MARRIGE TO A SMOKER MAY NOT BE A VALID MARKER OF EXPOSURE IN STUDIES RELATING ENVIRONMENTAL TOBACCO-SMOKE TO RISK OF LUNG-CANCER IN JAPANESE NONSMOKING WOMEN

There is no direct evidence that workplace environmental tobacco smoke (ETS) increases lung cancer risk. Demands for regulation of workplace smoking are based on studies reporting increased risk in non-smoking women whose husbands smoke. Although denying smoking can artificially elevate risk estimates, and although many studies reporting an increas e have been conducted in Asia, no previous study of smoking habit misc lassification has been conducted there. In this study 400 married Japa nese women answered questions on smoking and ETS exposure and supplied urine for cotinine analysis. Of 106 with a cotinine/creatinine ratio (CCR) indicating current smoking (>100 ng/mg), 22 reported never smoki ng. These misclassified smokers had a median CCR (1408 ng/mg) similar to the 78 self-reported current smokers (1483 ng/mg). Of current smoke rs, 89.7% had a currently smoking husband, while this was true of 51.0 % of non-smokers. Among 264 confirmed non-smokers (with CCR < 100 ng/m g), CCR was non-significantly lower if the husband smoked (11.51 vs 17 .98 ng/mg) and was unrelated to various indices of smoking by the husb and. Japanese epidemiological studies using ''marriage to a smoker'' t o index ETS exposure may therefore have compared groups with similar E TS exposure, suggesting that associations reported between lung cancer and this index in some of these studies may result from bias. While o ther biases, including confounding, may also be important, bias result ing from smoking misclassification combined with husband/wife smoking concordance is shown to be of major concern. The high misclassificatio n rates in Japan, much higher than in Western populations, undermine c onclusions from epidemiological studies conducted there.