Association between serum insulin levels and self-reported walking difficulty among adults with a history of stroke: A cross-sectional study of NHANES 1999–2018

Stroke is one of the leading causes of long-term disability worldwide. Walking difficulty is an important functional limitation among adults with a history of stroke. However, the association between serum insulin levels and self-reported walking difficulty in this population remains insufficiently studied. This study analyzed data from the National Health and Nutrition Examination Survey (NHANES) 1999-2018 to evaluate the association between serum insulin levels and self-reported walking difficulty among adults with a self-reported history of stroke. Weighted logistic regression models were used to adjust for confounders. Restricted cubic spline (RCS) analysis was conducted to explore potential nonlinear relationships. Sensitivity analyses were performed to assess the robustness of the findings. Subgroup analyses and interaction effect tests were conducted to examine heterogeneity across different populations. A total of 488 adults with a self-reported history of stroke were included in this study, representing 15,92,140 individuals in the US population. In the fully adjusted model, each 1 µU/mL increase in serum insulin level was associated with 5% higher odds of self-reported walking difficulty (OR = 1.05, 95% confidence interval: 1.01-1.09, P = .028). Quartile-based analysis showed that higher insulin levels (Q3, Q4) were significantly associated with greater odds of self-reported walking difficulty, with the highest quartile (Q4) showing an OR of 5.10 (95% confidence interval: 1.93-13.48, P = .001). RCS analysis suggested a possible nonlinear association between serum insulin levels and self-reported walking difficulty (P for non-linearity = .032). The associations observed in the sensitivity analyses were in the same direction as those in the primary analysis. Higher serum insulin levels were associated with greater odds of self-reported walking difficulty among adults with a self-reported history of stroke. These findings do not establish causality or a role for insulin in stroke-related motor recovery.