Table 1—

Characteristics of cases and noncases from the population at risk

	Onset asthma			Incident asthma
	Cases	Noncases	p-value	Cases	Noncases	p-value
Total n	116	3708		58	3766
Males n	41	1739		18	1762
Females n	75	1969	0.01^¶	40	2004	0.02
BMI mean kg·m²	25.4	24.7	0.06⁺	25.3	24.7	0.26⁺
Age in 1999 mean yrs	39.4	39.7	0.61⁺	39.7	39.7	0.97⁺
Smoking % never/former/current	46/29/25	51/25/24	0.50^§	41/32/27	51/25/24	0.32^§
Hay fever %	48.7	18.6	<0.00^§	40.4	19.2	<0.00^§
Water/mould^# %	24.3	23.2	0.74^§	20.7	23.3	0.76^§

The table includes those who received a modelled value of nitrogen dioxide and could be classified as cases or noncases according to the definition of onset and incident asthma. BMI: body mass index. ^#: water damage or mould in the home at any time during the last 8 yrs; ^¶: Pearson’s Chi-squared test comparing the proportional difference of males and females among cases; ⁺: unpaired t-test comparing cases with asthma with those without asthma; ^§: Pearson’s Chi-squared test comparing cases with asthma with those without asthma.