MISCLASSIFICATION OF SMOKING-HABITS AS A SOURCE OF BIAS IN THE STUDY OF ENVIRONMENTAL TOBACCO-SMOKE AND LUNG-CANCER

The relationship of environmental tobacco smoke to lung cancer risk in lifelong non-smokers is commonly studied using marriage to a smoker a s the index of exposure. As smokers tend to marry smokers, relative ri sk estimates will be biased if some current or former smokers are misc lassified as lifelong non-smokers. This paper shows how various factor s affect the magnitude of the bias and describes a method for obtainin g misclassification-adjusted relative risk estimates. Application of t he method to U.S. and Asian data for women suggests misclassification is an important determinant of the slight excess risk observed in non- smokers married to smokers. Reasons why our conclusions differ from th ose of others are discussed, as are other difficulties in interpreting the association between spousal smoking and lung cancer risk.