Differences in spirometry and peak flow and odds ratios for eNO, in 2007 and 2008 relative to 2006, adjusted for change in the control zone (n = 380).

aBaseline models adjusted for: age; age2; height; gender; gender*age; gender*age2; gender*height. bAll adjusted models additionally adjusted for: diagnosed asthma at baseline; smoking; gas cooker or oven; unflued gas heating; ETS; education and employment status. cBaseline models adjusted for: age, gender, gender*age. dPEF recorded three times twice daily at morning and evening. eAdjusted for age and gender.