Table 3.

Hazard ratios of attention-deficit/hyperactivity disorder according to maternal and paternal asthma exacerbations

Parental asthma exacerbations	Offspring ADHD (n)	N	Person- years at risk	Crude HR	Adjusted HR (95% CI)
Asthmatic mothers
No exacerbations	2,520	69,746	731,491	1 (ref)	1 (ref)
Timing at exacerbations
Exacerbations before pregnancy	341	7,573	82.719	1.16 (1.04 – 1.30)	1.12 (1.00 – 1.25)
Exacerbations during pregnancy	106	2,103	23,158	1.28 (1.05 – 1.55)	1.21 (1.00 – 1.47)
During early pregnancy	49	891	9,758	1.41 (1.06 – 1.87)	1.31 (0.99 – 1.74)
During late pregnancy	57	1,212	13,400	1.18 (0.91 – 1.54)	1.13 (0.87 – 1.47)
Exacerbations after delivery	194	3,844	43,034	1.25 (1.08 – 1.45)	1.25 (1.08 – 1.44)
Number of exacerbations before, during pregnancy and after delivery
One	331	7,176	78,830	1.18 (1.05–1.32)	1.18 (1.05 – 1.32)
Two	123	2,796	30,631	1.13 (0.94–1.35)	1.12 (0.94 – 1.35)
Three	71	1,407	15,169	1.33 (1.05–1.69)	1.35 (1.07 – 1.71)
≥four	116	2,141	24,281	1.31 (1.09–1.58)	1.28 (1.07 – 1.55)
Asthmatic fathers
No exacerbations	1,418	53,043	554,163	1 (ref)	1 (ref)
Exacerbations before pregnancy	182	5,765	63,433	1.08 (0.92 – 1.26)	1.07 (0.92 – 1.25)
Exacerbations during pregnancy	172	4,864	53,904	1.19 (1.02 – 1.40)	1.17 (1.00 – 1.37)
Exacerbations after delivery	129	3,492	39,849	1.18 (0.99 – 1.42)	1.18 (0.98 – 1.41)

Abbrevations: HR, hazard ratio; CI, confidence interval.

Adjusted for maternal age at delivery, parity, maternal smoking during pregnancy, maternal mental disorders before pregnancy, maternal cohabiting status, place of residence at delivery, low social class at delivery, large family size, sex of the child, and calendar year of birth. Maternal asthma exacerbations and paternal asthma exacerbations were mutually adjusted in the models.