Social determinants of lung cancer incidence in Canada: A 13-year prospective study.

BACKGROUND The risk of lung cancer has been shown to be inversely related to socioeconomic status (SES). Because the Canadian Cancer Registry does not contain socioeconomic data, the 1991 Canadian Census Cohort was used to study social determinants of lung cancer risk in the general Canadian population. DATA AND METHODS This study examines incidence rates of lung cancer and histologic subtypes by educational attainment, income and occupation in a broadly representative sample of Canadians aged 25 or older. Data for the 1991 Canadian Census Cohort were analyzed. The cohort comprised 2,734,835 individuals, among whom 215,700 new cancer cases were diagnosed from 1991 through 2003. Age-standardized incidence rates were calculated by age, sex, and SES using the direct method. Rate ratios, rate differences, and excess incidence were also calculated. RESULTS An inverse risk between lung cancer incidence and educational attainment, income and occupation emerged among men and women, and a stepped negative gradient in RRs was evident for all SES variables and age groups. If all cohort members had experienced the rate of those with a university degree, lung cancer incidence would have been 56% lower in men and 55% lower in women. If all cohort members had experienced the incidence rate of those in the highest income quintile, incidence would have been 33% lower in men and 25% lower in women. If all cohort members had experienced the rate of those in managerial occupations, incidence would have been 54% lower in men and 44% lower in women. INTERPRETATION A negative gradient in lung cancer risk was evident for all SES variables studied.