Hypertension Most Important Risk Factor for Stroke

A new study reveals that 10 easily measurable and modifiable factors could account for the vast majority of stroke risk in all regions.

Researchers at McMaster University (Hamilton, Canada), the HRB-Clinical Research Facility (Galway, Ireland), and other institutions conducted the INTERSTROKE study to evaluate a range of risk factors for stroke. The study concluded that 10 risk factors influenced stroke risk- hypertension, lipids, smoking, physical inactivity, abdominal obesity, cardiac causes, diet, alcohol, diabetes mellitus and psychosocial factors; of these, hypertension is the most important.

Regarding the risk factors for ischemic stroke, those who had a clinical event were three times more likely to have hypertension compared with controls, and were twice as likely to have an elevated apolipoprotein B/apolipoprotein A1 (apoB/A1) ratio. In addition, cardiac causes were also a risk factor for ischemic stroke. Current smoking, obesity, poor diet, and physical inactivity, among others, were also associated with an increased risk of ischemic stroke.

As for intracerebral hemorrhage, those who had an event were nearly eight times more likely to have hypertension compared with controls. Current smoking, obesity, poor diet, alcohol binges, and psychosocial stress were also more significantly common among those with an intracerebral hemorrhage compared with controls. The researchers now plan to investigate the risk factors in more depth, for example, analyzing hemoglobin A1c levels instead of just a history of diabetes and teasing out the dietary risk scores better.

Whereas the first feasibility phase of the INTERSTROKE study included just 6,000 patients from 22 countries, the second phase includes 27,011 individuals from 32 countries, including 13,604 with stroke and 13,407 age- and sex-matched controls. Patients were recruited from centers in North America; Western, Central, and Northern Europe; the Middle East; South America; China, South and Southeast Asia; and Africa. The study results were presented at the World Heart Federation World Congress of Cardiology (WCC), held during May 2014 in Melbourne (Australia).

“One aspect that's interesting is that this study helps us understand the genetic contributions to stroke,” said lead author Martin O’Donnell, MD, of the McMaster Population Health Research Institute, in an interview with heartwire. “The days of us thinking that genetics would have a large main effect, that it would be up there with lipids, is untrue. Likely, genetics have a modifying effect. If you carry a certain polymorphism, you're more prone to blood-pressure effects. We conducted this study so that we could answer such pivotal questions.”

“The INTERSTROKE study represents an important resource to progress our understanding of the causes of stroke, both in estimating the contribution of known modifiable risk factors for stroke and in identifying and clarifying the role of new ones, such as genetics,” added Dr. O’Donnell. “These results are the completion of eight years of work and, on behalf of the INTERSTROKE group, we are delighted to share them with colleagues from around the world today in this preliminary analysis.”

Related Links:
McMaster University
HRB-Clinical Research Facility