U-shaped Association Between Weight-Adjusted-Waist Index and Arterial Stiffness Among Adult Hypertensive Patients: A Population-Based Study in the United States

The weight-adjusted-waist index (WWI) is an innovative measure of obesity that appears to surpass body mass index (BMI) in assessing lean body mass and fat mass. This study aimed to evaluate the relationship between WWI and AS in hypertensive adults in the United States. The study included 9753 adults diagnosed with hypertension from the National Health and Nutrition Examination Survey (NHANES), which spanned the years 2007-2016. WWI was calculated by dividing waist circumference (in cm) by the square root of body weight (in kg), and arterial stiffness (represented by estimated pulse wave velocity [ePWV]) was analyzed as the outcome. Weighted multiple linear regression and smooth curve fitting were used to test for linear and nonlinear associations. Threshold effects were determined using a two-part linear regression model. Additionally, subgroup analyses and interaction tests were conducted to gain a more in-depth understanding of the observed associations. The mean WWI of the participants was 11.32 ± 0.76. After multivariable adjustment, WWI showed a significant nonlinear association with ePWV, with a U-shaped association observed between the two. Specifically, WWI below the threshold of 10.23 was negatively associated with arterial stiffness (β = -0.39, 95% CI: -0.54 to -0.25), while WWI above the threshold of 10.23 was positively associated with arterial stiffness (β = 0.04, 95% CI: 0.01-0.07). To conclude, the present findings imply that maintaining WWI within an optimal range could reduce AS in hypertensive individuals and potentially decrease cardiovascular risk. However, this observation needs to be confirmed in large clinical trials.