Body-Mass Index and Mortality in Korean Men and Women
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《新英格兰医药杂志》
To the Editor: Jee et al. (Aug. 24 issue)1 report the association between body-mass index (BMI) (the weight in kilograms divided by the square of the height in meters) and mortality. We have published articles elsewhere on similar issues with the use of similar data from the National Health Insurance Corporation in Korea.2,3
Jee et al. obtained the causes of death among men and women in this study from the Korea National Statistical Office. Since all deaths in Korea are required by law to be reported to this office, the data on death from any cause used in this study can be regarded as accurate. However, there have been debates about the accuracy of the data on the cause of death, and investigations have pointed out the questionable accuracy of these data from this source.4,5 Although many improvements have been made during the past several years, the accuracy still may be questionable. Therefore, the results of this study should be interpreted with caution.
Sang Woo Oh, M.D.
Inje University Ilsan-Paik Hospital
Gyeonggi-Do, 411-706 Korea
osw6021@yahoo.co.kr
References
Jee SH, Sull JW, Park J, et al. Body-mass index and mortality in Korean men and women. N Engl J Med 2006;355:779-787.
Oh SW, Shin SA, Yun YH, Yoo T, Huh BY. Cut-off point of BMI and obesity-related comorbidities and mortality in middle-aged Koreans. Obes Res 2004;12:2031-2040.
Oh SW, Yoon YS, Shin SA. Effects of excess weight on cancer incidences depending on cancer sites and histologic findings among men: Korea National Health Insurance Corporation Study. J Clin Oncol 2005;23:4742-4754.
Park DK, Kim SY, Kang JH, et al. Errors in death certificates in Korea. J Korean Acad Fam Med 1992;13:442-9.
Kim KS, Lim YS, Rhee JE, et al. Problems in completing a death certificate. J Korean Soc Emerg Med 2000;11:443-9.
The authors reply: Oh correctly describes the current situation with regard to death registration in Korea, citing two studies that describe inaccuracies in the completion of death-certificate information by medical personnel there.1,2 Undoubtedly, there is some misclassification of the causes of death in Korea, as elsewhere. As Oh notes, such misclassification has no implications for analyses of total mortality. If the degree of misclassification does not vary according to BMI, our findings regarding the associations of BMI with broad categories of cardiovascular and respiratory disease and cancer would not be the consequence of any resulting bias in the hazard ratios. Random misclassification, if present, would tend to reduce the strength of the associations. The classification of causes of death by clinicians might depend on the BMI; for example, deaths among obese people might be more likely to be wrongly attributed to cardiovascular disease. However, the potential for such bias has not been assessed in Korea. If misclassification is random, our findings may understate the effect of obesity on mortality, and consequently, we do not consider inaccuracies in the classification of the causes of death to be a major limitation of our study.
Sun Ha Jee, Ph.D.
Jonathan M. Samet, M.D.
Johns Hopkins Bloomberg School of Public Health
Baltimore, MD 21205
jsunha@yumc.yonsei.ac.kr
References
Park DK, Kim SY, Kang JH, et al. Errors in death certificates in Korea. J Korean Acad Fam Med 1992;13:442-9.
Kim KS, Lim YS, Rhee JE, et al. Problems in completing a death certificate. J Korean Soc Emerg Med 2000;11:443-9.
Jee et al. obtained the causes of death among men and women in this study from the Korea National Statistical Office. Since all deaths in Korea are required by law to be reported to this office, the data on death from any cause used in this study can be regarded as accurate. However, there have been debates about the accuracy of the data on the cause of death, and investigations have pointed out the questionable accuracy of these data from this source.4,5 Although many improvements have been made during the past several years, the accuracy still may be questionable. Therefore, the results of this study should be interpreted with caution.
Sang Woo Oh, M.D.
Inje University Ilsan-Paik Hospital
Gyeonggi-Do, 411-706 Korea
osw6021@yahoo.co.kr
References
Jee SH, Sull JW, Park J, et al. Body-mass index and mortality in Korean men and women. N Engl J Med 2006;355:779-787.
Oh SW, Shin SA, Yun YH, Yoo T, Huh BY. Cut-off point of BMI and obesity-related comorbidities and mortality in middle-aged Koreans. Obes Res 2004;12:2031-2040.
Oh SW, Yoon YS, Shin SA. Effects of excess weight on cancer incidences depending on cancer sites and histologic findings among men: Korea National Health Insurance Corporation Study. J Clin Oncol 2005;23:4742-4754.
Park DK, Kim SY, Kang JH, et al. Errors in death certificates in Korea. J Korean Acad Fam Med 1992;13:442-9.
Kim KS, Lim YS, Rhee JE, et al. Problems in completing a death certificate. J Korean Soc Emerg Med 2000;11:443-9.
The authors reply: Oh correctly describes the current situation with regard to death registration in Korea, citing two studies that describe inaccuracies in the completion of death-certificate information by medical personnel there.1,2 Undoubtedly, there is some misclassification of the causes of death in Korea, as elsewhere. As Oh notes, such misclassification has no implications for analyses of total mortality. If the degree of misclassification does not vary according to BMI, our findings regarding the associations of BMI with broad categories of cardiovascular and respiratory disease and cancer would not be the consequence of any resulting bias in the hazard ratios. Random misclassification, if present, would tend to reduce the strength of the associations. The classification of causes of death by clinicians might depend on the BMI; for example, deaths among obese people might be more likely to be wrongly attributed to cardiovascular disease. However, the potential for such bias has not been assessed in Korea. If misclassification is random, our findings may understate the effect of obesity on mortality, and consequently, we do not consider inaccuracies in the classification of the causes of death to be a major limitation of our study.
Sun Ha Jee, Ph.D.
Jonathan M. Samet, M.D.
Johns Hopkins Bloomberg School of Public Health
Baltimore, MD 21205
jsunha@yumc.yonsei.ac.kr
References
Park DK, Kim SY, Kang JH, et al. Errors in death certificates in Korea. J Korean Acad Fam Med 1992;13:442-9.
Kim KS, Lim YS, Rhee JE, et al. Problems in completing a death certificate. J Korean Soc Emerg Med 2000;11:443-9.