Benefits and harms of antihypertensive treatment for uncomplicated mild hypertension in primary care: an observational cohort study in the clinical practice research datalink

Problem

Evidence to support initiation of pharmacological treatment in patients with uncomplicated (low risk) mild (stage 1) hypertension is inconclusive and clinical guidelines are contradictory. The aim of this study was to use electronic health records and statistical methods which minimise bias in non-randomised studies to examine whether treatment is safe and effective at reducing the risk of mortality and cardiovascular disease in uncomplicated mild hypertensives.

Approach

This study had a longitudinal cohort design using electronic health records from Primary Care. Data were extracted from patients in the Clinical Practice Research Datalink from England, aged 18-74 years, with stage 1 hypertension (blood pressure between 140/90-159/99mmHg), no cardiovascular disease (CVD) risk factors and no treatment, from 1998-2015. Patients exited if follow-up records became unavailable due to death or moving away from a participating practice. Propensity scores predicting likelihood of treatment were constructed using a logistic regression model. Individuals on treatment were matched to those not on treatment 12 months after a diagnosis of hypertension, by propensity score using the nearest neighbour method. The rate of mortality, cardiovascular disease and adverse events in patients on treatment were compared to those not on treatment using Cox regression.

Findings

A total of 19,143 untreated patients (mean age 54.7±12.2 years, 56.0% female) were matched to 19,143 similar patients on treatment. During a period of up to 15 years follow-up, no association was found between antihypertensive treatment and mortality (HR 1.07, 95%CI 0.97-1.18), cardiovascular disease (HR 1.02, 95%CI 0.92-1.14) or any individual cardiovascular disease endpoints. Treatment was associated with an increased risk of adverse events including hypotension (HR 1.63, 95%CI 1.34-1.97), syncope (HR 1.26, 95%CI 1.12-1.42), electrolyte abnormalities (HR 1.50, 95%CI 1.09-2.07) and acute kidney injury (HR 1.41, 95%CI 1.13-1.76).

Consequences

This appropriately powered study found no evidence to support the initiation of antihypertensive treatment in patients with uncomplicated mild hypertension. However, there was evidence of an increased risk of adverse events and clinicians should refrain from using treatment in this population, since it may do more harm than good.