Letters to the Editor 132:962-72. 3. Covey LS, Glassman AH, Dalack GW. Re: "Depressed mood and development of cancer." (Letter). Am J Epidemiol 1991 ;134:324-5. 4. Linkins RW, Comstock GW. Re: "Depressed mood and development of cancer." The authors reply. (Letter). Am J Epidemiol 1991;134:325-6. 5. Craig TJ, Van Natta PA. Current medication use and symptoms of depression in a general population. Am J Psychiatry 1978; 135:1036-9. 6. Cox D. Regression models and life tables. J R Stat Soc[B] 1972;34:187-220.
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Robert W. Linkins Division of Immunization Centers for Disease Control Atlanta, GA 30333 George W. Comstock Training Center for Public Health Research The Johns Hopkins University School of Hygiene and Public Health Hagerstown, MD 21742-2067
RE: "BODY MASS INDEX AND LUNG CANCER RISK" In a recently published case-control study, Rabat and Wynder (1), reported a significant trend of increasing lung cancer risk with decreasing body mass index (weight (kg)/height (m)2). For cases, body mass index was assessed using the self-reported weight 5 years prior to lung cancer diagnosis. When the authors examined body mass index based on self-reported weight 1 year prior to diagnosis, they observed the same trend. This is somewhat disconcerting, since the body weight of cases in the year before diagnosis may be decreased as a consequence of the cancer. We wonder whether the authors analyzed body mass index calculated using weight from, say, 10 or more years prior to diagnosis. We present data from a prospective study in which we find a significant inverse correlation between body mass index and lung cancer in the first 11-15 years that disappears with longer follow-up. One possible explanation for this observation is that the bias due to cancer-induced weight loss may persist for as long as 11-15 years. In 1962 or 1966 (hereafter referred to as 1962/ 1966) we mailed questionnaires enquiring about health habits and medical history to surviving
alumni who had matriculated as undergraduates at Harvard University between 1916 and 1950. A total of 21,582 men responded. We then excluded alumni reporting any cancer on the questionnaire as well as those not providing complete data on weight, height, physical activity, and cigarette smoking habits. This left 16,355 eligible subjects, of whom 13,846 (85%) were successfully followed up through 1988. We ascertained lung cancer occurrence via two further questionnaires mailed in 1977 and 1988, and via death certificates. Self-reported cancer in this population is believed to be valid (2, 3). Between 1962/1966 and 1988, eight cases of lung cancer occurred among never smokers (n = 3,568), 66 among former smokers (n = 4,507) and 212 among current smokers (n = 5,771). The small number of lung cancers among never or former smokers precluded analyses by time period. Thus, we present results from analyses of current smokers only. We categorized current smokers according to body mass index using the cutpoints of Kabat and Wynder. Instead of their four categories, we created three: we combined their highest and second levels of body mass index into a single
TABLE 1. Relative risks of lung cancer in current smokers in a cohort of Harvard University alumni, according to body mass index assessed in 1962 or 1966 Body mass index* and followup period
No. of cases/ no. of men
Relative risk
1962 or 1966 through 1977 >25 22-24.9 25 22-24.9 10 years) but was strongest for the period of >10 years. Thus, it appears that the association is with leanness that predates lung cancer and not with weight loss due to preclinical cancer. It is difficult to imagine that a lung tumor could cause weight loss 10 years before its clinical manifestation. In view of this, it would be of interest to know whether the association reported by Lee and Paffenbarger for the first 11-15 years of followup differed by 1-5 years or 6-11 years. If they are right, the association should be stronger in the period of 1-5 years. There is another possible explanation of our results which, though not raised by Lee and Paffenbarger, merits discussion. That is, if heavy smokers tended to be leaner, the association between lung cancer and leanness might be confounded by the intensity of smoking. Although smokers tend to be leaner than nonsmokers, in our data, heavier smokers were not leaner than lighter smokers. This is consistent with the findings of seven other studies that looked at body mass index or weight by level of smoking among current smokers (4-10). In three studies, there was a U-shaped relation between body mass index or weight and level of smoking; in two there was no association; and in the remaining two, heavy smokers tended to have a higher body mass index. In our data, too, heavy smokers tended to have a higher body mass index. Thus, adjustment in our data for the amount smoked did not reduce, but rather slightly increased, the magnitude of the association with low body mass index. Also, the magnitude of the association of leanness and lung cancer was comparable in light current smokers of both sexes and in heavy current smokers. To date, results from prospective studies, including those of Lee and Paffenbarger, have related body mass index based on weight at baseline to subsequent lung cancer risk. As we concluded in our article, the relation between leanness and the development of lung cancer could be further clarified in existing prospective data sets with repeated measurements of the subjects' weight over time.
1417
Robert W. Linkins Division of Immunization Centers for Disease Control Atlanta, GA 30333 George W. Comstock Training Center for Public Health Research The Johns Hopkins University School of Hygiene and Public Health Hagerstown, MD 21742-2067
RE: "BODY MASS INDEX AND LUNG CANCER RISK" In a recently published case-control study, Rabat and Wynder (1), reported a significant trend of increasing lung cancer risk with decreasing body mass index (weight (kg)/height (m)2). For cases, body mass index was assessed using the self-reported weight 5 years prior to lung cancer diagnosis. When the authors examined body mass index based on self-reported weight 1 year prior to diagnosis, they observed the same trend. This is somewhat disconcerting, since the body weight of cases in the year before diagnosis may be decreased as a consequence of the cancer. We wonder whether the authors analyzed body mass index calculated using weight from, say, 10 or more years prior to diagnosis. We present data from a prospective study in which we find a significant inverse correlation between body mass index and lung cancer in the first 11-15 years that disappears with longer follow-up. One possible explanation for this observation is that the bias due to cancer-induced weight loss may persist for as long as 11-15 years. In 1962 or 1966 (hereafter referred to as 1962/ 1966) we mailed questionnaires enquiring about health habits and medical history to surviving
alumni who had matriculated as undergraduates at Harvard University between 1916 and 1950. A total of 21,582 men responded. We then excluded alumni reporting any cancer on the questionnaire as well as those not providing complete data on weight, height, physical activity, and cigarette smoking habits. This left 16,355 eligible subjects, of whom 13,846 (85%) were successfully followed up through 1988. We ascertained lung cancer occurrence via two further questionnaires mailed in 1977 and 1988, and via death certificates. Self-reported cancer in this population is believed to be valid (2, 3). Between 1962/1966 and 1988, eight cases of lung cancer occurred among never smokers (n = 3,568), 66 among former smokers (n = 4,507) and 212 among current smokers (n = 5,771). The small number of lung cancers among never or former smokers precluded analyses by time period. Thus, we present results from analyses of current smokers only. We categorized current smokers according to body mass index using the cutpoints of Kabat and Wynder. Instead of their four categories, we created three: we combined their highest and second levels of body mass index into a single
TABLE 1. Relative risks of lung cancer in current smokers in a cohort of Harvard University alumni, according to body mass index assessed in 1962 or 1966 Body mass index* and followup period
No. of cases/ no. of men
Relative risk
1962 or 1966 through 1977 >25 22-24.9 25 22-24.9 10 years) but was strongest for the period of >10 years. Thus, it appears that the association is with leanness that predates lung cancer and not with weight loss due to preclinical cancer. It is difficult to imagine that a lung tumor could cause weight loss 10 years before its clinical manifestation. In view of this, it would be of interest to know whether the association reported by Lee and Paffenbarger for the first 11-15 years of followup differed by 1-5 years or 6-11 years. If they are right, the association should be stronger in the period of 1-5 years. There is another possible explanation of our results which, though not raised by Lee and Paffenbarger, merits discussion. That is, if heavy smokers tended to be leaner, the association between lung cancer and leanness might be confounded by the intensity of smoking. Although smokers tend to be leaner than nonsmokers, in our data, heavier smokers were not leaner than lighter smokers. This is consistent with the findings of seven other studies that looked at body mass index or weight by level of smoking among current smokers (4-10). In three studies, there was a U-shaped relation between body mass index or weight and level of smoking; in two there was no association; and in the remaining two, heavy smokers tended to have a higher body mass index. In our data, too, heavy smokers tended to have a higher body mass index. Thus, adjustment in our data for the amount smoked did not reduce, but rather slightly increased, the magnitude of the association with low body mass index. Also, the magnitude of the association of leanness and lung cancer was comparable in light current smokers of both sexes and in heavy current smokers. To date, results from prospective studies, including those of Lee and Paffenbarger, have related body mass index based on weight at baseline to subsequent lung cancer risk. As we concluded in our article, the relation between leanness and the development of lung cancer could be further clarified in existing prospective data sets with repeated measurements of the subjects' weight over time.
