Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and a relative deficiency of insulin. Its prevalence has been increasing rapidly worldwide.1 According to the International Diabetes Mellitus Federation reported that approximately 537 million adults were living with diabetes mellitus in 2021, and this number is projected to rise to 783 million by 2045.2 The multifaceted nature of T2DM leads to serious complications that significantly impact morbidity, mortality, and overall healthcare costs. Among these complications, lower extremity arterial disease (LEAD) represents a major public health concern, as it can lead to critical limb ischemia, amputations, and an elevated incidence of cardiovascular events.3 LEAD is characterized by atherosclerosis in the peripheral arteries, particularly those in the lower limbs, and is especially prevalent among individuals with T2DM due to risk factors such as dyslipidemia, hypertension, and obesity.4 Studies have shown that individuals with T2DM have a higher prevalence of LEAD compared to those without diabetes.5, 6, 7 This condition not only limits mobility and reduces quality of life but also threatens limb viability and significantly increases the risk of cardiovascular complications. Therefore, early identification and risk assessment in patients with T2DM are essential for effective management and intervention.

Small dense low-density lipoprotein cholesterol (sdLDL-C) has emerged as an important marker for cardiovascular risk and may contribute to the development of atherosclerosis.8,9 Compared to standard LDL-C, sdLDL-C particles are smaller and denser, enabling them to more easily penetrate the arterial wall, resulting in increased retention and the initiation of atherogenic processes. This particular subset of lipoproteins has attracted attention due to its unique biochemical properties and its association with various metabolic disorders, particularly T2DM. Research suggests that sdLDL-C not only serves as indicator of lipid dysregulation but may also directly promote vascular inflammation, oxidative stress, and endothelial dysfunction-all of critical factors in the formation of atherosclerotic lesions.10,11 The relationship between T2DM and sdLDL-C is intricate, as chronic hyperglycemia and insulin resistance substantially influence lipid metabolism. Dyslipidemia is commonly observed in individuals with T2DM, with numerous studies reporting elevated sdLDL-C levels.12 This elevation is believed to result from hepatic production and alterations in lipolysis, which contributes to a heightened risk of cardiovascular events and peripheral vascular diseases in diabetic patients. Nonetheless, the specific role of sdLDL-C in the context of LEAD among T2DM patients has not been thoroughly explored.

Our study aimed to investigate the association between sdLDL-C levels and the incidence of LEAD in individuals with T2DM. We hypothesized that elevated sdLDL-C levels might act as an independent risk factor for LEAD within this population. By analyzing the relationships between sdLDL-C and various metabolic indicators, such as fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), and apolipoprotein B (ApoB), we sought to elucidate the role of sdLDL-C in the vascular complications associated with T2DM. Our research may provide valuable insights into novel therapeutic targets and preventive strategies for mitigating cardiovascular risks in T2DM patients, ultimately enhancing their care and quality of life. This study underscored the significance of sdLDL-C as a risk marker and its importance in understanding the vascular complications linked to T2DM.