Severity of Hypertension Mediates the Association of Hyperuricemia With Stroke in the REGARDS Case Cohort Study

Abstract

Previous studies do not widely support hyperuricemia as a risk factor for stroke and other cardiovascular diseases. We assessed the relationship between hyperuricemia and ischemic stroke (≈900 cases) using a large data set from the REGARDS study (Reasons for Geographic and Racial Differences in Stroke). We employed a case-cohort design (incident stroke cases and randomly selected cohort participants) and weighted Cox-proportional hazard models to estimate the association of serum urate level ≥6.8 mg/dL (ie, hyperuricemia) and 6.0 to <6.8 mg/dL versus <6.0 mg/dL (reference) with incident stroke. Analyses were stratified by race, gender, and age. Mediation of cardiovascular disease comorbidities on the serum urate-stroke association was tested. Hyperuricemia was associated with stroke (hazard ratio, 1.40 [95% CI, 1.10-1.78]) after adjustment for demographic variables and systolic and diastolic blood pressure. This association was substantially attenuated (hazard ratio, 1.17 [95% CI, 0.90-1.51]) by additional covariate adjustment. In particular, apparent treatment-resistant hypertension (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg on 3 antihypertensive medications or use of ≥4 antihypertensive medications) and the count of antihypertensive medication classes significantly reduced the effect of hyperuricemia on ischemic stroke. Specifically, apparent treatment-resistant hypertension and number of antihypertensive, respectively, mediate 45% and 43% of the association. There was no effect modification in the association between hyperuricemia and stroke by age, race, or gender. We conclude that hyperuricemia may be a risk factor for stroke. The substantial attenuation of this association by apparent treatment-resistant hypertension and number of antihypertensive suggests that severe hypertension may be a mediator.

Keywords: blood pressure; comorbidity; hypertension; hyperuricemia; uric acid.