DBP ‘remains relevant’ in stroke risk assessment

By Eleanor McDermid, Senior medwireNews Reporter

A large study has shed light on the relationship of systolic and diastolic blood pressure (SBP and DBP) with stroke risk as people age.

The findings show that SBP and DBP are equally important for predicting stroke risk in young people, but SBP becomes gradually more important than DBP as people age, although very low DBP may also be harmful in older people.

"The take home message is that it is still important to measure and consider the DBPs for the management of the patient with hypertension," writes John Chalmers (George Institute for Global Health, Sydney, Australia) in a related editorial in Hypertension.

He observes that the measurement of BP and its relationship to stroke has become increasingly involved over the past 4 to 5 decades. "In the midst of all this complexity, it is refreshing to get some clarity even if only on one limited aspect of the problem."

The researchers drew on data for 68,551 people, aged 19 to 78 years, from the MOnica, Risk, Genetics, Archiving, and Monograph (MORGAM) Project. None of the participants had cardiovascular disease at baseline, none were taking antihypertensive medication, and 2.8% had a stroke during 13.2 years of follow up.

The MORGAM participants were derived from 34 European cohorts, and Chalmers notes that the study's conclusions may not apply to Asian populations, which have different patterns of stroke incidence from those seen in White populations.

Overall, stroke risk rose in line with SBP, but there was a nonlinear relationship with DBP. Specifically, for DBP of 71 mmHg or more stroke risk rose by 6% with each 5 mmHg rise in DBP, but for DBP below 71 mmHg stroke risk fell by 12% with each 5 mmHg rise.

Stroke risk rose in line with rising SBP and DBP in people up to the age of 62 years, but from the age of 47 years stroke was more strongly associated with SBP than DBP. The adverse effect of low DBP came into play at the age of 50 years.

However, Julie Vishram (Glostrup University Hospital, Denmark) and team say that the clinical relevance of low DBP is "questionable," because this subgroup was very small (0.7% of the total) and studies have shown that antihypertensive treatment can reduce stroke risk in patients with isolated systolic hypertension.

They conclude this finding should therefore "be interpreted with caution until more research is available."

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