U-Shaped Relationship Between Serum Lactate Dehydrogenase With Diabetic Lower Extremity Ulcers Among Diabetic Patients Aged ≥ 40 Years in NHANES.

Elevated lactate dehydrogenase (LDH) levels are associated with tissue hypoxia, ischemia and inflammation, and have been linked to increased risks of multiple diseases. However, evidence regarding the association between LDH and diabetic lower extremity ulcers (DLEU) remains limited. This cross-sectional study aimed to evaluate this relationship using data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). Among 1620 enrolled diabetic participants, DLEU prevalence was 8.1% (131/1489). Serum LDH levels were categorised into sextiles: < 113, 113-125, 126-137, 138-152, 153-172 and > 172 U/L. Multivariable logistic regression, subgroup analysis, restricted cubic spline (RCS) modelling and sensitivity analysis revealed a U-shaped association between LDH and DLEU. The inflection point occurred at approximately 125 U/L: Below 125 U/L, each 10-U/L increase in LDH was associated with a 26% reduction in DLEU risk (odds ratio [OR] 0.740, 95% confidence interval [CI]: 0.560-0.978, p = 0.034); above 125 U/L, each 10-U/L increment corresponded to a 6.5% increase in DLEU risk (OR 1.065, 95% CI: 1.003-1.131, p = 0.039). Thus, analysis of this nationally representative cohort demonstrates a nonlinear relationship between LDH and DLEU incidence, characterised by distinct risk thresholds.