Various Obesity Indices and Arterial Function Evaluated with CAVI - Is Waist Circumference Adequate to Define Metabolic Syndrome?

Obesity has been known to relate to various diseases and metabolic disorders. Since the implication of body shape has been mentioned, obesity can be divided into visceral obesity and subcutaneous obesity. The former is considered the upstream pathophysiology of metabolic syndrome (MetS), and has been emphasized worldwide for the prevention of cardiovascular diseases in the last quarter century. However, some prospective studies have shown that cardiovascular mortality and morbidity are not necessarily higher in patients with MetS compared to those without. Recently, cardio-ankle vascular index (CAVI) has been established as an indicator of arteriosclerosis. This parameter is independent of blood pressure at the measuring time, and reflects systemic arterial stiffness from the aortic origin to the ankle. However, since CAVI is not necessarily high in MetS patients, attempts have been made to clarify this unexpected phenomenon. In several studies, CAVI was found to correlate negatively with body mass index (BMI), and also with waist circumference (WC) which is a widely used representative visceral obesity index. On the other hand, a body shape index (ABSI) is also a visceral obesity index designed to be minimally associated with BMI, and is calculated by dividing WC by an allometric regression of weight and height. Replacing high WC with high ABSI in MetS diagnosis promoted the identification of MetS patients with increased CAVI in cross-sectional studies on Japanese and Korean populations. Additionally, the incidence of MetS diagnosed using high ABSI was associated with significant increase in CAVI after 1 year of observation. Enhanced predictive ability for renal function decline by replacing WC with ABSI in MetS diagnosis was also observed in a longitudinal study in Japanese urban residents. These findings suggest that MetS diagnosis using high ABSI instead of high WC as a visceral obesity index needs to be reconsidered. However, further research is desirable on Caucasian, whose body shape differs slightly from that of Asians.