Table 1

Baseline characteristics by use of hormonal contraceptives in reproductive-age (16–45 years) women with asthma and mean number of severe asthma exacerbations

Background characteristicFrequency
(n=83 084)
n (%)
Used any hormonal contraceptives (n=28 575, 34%)
% (95% CI)*
Used combined hormonal contraceptives (n=20 629, 25%)
% (95% CI)*
Used progesterone-only hormonal contraceptives (n=7946, 9%)
% (95% CI)*
Severe asthma exacerbations at baseline (n=8024, 10%)
% (95% CI)*
Age (years)
 16–2024 504 (29.5)42.6 (41.9 to 43.2)35.3 (34.7 to 35.9)7.2 (6.9 to 7.5)8.3 (8.0 to 8.7)
 21–2511 754 (14.1)47.4 (46.5 to 48.3)36.7 (35.8 to 37.6)10.7 (10.2 to 11.3)9.1 (8.6 to 9.6)
 26–3013 870 (16.7)38.5 (37.7 to 39.3)26.9 (26.2 to 27.7)11.5 (11.0 to 12.1)10.0 (9.5 to 10.5)
 31–3514 985 (18.0)28.0 (27.3 to 28.7)16.7 (16.1 to 17.3)11.3 (10.8 to 11.8)10.3 (9.8 to 10.8)
 36–4012 456 (15.0)18.8 (18.2 to 19.5)9.3 (8.8 to 9.8)9.6 (9.1 to 10.1)10.6 (10.0 to 11.1)
 41–455515 (6.6)12.5 (11.7 to 13.4)4.7 (4.2 to 5.3)7.8 (7.1 to 8.6)12.1 (11.2 to 13.0)
Smoking status
 Non-smokers39 982 (48.1)34.6 (34.1 to 35.1)26.2 (25.7 to 26.6)8.4 (8.1 to 8.7)8.0 (7.8 to 8.3)
 Ever smokers43 102 (51.9)34.2 (33.7 to 34.6)23.6 (23.2 to 24.0)10.6 (10.3 to 10.9)11.1 (10.9 to 11.4)
Body mass index (kg/m2)
 <2540 018 (48.2)37.8 (37.3 to 38.3)29.9 (29.5 to 30.3)7.9 (7.6 to 8.1)8.0 (7.7 to 8.3)
 25–29.921 555 (25,9)35.1 (34.4 to 35.7)25.5 (24.9 to 26.0)9.6 (9.2 to 10.0)9.5 (9.2 to 10.0)
 ≥3021 511 (25,9)27.4 (26.8 to 28.0)14.7 (14.2 to 15.2)12.7 (12.2 to 13.1)12.8 (12.4 to 13.3)
Gravidity
 050 772 (61.1)34.9 (34.5 to 35.3)27.7 (27.3 to 28.1)7.2 (7.0 to 7.4)8.7 (8.4 to 8.9)
 115 319 (18.4)36.5 (35.7 to 37.2)24.7 (24.0 to 25.4)11.8 (11.3 to 12.3)10.1 (9.6 to 10.6)
 29560 (11.5)33.2 (32.2 to 34.1)18.7 (18.0 to 19.5)14.4 (13.7 to 15.2)11.3 (10.7 to 12.0)
 3+7433 (9.0)28.2 (27.2 to 29.2)13.5 (12.8 to 14.3)14.7 (13.9 to 15.5)13.1 (12.4 to 13.9)
Any gynaecological condition†
 No62 729 (75.5)34.0 (33.7 to 34.4)25.5 (25.1 to 25.8)8.5 (8.3 to 8.8)8.6 (8.4 to 8.9)
 Yes20 355 (24.5)35.5 (34.8 to 36.1)22.8 (22.2 to 23.4)12.7 (12.2 to 13.1)12.7 (12.3 to 13.2)
Charlson Comorbidity Index
 078.749 (94.8)34.8 (34.5 to 35.1)25.3 (25.0 to 25.6)9.4 (9.3 to 9.7)9.3 (9.1 to 9.5)
 14335 (5.2)26.8 (25.5 to 28.2)15.8 (14.7 to 16.9)11.0 (10.1 to 12.0)15.7 (14.6 to 16.8)
Index of Multiple Deprivation quintiles
 First quintile (least deprived)16 968 (20.4)28.8 (28.1 to 29.5)21.0 (20.4 to 21.6)7.7 (7.3 to 8.1)9.1 (8.7 to 9.6)
 Second quintile15 732 (18.9)34.0 (33.2 to 34.7)24.7 (24.1 to 25.4)9.2 (8.8 to 9.7)10.6 (10.2 to 11.1)
 Third quintile16 554 (19.9)36.6 (35.9 to 37.4)26.2 (25.5 to 26.9)10.4 (9.9 to 10.9)9.0 (8.6 to 9.5)
 Fourth quintile17 004 (20.5)35.2 (34.5 to 35.9)25.3 (24.6 to 26.0)9.9 (9.5 to 10.4)10.5 (10.1 to 11.0)
 Fifth quintile (most deprived)16 826 (20.2)37.4 (36.7 to 38.1)26.8 (26.2 to 27.5)10.5 (10.1 to 11.0)9.0 (8.6 to 9.4)
  • *Difference between groups of background variables were statistically significant (p<0.001).

  • †Defined as having any of the following conditions: endometriosis, polycystic ovary syndrome, menorrhagia, acne, metrorrhagia, bilateral salpingo-oophorectomy (BSO), hysterectomy BSO, hysterectomy, fibroids and menometrorrhagia.