Table 2

Crude and adjusted rate ratios of invasive meningococcal disease for parental smoking and socioeconomic circumstances

		Crude RR				Adjusted RR^2-150
		RR	95% CI			RR	95% CI
Parental smoking
Mother (Yes vNo)	4.89	2.29–10.5		3.52	1.42–8.68
Father (YesvNo)	3.73	1.95–7.15		3.21	1.49–6.94
None	1.0			1.0
Mother only	2.01	0.54–7.43		1.00	0.21–4.79
Father only	1.57	0.70–3.53		1.47	0.55–3.95
Both parents	8.79	3.42–22.6		8.23	2.30–29.3
Smoking at home
Per 20 cigarettes a day	3.48	1.89–6.42		2.65	1.31–5.35
Mother's education
Primary	1.0			1.0
Apprenticeship	0.23	0.07–0.72		0.50	0.11–2.30
Secondary	0.12	0.03–0.42		0.45	0.08–2.70
University	0.08	0.01–0.45		0.25	0.03–2.23
		p trend <0.001			p trend 0.287
Father's education
Primary	1.0			1.0
Apprenticeship	0.43	0.14–1.36		0.40	0.08–2.03
Secondary	0.33	0.10–1.14		0.58	0.09–3.59
University	0.30	0.06–1.58		0.52	0.05–5.53
		p trend 0.099			p trend 0.987
Car ownership
Yes	0.44	0.22–0.85		0.49	0.19–1.24
Weekend house
Yes	0.23	0.07–0.83		0.28	0.04–1.80
Crowding
>1 person per room	2.18	1.12–4.25		1.13	0.44–2.88
No. of siblings
None	1.0			1.0
1	1.25	0.49–3.16		1.20	0.41–3.34
2	3.21	0.79–13.1		1.18	0.31–4.51
3+	3.67	0.40–33.3		0.80	0.10–6.17
		p trend 0.087			p trend 0.968
Spending weekends out of town
<1 day a month	1.0			1.0
1–5 days a month	0.43	0.15–1.21		0.94	0.20–4.32
>5 days a month	0.18	0.05–0.57		0.41	0.10–1.74
		p trend 0.004			p trend 0.166
Heating
Central	1.0			1.0
Gas	0.71	0.27–1.90		0.43	0.11–1.75
Coal	3.10	0.91–10.6		1.26	0.20–7.92
Cooking
Gas	1.0			1.0
Electricity	0.30	0.06–1.43		0.60	0.10–3.74
Coal	1.79	0.25–12.9		1.69	0.03–98.4

↵2-150 Each variable was adjusted for smoking, mother's and father's education, ownership of car and cottage, and crowding. Only one indicator of smoking was included in each model. Non-smoking variables were adjusted for categorical measure of parental smoking (none, mother only, father only, both).