Stroke prevention: a major public health challenge in elderly Spanish individuals The PREV-ICTUS trial

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14 August 2008

24% ten-year risk of stroke in elderly hypertensive individuals attracts attention to blood pressure control: a more comprehensive approach to stroke prevention is clearly needed

Redón J, Cea-Calvo L, Lozano JV, Martí-Canales JC, Llisterri JL, Aznar J, González-Esteban J; Investigators of the PREV-ICTUS study.

STUDY SUMMARY

Methods

PREV-ICTUS was a population-based, cross-sectional study performed in Spanish primary care centers to estimate the impact of high blood pressure on the 10-year risk of stroke in the general population aged 60 years or older. The investigators selected a representative sample of the elderly population because these subjects concentrate the greatest stroke risk levels.
A total of 7,343 subjects (mean age, 71.6 ± 7.0 years; 53.4% women, 34.4% obese subjects, and 27.1% diabetic subjects) were included. Stroke risk was estimated in the 6,304 patients without previous history of stroke, for whom all the necessary information was available.
Variables included in the Framingham stroke risk scale1 (sex, age, systolic blood pressure [SBP], smoking, past or present cardiovascular disease, atrial fibrillation, and ECG signs of left ventricular hypertrophy [LVH]) were collected, as well as diastolic blood pressure (DBP), lifestyle habits, and biochemical data available in the previous 6 months or measured at study entry.
The subjects were divided as:

Normotensive (BP not elevated, no previous diagnoses of hypertension): 14.2% of the study population.
Known hypertensive (subjects with previously diagnosed hypertension): 73.0% of the study population.
Subjects with elevated BP but no previous diagnosis of hypertension: 12.8% of the study population.

BP values were considered controlled if <140/90 mm Hg for nondiabetic subjects and <130/80 mm Hg for diabetic subjects.

Main results

The estimated 10-year stroke risk was greater in hypertensive patients (23.7 ± 18.5%) than in patients with high blood pressure without known hypertension (12.4 ± 9.2%), or in normotensive subjects (5.3 ± 0.2%; p <0.001 for all comparisons) (Figure 1). In all 3 categories, stroke risk was significantly higher in men than in women (p <0.001).

Figure 1. Estimated 10-year risk of stroke in Spanish subjects aged 60 years and older divided
into 3 blood pressure categories. Stroke risk was calculated using the Framingham stroke risk scale.1

COMMENT

This study confirms the importance of hypertension as a risk factor for stroke. It also confirms data from previous studies showing that Spain is one of the countries with the highest prevalence of hypertension and with the lowest rate of BP control.2 In the whole study population, only 35.7% of subjects presented BP values within controlled range. SBP was below therapeutic control threshold in 37.7% of cases, whereas DBP was below threshold in 71.6%. Only 29.1% of hypertensive subjects included in the study had their blood pressure at target level.

An unexpected result was that stroke risk was almost doubled in patients with diagnosed hypertension compared with those with undiagnosed hypertension. The authors stress that, compared with subjects with elevated BP but no diagnosed hypertension, those with diagnosed hypertension showed a significantly higher prevalence of other stroke risk factors (LVH, 16.9% versus 4.9%, p <0.001; diabetes mellitus, 31.4% versus 26.5%; p = 0.003; established cardiovascular disease, 36.4% versus 10.8%, p <0.001; and atrial fibrillation, 0.6% versus 3.0%, p <0.001). That implied, for one same BP level, an additional risk of stroke in those with HT diagnosed. The authors speculate that subjects with high BP but no diagnosed hypertension may recruit individuals with intermittent BP elevations, or with recent-onset hypertension not previously diagnosed.

Comprehensive preventive strategy warranted

Stroke prevention has become a major public health challenge, especially in consideration of the population aging that is expected to continue in the near future. The results of this study are a call to better prevention of stroke through better detection of hypertension and better control of blood pressure in elderly individuals. As stressed by the authors, however, the Framingham stroke risk indicator does not consider the potential impact of some documented risk factors for stroke. For example, the SPARCL trial reported significant benefits of intensive LDL-lowering pharmacotherapy in secondary prevention of cerebrovascular events (stroke and AIT).3 Subanalyses of the SPARCL data showed that low HDL cholesterol levels at baseline were associated with a large percentage of the residual risk of stroke persisting even after aggressive statin therapy.4 Effective stroke prevention cannot be based on blood pressure control only. The most effective strategy for stroke prevention is a comprehensive approach aiming at detecting and controlling all known modifiable stroke risk factors at the individual level.

References

D’Agostino R, Wolf PA, Belanger A, Kannel W. Stroke risk profile: adjustment for antihypertensive medication. The Framinghan Study. Stroke 1994;25:40–3.
Wolf-Maier K, Cooper RS, Banegas JR, et al. Hypertension prevalence and blood pressure levels in 6 European countries, Canada, and the United States. JAMA 2003;289:2363–9.
The Stroke Prevention by Aggressive Reduction in Cholesterol Levels (SPARCL) Investigators. High-dose atorvastatin after stroke or transient ischemic attack. N Engl J Med 2006;355:549–59.
Amarenco P, Goldstein LB, Callahan A 3rd, et al., on behalf of the SPARCL Investigators. Baseline blood pressure, low- and high-density lipoproteins, and triglycerides and the risk of vascular events in the Stroke Prevention by Aggressive Reduction in Cholesterol Levels (SPARCL) trial. : Atherosclerosis 2008 Sep 18. [Epub ahead of print]