Association With Incidence of Ischemic Heart Disease Based on the Estimated Glomerular Filtration Rate in the Population of the Three Southern Border Provinces of Thailand

Background: Declining kidney function, as reflected by a reduced estimated glomerular filtration rate (eGFR), has been associated with an increased risk of ischemic heart disease (IHD). However, limited evidence is available in the population residing in Thailand’s three southern border provinces. Objective: This study aimed to examine the association between estimated eGFR and the incidence of IHD in the population of Thailand’s three southern border provinces. Methods: A retrospective cohort study was conducted using electronic medical records from three government hospitals between October 1, 2018, and September 30, 2023. Adults aged 30 years or older with baseline eGFR data were categorized into five groups based on their eGFR levels. The outcome was incident IHD, identified using ICD-10 codes. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for relevant covariates. Results: Among 16,763 participants followed for a total of 53,360 person-years, 746 developed IHD. The cumulative incidence was 4.5% (95% CI: 4.0–5.0%), and the incidence density was 13.98 cases per 1,000 person-years. A significant inverse relationship was observed between eGFR and IHD incidence (p < 0.001). Compared with participants with eGFR ≥90.00 mL/min/1.73 m², the adjusted HRs for IHD were 1.89 (95% CI: 1.58-2.25) for eGFR 60.00-89.99, 2.65 (95% CI: 2.16-3.24) for 30.00–59.99, 4.96 (95% CI: 3.62-6.81) for 15.00-29.99, and 3.74 (95% CI: 2.34-5.99) for <15.00 mL/min/1.73 m². A graded increase in IHD risk was observed across lower eGFR groups. Other significant risk factors included older age, sex, higher systolic blood pressure, and atrial fibrillation, while higher high-density lipoprotein cholesterol (HDL-C) levels were associated with a reduced risk of IHD. Conclusion: Reduced eGFR was independently associated with a higher risk of IHD, even among individuals with mildly impaired kidney function. These findings support the potential role of eGFR in cardiovascular risk assessment and the development of targeted prevention strategies in high-risk populations.