Dynapenia in Patients with Diabetic Nephropathy: A Cross-Sectional Comparative Study

Abstract Background and objective: Diabetic nephropathy is a frequent microvascular complication of type 2 diabetes mellitus (T2DM), and both conditions have been linked to loss of muscle strength (dynapenia). Whether the presence of nephropathy adds to the muscle-strength deficit already associated with diabetes remains incompletely defined. We compared handgrip strength, functional mobility and body composition among healthy controls, patients with isolated T2DM, and patients with diabetic nephropathy, restricting enrollment to individuals with a preserved skeletal muscle mass so that strength loss could be evaluated independently of muscle mass loss. Methods In this single-center, cross-sectional, descriptive-analytical study conducted between February and April 2024, 117 adults attending family medicine and nephrology outpatient clinics were allocated to three equal groups of 39: healthy controls, patients with T2DM without nephropathy, and patients with diabetic nephropathy (defined by a urine albumin-to-creatinine ratio > 300 mg/g). All participants underwent laboratory testing, bioelectrical impedance analysis, handgrip dynamometry and the Timed Up and Go (TUG) test. Dynapenia was defined as handgrip strength below 28.5 kg in men and 18.5 kg in women. Group comparisons used the Kruskal-Wallis test with Bonferroni post-hoc correction, chi-square or Fisher's exact tests, and Spearman correlation. Results Dynapenia was present in 0% of controls, 28.2% of patients with isolated T2DM, and 38.5% of patients with diabetic nephropathy. Mean handgrip strength was significantly lower in both diabetic groups than in controls (31.85 ± 8.58 kg in controls vs 26.25 ± 8.97 kg in isolated diabetes and 24.95 ± 7.17 kg in diabetic nephropathy; p = 0.001), with no significant difference between the two diabetic groups. TUG duration was significantly longer in the diabetic nephropathy group (13.73 ± 1.49 s) than in controls (10.48 ± 1.4 s) and isolated diabetes (11.31 ± 1.61 s; p < 0.001). Across the whole cohort, handgrip strength correlated inversely with body mass index, waist and hip circumference, TUG duration, body-fat percentage, fasting glucose and HbA1c, and positively with skeletal muscle percentage and total protein (all p < 0.05). Conclusions Diabetes mellitus was associated with reduced handgrip strength irrespective of nephropathy status, but the additional presence of diabetic nephropathy was associated with a higher prevalence of dynapenia and a marked prolongation of TUG performance, indicating a greater impact on functional mobility once nephropathy develops. Simple, low-cost functional assessments may help identify diabetic patients at greatest risk of functional decline.