High or rapidly rising BP poses greatest stroke, mortality risk

By Eleanor McDermid

Findings from the Rotterdam study show how the trajectories of people's blood pressure (BP) in mid to late life have varying effects on their risk of having a stroke or dying.

In previous research, M Arfan Ikram (Erasmus MC University Medical Center, Rotterdam, the Netherlands) and colleagues found that young and middle-aged people with relatively high BP over the long term were at increased risk of cardiovascular pathology.

And their latest analysis, involving 6745 Rotterdam study participants aged between 55 and 106 years, shows that at this stage of life people with persistently high BP or a rapid increase in BP over 5 decades have the greatest risk of stroke or mortality.

The research as a whole "shows that single values of blood pressure do not tell the whole story", Ikram et al write in Hypertension.

The team's statistical analysis groups participants into four systolic BP trajectories during an average 13.5 years of follow-up. The largest group included 4938 people whose BP started at around 120 mmHg from age 55 years and increased gradually over time to about 160 mmHg.

A second group, of 822 people, had a much steeper increase, up to around 200 mmHg. They had a higher cumulative incidence of stroke than the group with the slower increase, ranging from 8.1% at age 70 to 24.2% at age 90 years, compared with a respective 0.71% and 15.3%. However, their risk for nonstroke mortality was no greater, with incidences in both groups of around 1% and 53% at ages 70 and 90 years, respectively.

A third group of 870 people who consistently had BP of around 140 mmHg also had an increased stroke risk, with incidences of 4.7% and 28.8% at age 70 and 90 years, respectively. And this group also had a high mortality risk, with corresponding rates of 32.7% and 73.4%.

The smallest group, of 115 people, had BP that started at about 160 mmHg but then fell after age 65 years. Their stroke risk was the highest out of all the groups at age 70, at 13.6%, but it then rose only slightly to 19.4%. However, their mortality risk was on a par with that of the group with consistently high BP, with rates of 15.7% and 78.7% at ages 70 and 90 years, respectively.

The researchers caution that the BP trajectories may not directly account for the observed stroke and mortality rates, with other factors such as lifestyle, healthcare utilisation and competing risks also playing a part.

As such, they say, their findings lay the ground for research addressing how antihypertensive treatment affects vascular risk for people in these categories, although they add that the "trajectories may inform physicians about people who need further attention for their high risk of stroke or death."

Source: Hypertension 2016; Advance online publication

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