#2293 Cardiac autonomic neuropathy: an independent risk factor for renal decline in diabetic kidney disease
Authors: Soe Kywe , Robinson Emma , Oleolo Misbah , Tesfaye Solomon , Marques Jefferson , Sharma Kanishka , Periquito Joao , Sourbron Steven , Gomez Maria , Selvarajah Dinesh 
Published: May 2024

Abstract

Background and Aims
Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease (CKD) and end stage kidney disease (ESKD) in the UK and worldwide. Due to its unpredictability and incurable nature, novel risk factors associated with incidence and progression of DKD need to be identified. One such factor is cardiac autonomic neuropathy (CAN).
Many studies over last 30 years had demonstrated a significant relationship between CAN and incidence and progression of DKD using estimated glomerular filtration rate (eGFR) and urinary albumin creatinine ratio (UACR) as end points. However, no prospective studies have looked into relationship between CAN diagnosed by gold standard cardiac autonomic reflex tests (CARTs) and DKD with different prognostic risks as per KDIGO classification. The aim of the study is to examine this relationship further.

Method
Data from 91 participants (type 1 and type 2 DM) with eGFR &gt;30 ml/min/1.73 m2 who underwent assessment for CAN using CARTs as per O'Brien's and Ewing's criteria during baseline visits performed between 2007 and 2010 were collected. Additional participants (n = 113) were also recruited in 2021 as part of iBEAt study which is an EU-funded, multi-centre renal imaging study to identify novel biomarkers for DKD. Data analysis for 204 participants in total was performed for this study.
CAN was defined as 2 or more abnormal CARTs out of 5 (Table 1). The level of prognostic risk was calculated based on eGFR (G1-G5) and UACR (A1-A3), following KDIGO risk table from 2012 CKD guidelines. eGFR was calculated by chronic kidney disease epidemiology collaboration (CKD-EPI) equation and UACR was assessed by early morning urine sample.
Participants were categorised as follow: low risk, moderate risk and high risk. Due to limited numbers of participants with G3 in eGFR, we have combined ‘high risk’ and ‘very high risk’ into one group. CAN was divided into 2 groups—with and without CAN. Differences in proportions were examined using chi-square test. The association between baseline CAN and risk of renal decline was assessed using multinominal logistic regression adjusted for baseline age, HbA1c, ACEi/ARBs use, retinopathy status, total cholesterol and triglyceride. If significant differences were found, individual groups were compared by Bonferroni post hoc test. All analyses were performed in SPSS (version 29.0) and correlations were considered significant if p &lt; 0.05.

Results
We analysed data of 204 participants (130 T1DM, 74 T2DM), 44.6% (n = 91) of them were women, mean (SD) age at baseline visit was 51 (15.7) years, eGFR 82.6 (13) ml/min/1.73 m2, UACR 5.2 (21.8) mg/mmol, duration of diabetes at baseline 19.7 (12.3) years and 36.8% had hypertension. Baseline eGFR and UACR were available for 198 and 193 participants respectively. Of these, 42.9% (85/198) had G1, 47.5 (94/198) had G2 and 9.6 (19/198) had G3. For UACR, 80.8% (156/193) had A1, 15.5% (30/193) had A2 and 3.6% (7/193) had A3. 53.4% (103/204) of participants had CAN and 46.6% (101/204) had no CAN.
A higher proportion of participants was in low prognostic risk category 77.8% (154/198), followed by 13.1% (26/198) with moderate risk and 9.8% (18/198) with high risk for CKD progression. The risk of DKD progression was significantly associated with presence of CAN in multinominal logistic regression analysis (p = 0.020). The presence of CAN was closely related to low risk (95% CI: 1.44 to 22.04, p = 0.013) and moderately increased risk (95% CI: 1.03 to 24.7, p = 0.04). The participants with moderate and high risk had lower eGFR (p &lt; 0.001) and higher UACR with increased risk (p &lt; 0.001) (Table 2). This finding was independent of baseline age, HbA1C, retinopathy, ACEI/ARB use, type of diabetes, cholesterol and triglyceride levels at baseline as measured by logistic regression.

Conclusion
To our knowledge, this is one of the first studies to examine the relationship between presence of CAN in three stages of prognostic risk in DKD. We demonstrated that presence of CAN was an independent risk factor for decline in renal function in DKD.
Further large prospective studies are required to confirm the findings of this study and examine the underlying mechanisms how CAN leads to greater risk of DKD.