Cross-sectional study links iodine nutritional status and demographic factors to low handgrip strength in Chinese adults.

BackgroundGrip strength is a key marker for sarcopenia screening, yet the influence of iodine nutritional status on low grip strength (LGS) remains poorly understood.MethodsThis cross-sectional study analyzed 810 community-dwelling adults in Lanzhou, China, randomly assigned to training (n = 568) and validation (n = 242) cohorts. Logistic regression analyses identified factors associated with LGS. A nomogram integrating urinary iodine concentration (UIC), systolic blood pressure (SP), and routine clinical variables was constructed. Model performance was evaluated using ROC curves, Hosmer-Lemeshow test, and Brier scores. Restricted cubic spline (RCS) analysis assessed the dose–response relationship between UIC and LGS, with subgroup analyses by thyroid function.ResultsLGS prevalence was 18.8% in the training cohort. Multivariate analysis showed female sex (OR = 0.34), greater height (OR = 0.94), and excessive iodine (OR = 0.36) were inversely associated with LGS, whereas age (60–74 years: OR = 2.20; ≥75 years: OR = 9.73), smoking (OR = 3.20), and SP (OR = 1.02) correlated with higher LGS odds. The nomogram demonstrated moderate discrimination (AUC: 0.723 training, 0.662 validation) with good calibration (Brier scores: 0.134 training, 0.147 validation; H-L p > 0.05). RCS analysis revealed a U-shaped association between UIC and LGS in unadjusted analyses, with the inverse associations most evident among euthyroid participants.ConclusionThe nomogram provides a practical, objective tool for early identification of individuals at high probability of LGS. Moderate-to-high UIC is associated with LGS odds, particularly in euthyroid adults. This model may guide targeted screening and interventions in community settings. In the cross-sectional design, causal inferences cannot be drawn; Further research is warranted to elucidate these complex relationships.