Association of serum calcium levels with diabetic kidney disease in normocalcemic type 2 diabetes patients: a cross-sectional study

To explore the association between serum calcium levels within normal ranges and Diabetic Kidney Disease (DKD) in type 2 diabetes patients. In this cross-sectional study, we analyzed clinical data from type 2 diabetes patients admitted to the Endocrinology Department of the Affiliated Hospital of Qingdao University from January 1, 2021, to December 1, 2022. We measured serum calcium levels, corrected for albumin, and screened for diabetes-related complications, including DKD. The association between corrected serum calcium levels and DKD was evaluated using logistic regression, with adjustments made for potential confounders and a generalized additive model (GAM) to explore non-linear relationships, supplemented by subgroup analyses. Among the 3016 patients (52.55% male, 47.45% female), the mean corrected serum calcium was 2.29 ± 0.08 mmol/L. DKD was present in 38.73% of patients. A 0.1 mmol/L increase in corrected serum calcium was associated with a 44% increased risk of DKD (OR = 1.44, 95% CI 1.28-1.61, p < 0.0001). The GAM indicated a linear relationship between corrected serum calcium and DKD risk, consistent across subgroups. Corrected serum calcium levels were linearly associated with DKD risk in type 2 diabetes patients, underlining its potential role in risk assessment. These findings emphasize the clinical importance of monitoring serum calcium levels. However, the need for further prospective studies to confirm these findings is underscored by the study's cross-sectional design.