Ischemic Stroke Risk Factors Are on the Rise in Native Americans

From 2000 to 2016, prevalence of a multitude of risk factors for ischemic stroke — a condition that disproportionally affects Native Americans — was high and significantly increasing among that ethnic group. So finds a collaborative study being presented in a poster session this week at the 2019 International Stroke Conference in Honolulu.

“Many of the risk factors identified as high and increasing among Native Americans are modifiable,” says lead author Dinesh Jillella, MD, a vascular neurology fellow and Clinical Instructor of Medicine at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University. “These study findings indicate where we should aim our efforts to improve the health of this population from a stroke standpoint.”

Earlier research has revealed that Native Americans, who make up less than 2 percent of the U.S. population, have a higher incidence of stroke than other ethnic groups. However, little is known about which individual factors are to be blamed and their prevalence trends over the past two decades. The current study — a collaboration of investigators from Cleveland Clinic and the University of New Mexico— was undertaken to address that dearth of data.

Study design and findings

The researchers extracted data from the Cerner electronic health records database, a registry that includes approximately 700 U.S. hospitals nationwide. Demographic data and cerebrovascular risk factors were prospectively analyzed from 4,729 Native Americans (46 percent male, 54 percent female) who had been diagnosed with ischemic stroke from 2000 to 2016.

The analysis showed the risk factors below to be present at the following rates:

• Hypertension: 66.6 percent
• Diabetes mellitus: 38.8 percent
• Coronary artery disease: 23.4 percent
• Smoking: 21.6 percent
• Heart failure: 12.3 percent
• Atrial fibrillation: 10.5 percent
• Atrial flutter: 1.4 percent

Trends in risk factors over time were analyzed using a logistic regression model adjusted for age and sex. The researchers found that prevalence significantly increased during the years of the study in all identified risk factors except for diabetes: hypertension (P < .001), coronary artery disease (P < .015), smoking (P < .001), heart failure (P = .02), atrial fibrillation (P < .006), and atrial flutter (P = .01).

“The significant rise in prevalence of almost all the risk factors we looked at was a dramatic finding,” says Dr. Jillella. “It points to the urgency with which public health officials and clinicians who work with Native Americans should be aggressively addressing modifiable risk factors, especially high blood pressure and smoking.”

The increasing prevalence of smoking is especially striking, as it contrasts with a concurrent decline in smoking rates within the general U.S. adult population, which fell from 20.9 percent in 2005 to 15.5 percent in 2016, according to data from the Centers for Disease Control and Prevention.

Next research steps

Dr. Jillella points out that the study may have been limited by possible coding errors when diagnostic and risk factor data were entered, a problem inherent in any database research. At the same time, the study’s use of a national electronic database has the advantage of providing a large sample size, likely mitigating the effects of occasional errors.

The researchers are continuing their investigations into cardiovascular risk in Native Americans. They are currently assessing how the risk factors identified as high in this study compare with the prevalence in other racial groups that have a lower incidence of stroke.

They also are examining risk factors specific to hemorrhagic strokes; in addition to hypertension and smoking, these include use of certain prescription and illicit drugs, excessive alcohol intake and dyslipidemia.

“There is a paucity of studies examining the health burden of cerebrovascular risk factors in Native Americans,” concludes Dr. Jillella. “Stroke is a big problem in this group, and we hope that better defining the causes will be an important step toward more effective preventive healthcare.”