Skip navigation
Link to Back issues listing | Back Issue Listing with content Index | Subject Index

Headache and Antihypertensives

Systematic review
Results
Comment

Headache is meant to be a classic sign of hypertension, but probably isn't [1], and may be one of those classic myths. Yet there have been several observations that lowering blood pressure prevented headache. An obvious case for a meta-analysis, and one such [2] does indicate a small but consistent reduction of headache after lowering blood pressure.

Systematic review


A large systematic review of randomised placebo controlled trials of five classes of blood pressure lowering drugs was used as a source of trials. It used several electronic databases, and found 354 studies published to 2001. All double blind trials lasting two weeks or longer were included for this analysis, with exclusions for calcium channel blockers, which cause headaches, studies with dose titration, where some control patients were treated, use of drug combinations, and trials including patients with heart failure or after myocardial infarction. Trials had to report headache.

Results


After exclusions, 94 trials (84 parallel group, 10 crossover) with 23,599 participants were included. The mean age of patients was 53 years, and the mean duration of trials was eight weeks.

Table 1 shows the results for four classes of blood pressure lowering drug and for all combined. The mean blood pressure reduction (treatment minus placebo) was 8-10 mmHg systolic and 4-7 mmHg diastolic. All four classes reduced headache incidence (Figure 1), with an overall relative risk for treatment compared with placebo of 0.65 (95% CI 0.60 to 0.71). The average absolute difference in the proportion of people reporting headache in treatment and placebo groups was 3.5%, with headache prevented by treatment for about one person in 30.


Table 1: Blood pressure lowering treatment versus placebo, and effects on headache for four different drug classes, and all drugs combined



Number of
Mean reduction in blood pressure
mmHg
Percent with headache
Class of drug
Trials
Patients
Systolic
Diastolic
Treated
Placebo
Thiazide
26
4094
8.7
4.4
7.3
11.4
ß-blocker
19
3018
8.4
6.9
5.1
11.9
ACE inhibitor
39
6601
9.6
5.4
9.8
11.9
Angiotensin II receptor antagonist
28
11715
10.0
5.7
8.1
13.4
All drugs
94
24244
9.4
5.5
8.0
12.4
Blood pressure reduction is treatment specific (treated minus placebo)
Some trials had more than one treatment group




Figure 1: Headache with blood pressure lowering treatment and placebo






There was little relationship between extent of mean blood pressure reduction and headache frequency. Both parallel and crossover trials showed much the same effect. In placebo groups, there was a tendency for lower prevalence of headache with lower diastolic blood pressure, by about 17% (95%CI -31% to 1%) for a 5 mmHg lower diastolic blood pressure.

Comment


Whatever the relationship between headache and hypertension, there is a small but useful preventative effect of blood pressure lowering drugs. That it is lowering of blood pressure itself that is important is indicated by the fact that four different classes of drug, with different mechanisms of action, showed much the same effect.

Reference:


  1. FD Fuchs et al. Headache is not more frequent among patients with moderate to severe hypertension. Journal of Human Hypertension 2003 17: 787-790.
  2. M Law et al. Headaches and the treatment of blood pressure. Results from a meta-analysis of 94 randomized placebo-controlled trials with 24,000 participants. Circulation 2005 112: 2301-2306.

previous or next story