Evaluate Cardiometabolic Risk in Youth

While waist-to-height ratios calculated using World Health Organization (WHO) and National Health and Nutrition Survey (NHANES) protocols both indicate cardiometabolic risk in youth with diabetes, the WHO waste circumference protocol may be preferable, according to a study published online in the International Journal of Child Health and Nutrition.

Central adiposity is a well-known cardiometabolic risk factor in adults with diabetes, though less is known in youth. While BMI is often used to indicate cardiometabolic risk, BMI cannot distinguish body fat distribution. The waist-to-height ratio has been proposed as a solution.

“Our results indicate that waist-to-height ratio may be added as a useful indicator for assessing cardiometabolic risk. In addition, our data suggest that the WHO protocol is more strongly correlated to some cardiometabolic risk factors compared to the NHANES protocol in youth at certain levels of body composition,” wrote first author Lenna Liu, MD, of the University of Washington and Seattle Children’s Hospital, Seattle, WA, and colleagues.

The study is the largest so far to evaluate how well waist-to-height ratios calculated using NHANES and WHO protocols indicate cardiometabolic risk in youth with diabetes. 

Studies have suggested that the mean NHANES waist circumference measurement may be greater than the mean WHO waist circumference measure, especially for females, older individuals, and those with higher BMIs. In the NHANES method, waist circumference is measured just above the iliac crest at the midaxillary line. In the WHO protocol, waist circumference is measured halfway between the lowest rib margin and the iliac crest in the mid axillary line. 

The study drew participants from the SEARCH cohort, the largest, ethnically diverse population-based study of youth with diabetes in the US. It included youth 10-19 years old with T1DM (n=3082) and T2DM (n=533). Participants came from centers in Ohio, Colorado, South Carolina, Washington, the Indian Health Service, and California. Researchers measured waist circumference using NHANES and WHO protocols, weight, height, fasting lipids (total cholesterol, triglycerides, HDL, non-HDL), and blood pressure. Then they categorized youth by lower BMI (<85^th BMI percentile, n=2071) and higher BMI (≥85^th percentile, n=1594).

Key results:

• Waist circumference and waist-to-height ratios consistently larger for NHANES vs WHO

• Lower BMI group: NHANES and WHO waist-to-height ratios significantly linked to all cardiometabolic risk factors (P<0.005), except blood pressure

♦ WHO waist-to-height ratio more strongly linked to triglycerides, non-HDL cholesterol, and systolic blood pressure than NHANES (P<0.05)

• Higher BMI group: both NHANES and WHO waist-to-height ratios significantly linked to all cardiometabolic risk factors (P<0.05)

♦ WHO waist-to-height ratio was more strongly linked to triglycerides and systolic blood pressure than NHANES (P<0.05)

While the study could not evaluate why the WHO waist-to-height ratio is more strongly linked to cardiometabolic risk than the NHANES protocol, the authors provided several possible explanations.  The NHANES waist circumference measurement may be limited by the fixed bone anatomy of the hip, they wrote, while the WHO measurement may measure soft tissue variations. Also, the higher location of the WHO measurement may more accurately indicate visceral adiposity than the NHANES measurement.

Limitations include uneven sample sizes between T1DM and T2DM. Also, accurate waist measurement may prove more challenging among overweight youth, which could make the findings less precise in this group.

“Nonetheless, our study demonstrates the association of waist-to-height ratio to cardiometabolic risk factors in youth with diabetes and some support for a stronger association using the WHO protocol,” they concluded, “Further research is needed to explore these relationships among youth with diabetes, including longitudinal analyses and comparisons with novel measures of cardiometabolic risk.”

Take-home Points

• The largest study so far to evaluate how well NHANES and WHO waist circumference protocols indicate cardiometabolic risk in youth with diabetes found that the WHO protocol is more strongly linked to some cardiometabolic risk factors than the NHANES protocol.

• Waist-to-height ratios found using WHO and NHANES protocols both indicate cardiometabolic risk in youth with diabetes.

• Waist circumference and waist-to-height ratios are consistently larger for NHANES vs WHO.

The study was supported by the Centers for Disease Control and the National Institute of Diabetes and Digestive and Kidney Diseases.

Reference: Liu LL, et al. Comparing two waist-to-height ratio measurements with cardiometabolic risk factors among youth with diabetes. Int J Child Health Nutr. 2016;5(3):87-94.