Table 4.

Effect of heater type (unflued gas heater – flued gas heater) on lung function.^a

	FEV1 morning (L)					FEV1 evening (L)					PEF morning (L/min)					PEF evening (L/min)
Population	Unflued	Flued	Diff	95% CI	p-Value	Unflued	Flued	Diff	95% CI	p-Value	Unflued	Flued	Diff	95% CI	p-Value	Unflued	Flued	Diff	95% CI	p-Value
ITT analysisb	1.95	1.95	0.004	−0.009 to 0.017	0.55	1.96	1.96	0.000	−0.014 to 0.014	0.99	271	270	0.719	−1.239 to 2.677	0.47	279	278	0.994	−0.995 to 2.983	0.33
Per protocol: days with heater use ≥ 30%c	1.91	1.88	0.030	0.003 to 0.057	0.03	1.91	1.91	0.008	−0.021 to 0.037	0.59	269	268	0.832	−3.505 to 5.168	0.71	277	272	5.185	1.032 to 9.338	0.01
Asthma subgroup, ITT analysisd	1.84	1.84	0.001	−0.038 to 0.041	0.95	1.84	1.85	−0.017	−0.061 to 0.027	0.45	253	250	2.285	−4.954 to 9.524	0.54	260	253	7.130	0.578 to 13.682	0.03
Asthma subgroup, per-protocol analysise	1.84	1.79	0.056	−0.027 to 0.139	0.19	1.74	1.80	−0.059	−0.174 to 0.056	0.31	255	255	0.021	−11.637 to 11.679	1.00	260	251	8.910	−7.543 to 25.362	0.29

Diff, difference.

^aThe means and differences and the 95% CIs for the differences are derived from mixed model regression. Fixed effects were the heater type allocation, study period (first, second, or third pair of weeks), and day of the week. Schools and subjects within schools were both treated as random intercepts, and a variance components correlation structure was assumed.

^bAll observations were analyzed according to the heater type exposure to which they were assigned. There were 6,776 observations for FEV₁ morning and PEF morning and 6,504 observations for FEV₁ evening and PEF evening

^cThe analysis was limited to schools and days for which heater use was estimated as ≥ 30%. There were 1,249 observations for FEV₁ morning and PEF morning and 1,441 observations for FEV₁ evening and PEF evening.

^dAll observations in subjects with current asthma at baseline were analyzed according to the heater type exposure to which they were assigned. There were 982 observations for FEV₁ morning and PEF morning and 987 observations for FEV₁ evening and PEF evening.

^eThe analysis was limited to schools and days for which heater use was estimated as ≥ 30% in subjects with asthma. There were 169 observations for FEV₁ morning and PEF morning and 213 observations for FEV₁ evening and PEF evening.