Association of Genetic West African Ancestry, Blood Pressure Response to Therapy, and Cardiovascular Risk Among Self-reported Black Individuals in the Systolic Blood Pressure Reduction Intervention Trial (SPRINT)

Abstract

Importance: Self-identified Black race is associated with higher hypertension prevalence and worse blood pressure (BP) control compared with other race/ethnic groups. The contribution of genetic West African ancestry to these racial disparities appears not to have been completely determined.

Objective: To determine the association between the proportion of West African ancestry with the response to antihypertensive medication, BP control, kidney function, and risk of adverse cardiovascular (CV) events among self-identified Black individuals in the Systolic Blood Pressure Intervention Trial (SPRINT).

Design, setting, and participants: This post hoc analysis of the SPRINT trial incorporated data from a multicenter study of self-identified Black participants with available West African ancestry proportion, estimated using 106 biallelic autosomal ancestry informative genetic markers. Recruitment started on October 20, 2010, and ended on August 20, 2015. Data were analyzed from May 2020 to September 2020.

Main outcomes and measures: Trajectories of BP and kidney function parameters on follow-up of the trial were assessed across tertiles of the proportion of West African ancestry using linear mixed-effect modeling after adjustment for potential confounders. Multivariable adjusted Cox models evaluated the association of West African ancestry with the risk of composite CV events (nonfatal myocardial infarction, CV death, and heart failure event).

Results: Among 2466 participants in the current analysis (1122 women [45.5%]; median West African ancestry, 81% [interquartile range, 73%-87%]), there were 120 composite CV events (4.9%) over a mean (SD) of 3.2 (0.9) years of follow-up. At baseline, mean (SD) high-density lipoprotein cholesterol levels were higher (tertile 3: 56.5 [15.0] mg/dL vs tertile 1: 54.2 [14.9] mg/dL; P = .006), smoking prevalence (never smoking: tertile 3: 367 [47.9%] vs tertile 1: 372 [42.2%]; P = .009) and mean (SD) Framingham Risk scores (tertile 3: 16.7 [9.7] vs tertile 1: 18.1 [10.2]; P = .01) were lower, and baseline BP was not different across increasing tertiles of West African ancestry. On follow-up, there was no evidence of differences in longitudinal trajectories of BP, kidney function parameters, or left ventricular mass (Cornell voltage by electrocardiogram) across tertiles of West African ancestry in either intensive or standard treatment arms. In adjusted Cox models, higher West African ancestry was associated with a lower risk of a composite CV event after adjustment for potential confounders (adjusted hazard ratio per 5% higher West African ancestry, 0.92 [95% CI, 0.85-0.99]).

Conclusions and relevance: Among self-reported Black individuals enrolled in SPRINT, the trajectories of BP, kidney function, and left ventricular mass over time were not different across tertiles of the proportion of West African ancestry. A higher proportion of West African ancestry was associated with a modestly lower risk for CV events. These findings suggest that extrinsic and structural societal factors, more than genetic ancestry, may be the major drivers of the well-established racial disparity in cardiovascular health associated with hypertension.

Figure 1.. Trajectories of Systolic Blood Pressure, Number of Antihypertensive Medications, and Kidney Function Parameters Across West African Ancestry Based Study Groups in the Intensive Treatment and Standard Arms

A, Mean systolic blood pressure. B, Mean number of antihypertensive medications. C, Mean estimated glomerular filtration rate. D, Mean blood urea nitrogen. E, Mean urine albumin-creatinine ratio over time by treatment group and ancestry tertile.

Figure 2.. Association of West African Ancestry Proportions With Risk of Primary Composite Outcome

Continuous association (solid blue line) and 95% CIs (shaded region) between West African ancestry and risk of primary composite outcome using restricted cubic splines. The model was adjusted for age, sex, treatment arm, smoking status, education level, estimated glomerular filtration rate, systolic blood pressure, smoking status, total cholesterol, high-density lipoprotein cholesterol, APOL1 count, and trial site. Primary composite outcome is a composite of myocardial infarction, non–myocardial infarction acute coronary syndrome, stroke, acute decompensated heart failure, or cardiovascular death.