심장질환자에서 비만이 생존에 미치는 영향 : 비만 역설

Abstract

Background and Purpose : Obesity is known as a risk factor to make structure and function of the heart change and it could increase possibility to cause cardiovascular disease and heart failure. However recently, it is interesting to report that as the body mass index of heart disease patients became more overweighted or obese they had the better prognosis rather than some people who are in normal group. This phenomenon is called ‘obesity paradox’, and its exact cause and mechanism are not known yet. In particular, large-scale cohort studies on the obesity paradox have not been conducted in Korea, and most research just focused on some patients in a hospital. Therefore, this study is to identify whether Korean people would have the obesity paradox by using cohort data of National Health Insurance Service Physical Health Examination Cohort, and it is to suggest basic data to prevent and manage heart disease by researching various variables related to obesity and heart disease. Research objectives and Methods : This study is a retrospective cohort research, utilizing cohort data of National Health Insurance Service Physical Health Examination Cohort from 2002 to 2013, and it analyzed whether there is a difference of the risk of death depending on the body mass index of heart disease patients. In order to choose heart disease patients, this study selected participants who are over 40 years old and since 2004 they are newly diagnosed with heart disease by specifying Ischemic heart diseases, Heart Failure, and Atrial Fibrillation and Flutter. In order to analyze the risk of death depending on body mass index, this study classified causes of deaths into total deaths, deaths due to disease except accidents, and deaths due to heart disease, by utilizing the health examination results, closest to the date of heart disease diagnosis. This study analyzed time scale by using Cox Proportional Hazards Model after applying Time-on Study and Attained age. It analyzed the body mass index after applying both WHO and WHO-WPRO classification standards. It set control variables including age, gender, smoking, drinking, waist circumference, exercise status, diabetes, high blood pressure, hyperlipidemia, and Charlson comorbidity index into the analysis and then it revised them. It utilized SAS version 9.4 for every statistical analysis. Research Results : This study confirmed that when the body mass index of heart disease patients was underweight the risk of death was more increased than people in a normal group and when the body mass index of heart disease patients was overweight, obese, or highly obese the risk of death was decreased. In a case of the Cox Proportional Hazards Model which further analyzed time scale with the attained age, this study found that when the body mass index of heart disease patients was underweight the risk of death was more increased than a people in a normal group and when the body mass index of heart disease patients was overweight, obese, or highly obese the risk of death was decreased. However, in a case of abdominal obesity group among risk factors, which set standards with waist circumference, this study identified that as the patients were more obese, the risk of death was statistically significantly increased unlike the body mass index. As a result of analyzing subgroups, this study found that every group except a female group in their 40s had a tendency of the ‘obesity paradox’. Conclusion: This study has a significance. It provided evidence indicating that there is the ‘obesity paradox’ in Korean heart disease patients through large-scale cohort studies, and it suggested basic data for follow-up research by examining the relation between death incidence and risk factors of heart disease depending on each of the body mass index. However, this study also had some limitations that it did not consider death incidence risk based on change of the body mass index during follow-up period, it could not identify the ‘obesity paradox’ out of the other obesity diagnostic standards like ‘waist circumference / height’ ratio, and it included research subjects that had been diagnosed with some disease causing weight loss (Chronic Obstructive Pulmonary Disease, tuberculosis, and some cancers). Through continuous cohort follow-up research that complement those limitations, it would be necessary to confirm the exact cause and mechanism of the obesity paradox.