© 1999 by Oxford University Press
Journal of the National Cancer Institute, Vol. 91, No. 12, 1081-1082,
June 16, 1999
© 1999 Oxford University Press
CORRESPONDENCE |
Revisiting: Involuntary Smoking and Lung Cancer: a Case-Control Study
Affiliations of authors: A. J. Wells, Kennett Square, PA; S. J. Henley, Epidemiology and Surveillance Research, American Cancer Society, Atlanta, GA.
Correspondence to: A. Judson Wells, Ph.D., 5 Ingleton Circle, Kennett Square, PA 19348.
Lee (1) has commented on our letter (2) concerning errors in the study of environmental tobacco smoke (ETS) and lung cancer by Garfinkel et al. (3). He finds no fault with our suggestion that the cell counts from Garfinkel et al. (3) rather than the confidence intervals reported in that paper be used for calculation of weights when point estimates from that study are used in meta-analyses. However, he took issue with our use of the procedure of Rothman and Boice (4) for the calculation of confidence intervals and, hence, variances. This criticism has been adequately covered by Rothman and Boice in their response to Lee's letter (1).
We are concerned, however, with Lee's statement (1) that the use of the corrected data does not affect the general results of his fixed-effects meta-analysis of lung cancer and workplace exposure to ETS, for which he now calculates the relative risk (RR) to be equal to 1.06 (95% confidence interval [CI] = 0.98-1.15). Lee's estimate is in sharp contrast to an estimate by one of us [Wells, (5)] that, if reasonable quality criteria are used, the overall RR for workplace exposure to ETS is 1.39 (95% CI = 1.15-1.68). However, even if all of the studies of workplace exposure then available are included without regard to quality restrictions, but with correction of errors in three of the underlying studies [including the error in Garfinkel et al.(3)], Wells (5) found that the overall workplace RR would be 1.19 (95% CI = 1.07-1.34). This estimate was compared in (5) to three estimates made earlier by tobacco consultants, all of whom, including Mr. Lee, found combined workplace RR's ranging from 0.99 to 1.02. In none of these estimates were the errors in the three underlying studies corrected.
The most important of the three errors not detected by the tobacco consultants is an underestimation of the variance and, hence, overestimation of the weight, for the workplace RR in Janerich et al. (6). As noted in (5), the RR of 0.91 reported in Janerich et al. should not be used in workplace meta-analyses because it is derived from a continuous variable calculation. However, if it is used, it should have a weight of about 24 rather than the 223 used by the tobacco consultants. Lee has used the correct weight for Garfinkel et al. in his current workplace estimate of 1.06 (95% CI = 0.98-1.15), but apparently he is still using the erroneous weight for Janerich et al. (6). If he omitted the Janerich et al. RR from his calculation, he would get a combined RR of 1.16 (95% CI = 1.05-1.28). If he uses the Janerich et al. RR of 0.91 but corrects for the erroneous weight, he would get 1.14 (95% CI = 1.04-1.26), both of which are statistically significant and more consistent with the estimate in the U.S. Environmental Protection Agency's report (7) of 1.19 (90% CI = 1.01-1.35) for spousal exposure.
NOTES
Editor's note: Dr. Wells has served as an unpaid volunteer for the American Lung Association. The opinions he expressed herein are solely his own.
REFERENCES
1
Lee PN. More about: involuntary smoking and lung cancer: a
case-control study [letter]. J Natl Cancer Inst 1998;90:1746. Rothman KJ, Boice JD
Jr. Response [letter]. J Natl Cancer Inst 1998;90:1746.
2
Wells AJ, Henley SJ. Re: involuntary smoking and lung cancer: a
case-control study [letter]. J Natl Cancer Inst 1997;89:821-2.
3 Garfinkel L, Auerbach O, Joubert L. Involuntary smoking and lung cancer: a case-control study. J Natl Cancer Inst 1985;75: 463-9.cancerlit;85294048
4 Rothman KJ, Boice JD Jr. Epidemiologic analysis with a programmable calculator. DHEW Publ No. (NIH)79-1649. Washington (DC): U.S. Department of Health, Education, and Welfare; 1979. Reprinted in part: Boston (MA): Epidemiology Resources; 1982.
5
Wells AJ. Lung cancer from passive smoking at work. Am
J Public Health 1998;88: 1025-9.
6 Janerich DT, Thompson WD, Varela LR, Greenwald P, Chorost S, Tucci C, et al. Lung cancer and exposure to tobacco smoke in the household. N Engl J Med 1990;323: 632-6.[Abstract]cancerlit;90348726
7 U.S. Environmental Protection Agency. Respiratory effects of passive smoking: lung cancer and other disorders. EPA publication 600/6-90/006F. Washington (DC): U.S. Environmental Protection Agency; 1992.
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