A case control study of lung cancer in Florence, Italy. II. Effect of migration from the south.

Risk of lung cancer related to region of birth in Italy was investigated among migrants to Florence, in a case control study of all histologically confirmed incident cases of primary lung cancer in a three year period in that city (n = 376). Controls (n = 892) were patients in the same hospital of similar age, sex, date of admission, and smoking status with discharge diagnoses other than lung cancer or suicide. Information on place of birth and year of migration to Florence was collected directly from each subject, along with a detailed occupational history. Logistic regression models were used to calculate the odds ratio for birth in the south of Italy relative to birth elsewhere. Male migrants from the south have an odds ratio of lung cancer of 0.5 (95% limits 0.3 to 0.7) relative to those born elsewhere. This "protective effect" is not explained by smoking or by any known occupational risk. The risk is lowest among those born on the island of Sicily (odds ratio 0.2 compared to those born in the centre-north).