Table 2

Incidence and prognosis of asthma or wheeze by parental smoking

Reference	Age at start/end		Duration of follow up	Smoking exposure	Outcome	Cases	Non-cases	Odds ratio (95% CI)
Incidence studies:
9	0	3		Mother ⩾10 cigs/day	Wheeze	247	515	2.07 (1.34 to 3.19)
9	3	6		Mother ⩾10 cigs/day	Wheeze	112	403	1.59 (0.89 to 2.84)
9	0	6		Mother ⩾10 cigs/day	Wheeze	359	403	1.91 (1.28 to 2.86)2-150
4	0	6		Mother smoking	Asthma	141	891	0.88 (0.61 to 1.27)2-150
				Father smoking	Asthma	141	891	1.27 (0.89 to 1.81)
10	0	5		Mother in pregnancy	Wheeze	2616	9914	1.34 (1.22 to 1.45)2-150
6	1	10		Mother smoking at any age	Wheeze	1662	8016	1.11 (1.02 to 1.21)2-150
7	<5	?	12 years	Mother ⩾10 cigs/day	Asthma	86	653	1.68 (1.10 to 2.58)2-150
				Father ⩾ 10 cigs/day	Asthma	78	622	1.06 (0.67 to 1.69)
8	5–9	?	9 years	Mother smoking	Asthma	43	679	0.97 (0.51 to 1.84)2-150
				Father smoking	Asthma	43	679	0.91 (0.49 to 1.69)
12	0	7		Mother in pregnancy	Asthma or WB	1026	4583	1.25 (1.08 to 1.44)2-150
12	7	16		Mother in pregnancy	Asthma or WB	368	4215	0.99 (0.78 to 1.25)
				Mother at 16 y follow up	Asthma or WB	368	4215	1.14 (0.92 to 1.41)2-150
				Father at 16 y follow up	Asthma or WB	368	4215	1.10 (0.88 to 1.36)
Natural history studies:
15	<2	8		Either parent smoking	Persistent wheeze	26	33	1.45 (0.45 to 4.70)2-150
17	<2	5		Either parent smoking	Persistent wheeze	26	54	3.10 (1.08 to 8.91)2-150
18	<3	?	22–44 months	Household members smoke	Recent wheeze	18	22	11.80 (1.32 to 105)2-150
19	<3	?	4 years	Either parent smoking	Recent wheeze	22	45	0.80 (0.28 to 2.27)2-150
9	<3	6		Mother ⩾10 cigs/day	Recent wheeze	100	147	0.99 (0.53 to 1.86)2-150
10	<5	16		Mother in pregnancy	Wheeze past year	218	1259	0.86 (0.64 to 1.15)2-150
20	<7	11		Mother in pregnancy	As/WB past year	203	887	0.56 (0.40 to 0.78)2-150
20	<7	23		Mother in pregnancy	As/WB past year	101	989	0.70 (0.50 to 0.98)

↵2-150 Odds ratios used in meta-analyses (see text). WB=wheezy bronchitis.