Aging attenuates the association of central obesity with the accumulation of metabolic risk factors when assessed using the waist circumference measured at the umbilical level (the Japanese standard method)

OBJECTIVE: The objective of this study was to clarify the generation and gender differences in the association between central obesity and the accumulation of metabolic risk factors (RFs) in the Japanese population. MATERIAL AND METHODS: A total of 12 389 subjects (age: 18–80 years) without receiving medication for diabetes, dyslipidemia or hypertension were enrolled in this study and divided according to age and gender. In each group, we performed analyses as follows: (1) a receiver operating characteristic (ROC) analysis to evaluate the utility of the waist circumference (WC) for detecting subjects with multiple RFs of metabolic syndrome (MS); (2) a cross-sectional study to examine the relationship between the WC and the odds ratio (OR) for detecting those subjects and (3) a longitudinal study to examine how longitudinal changes (Δ) in WC over a 1-year period affected the values of each metabolic RF. RESULTS: With age, the WC cutoff values yielding the maximum Youden index for detecting subjects with multiple RFs increased only in women, and the areas under the curves of the ROC analysis of WC for detecting those subjects decreased in both genders. The positive correlation between the WC and the OR for detecting subjects with multiple RFs became weaker with age, especially in women. In the longitudinal study, the significant correlation between ΔWC and Δ each metabolic RF, except for hypertension, and between ΔWC and Δ the number of RFs became weaker with age in women, whereas the significant correlation between ΔWC and Δ the number of RFs was not affected with age in men. In women aged ⩾60 years, none of the changes in each metabolic RF were significantly associated with ΔWC. CONCLUSIONS: Aging attenuates the association of central obesity with the accumulation of metabolic RFs, especially in women.