Based on data from the National Health and Nutrition Examination Survey (NHANES),
to evaluate the association between a residual vulnerability index (RVI) score—integrating inflammation, muscle
reserve, and comorbidity status—and the risk of functional impairment (FI) in adults, and to examine the
robustness of this association and its clinical utility. Methods: A cross-sectional study was conducted using 2,478
adult participants aged ≥20 years from the NHANES 2017～2018 cycle. The RVI score was constructed by
Z-score standardization of high-sensitivity C-reactive protein (hs-CRP, reflecting systemic inflammation), muscle
index (appendicular lean mass divided by body mass index, reflecting muscle reserve), and the number of
comorbidities. FI was defined based on the physical functioning questionnaire. The random forest (RF) algorithm
was used to screen key predictive features. A multivariable weighted logistic regression model was built to
analyze the independent association between the RVI score and FI risk, with odds ratios (ORs) and 95%
confidence intervals (CIs) calculated. Restricted cubic spline (RCS) models were fitted to model the
dose-response relationship. Subgroup analyses, E-value sensitivity analysis, and decision curve analysis (DCA)
were performed to verify the robustness and clinical value of the results. Results: The RVI score was
significantly higher in the FI group than in the non-FI group (P<0.001). RF analysis showed that the RVI score
ranked third in predictive importance, surpassing depression scores and sleep duration. Multivariable logistic
regression analysis revealed that, after adjusting for confounders, each 1-standard-deviation (SD) increase in the
RVI score was significantly associated with an increased risk of FI [OR=1.912(95% CI 1.548～2.361), P<0.001].
Quartile-based analysis showed that the highest quartile group had a significantly higher risk of FI compared with
the lowest quartile group [OR=6.204(95% CI 3.013～12.777), P=0.003], with a significant linear trend (P for
trend<0.001). The RCS model indicated a significant nonlinear positive association between the RVI score and FI
risk (nonlinearity P<0.001). Subgroup analyses demonstrated that this association remained generally consistent
across different population subgroups and was more pronounced among overweight/obese individuals (P=0.002
for interaction). Sensitivity analysis yielded an E-value point estimate of 2.115. DCA results showed that the prediction model
incorporating the RVI score provided superior clinical net benefit over the base model across a range of threshold probabilities.
Conclusion: The RVI score is an independent nonlinear risk factor for FI in adults.
PDF(1068 KB)
