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. 2012 Nov 29;7(11):e48921. doi: 10.1371/journal.pone.0048921

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© 2012 Cowie et al

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.

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¹ Estimate derived from census of households within the study area. ^∧ Eligible cohort = 2007 cohort + additional households potentially eligible to be interviewed in 2008. ^∧∧ Subjects approached to participate in panel study. ^* Subjects who took part in spirometry and eNO measurement. ^** Subjects who took part in daily lung function and symptom diary. Blue arrow: Household and participant participation. Red arrow: Loss to follow-up.