Comment on ‘Glycemic control and renal function decline in patients with chronic coronary syndrome: A multicenter cohort study’

Dear Editor,

We read with great interest the multicenter cohort study by Cheng et al., which explored the association between glycemic control and renal outcomes in patients with chronic coronary syndrome (CCS) ¹ . The finding that an HbA1c range of 6.5%–6.9% was associated with the lowest risk of eGFR decline offers a potentially useful reference for this high‐risk population. However, we would like to raise several methodological considerations that may affect the interpretation of the reported ‘optimal’ glycemic target.

First, the primary outcome was defined as a > 25% decline in estimated glomerular filtration rate (eGFR). While this threshold has been used in some regional studies, current international consensus—including large meta‐analyses from the CKD Prognosis Consortium—and regulatory standards from the FDA and EMA generally endorse a confirmed eGFR reduction of ≥30% or ≥ 40% as a valid surrogate for end‐stage renal disease ² . A 25% decline is particularly vulnerable to transient hemodynamic changes, such as the initial dip in eGFR commonly observed after initiating renin–angiotensin system inhibitors or SGLT2 inhibitors. In a CCS cohort with frequent medication adjustments, this endpoint may inadvertently capture physiological adaptation rather than true structural kidney damage.

Second, the analysis relied on standard Cox proportional hazards models, treating death as independent censoring. However, in elderly patients with established coronary disease, cardiovascular mortality is a substantial competing risk that precludes the observation of renal events ³ . Notably, the low HbA1c group (<6.5%) often includes individuals with frailty, multimorbidity, or ‘burnt‐out diabetes’—conditions that both lower HbA1c spontaneously and increase mortality. Without subdistribution hazard modeling (e.g., Fine–Gray analysis), the observed association between low HbA1c and renal decline may be confounded by terminal illness rather than reflecting a causal relationship.

Finally, data were collected during 2012–2017, prior to the widespread adoption of SGLT2 inhibitors and GLP‐1 receptor agonists. Current ADA and KDIGO guidelines (2025–2026) now prioritize these organ‐protective agents as first‐line therapy, with renal benefits largely independent of baseline HbA1c ⁴ , ⁵ . Thus, a fixed HbA1c target derived from the pre‐SGLT2i era may have limited relevance in contemporary clinical practice.

We commend the authors for their valuable contribution and suggest that future studies validate these findings using more stringent renal endpoints, competing risk methodologies, and modern treatment contexts—steps that could enhance the precision of glycemic management in high‐risk patients.

FUNDING

This study did not receive external funding.

DISCLOSURE

The author declares no conflicts of interest.

Approval of the research protocol: N/A.

Informed consent: N/A.

Registry and the registration no. of thestudy: N/A.

Animal studies: N/A.

DATA AVAILABILITY STATEMENT

Data sharing not applicable to this article as no datasets were generated or analysed during the current study.