Prehypertension linked to increased stroke risk

Megan Brooks

September 29, 2011

New York, NY - Prehypertension independently raises the risk of stroke by about 50%, according to results of a new review [1].

Prehypertension is defined by a systolic blood pressure (BP) between 120 and 139 mm Hg or diastolic BP between 80 and 89 mm Hg. "Importantly," the authors say, the risk of stroke appeared more strongly driven by higher systolic or diastolic BP values within the prehypertensive range. It's appropriate to "recommend and monitor therapeutic lifestyle changes" in patients who have BP that falls within the higher range of prehypertension, that is systolic BP (SBP) 130-139 mm Hg or diastolic BP (DBP) 85-89 mm Hg, author Dr Bruce Ovbiagele (University of California, San Diego), said in an interview.

These lifestyle changes, he noted, could include a low-salt diet, consuming no more than 2 g of sodium per day, regular exercise consisting of 30 minutes of aerobic exercise at least four days a week, and maintaining a normal body-mass index between 18.5 and 24.9 kg/m2.

"So far," Ovbiagele noted, "no randomized studies have shown that therapeutic lifestyle changes will specifically reduce the risk of incident hypertension or avert stroke in patients with prehypertension." Nonetheless, these lifestyle approaches "do lower blood pressure modestly, are relatively safe, and will likely enhance global vascular risk reduction."

Their findings are published online September 28, 2011 in Neurology.

Some prehypertensives may need more

For some adults with prehypertension, lifestyle changes may not be enough, Dr Amytis T owfighi (Rancho Los Amigos National Rehabilitation Center, Downey, CA) said. "In certain populations, such as those with diabetes, kidney disease, or a Framingham coronary risk score of >10%, it is reasonable to start medications if lifestyle changes alone do not achieve a blood pressure of lower than 130/80," she said.

Towfighi was not involved in the study but coauthored a linked commentary with Dr Gordon Kelley (Shawnee Mission Medical Center, KS) [2].

Included in the meta-analysis were 12 prospective cohort studies that reported multivariate-adjusted relative risks of stroke with respect to baseline prehypertension among 518 520 adults in middle age and older. Length of follow-up in the studies ranged from 2.7 years to 32 years. The prevalence of prehypertension ranged from 25% to 46%. After adjustment for age, sex, and established cardiovascular risk factors including diabetes, obesity, cholesterol, and smoking, the overall relative risk of stroke with prehypertension was 1.55 (95% CI 1.35-1.79; p<0.001). Seven of the 12 studies made a distinction between a low prehypertensive population (systolic 120-129 mm Hg or diastolic 80-84 mm Hg) and a high prehypertensive population (systolic 130-139 mm Hg or diastolic 85-89 mm Hg).

Adults with lower-range prehypertension did not have a significantly increased of stroke, but those with higher-range prehypertension did.

Risk of stroke by prehypertension category

Prehypertension r ange (mm Hg)
Relative r isk (95% CI)
SBP 120-129 or DBP 80-84
1.22 (0.95-1.57)
SBP 130-139 or DBP 85-89
1.79 (1.49-2.16)

In a subgroup analysis, elderly adults with prehypertension did not have a higher risk of incident stroke. This may not be that surprising, the researchers say, "given the immense impact of elderly status itself on stroke risk, as well as observational data indicating that the contribution of frank hypertension to the risk of stroke is rather diminished in elderly cohorts."

Lower threshold for treatment?

In most studies reviewed, baseline BP was obtained by a single-day measurement, which may lead to misclassification of BP levels and a dilution bias, the authors note. On the other hand, previous epidemiologic evidence suggests that BP measurements taken on a single day may be adequate, they point out. However, a single-day measurement isn't sufficient to characterize BP variability, and data on BP variability were not available in the studies analyzed.

Despite these and other potential limitations, "the results of this systematic review probably represent the most precise and accurate estimate of the strength of the relation between prehypertension and incident stroke currently available," the authors conclude. Based on their findings, they suggest randomized trials to evaluate the efficacy of lowering BP levels in those with higher values within the prehypertension range are warranted.

Towfighi agrees. "Further studies are needed to determine if treating prehypertension with medications lowers the risk of stroke. In the future, the threshold for starting antihypertensives may be lower," she said in an interview.

Ovbiagele has disclosed no relevant financial relationships. Disclosures for the coauthors are listed in the paper. Towfighi serves on speaker ' s bureaus for and has received speaker honoraria from Ferrer and Boehringer Ingelheim and receives research support from Kaiser Permanente. Kelly has no disclosures.

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