Pet birds as an independent risk factor for lung cancer: case-control study.

OBJECTIVE

To test the hypothesis that exposure to pet birds increases risk of developing lung cancer.

DESIGN

Case-control study. Computerised interviews were used to assess previous exposure to pets and other risk factors for lung cancer.

SETTING

Three major hospitals treating respiratory disease in former West Berlin.

SUBJECTS

All people newly diagnosed as having primary malignant neoplasm of the trachea, bronchi, or lung who were 65 or younger and control subjects matched for age and sex from the general population of former West Berlin. 279 cases and 635 controls qualified for the study; 239 cases and 429 controls participated.

MAIN OUTCOME MEASURES

Odds ratio of developing lung cancer according to whether or not pet birds were kept and the duration of keeping pet birds.

RESULTS

In addition to the risk of lung cancer imposed by smoking, passive smoking, and occupational exposure to carcinogens, an increased relative risk of 2.14 (95% confidence interval 1.35 to 3.40) was found among people exposed to pet birds. The adjusted odds ratio for exposures longer than 10 years was 3.19 (1.48 to 8.21).

CONCLUSIONS

Avian exposure seems to carry a risk of lung cancer. Until the pathogenesis is understood, long term exposure to pet birds in living areas should be avoided, especially among people at high risk of developing lung cancer.