Prehypertension Linked to Increased Stroke Risk

Megan Brooks

September 28, 2011

September 28, 2011 — Prehypertension independently raises the risk for stroke by about 50%, according to results of a new review of relevant research.

Prehypertension is defined by a systolic blood pressure (BP) between 120 and 139 mm Hg, or a diastolic BP between 80 and 89 mm Hg. "Importantly," the authors say, the risk for 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 a BP that falls within the higher range of prehypertension (ie, systolic BP, 130 - 139 mm Hg; or diastolic BP, 85 - 89 mm Hg), first author Bruce Ovbiagele, MD, from the University of California, San Diego, told Medscape Medical News.

These lifestyle changes, he noted, could include a low-salt diet, consuming no more than 2 g sodium per day; regular exercise, consisting of 30 minutes of aerobic exercise at least 4 days a week; and maintaining a normal body mass index between 18.5 and 24.9 kg/m2.

"So far," Dr. 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 [BP] modestly, are relatively safe, and will likely enhance global vascular risk reduction."

The findings were published online September 28 in Neurology.

Some Prehypertensives May Need More

For some adults with prehypertension, lifestyle changes may not be enough, Amytis Towfighi, MD, chair of the Department of Neurology, associate chief medical officer, Rancho Los Amigos National Rehabilitation Center in Downey, California, told Medscape Medical News.

"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 [BP] of lower than 130/80," she said.

Dr. Towfighi was not involved in the study but coauthored a linked commentary with Gordon Kelley from the Stroke Program, Shawnee Mission Medical Center, Kansas.

Included in the meta-analysis were 12 prospective cohort studies that reported multivariate-adjusted relative risks for stroke with respect to baseline prehypertension among 518,520 adults in middle age and older.

The overall quality of the studies was good, the researchers note, with a median score of 7 on a scale of 8 (range, 5 - 8). Length of follow-up in the studies ranged from 2.7 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 for stroke with prehypertension was 1.55 (95% confidence interval, 1.35 - 1.79; P < .001).

Seven of the 12 studies made a distinction between a low prehypertensive population (systolic BP, 120 - 129 mm Hg; diastolic BP, 80 - 84 mm Hg) and a high prehypertensive population (systolic BP, 130 - 139 mm Hg; diastolic BP, 85 - 89 mm Hg).

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

Table. Risk for Stroke by Prehypertension Category

Prehypertension Range Relative Risk (95% Confidence Interval)
Systolic BP, 120 - 129; diastolic BP, 80 - 84 mm Hg 1.22 (0.95 - 1.57)
Systolic BP, 130 - 139; diastolic BP, 85 - 89 mm Hg 1.79 (1.49 - 2.16)

In a subgroup analysis, elderly adults with prehypertension did not have a higher risk for 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. In contrast, previous epidemiologic evidence suggests that BP measurements taken on a single day may be adequate, they point out.

However, a single-day measurement is not 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.

On the basis of their findings, they suggest that randomized trials to evaluate the efficacy of lowering BP levels in those with higher values within the prehypertension range are warranted.

Dr. 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 told Medscape Medical News.

Dr. Ovbiagele has disclosed no relevant financial relationships. A complete list of author disclosures is listed with the original article. Dr. Towfighi serves on speakers' bureaus for and has received speaker honoraria from Ferrer and Boehringer Ingelheim and receives research support from Kaiser Permanente. Dr. Kelly has disclosed no relevant financial relationships.

Neurology. 2011;77:1330-1337. Article abstract, Commentary

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