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Chinese T2DM assessment

China: waist circumference best measure for T2DM

Study finds that waist circumference is the most appropriate measure for identifying patients who could develop T2DM.

According to new research that evaluated several indicators of type 2 diabetes mellitus (T2DM), waist circumference is the best anthropometric measure for detecting the condition in the Chinese population.

The researchers from Capital Medical University (Beijing), Tianjin Medical University and PLA 305 Hospital (Beijing), concluded that their results indicate that the appropriate cutoffs of the waist circumference were 90cm in men and 86 cm in women for detecting T2DM. The investigators hope the study will help general practitioners to assess the risks of their patients quickly and easily.

Study

The study was undertaken to identify which obesity indicator and its optimal cutoff points (sensitivity and specificity) are the best predictors of T2DM.

The researchers compared the performance of body mass index, waist circumference, waist to hip ratio and waist-to-height ratio to diagnose T2DM, using undiagnosed diabetes and an oral glucose tolerance test, to assess diabetes risk in the Chinese population.

Study patients were selected from an on-going large-scale population-based Beijing Community Pre-Diabetes (BCPD) study cohort, a study designed to facilitate the conduct of genetic epidemiology investigations and clinical trials. Subjects originated from the settled community of Nanfaxin.

Participants without previously known diabetes were selected from the 2,826 registered individuals aged ≥35 years in the year 2007. All subjects were invited to attend a baseline examinations including anthropometric and blood pressure measurements, in addition to completing a general health questionnaire.

Subjects whose fasting plasma glucose (FPG) was ≥5.6mmol/L performed a 75g oral glucose tolerance test. A total of 220 new cases of T2DM and 1,868 normal blood glucose subjects were recorded.

Anthropometric measurements

Participants’ body weight (kg) and height (cm) were recorded. Waist circumference and hip circumference were obtained using a cloth tape. The waist circumference was defined as the midpoint between the peak of the iliac crest and the nadir of the costal margin in the midaxillary line.

The hip circumference was measured at the level of the greater femoral trochanters. These measurements were used to compute the waist circumference divided by the hip circumference (waist-hip ratio) and waist circumference divided by the height (waist-to-height ratio). BMI was calculated by dividing the weight in kilograms by the square of the height in meters.

Receiver operating characteristic curve analyses was used to compare the association of different obesity indicators for identifying T2DM in men and women.

Results

The results revealed that all patients with T2DM, rated significantly higher in weight, waist circumference, hip circumference, body mass index, waist-to-hip ratio and waist-to height ratio, compared with subjects with normal blood glucose (p<0.001). All study cohort characteristics are identified in Table 1.

Table 1 Characteristics of study cohorts

Normal

T2DM

p-value

Subjects   (n)

1868

220

Age   (year)

51.66   ±10.35

56.22   ±10.06

<0.001

Height   (cm)

Men

167.02 ± 6.54

166.56 ±   6.03

0.499

Women

156.68 ±   5.61

155.96 ±   5.81

0.193

Weight   (Kg)

Men

71.61 ±   11.54

77.97 ±   11.87

<0.001

Women

63.36 ± 10.11

67.50 ±   11.04

<0.001

Hip   circumference (cm)

Men

97.99 ±   7.11

102.46 ± 6.94

<0.001

Women

98.22 ±   7.84

101.08 ±   7.67

<0.001

WC (cm)

Men

88.58 ±   9.96

95.92 ±   10.12

<0.001

Women

83.83 ±   9.92

91.33 ±   9.85

<0.001

BMI   (kg/m2)

Men

25.63 ±   3.62

28.05 ±   3.67

<0.001

Women

25.76 ±   3.79

27.77 ±   4.18

<0.001

WHR

Men

0.90 ±   0.06

0.94 ±   0.06

<0.001

Women

0.85 ±   0.06

0.90 ±   0.06

<0.001

WHTR

Men

0.53 ±   0.06

0.58 ±   0.06

<0.001

Women

0.54 ±   0.07

0.59 ±   0.07

<0.001
Unpaired t-tests were performed to determine statistical significance. All values are reported as means ± standard deviation (BMI, body mass index; WC, waist circumference; WHR, waist-to-hip ratio; WHTR, waist-to height ratio.

In women, waist circumference, waist-to-hip ratio and waist-to height ratio were similar, but were better in identifying T2DM when compared with BMI (p<0.0001, p=0.0016 and p=0.0001, respectively).

In men, waist circumference, waist-to height ratio and BMI were similar, but waist circumference and waist-to height ratio were better than waist-to-hip ratio (p=0.0234, p=0.0101, respectively).

For women, 86cm was the optimal waist circumference cut-off point, and its sensitivity and specificity were 0.714 and 0.616. For men, the optimal cut-off point was 90cm, and its sensitivity and specificity were 0.722 and 0.571.

Limitations

The authors acknowledge that there are several potential, not least that it is a cross-sectional study, and conclusions cannot been drawn about cause and effect relationships between waist circumference and T2DM. There are also variations in the waist circumference and BMI among Chinese in different regions.

Subjects were selected from the northern regions of China and therefore the results may not represent the whole population. They recommended that further research in other regions in China is needed to identify the best cutoff of T2DM and anthropometric indices.

Finally, not all subjects performed OGTT. Therefore, it is possible that the frequency of T2D had been under-estimated.

Conclusion

Despite these limitations, the researchers concluded waist circumference and waist-to height ratio perform significantly better than others for identifying T2DM irrespective of gender. However, waist circumference is easier to be obtained and understood than waist-to height ratio, and therefore a superior tool for discriminating obesity related T2DM risk evaluation in Chinese population.