Aims: The purpose of this study was to clarify the prevalence of diabetic foot lesions and their association with lower-limb amputations and/or foot ulcers. Materials and Methods: In this cross-sectional study, 968 patients with diabetes were surveyed. Diabetic foot lesions were defined according to the broad national criteria, which encompass both mild abnormalities and more advanced conditions. Based on this definition, foot lesions were assessed using a questionnaire comprising the following 10 items: a history of lower-limb amputations, a history of treatment of foot lesions, numbness/loss of sensation/pain, skin discolorations, skin symptoms, nail abnormalities, foot ulcers/gangrene, foot deformities, foot infection, and intermittent claudication. Logistic regression analysis was used to examine risk factors for foot lesions. Area under the curve (AUC) of the number of foot lesions for lower-limb amputations or foot ulcers/gangrene was calculated using the receiver operating characteristic curve (ROC) analysis. Results: Approximately two-thirds of the patients had at least one type of diabetic foot lesion. Logistic regression analysis revealed that women, past or current smoking, a history of cardiovascular disease, and nephropathy were associated with the risk of diabetic foot lesions. According to the ROC analysis, the optimal cut-off point of number of diabetic foot lesions was three for identifying patients with a history of lower-limb amputation and/or the presence of foot ulcers or gangrene (AUC 0.80 (95% CI, 0.70–0.91), p < 0.01). Conclusions: Diabetic foot lesions are common in patients with diabetes and the prevalence of diabetic foot lesions was higher in patients with a history of lower-limb amputations and/or the presence of foot ulcers or gangrene. Early detection and care of diabetic foot lesions are necessary to prevent lower-limb amputations and foot ulcers.

Background: Type 2 diabetes (T2D) has been linked to impairments in skeletal muscle performance, encompassing reductions in both muscle strength and muscle quality. While malnutrition is a known modifiable factor contributing to muscle quality deterioration, its specific relationship with the Geriatric Nutritional Risk Index (GNRI) in T2D remains underexplored. Using data from 743 participants in the KAMOGAWA-A cohort, this cross-sectional study evaluated the association between muscle quality and GNRI in individuals with type 2 diabetes. Methods: Muscle quality was defined as handgrip strength divided by arm lean mass. GNRI was calculated using serum albumin and body mass index. Multiple linear regression models were used to assess associations between GNRI and muscle quality. To account for BMI-related dependency in muscle quality measurements, we derived BMI-adjusted GNRI residuals and performed the same regression analysis to evaluate the stability of the observed relationship beyond BMI-induced confounding. Results: In the overall population, GNRI was inversely associated with muscle quality (β = −0.17, p < 0.001). Conversely, residual GNRI demonstrated a significant positive association with muscle quality (β = 0.13, p < 0.001), especially among men, individuals under 65 years of age, and across all BMI categories. Stratified analyses suggested that the strength and direction of associations varied by age, sex, and glycemic control status. Conclusions: The GNRI showed an inverse correlation with muscle quality, whereas residual GNRI showed a consistent positive relationship. These findings suggest that improving nutritional status may support muscle function in T2D, but BMI confounds the interpretation of GNRI in this context.