Efficacy of Folic Acid Therapy on the Progression of Chronic Kidney Disease: The Renal Substudy of the China Stroke Primary Prevention Trial

Abstract

Importance: The efficacy of folic acid therapy on renal outcomes has not been previously investigated in populations without folic acid fortification.

Objective: To test whether treatment with enalapril and folic acid is more effective in slowing renal function decline than enalapril alone across a spectrum of renal function at baseline from normal to moderate chronic kidney disease (CKD) among Chinese adults with hypertension.

Design, setting, and participants: In this substudy of eligible China Stroke Primary Prevention Trial (CSPPT), 15 104 participants with an estimated glomerular filtration rate (eGFR) 30 mL/min/1.73 m2 or greater, including 1671 patients with CKD, were recruited from 20 communities in Jiangsu province in China.

Interventions: Participants were randomized to receive a single tablet daily containing 10 mg enalapril and 0.8 mg folic acid (n = 7545) or 10 mg enalapril alone (n = 7559).

Main outcomes and measures: The primary outcome was the progression of CKD, defined as a decrease in eGFR of 30% or more and to a level of less than 60 mL/min/1.73 m2 if the baseline eGFR was 60 mL/min/1.73 m2 or more, or a decrease in eGFR of 50% or more if the baseline eGFR was less than 60 mL/min/1.73 m2; or end-stage renal disease. Secondary outcomes included a composite of the primary outcome and all-cause death, rapid decline in renal function, and rate of eGFR decline.

Results: Overall, 15 104 Chinese adults with a mean (range) age of 60 (45-75) years were recruited; median follow-up was 4.4 years. There were 164 and 132 primary events in the enalapril group and the enalapril-folic acid group, respectively. Compared with the enalapril group, the enalapril-folic acid group had a 21% reduction in the odds of the primary event (odds ratio [OR], 0.79; 95% CI, 0.62-1.00) and a slower rate of eGFR decline (1.28% vs 1.42% per year; P = .02). Among the participants with CKD at baseline, folic acid therapy resulted in a significant reduction in the risks for the primary event (OR, 0.44; 95% CI, 0.26-0.75), rapid decline in renal function (OR, 0.67; 95% CI, 0.47-0.96) and the composite event (OR, 0.62; 95% CI, 0.43-0.90), and a 44% slower decline in renal function (0.96% vs 1.72% per year, P < .001). Among those without CKD at baseline, there was no between-group difference in the primary end point.

Conclusions and relevance: Enalapril-folic acid therapy, compared with enalapril alone, can significantly delay the progression of CKD among patients with mild-to-moderate CKD.

Trial registration: clinicaltrials.gov Identifier: NCT00794885.