A meta-analysis confirms that having blood pressure (BP) at the upper end of the normal range increases people’s risk of a stroke.
If confirmed, the findings have important implications, said study author Dingli Xu (Southern Medical University, Guangzhou, China) in a press statement. “Considering the high proportion of the population who have higher than normal blood pressure, successful treatment of this condition could prevent many strokes and make a major difference in public health.”
Xu and co-workers also argue that their study supports labelling BP in the 120 to 139/80 to 89 mmHg range as prehypertension, as per the US guidelines, rather than high–normal BP, as it is referred to in European guidelines.
The team’s meta-analysis, which appears in Neurology, includes 19 prospective cohort studies with 762,393 participants. Thirteen of the studies were conducted in Asia, and the other six in Europe or the USA. The prevalence of prehypertension in these studies ranged from 25.2% to 54.2%, and the participants were followed-up for between 4 and 36 years.
Overall, having prehypertension increased people’s stroke risk by 66% versus having optimal BP, giving a population-attributable risk of 19.6%.
Findings from 11 studies showed that the increased risk extended to people whose BP was in the lower end of the prehypertensive range (120–129/80–84 mmHg), at a significant 44% increase in risk. The effect was even stronger for those in the higher end of the range (130–139/85–89 mmHg), at a 95% risk increase.
Having prehypertension had a similar effect on the risk of ischaemic and haemorrhagic stroke, on fatal and nonfatal stroke, and was present regardless of age and baseline cardiovascular disease.
The researchers note that most of the studies measured BP at a single point at baseline, which may misclassify some patients (eg, with white-coat or masked hypertension) and which cannot account for the effects of BP variability.
“Nevertheless, our results are indicative that, based on ‘snapshot’ BP measurements, prehypertension is associated with increased risk of stroke”, they say.
The team believes that lifestyle modification should be the main approach to managing prehypertension, but says that “because the incidence of stroke increased across the range of prehypertension, high-risk subpopulations with prehypertension are needed for future controlled trials of pharmacologic treatment.”
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