Table 2.

IRR and 95% CIs for primary and secondary outcomes

Outcome and cohort	Events	Person-time, years	Crude IRR (95% CI)^a	Adjusted IRR (95% CI)^b
Asthma hospital admissions
Active asthma	9904	54 179	Reference	Reference
Resolved asthma	1472	31 965	0.28 (0.26 to 0.31)	0.29 (0.27 to 0.32)

URTI hospital admissions
Non-asthma	63	42 969	Reference	Reference
Active asthma	138	56 741	1.65 (1.19 to 2.30)	0.92 (0.62 to 1.37)
Resolved asthma	63	31 965	1.36 (0.92 to 1.99)	0.89 (0.55 to 1.44)

LRTI hospital admissions
Non-asthma	66	42 969	Reference	Reference
Active asthma	410	56 741	4.52 (3.37 to 6.05)	3.04 (2.22 to 4.18)
Resolved asthma	82	31 965	1.82 (1.22 to 2.72)	1.30 (0.87 to 1.95)

Flu or pneumonia hospital
admission
Non-asthma	123	42 969	Reference	Reference
Active asthma	443	56 741	2.70 (2.13 to 3.41)	1.80 (1.40 to 2.31)
Resolved asthma	122	31 965	1.39 (1.02 to 1.90)	1.08 (0.78 to 1.50)

GP asthma exacerbation consultations
Active asthma	3816	56 741	Reference	Reference
Resolved asthma	108	31 965	0.05 (0.04 to 0.07)	0.05 (0.04 to 0.07)

GP LRTI consultations
Non-asthma	804	42 969	Reference	Reference
Active asthma	6985	56 741	6.19 (5.68 to 6.74)	5.27 (4.79 to 5.78)
Resolved asthma	1489	31 965	2.87 (2.57 to 3.19)	2.34 (2.08 to 2.64)

GP all-cause antibiotic prescriptions
Non-asthma	17 285	42 969	Reference	Reference
Active asthma	63 222	56 741	2.64 (2.54 to 2.73)	2.08 (1.99 to 2.17)
Resolved asthma	20 543	31 965	1.83 (1.75 to 1.91)	1.37 (1.30 to 1.44)

↵a Unadjusted models matched on age and sex with the practice included as a random effect to account for clustering.
↵b Models adjusted for age, sex, Index of Multiple Deprivation, Charlson score, and smoking status (imputed where missing), with the practice included as a random effect. CI = confidence interval. IRR = incidence rate ratio. LRTI = lower respiratory tract infection. URTI = upper respiratory tract infection.