Blood pressure effects unclear in long-term stroke survivors

Feb 17 2014

By Eleanor McDermid, Senior medwireNews Reporter

Long-term survivors of stroke whose blood pressure (BP) is at target levels have worse outcomes than those with slightly elevated levels, research suggests.

The study involved 483 participants of the North East Melbourne Stroke Incidence Study, who had a stroke 5 years previously and were followed up for a further 5 years. During this time there was a U-shaped relationship between BP and outcomes, such that patients with systolic BP of 131 to 141 mmHg had the lowest risk of death, myocardial infarction and recurrent stroke.

“Observational studies such as ours are hypothesis-generating and do not provide conclusive evidence of benefit or harm as in randomized controlled trials,” caution Amanda Thrift (Monash University, Melbourne, Australia) and team.

Relative to patients in the 131 to 141 mmHg group, those with BP of 121 to 130 mmHg and 142 to 210 mmHg had respective nonsignificant 16% and 25% increases in the risk of poor outcomes. And those with the lowest BP, of 92 to 120 mmHg, had a significant 61% increased risk.

This was despite patients with lower BP being less likely to have risk factors such as diabetes and elevated cholesterol. However, they were more often disabled and living in an institution.

Thrift et al suggest that cerebral perfusion could be compromised in patients with low BP, leading to falls, recurrent stroke and dementia.

“The findings are of relevance to the guidelines on secondary stroke prevention, where there is uncertainty with respect to the target blood pressure levels and ‘normal’ blood pressure is defined as below 120/80 mmHg,” they write in the Journal of Hypertension.

“Whether lowering blood pressure to these levels is of benefit to long-term survivors of stroke appears to require further investigation.”

Use of specific classes of antihypertensives did not explain the association between BP and outcome. However, the team notes that patients with normotension tended to be preferentially prescribed certain classes of antihypertensives and were also more often disabled.

“This raises the possibility that comorbidities may complicate the prescription of antihypertensive medications in long-term survivors of stroke,” they say.

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