{'fraction_non_alphanumeric': 0.02633658151171978, 'fraction_numerical': 0.004213853041875165, 'mean_word_length': 5.205882352941177, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Re: Environmental tobacco smoke and lung cancer risk in nonsmoking women.

The report by Stock well et al. (7) adds little to the data on environmental tobacco smoke and lung cancer. Various biases could have contributed to the associations noted between lung cancer and some indices of environmental tobacco smoke exposure. One concern relates to the use of healthy control subjects who were obtained by random-digit dialing, resulting in possible recall and nonresponse bias. Another concern, perhaps more so than in other lung cancer-environmental tobacco smoke studies, is information bias. Thus, all control subjects provided data directly, but surrogates provided data for 67% of case patients, many of whom were dead. There were also notable casecontrol differences in the proportions of interviews conducted face to face, by telephone, or by mail. Much attention has been given to bias from the misclassification of smoking habits (2), but, although Stockwell et al. (7) refer to this misclassification, they attempt no statistical adjustment and do not present a comparison of smoking status as recorded at various stages of their study. They also fail to consider confounding by diet. This failure is remarkable, since in another paper (3), apparently based on the same study, they report a strong protective effect against lung cancer among nonsmokers that is associated with total vegetable consumption and with intake of carotene, and, as I have reviewed elsewhere (2), a reduced consumption of vegetables is associated with marriage to a smoker. Adjustment for this source of bias alone could well render the reported association between lung cancer and exposure to environmental tobacco smoke not statistically significant. There are also severe problems regarding presentation of results in the report by Stockwell et al. How can one update meta-analyses for differing indices of environmental tobacco smoke exposure when risk estimates are presented only for those indices for which an association is reported? What were the odds ratios and confidence intervals for environmental tobacco smoke exposure at work or during social activities? Meta-analysis would also be assisted by presenting, as other investigators do (4,5), numbers of cases and controls by exposure. Another difficulty is the unusual method of analysis for spousal environmental tobacco smoke exposure, with the referent group not, as is customary (2), married women whose husbands did not smoke, but instead women (married and unmarried) unexposed to household environmental tobacco smoke from any source. The relative risk estimate is thus not comparable with that for other studies (2). Furthermore, because of the strong association of the indices of environmental tobacco smoke used with both marital status and household size (the larger the family, the more likely is exposure), there are additional possibilities of confounding. The referent exposure group is identical for all analyses in Tables 2 and 3 of the report by Stockwell et al. (/); therefore, the cited risks for different indexes of environmental tobacco smoke exposure are not independent and could all be affected by an unusually low proportion of unexposed cases, perhaps resulting from recall bias. In any event, the results of the study by Stockwell et al. (7) have no real effect on the overall data. Based on all data available before this study, meta-analysis (Table 1) gives no overall statistically significant association of lung cancer to workplace or childhood environmental tobacco smoke exposure and only a small positive association with a husband's smoking, which, as I have previously shown, can be explained in terms of misclassification of smoking habits, confounding, publication bias, and specific study weaknesses (2).