)
  36142 (18.4)3236 (18.2)971 (18.2)611 (19.5)10 960 (18.4)
  46528 (19.6)3326 (18.8)937 (17.6)512 (16.3)11 303 (19.0)
  5 (most)9048 (27.1)4574 (25.8)1300 (24.4)692 (22.1)15 614 (26.2)
  Missing184 (0.6)92 (0.5)40 (0.8)20 (0.6)336 (0.6)
 Ethnic concentration
 quintile, n (%)
  1 (least)5161 (15.5)2846 (16.0)830 (15.6)461 (14.7)9298 (15.6)<0.001
  25325 (16.0)2928 (16.5)856 (16.1)418 (13.3)9527 (16.0)
  36005 (18.0)3135 (17.7)848 (15.9)455 (14.5)10 443 (17.5)
  47207 (21.6)3567 (20.1)960 (18.0)560 (17.9)12 294 (20.7)
  5 (most)9450 (28.4)5168 (29.1)1798 (33.7)1219 (38.9)17 635 (29.6)
  Missing184 (0.6)92 (0.5)40 (0.8)20 (0.6)336 (0.6)
 Instability quintile, n (%)
  1 (least)6470 (19.4)3689 (20.8)1129 (21.2)712 (22.7)12 000 (20.2)<0.001
  26539 (19.6)3512 (19.8)949 (17.8)516 (16.5)11 516 (19.3)
  36224 (18.7)3264 (18.4)975 (18.3)560 (17.9)11 023 (18.5)
  46045 (18.1)3188 (18.0)1017 (19.1)535 (17.1)10 785 (18.1)
  5 (most)7870 (23.6)3991 (22.5)1222 (22.9)790 (25.2)13 873 (23.3)
  Missing184 (0.6)92 (0.5)40 (0.8)20 (0.6)336 (0.6)
 Rural residence, n (%)3046 (9.1)1738 (9.8)545 (10.2)307 (9.8)5636 (9.5)0.015
 Follow-up years
  Mean±sd8.82±3.258.82±3.179.07±3.359.01±3.588.85±3.25<0.001
  Median (IQR)8.50 (6.41–11.59)8.47 (6.41–11.55)8.75 (6.65–12.17)8.81 (6.56–12.34)8.53 (6.43–11.66)<0.001
 Number of comorbidities,
 n (%)
  07732 (23.2)4029 (22.7)1206 (22.6)626 (20.0)13 593 (22.8)0.001
  112 762 (38.3)6940 (39.1)2053 (38.5)1240 (39.6)22 995 (38.6)
  28260 (24.8)4407 (24.8)1396 (26.2)831 (26.5)14 894 (25.0)
  ≥34578 (13.7)2360 (13.3)677 (12.7)436 (13.9)8051 (13.5)
Outcomes
 Deaths, n (%)4487 (13.5)1942 (10.9)703 (13.2)552 (17.6)7684 (12.9)<0.001
 Severe asthma
exacerbation, n (%)
446 (1.3)642 (3.6)343 (6.4)295 (9.4)1726 (2.9)<0.001

SABA: short-acting β2-agonist; IQR: interquartile range; ICS: inhaled corticosteroid; ICS-LABA: ICS long-acting β2-agonist. #: p-values were calculated using Chi-squared statistics for categorical variables and ANOVA for numerical variables.