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Blood Pressure and Stroke Prevention

5th Edition
December 2014

The Canadian Stroke Best Practice Recommendations for the Secondary Prevention of Stroke, 5th Edition 2014 module is published in the International Journal of Stroke (IJS) (Online Open‑Access available December 2014; Printed Journal scheduled for April 2015).

To access the specific recommendations for Blood Pressure and Stroke Prevention and all other sections of the Secondary Prevention of Stroke module, please click on this URL which will take you to the recommendations online in the IJS:  http://onlinelibrary.wiley.com/doi/10.1111/ijs.12439/full. For the French version of these recommendations, open the appendix at this link : http://onlinelibrary.wiley.com/store/10.1111/ijs.12439/asset/supinfo/ijs12439-sup-0001-si.pdf?v=1&s=b0ed4fff1d7fc435cf4e2a83ccbcbffbdad767de.

All other supporting information, including performance measures, implementation resources, evidence summaries and references, remain available through www.strokebestpractices.ca, and not through the IJS.  Please click on the appropriate sections below for this additional content.


Elevated blood pressure is the single most important risk factor for stroke. One in five adult Canadians has blood pressure in the range of 130–139/85–89 mm Hg (labeled by some investigators as “pre-hypertension”), and up to 60 percent of them will develop hypertension within four years. Among persons aged 55 and older with normal blood pressure, 90 percent will develop hypertension if they live to an average age. All adults require ongoing assessment of blood pressure throughout their lives. Each 1 mm Hg increase in blood pressure increases the risk of poor late-life cognitive function by approximately one percent. Epidemiologic studies have shown a graded increase in the risk of stroke as blood pressure increases.

Numerous population-based studies have found that elevated blood pressure is a significant risk factor for first and recurrent stroke; hypertension is estimated to account for about 60 percent of the population-attributable risk for cerebrovascular disease. The InterStroke study reported an odds ratio of 2.64 for patients with hypertension experiencing a stroke. A number of trials have shown a 28 percent risk reduction in recurrent stroke in patients treated with blood pressure lowering medication.

The optimal target for blood pressure in people who have had a stroke and people at risk of stroke has not been formally defined through randomized controlled trials. The current treatment recommendation is to attain a blood pressure of consistently lower than 140/90 mm Hg for people who have had a cerebrovascular event. Epidemiologic data have shown that those with a response to treatment attaining blood pressure levels well below 140 systolic and 90 diastolic have better outcomes yet these treatment trials have not yet clearly defined how far blood pressure should be lowered.

System Implications
  • Coordinated hypertension awareness programs at the provincial and community levels that involve community groups, primary care providers (physicians, nurse practitioners and pharmacists) and other relevant partners.
  • Stroke prevention, including routine blood pressure monitoring, offered by primary care providers in the community as part of comprehensive patient management.
  • Increased availability and access to education programs about hypertension diagnosis and management for adults and children for healthcare providers across the continuum of care.
  • Increased support for home blood pressure monitors (e.g. programs or tax credits) for patients and families on home monitoring of blood pressure and blood pressure self-management programs.
  • Improved access to pharmaceuticals through private and public drug coverage plans.
Performance Measures
  1. Proportion of persons at risk for stroke who had their blood pressure measured at their last healthcare encounter; and within the last 12 months.
  2. Proportion of the population who have diagnosed elevated blood pressure (hypertension).
  3. Proportion of the population who are aware of hypertension and the risks of high blood pressure.
  4. Percentage of the population with known hypertension who are on blood pressure lowering therapy.
  5. Proportion of the population with hypertension who are being treated and have achieved control of their blood pressure within defined targets (as per Canadian Hypertension Education Program guidelines) though lifestyle changes and/or medication.
  6. Proportion of stroke and transient ischemic attack patients who have received a prescription for blood pressure lowering agents on discharge from acute care.
  7. Proportion of stroke and transient ischemic attack patients who have received a prescription for blood pressure lowering agents after assessment in a secondary prevention clinic.

Measurement Notes

  • Performance measures 1 through 3: data may be available through the Canadian Hypertension Education Program database, the Canadian Community Health Survey, and other provincial and local health surveys and patient self-reports.
  • Performance measures 4: data may be available through audit of primary care physician charts. Prescription information may also be available through provincial drug plan databases, although these may have limitations with respect to the age of those covered by the plans, and there is variation across provinces and territories.
  • Performance measures 7: prescriptions for blood pressure lowering agents may be given during the inpatient stay or during a secondary prevention assessment and follow- up. When tracking these performance rates, it is important to record the setting where this therapy is initiated. Data sources may include physician order sheets, physicians’ or nurses’ notes, discharge summaries or copies of prescriptions given to patients.
  • Prescriptions given to a patient do not imply compliance.
  • Algorithms to identify incidence and prevalence of hypertension from administrative databases have been validated in Canada and should be used for consistency in measurement when possible.104
Implementation Resources and Knowledge Transfer Tools

Health Care Provider Information

Patient Information

Summary of the Evidence, Evidence Tables and References

Blood Pressure and Stroke Prevention Evidence Tables and Reference List

Hypertension Increases the Risk of Stroke

There is a well-established association between hypertension and increased risk of stroke. In fact, it is regarded as the most important modifiable risk factor. Results from the INTERSTROKE study (O’Donnell et al. 2010), a case-controlled study examining the contribution of specific risk factors to the burden of stroke, indicated that five risk factors accounted for more than 80% of the risk for stroke. Among others including current smoking, abdominal obesity, diet, and physical activity, hypertension was found to be the most significant. Self-reported hypertension or blood pressure >160/90 mm Hg was associated with an increased risk of all stroke (OR=3.89, 95% CI 3.33-4.54). In another case-control study Du et al. (2000) reported the risk of stroke was significantly higher among subjects who were hypertensive (OR=2.45, 95% CI 1.62 to 3.71, p< 0.001) and the risk of stroke increased with additional risk factors including smoking and diabetes. The authors suggested that at least three-quarters of strokes in hypertensive patients are preventable given appropriate treatment and emphasized that strokes are not caused not by a single risk factor, but by the interaction of multiple risk factors, with some having a stronger independent relationship with stroke than others. A meta-analysis that included the results of one million adults from 61 prospective studies, Lewington et al. (2002) found that an increase of 20 mm Hg in systolic and 10 mm Hg in diastolic blood pressure led to a two-fold increase in stroke mortality in persons aged 40 – 69 years, without any evidence of a threshold down to at least 115/75 mm Hg for all vascular deaths. Age-specific associations were found to be similar for men and women and for cerebral hemorrhage and cerebral ischemia. Bestehorn et al. (2008) included the results from 47,394 patients under the care of 2,482 general physicians, diagnosed with hypertension and reported an overall 10-year stroke rate of 26%. The risk increased to 50% with the addition of other co-morbidities.

Pharmacological Treatment of Hypertension Reduces Stroke Risk

Many non-pharmacological approaches exist to reduce/manage blood pressure, including following a healthy diet, engaging in regular physical activity, consuming modest amounts of alcohol, reducing dietary sodium, avoiding tobacco exposure and managing high stress levels, and are described in other sections. The current recommendations do not advise any particular dose/agent or combinations of agents to meet target blood pressures of <140/90 mg/Hg, (or <130/80 in persons with diabetes and kidney disease), while suggesting that ACE inhibitor/diuretic combination is preferred. While the Canadian Hypertension Education program (CHEP), suggests a more conservative systolic blood pressure target for the elderly (≥80 years, 150 mm Hg) due to their increased risk for falls, the present Canadian Best Practice Recommendations for Stroke Care does not differentiate on the basis of age.

Numerous large, randomized controlled trials examining the effectiveness of a variety of antihypertensive agents, used alone, or in combination with other agents, have been published over the past 30 years. Many aimed to establish the superiority of one treatment regimen, or approach over another. These trials are characterized by large sample sizes, high methodological quality. The Losartan Intervention For Endpoint reduction in hypertension (LIFE, Dahlof et al. 2002) and Study on Cognition and Prognosis in the Elderly (SCOPE, Lithell et al. 2003) studies demonstrated the efficacy of angiotensin receptor blockers (ARBs) for both primary and secondary prevention of stroke. Treatment with ARBs was superior to either placebo or atenolol-based antihypertensive regimen. The risk of cardiovascular mortality, stroke and myocardial infarction (combined) was reduced by 13% and 11%. The results of the ACCOMPLISH trial (Jameson et al. 2008) suggested that a higher proportion of persons achieved adequate blood pressure control (defined as< 140/90 mm Hg), using a combination of benazepril–amlodipine compared with benazepril + hydrochlorothiazide (75.4% vs. 72.4%). There were fewer cardiovascular events/deaths associated with the addition of amlodipine (HR= 0.80, 95% CI, 0.72 to 0.90, p<0.001), with non-significant reductions in the risk of death from cardiovascular causes between groups or fatal/nonfatal stroke. The Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) compared the ACE inhibitor ramipril, the angiotensin-receptor blocker telmisartan and the combination of the 2 drugs in patients who could not tolerate ACE inhibitors, with vascular disease or high-risk diabetes (Yusef et al. 2008a). The researchers reported that telmisartan was equivalent to ramipril in patients with vascular disease or high-risk diabetes and was associated with less angioedema. The combination of the 2 drugs was associated with more adverse events without an increased benefit. In the Prevention Regimen For Effectively Avoiding Second Strokes (PRoFESS) Trial (Yusef et al. 2008b), the additional of telmisartan was not associated with a significant reduction in the risk of recurrent stroke within a median of 2.5 years follow up (HR=0.95, 95% CI 0.86 to 1.04, p= 0.23). The Secondary Prevention of Small Subcortical Strokes (SPS3 Trial) examined the effectiveness of medical management to reduce recurrent stroke. Lowering systolic blood pressure to a target of < 130 mm Hg resulted in a non-significant reduction on all stroke, disabling stroke, myocardial infarction and vascular death compared with target SBP levels of 130-149 mm Hg>

Studies examining the benefit vs. risk of hypertension management in the very elderly (≥80 years) have emerged in the past few years. In the HYVET study elderly patients were randomly assigned to receive either antihypertensive therapy, using indapamide as a first-line agent or matching placebo. Lowering mean blood pressure by 15.0/6.1 mm Hg was associated with a 30% reduction in the rate of fatal or nonfatal stroke (95% CI –1% to 51%, p = 0.06), a 39% reduction in the rate of death from stroke (95% CI 1% to 62%, p = 0.05), a 21% reduction in the rate of death from all causes (95% CI 4% to 35%, p = 0.02) and a 23% reduction in the rate of death from cardiovascular causes (95% CI –1% to 40%, p = 0.06) over a (median) follow-up period of 1.8 years. The authors concluded that antihypertensive treatment in patients 80 years of age or older was beneficial. The open-label active treatment extension of the HYVET study included 1682 patients both arms of the trial (Beckett et al 2012) with same target blood pressure levels <150/80 mm Hg. While there were no significant between-group differences in the incidence of fatal/nonfatal stroke, heart failure, or all cardiovascular events (12 vs. 13, HR= 0.78, 95% CI 0.36 to 1.72, p=0.55), the risks of all-cause mortality and cardiovascular mortality were significantly lower in patients previously receiving active treatment.

The results from several meta-analyses strengthen the evidence of benefit from pharmacological treatment for hypertension reduces stroke risk and mortality from stroke. Lee et al. (2012) included the results of 11 RCTs representing data from 42,572 participants (794 with previous stroke) who were at high risk for cardiovascular disease and compared treatment of tight BP control (SBP <130 mmHg) with usual control (SBP 130 to 139 mmHg) on subsequent stroke risk. Tight SBP target was associated with reduced risks of future stroke, and major vascular events, and major coronary events, but was not associated with a significantly lower risk of death. Patients with diabetes, those without a history of CVD, and younger than 65 years experienced the greatest stroke risk reduction. Law et al (2009) included the results of 147 RCTs (n=464,000) comparing i) blood pressure lowering medications vs. placebo or usual care and ii) trials compared different types of blood pressure medications. A blood pressure treatment-associated reduction of 10 mm Hg systolic and 5 mm Hg diastolic was associated with a reduced risk of stroke (RR=0.59, 95% CI 0.52-0.67). The risk of stroke was significantly reduced in trials that included persons with no prior history of stroke, a history of CHD, and a history of stroke. A Cochrane meta-analysis authored by Musini et al. (2009) included 15 trials, (24,055 subjects ≥ 60 years) with moderate to severe hypertension that were treated primarily with first-line thiazide diuretic therapy for a mean duration of treatment of 4.5 years. Treatment was associated with reduced total mortality, (RR= 0.90, 95% CI 0.84-0.97), and reduced total cardiovascular morbidity and mortality (RR=0.72, 95% CI 0.68-0.77). In the three trials restricted to persons with isolated systolic hypertension, the benefit was similar. In very elderly patients, ≥ 80 years the reduction in total cardiovascular mortality and morbidity was similar; however, there was no reduction in total mortality, (RR=1.01, 95% CI 0.90, 1.13). Withdrawals due to adverse effects were increased with treatment (RR= 1.71, 95% CI 1.45, 2.00).