Editorials

Pet birds and lung cancer

BMJ 1996; 313 doi: http://dx.doi.org/10.1136/bmj.313.7067.1218 (Published 16 November 1996) Cite this as: BMJ 1996;313:1218
  1. John Britton,
  2. Sarah Lewis
  1. Reader in respiratory medicine Statistician University of Nottingham, Division of Respiratory Medicine, City Hospital, Nottingham NG5 1PB

    Now no evidence of a link

    The question of whether keeping pet birds increases the risk of lung cancer was first raised by Holst.1 2 Having noted a higher occurrence of lung cancer among bird owners in a Dutch general practice population, he and colleagues carried out a case control study comparing hospital patients with community matched controls and showed a 6.7-fold increase in risk.3 Two subsequent studies produced further evidence in support of this observation: one reported a twofold increase in risk of lung cancer in relation to exposure to pet birds in a German population,4 while the other, from Scotland, showed no significant association with exposure to pet birds in general but a 3.5-fold increase in risk of lung cancer in those who kept pigeons.5

    At the time, we argued that, although of great importance if valid, these observations might have arisen from residual confounding by cigarette smoking.6 All of the case-control studies had controlled for smoking in their analysis but categorised cases and controls as smokers or non-smokers; the degree of …

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