Title : Prospective association of waist-to-thigh ratio with cardiovascular disease mortality: the NHANES 2009-2012 follow-up study
Objective: To evaluate the prospective association of waist-to-thigh ratio (WTR) with cardiovascular disease (CVD) mortality and compare with body mass index (BMI), waist circumference (WC), thigh circumference (TC), and waist-height ratio (WHtR).
Methods: The study population consisted of 5,663 adults aged 45 - 85 years or older who participated in the National Health and Nutrition Examination Survey (NHANES) 2009-2012. CVD deaths were ascertained from the National Death Index records using the National Center for Health Statistics linked mortality data through 2015. The causes of death were identified using the International Classification of Disease coding (ICD-10). WTR and other anthropometric measures were categorized into gender-specific quartiles. The prospective associations were assessed using a Cox proportional Hazards Model accounting for sampling design of the national survey.
Results. After up to 6 years of follow-up, there were total 342 deaths from CVD. In multivariable adjusted model adjusting for demographic variables and traditional risk factors of CVD, WTR was significantly associated with CVD death. The Hazard ratios (HR) and their 95% confidence intervals (CI) across the WTR quartiles were 1.38 (0.70, 2.78), 1.37 (0.61, 3.09) and 1.98 (1.02, 3.86) compared to the 1st quartile with a significant linear trend (P for trend=0.010). Consistently, we observed a similar association between WHtR and CVD mortality. HRs were 1.14 (0.65, 2.01), 1.39 (0.86, 2.27) and 1.70 (1.11, 2.61) across the quartiles with a significant linear trend (P for trend=0.039). No significant association was observed between BMI, WC, or TC and CVD mortality. In subgroup analysis, the association of WTR with CVD mortality was stronger among participants of age ≥ 75 years [HR=4.77 (1.93, 11.74) comparing the 4th to 1st quartile with P for trend<0.001].
Conclusions: In this national representative sample, compared with BMI, WC, TC, and WHtR, WTR is a stronger predictor for CVD mortality, especially among people over 75 years old. Well-controlled prospective studies are needed to confirm these findings.