Conflict of interest: H. Reddel reports grants and personal fees for data monitoring committee and advisory board work, providing independent medical education, and consultancy from AstraZeneca, grants, personal fees for data monitoring committee and advisory board work, providing independent medical education, and consultancy, and non-financial support (study medication) from GlaxoSmithKline, personal fees for data monitoring committee work from Merck, grants and personal fees for data monitoring committee and advisory board work, and providing independent medical education from Novartis, personal fees for providing independent medical education from Teva and Mundipharma, personal fees for providing independent medical education and advisory board work from Boehringer Ingelheim, personal fees for advisory board work from Sanofi-Genzyme, outside the submitted work; and is Chair of the GINA Scientific Committee.