Methods
Questionnaires were administered face-to-face by trained interviewers,usually at the home of the participant. Information on demographics (including ethnic group), smok-ing history, passive smoking exposure, recreational drug use, diet, occupation, income, education, alcohol consumption and
family history of malignancy was collected. A family history of lung cancer was defined as having a sibling or parent with lung cancer. Occupations associated with a higher risk of lung cancer were identified from the literature and subjects were assigned a ‘‘duration at risk’’ value in years. Ethnicity was derived by priority coding of the responses into the following three groups: Maori, Pacific Islander and ‘‘other’’. The highest level of educational attainment was recorded, as was income at diagnosis (or reference age). Alcohol consumption was calculated using a semi-quantitative score based on amount and frequency of consumption.