First line drug treatment for hypertension and reductions in blood pressure according to age and ethnicity: cohort study in UK primary care

OBJECTIVE: To study whether treatment recommendations based on age and ethnicity according to United Kingdom (UK) clinical guidelines for hypertension translate to blood pressure reductions in current routine clinical care. DESIGN: Observational cohort study. SETTING: UK primary care, from 1 January 2007 to 31 December 2017. PARTICIPANTS: New users of angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB), calcium channel blockers (CCB), and thiazides. MAIN OUTCOME MEASURES: Change in systolic blood pressure in new users of ACEI/ARB versus CCB, stratified by age (< v ≥55) and ethnicity (black v non-black), from baseline to 12, 26, and 52 week follow-up. Secondary analyses included comparisons of new users of CCB with those of thiazides. A negative outcome (herpes zoster) was used to detect residual confounding and a series of positive outcomes (expected drug effects) was used to determine whether the study design could identify expected associations. RESULTS: During one year of follow-up, 87 440 new users of ACEI/ARB, 67 274 new users of CCB, and 22 040 new users of thiazides were included (median 4 (interquartile range 2-6) blood pressure measurements per user). For non-black people who did not have diabetes and who were younger than 55, CCB use was associated with a larger reduction in systolic blood pressure of 1.69 mm Hg (99% confidence interval −2.52 to −0.86) relative to ACEI/ARB use at 12 weeks, and a reduction of 0.40 mm Hg (−0.98 to 0.18) in those aged 55 and older. In subgroup analyses using six finer age categories of non-black people who did not have diabetes, CCB use versus ACEI/ARB use was associated with a larger reduction in systolic blood pressure only in people aged 75 and older. Among people who did not have diabetes, systolic blood pressure decreased more with CCB use than with ACEI/ARB use in black people (reduction difference 2.15 mm Hg (−6.17 to 1.87)); the corresponding reduction difference was 0.98 mm Hg (−1.49 to −0.47) in non-black people. CONCLUSIONS: Similar reductions in blood pressure were found to be associated with new use of CCB as with new use of ACEI/ARB in non-black people who did not have diabetes, both in those who were aged younger than 55 and those aged 55 and older. For black people without diabetes, CCB new use was associated with numerically greater reductions in blood pressure than ACEI/ARB compared with non-black people without diabetes, but the confidence intervals were overlapping for the two groups. These results suggest that the current UK algorithmic approach to first line antihypertensive treatment might not lead to greater reductions in blood pressure. Specific indications could be considered in treatment recommendations.