Asthma in Competitive Cross-Country Skiers: A Systematic Review and Meta-analysis.

"Conflicts of interest Mr Mäki-Heikkilä declares receiving financial support from Tampere Tuberculosis Foundation and Tampere University to author this publication. Dr Karjalainen declares receiving grant from Tampere Tuberculosis Foundation, fees for consulting from Boehringer Ingelheim, Finnish Center for Integrity in Sports, GlaxoSmithKline, Merck Sharp & Dohme, Novartis and Teva and payments for lectures from ALK, AstraZeneca, Chiesi, Boehringer Ingelheim, GlaxoSmithKline, Leo Pharma, Mundipharma, Novartis and Orion Pharma. Dr Parkkari declares no conflicts of interest. Dr Valtonen declares employment for acting as team doctor for Finnish Ski Association via KIHU – Research Institute for Olympic Sports. Dr Lehtimäki declares having received fees for consulting from ALK, AstraZeneca, Boehringer Ingelheim, Chiesi, GSK, Orion Pharma, Mundipharma, Novartis, SanofiGenzyme and Teva, and payments for lectures from AstraZeneca, Boehringer Ingelheim, Chiesi, Circassia, GSK, Orion Pharma, Mundipharma, Novartis, SanofiGenzyme and Teva."

"Funding The study was supported by the Tampere Tuberculosis Foundation."

"This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines [] and was registered in the PROSPERO database (registration number CRD42017070940). PRD registration number: CRD42017070940."