Alcohol has a biphasic effect on blood pressure and increases heart rate

Review question

We reviewed available evidence about the short-term effects of different doses of alcoholic drinks compared to non-alcoholic drinks on blood pressure and heart rate in adults (≥ 18 years) with both normal and raised blood pressure.

Background

Drinking excessive alcohol is considered one of the most common causes of raised blood pressure. We wanted to quantify the effects of a single dose of alcohol on blood pressure and heart rate within 24 hours of consumption.

Study characteristics

We included 32 randomised controlled trials involving 767 participants published up to March 2019. Although these trials included adults from 18 to 96 years of age with various health conditions, most study participants were young healthy males. The source of funding was not reported for a majority of the studies.

Key results

For low doses of alcohol, we found that one glass of alcohol had little to no effect on blood pressure and increased heart rate within six hours of drinking.

We are moderately certain that medium-dose alcohol decreased blood pressure and increased heart rate within six hours of consumption. We did not see any significant change in blood pressure or heart rate after that, but the evidence was limited.

We are also moderately certain that high-dose alcohol decreased blood pressure within six hours, and the effect lasted up to 12 hours. After that, blood pressure was found to be increased. Heart rate increased significantly after alcohol consumption and remained increased at all times measured.

Thus alcohol decreases blood pressure initially (up to 12 hours after ingestion) and increases blood pressure after that. Alcohol consistently increases heart rate at all times within 24 hours of consumption. 

Authors' conclusions: 

High-dose alcohol has a biphasic effect on BP; it decreases BP up to 12 hours after consumption and increases BP > 13 hours after consumption. High-dose alcohol increases HR at all times up to 24 hours. Findings of this review are relevant mainly to healthy males, as only small numbers of women were included in the included trials.

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Background: 

Alcohol is consumed by over 2 billion people worldwide. It is a common substance of abuse and its use can lead to more than 200 disorders including hypertension. Alcohol has both acute and chronic effects on blood pressure. This review aimed to quantify the acute effects of different doses of alcohol over time on blood pressure and heart rate in an adult population.

Objectives: 

Primary objective

To determine short-term dose-related effects of alcohol versus placebo on systolic blood pressure and diastolic blood pressure in healthy and hypertensive adults over 18 years of age.

Secondary objective

To determine short-term dose-related effects of alcohol versus placebo on heart rate in healthy and hypertensive adults over 18 years of age.

Search strategy: 

The Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to March 2019: the Cochrane Hypertension Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 2), in the Cochrane Library; MEDLINE (from 1946); Embase (from 1974); the World Health Organization International Clinical Trials Registry Platform; and ClinicalTrials.gov. We also contacted authors of relevant articles regarding further published and unpublished work. These searches had no language restrictions.

Selection criteria: 

Randomised controlled trials (RCTs) comparing effects of a single dose of alcohol versus placebo on blood pressure (BP) or heart rate (HR) in adults (≥ 18 years of age).

Data collection and analysis: 

Two review authors (ST and CT) independently extracted data and assessed the quality of included studies. We also contacted trial authors for missing or unclear information. Mean difference (MD) from placebo with 95% confidence interval (CI) was the outcome measure, and a fixed-effect model was used to combine effect sizes across studies. 

Main results: 

We included 32 RCTs involving 767 participants. Most of the study participants were male (N = 642) and were healthy. The mean age of participants was 33 years, and mean body weight was 78 kilograms.

Low-dose alcohol (< 14 g) within six hours (2 RCTs, N = 28) did not affect BP but did increase HR by 5.1 bpm (95% CI 1.9 to 8.2) (moderate-certainty evidence).

Medium-dose alcohol (14 to 28 g) within six hours (10 RCTs, N = 149) decreased systolic blood pressure (SBP) by 5.6 mmHg (95% CI -8.3 to -3.0) and diastolic blood pressure (DBP) by 4.0 mmHg (95% CI -6.0 to -2.0) and increased HR by 4.6 bpm (95% CI 3.1 to 6.1) (moderate-certainty evidence for all). 

Medium-dose alcohol within 7 to 12 hours (4 RCTs, N = 54) did not affect BP or HR.

Medium-dose alcohol > 13 hours after consumption (4 RCTs, N = 66) did not affect BP or HR.

High-dose alcohol (> 30 g) within six hours (16 RCTs, N = 418) decreased SBP by 3.5 mmHg (95% CI -6.0 to -1.0), decreased DBP by 1.9 mmHg (95% CI-3.9 to 0.04), and increased HR by 5.8 bpm (95% CI 4.0 to 7.5). The certainty of evidence was moderate for SBP and HR, and was low for DBP.

High-dose alcohol within 7 to 12 hours of consumption (3 RCTs, N = 54) decreased SBP by 3.7 mmHg (95% CI -7.0 to -0.5) and DBP by 1.7 mmHg (95% CI –4.6 to 1.8) and increased HR by 6.2 bpm (95% CI 3.0 to 9.3). The certainty of evidence was moderate for SBP and HR, and low for DBP.

High-dose alcohol ≥ 13 hours after consumption (4 RCTs, N = 154) increased SBP by 3.7 mmHg (95% CI 2.3 to 5.1), DBP by 2.4 mmHg (95% CI 0.2 to 4.5), and HR by 2.7 bpm (95% CI 0.8 to 4.6) (moderate-certainty evidence for all). 

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