A J-shaped association between weight-adjusted waist index and cardiovascular disease: a longitudinal study from the CHARLS database

BACKGROUND: Weight-adjusted waist index (WWI) is a new obesity-related index, which has advantages in assessing central obesity. The aim of this study was to investigate the relationship between WWI and cardiovascular disease (CVD). METHODS: We collected a nationally representative sample of middle-aged and older adults over 45 years of age from the China Health and Retirement Longitudinal Study (CHARLS). WWI was calculated by dividing waist circumference by the square root of body weight, whereas CVD was defined as self-reported having heart disease and/or stroke. We used restricted cubic spline (RCS) curves to investigate whether there is a nonlinear relationship between WWI and CVD. Subsequently, a two-piece linear regression model was developed, and a recursive algorithm was utilized to determine the inflection point. RESULTS: A total of 13,046 participants were included, 9138 of whom were followed up until 2018. The average age among these sample was 59.24(SD = 9.54), and the 24.62% of individual was older people aged 65 years old and more. A J-relationship was found between WWI and incident CVD, with the turning point at 10. After this inflection point, there was a statistically significant association between WWI and incident CVD in middle-aged and older adults. In Model III of the threshold effect analysis, the odds ratio was 1.13 (95%CI:1.06-1.23, P < 0.001). Whereas, with the WWI ranged from 0 to 10, we did not observe a significant association between WWI and incident CVD(OR = 0.97,95%CI:0.91-1.04), P = 0.366). CONCLUSIONS: This prospective longitudinal study suggests a J-shaped relationship between WWI and incident CVD in Chinese population. WWI was positively associated with incident CVD only at WWI ≥ 10. This finding suggests that WWI may be an intervention indicator for reducing CVD.