The association between frailty index and abdominal aortic calcification in the middle-aged and older US adults: NHANES 2013-2014

Zhengjun Zhang^1,2Peng Wu^2,3Shaobin Yang^1,2Baozhen Zhu^2,3Dapeng Chen^1,2Xiaocheng Li⁴Yarong Wang²Ning Yan^1,2*

• ¹Department of Cardiology, Yinchuan, China
• ²General Hospital of Ningxia Medical University, Yinchuan, China
• ³First Clinical College of Ningxia Medical University, Yinchuan, China
• ⁴Xi’an Medical University, Xi'an, China

Background: Abdominal aortic calcification (AAC) is one of the earliest observed forms of atherosclerotic calcification and is crucial for early cardiovascular risk prediction. Frailty, a global clinical and public health challenge, is associated with increased risks of mortality, functional decline, and loss of independence. However, the relationship between the Frailty Index (FI) and AAC among middle-aged and older adults has yet to be explored.This study analyzed data from 2013-2014 National Health and Nutrition Examination Survey (NHANES) cohort, focusing on individuals aged ≥ 40 years. The FI was calculated using a 49-item model to assess frailty status and participants were stratified into three groups: non-frail (FI ≤ 0.15), pre-frail (0.15 < FI ≤ 0.25), and frail (FI > 0.25). AAC was measured by dual-energy X-ray absorptiometry and quantified by Kauppila scores. Severe AAC was defined as an AAC score > 6. The relationship between FI and AAC was investigated using multivariable logistic regression, sensitivity analyses, and smoothing curve fitting. Subgroup analyses and interaction tests were conducted to assess the stability of this association across different populations.Results: A total of 2572 participants were enrolled in this study. Following adjustment for potential confounders, FI exhibited a statistically significant positive association with both AAC score (β = 2.64, 95%CI = 1.20-4.08) and Severe AAC (OR = 6.36, 95%CI = 1.48-27.41). Similar trends (P for trend < 0.05) were observed when FI was analyzed as a categorical variable. Smooth curve fitting and subgroup analysis were used to investigate the relationship between baseline FI Z-score and AAC score and Severe AAC. Interestingly, we found that the FI Z-score was linearly related to the occurrence of severe AAC, while it was nonlinearly related to the AAC score. The FI-Z score was positively associated with the likelihood of AAC score before the breakpoint (K = 0.78), but not significant after the breakpoint. The association between FI-Z score and Severe AAC was stable in the different subgroups (all P for interaction ＞0.05).Our study indicated a stable positive correlation between FI and AAC. FI may serve as a biomarker for early subclinical atherosclerosis detection in middleaged and older US adults.