Blood pressure and renal function decline in apparently healthy adults: the tehran lipid and glucose study

We investigated the association between blood pressure (BP) and renal function decline (RFD) in individuals with preserved kidney function (estimated glomerular filtration rate [eGFR] ≥60 mL/min/1.73 m²) and without cardiovascular disease, hypertension, diabetes, dyslipidemia, and smoking. In total, 3455 eligible participants (mean age: 37.8 years; 67.6% women) free of cardiometabolic risk factors were followed until 2021 (median follow-up [interquartile range]: 15.3 [13.4-16.8] years). RFD was defined as an eGFR of <60 mL/min/1.73 m² accompanied by a ≥ 30% decrease from baseline values. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for RFD across BP categories and per 10 mm Hg increase in systolic blood pressure (SBP) and per 5 mm Hg increase in diastolic blood pressure (DBP). After adjustment for a comprehensive set of confounders, each 10 mm Hg increase in SBP and each 5 mm Hg increase in DBP were associated with 1.20 (95% CI: 1.07-1.35) and 1.20 (1.11-1.31) times higher risk of RFD, respectively. However, when both SBP and DBP were included in the models, SBP was no longer significantly associated with RFD (HR: 1.04; 95% CI: 0.90-1.21), whereas DBP remained significantly and linearly associated (1.19; 1.07-1.31). The association between DBP and RFD persisted when restricted to individuals with BP < 120/ < 80 mm Hg, with each 5 mm Hg increase associated with 29% higher risk. In conclusion, higher BP levels, even within the conventionally normal range, are associated with an increased risk of RFD in the absence of traditional cardiometabolic risk factors.