Original article A case-control study of the relation between plasma selenium and asthma in European populations: a GA 2 LEN project* Background: There is evidence that selenium levels are relatively low in Europe and may be falling. Low levels of selenium or low activity of some of the enzymes dependent on selenium have been associated with asthma. Methods: The GA 2 LEN network has organized a multicentre case–control study in Europe to assess the relation of plasma selenium to asthma. The network compared 569 cases in 14 European centres with a diagnosis of asthma and reporting asthma symptoms in the last 12 months with 576 controls from the same centres with no diagnosis of asthma and no asthmatic symptoms in the last 12 months. Results: All cases and controls were selected from the same population defined by age and place of residence. Mean plasma selenium concentrations among the controls ranged from 116.3 lg/l in Palermo to 67.7 lg/l in Vienna and 56.1 lg/l among the children in Oslo. Random effects meta-analysis of the results from the centres showed no overall association between asthma and plasma selenium [odds ratio (OR)/10 lg/l increase in plasma selenium: 1.04; 95% confidence interval (CI): 0.89–1.21] though there was a significantly protective effect in Lodz (OR: 0.48; 95% CI: 0.29–0.78) and a marginally significant adverse effect in Amsterdam (OR: 1.68; 95% CI: 0.98–2.90) and Ghent (OR: 1.35; 95% CI: 1.03– 1.77). Conclusion: This study does not support a role for selenium in protection against asthma, but effect modification and confounding cannot be ruled out. P. Burney 1 , J. Potts 1 , J. Makowska 12 , M. Kowalski 12 , J. Phillips 1 , L. Gnatiuc 1 , S. Shaheen 1 , G. Joos 2 , P. Van Cauwenberge 2 , T. van Zele 2 , K. Verbruggen 2 , Y. van Durme 2 , I. Derudder 2 , S. Wohrl 3 , J. Godnic- Cvar 3 , B. Salameh 3 , L. Skadhauge 4 , G. Thomsen 4 , T. Zuberbier 5 , K. C. Bergmann 5 , L. Heinzerling 5 , H. Renz 6 , N. Al-Fakhri 6 , B. Kosche 6 , A. Hildenberg 6 , N. G. Papadopoulos 7 , P. Xepapadaki 7 , K. Zannikos 7 , M. Gjomarkaj 8 , A. Bruno 8 , E. Pace 8 , S. Bonini 9 , M. Bresciani 9 , C. Gramiccioni 9 , W. Fokkens 10 , E. J. M. Weersink 10 , K.-H. Carlsen 11 , E. Bakkeheim 11 , C. Loureiro 13 , C. M. Villanueva 13 , C. Sanjuas 13 , J.-P. Zock 14 , B. Lundback 15 , C. Janson 16 1 National Heart Lung Institute Imperial College, London UK; 2 University of Ghent, Ghent, Belgium; 3 Univeristy of Vienna Medical School, Vienna, Austria; 4 Odense University Hopital, Odense, Denmark; 5 Charite Medical Faculty, Humbolt University, Berlin, Germany; 6 Philipps University, Marburg, Germany; 7 National and Kapodistrian University, Athens, Greece; 8 Consilio Nazionale delle Ricerche, Palermo, Italy; 9 Consilio Nazionale delle Ricerche, Rome, Italy; 10 Academic Medical Centre, Amsterdam, Netherlands; 11 Voksentoppen BKL, National Hospital, Oslo, Norway; 12 Medical University, Lodz, Poland; 13 Universitad de Coimbra, Coimbra, Portugal; 14 lnstitut Municipal Investigacio Medica, Barcelona, Spain; 15 Karolinska Institutet, Stockholm Sweden; 16 Uppsala University, Uppsala, Sweden Key words: allergy; asthma; environmental; selenium; tobacco smoke. P. Burney Imperial College London National Heart and Lung Institute Emmanuel Kaye Building Manresa Road London SW3 6LR UK *Participating centres are listed in the Appendix. Accepted for publication 20 February 2008 Allergy 2008: 63: 865–871 Ó 2008 The Authors Journal compilation Ó 2008 Blackwell Munksgaard DOI: 10.1111/j.1398-9995.2008.01716.x 865