Abstract Body: Objectives;
We aimed to evaluate heart rate variability (HRV) in patients with diabetes mellitus, classified by renal function.

Methods;
The patients with diabetes mellitus aged 20 to 79 years were recruited from two hospitals between January 2020 and December 2023. Exclusion criteria included the use of oral corticosteroids, adrenergic agonists or antagonists, and the presence of malignant tumors. Participants were categorized according to the classification of chronic kidney disease (CKD). HRV was measured using both a conventional index (SD-RR) and a novel index (SD-ΔRR) under three conditions: resting, standing, and deep breathing.

Results;
A total of 103 patients were analyzed. The distribution across KDIGO CKD classes was as follows: low risk (n=60), moderate risk (n=16), high risk (n=11), and very high risk (n=16). For comparison, patients were grouped into group 1 (low risk), group 2 (moderate & high risk), and group 3 (very high risk). The demographic data across these three groups were as follows. Mean Age: 52, 60, and 59 years, respectively. Mean HbA1c: 8.3%, 8.0%, and 8.1%. Prevalence of Diabetic Sensorimotor Neuropathy: 10%, 15%, and 50%. As for SD-RR, significant differences (p<0.05) were only observed during standing (40.4 vs. 29.7 vs. 21.6; group 1 vs. group 4). Differences during resting and deep breathing were not statistically significant. In contrast, as for SD-ΔRR, Significant differences were observed between group 1 and group 3 across all three conditions: SD-ΔRR during rest were 28.1, 24.7, and 20.2; during standing were 14.3, 12.6, and 7.5; and during deep breathing were 26.6, 23.7, and 15.9. In summary, while the significance of SD-RR was limited to the standing condition, the novel SD-ΔRR index consistently showed significant differences between renal function classes under all three evaluated conditions.

Conclusion;
In conclusion, our findings demonstrate that renal function, as categorized by the CKD classification, is closely associated with autonomic nervous system activity in patients with DM. Additionally, the result suggests that SD-ΔRR may serve as a more robust and comprehensive marker for evaluating the decline in heart rate variability associated with progressing renal dysfunction.