Table 6. Association of total caffeine consumption (mg) with potential confounders.

	N	Time
		18 week			47 month			145 month
		Beta	SE	P-Value	Beta	SE	P-Value	Beta	SE	P-Value
Year of Birth	7346–4320	0.780	0.352	2.70×10−02	−2.63	0.426	7.27×10−10	−0.538	0.502	2.83×10−01
Housing Tenure	6951–4134	26.60	2.497	2.71×10−26	19.33	3.207	1.78×10−09	16.51	4.090	5.53×10−05
Crowding Index	7063–4194	29.59	4.360	1.26×10−11	20.19	5.717	4.15×10−04	14.45	6.737	3.20×10−02
Educational Level	6637–4117	−14.97	1.430	1.83×10−25	−3.026	1.725	8.00×10−02	−6.54	1.988	1.00×10−03
Alcohol Consumption	7334–4244	3.958	0.461	1.18×10−17	2.673	0.571	2.94×10−06	1.180	0.681	8.30×10−02
Tobacco Consumption	7331–4267	7.908	0.315	4.13×10−133	6.870	0.422	2.48×10−58	6.317	0.542	6.74×10−31

Housing tenure was coded as: bought/mortgaged/owned with no mortgage to pay, rented from private landlord, rented from council/housing association. Crowding index was coded as number of people living in household divided by the number of rooms. Highest educational level was coded as the equivalent of: none, vocational, school to age 16, school to age 18, degree or higher. Alcohol consumption was measured in drinks per week. Tobacco consumption was measured in times per day. Linearity was imposed on the categorical variables (housing tenure, educational level). Measures of alcohol and tobacco consumption shown were taken at 18 weeks gestation, but results were similar at the other time points.