Pet birds and risk of lung cancer in Sweden: a case-control study.

OBJECTIVE: To investigate the association between keeping birds and the risk of lung cancer in Sweden. DESIGN: Case control study based on cases of lung cancer and community controls. Interviews were performed by two nurses specially trained for this project. SETTING: Three major referral hospitals located in southwest Sweden. SUBJECTS: All patients aged 75 and under with newly diagnosed lung cancer and of Scandinavian birth who lived in one of 26 municipalities in Gothenburg and Bohus county or Alvsborg county. Potential control subjects matched on county of residence, sex, and closest date of birth were selected from population registries. In the context of a larger case-control study, information on pet birds was obtained from 380 patients with lung cancer (252 men) and 696 controls (433 men). MAIN OUTCOME MEASURES: Odds ratios for lung cancer in relation to whether or not pet birds were kept and the duration of keeping pet birds. RESULTS: The adjusted odds ratio for ever versus never exposed to pet birds at home was 0.94 (95% confidence interval 0.64 to 1.39) for men and 1.10 (0.64 to 1.90) for women. There was no evidence of a trend for increased risk of lung cancer with duration of bird ownership. CONCLUSION: Bird keeping does not seem to confer any excess risk of lung cancer to Swedish men or women.