Trajectories of blood pressure in mid to late life are associated with incident stroke and mortality, according to research published online ahead of print May 9 in Hypertension.
Most associations between blood pressure—a major modifiable risk factor for stroke—and incident stroke have been based on blood pressure measurements taken at a single time point.
Although long-term trajectories of blood pressure can vary considerably in the elderly, studies have not looked at the long-term blood pressure trajectories in mid to late life or at whether such trajectories relate to stroke, said M. Arfan Ikram, MD, PhD, senior study author and Associate Professor of Neuroepidemiology at Erasmus University Medical Center in Rotterdam, the Netherlands.
M. Arfan Ikram, MD, PhD
To identify long-term trajectories of blood pressure in a population-based study and examine the risk of stroke within those trajectories, Dr. Ikram and colleagues evaluated the course of systolic blood pressure in 6,745 participants within the Rotterdam Study.
Participants resided in Ommoord, a suburb of Rotterdam, and received baseline examinations starting in 1990. The investigators used data from five follow-up visits, which occurred every three to four years from 1990 to 2011. During each follow-up visit, blood pressure was measured twice in the right arm, in sitting position, after a resting period of five minutes. Researchers used the average of the two measurements. The investigators focused on systolic blood pressure because it is the best predictor of cardiovascular events.
Participants’ ages ranged from 55 to 106, and 60% were women. Participants had a mean follow-up of 13.5 years.
Four Trajectories
The investigators jointly modeled participants’ risk of stroke and competing causes of death using joint latent class mixed modeling. When assessing blood pressure trajectories, the researchers found that the joint latent class model with four trajectory classes had the best fit.
Class 1, the largest class, included 4,938 participants. It was characterized by a gradually increasing blood pressure, starting at an average of 120 mm Hg at age 55 and increasing to an average of 160 mm Hg at age 95. Class 2, with 822 participants, was characterized by a similar blood pressure at age 55, but a much steeper increase in blood pressure, to an average of 200 mm Hg. The two other classes were characterized by a relatively higher baseline blood pressure. In class 3 (870 participants), the average baseline blood pressure of 140 mm Hg had modest variation over time. In class 4 (115 patients), the average baseline blood pressure of 160 mm Hg decreased after age 65.
People in class 4 were more frequently men. Use of blood pressure-lowering medication was similar between classes at baseline. At the end of follow-up, classes 3 and 4 had higher proportions of blood pressure-lowering medication users. Frequency of current smokers varied between classes, with particularly higher frequencies in classes 2 and 4.
Groups’ Risk Varied
During the study period, 1,053 participants had a stroke. Researchers also studied the number of deaths that occurred from nonstroke health events. They adjusted for sex and baseline blood-pressure lowering medication.
Classes 2, 3, and 4 had a significantly and substantially higher risk of stroke, compared with class 1 (ie, 4.7% to 13.6% vs 0.7%). Classes 2 and 4 had the highest risk of dying of other causes. The risk of dying of other causes in class 3 was similar to that of class 1. The risk of stroke in class 3, however, continued to increase until older age and was highest overall.
In all, 2,546 people (51.5%) in class 1, 575 (70.0%) people in class 2, 288 (33.1%) people in class 3, and 87 (75.7%) people in class 4 died due to a nonstroke-related cause. Between 25% and 38% of nonstroke deaths were due to cardiovascular events.
In multivariable-adjusted models that controlled for cholesterol, lipid-lowering medication, BMI, smoking, alcohol use, diabetes mellitus type 2, and antithrombotic medication, the results were relatively similar, the researchers said. The risk of stroke in classes 2 and 4 was attenuated by data adjustment, whereas the risk increased in class 3.
“Assessing trajectories of blood pressure provides a more nuanced understanding of the associations between blood pressure, stroke, and mortality,” the authors said.
The researchers noted that people in class 2 with steep increases in blood pressure might not receive effective treatment in time under current guidelines, and future studies could determine whether this class can be a target for prevention.
Effect of Slope
Prior studies that examined blood pressure trajectories in young to middle-aged people identified several parallel trajectories and found that long-term higher blood pressure related to more cardiovascular pathology.
