Objective: To describe the characteristics for distribution of waist circumference (WC) and validate the cut-offs of WC in defining the central obesity among Chinese elderly and tall adults.
Methods: Data from the 2002 National Nutrition and Health Survey was used to analyze the characteristics of WC distribution among subjects aged 45 and above and their height beyond the P85 percentile of Chinese adults. Kappa test was used to estimate the consistency of different cut-offs for WC with body mass index (BMI) ≥ 24 in defining obesity. The odds ratios of diabetes and impaired fasting glucose in different cut-offs on WC were calculated by multiple logistic regression. ROC curves analysis was used to determine the cut-offs.
Results: The means of WC were: 80.8 cm in male elderly, 79.4 cm in female elderly, 84.1 cm in tall male and 77.9 cm in tall female, respectively. The WC at 85 cm for male and 80 cm for female elderly had the best consistency with BMI at 24, and the distance of ROC curve was the shortest. The odds ratios for diabetes significantly increased from WC categories of 85-cm (OR = 2.1, 95%CI: 1.6 - 2.8), 90-cm (OR = 3.0, 95%CI: 2.3 - 4.0), and 95-cm (OR = 4.5, 95%CI: 3.4 - 5.8) in male elderly, and 80-cm (OR = 1.9, 95%CI: 1.4 - 2.6), 85-cm (OR = 3.2, 95%CI: 2.4 - 4.3), and 90-cm (OR = 4.8, 95%CI: 3.7 - 6.1) in female elderly (P < 0.01). The odds ratios for impaired fasting glucose also significantly increased from WC categories of 85-cm (OR = 1.6, 95%CI: 1.2 - 2.2), 90-cm (OR = 2.6, 95%CI: 1.9 - 3.5), and 95-cm (OR = 3.5, 95%CI: 2.6 - 4.6) in male elderly, and 80-cm (OR = 2.5, 95%CI: 1.8 - 3.4), 85-cm (OR = 3.2, 95%CI: 2.4 - 4.4), and 90-cm (OR = 4.2, 95%CI: 3.2 - 5.6) in female elderly (P < 0.01). The odds ratios for diabetes (OR = 3.6, 95%CI: 2.1 - 6.4) and impaired fasting glucose (OR = 5.5, 95%CI: 3.0 - 10.1) significantly increased from WC ≥ 95 cm in tall males. The odds ratios for diabetes significantly increased from WC categories of 85-cm (OR = 5.0, 95%CI: 2.7 - 9.4) and 90-cm (OR = 8.0, 95%CI: 4.6 - 14.1), and odds ratio for impaired fasting glucose of WC ≥ 90 cm was 3.7 (95%CI: 2.0 - 6.9) in tall females.
Conclusion: The recommended cut-off points of WC were 85 cm for elderly males and 80 cm for elderly females. The cut-offs of WC were also effective predictors for impaired fasting glucose among tall adults. The cut-offs of WC in the Guidelines for Overweight and Obesity Prevention and Control for Chinese Adults were verified and should be applied as preventive indicators.