Problems in the Japanese criteria for metabolic syndrome

Dear Editor, Ogawa et al. studied the cut-off point of waist circumference (WC) for the clustering of two or more metabolic risk factors among the three non-WC components of Japanese metabolic syndrome (JMetS) and proposed to amend JMetS regarding the cut-off point of WC for women. However, the most dangerous drawback of JMetS criteria is that it makes abdominal obesity a necessary component. Other problems of JMetS criteria are the cut-off point of impaired fasting glucose, the unnecessary combination of two components (hypertriglyceridemia and hypohigh-density lipoprotein cholesterolemia into one component) and the cut-off point of high-density lipoprotein cholesterol for women. In 2009, a worldwide consensus statement for the criteria of metabolic syndrome (MetS) was jointly issued by the International Diabetes Federation (IDF) Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute (NHLBI); American Heart Association (AHA); World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. In this statement, the revised National Cholesterol Education Program (NCEP) criteria (AHA ⁄NHLBI criteria) where abdominal obesity is not a necessary component was adopted as the worldwide definition of MetS. The 2005 IDF criteria of MetS where abdominal obesity is a necessary component were withdrawn by the IDF itself. However, the cut-off points of WC could not be determined for any ethnic groups. In 2007, the Association for Weight Management and Obesity Prevention, the Obesity Society, the American Society for Nutrition, and the American Diabetes Association issued a consensus statement regarding WC, where they stated that there is not yet a compelling body of evidence showing that WC provides clinically meaningful information that is independent of well-known cardiometabolic risk factors. Although the cut-off points of WC were controversial, those of body mass index (BMI) were widely accepted as 25 kg ⁄m for overweight and 30 kg ⁄m for obesity. We compared BMI, WC and percentage of body fat as markers for the clustering of metabolic risk factors in 2444 Japanese men and 1442 Japanese women, and found no significant difference among these three obesity parameters as a marker of metabolic risk clustering. Therefore, both a BMI cut-off point of 25 kg ⁄m and a WC cutoff point of 85 cm for men and 80 cm for women might be appropriate for a cut-off point of an obesity component of MetS. However, the most important point is that obesity is not a necessary component of MetS. It was pointed out by NIPPON DATA90 that the definition of MetS where obesity is a necessary component is dangerous, because normal-weight individuals have a high mortality risk and are more prevalent than obese or overweight subjects in Japan. A Japan Public Health Centerbased (JPHC) study also concluded that the MetS definition requiring obesity or overweight as a necessary component might not necessarily identify normalweight individuals who have a high mortality risk and are more prevalent than subjects with JMetS, and suggested that MetS based on the AHA ⁄NHLBI criteria predicts cardiovascular disease better than MetS based on the 2005 IDF criteria where abdominal obesity is a necessary component.