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What to Do About the Disproportionately Increased Risk of Non-Hemorrhagic Stroke in Native Americans

Article In Brief

New research shows a higher risk of non-hemorrhagic stroke in Native Americans when compared with other racial groups. Neurologists and other physicians who work with Native Americans highlight public health and outreach strategies to address the increased risk for stroke in this population.

Stroke is the sixth-leading cause of death in American Indians and Alaska Natives, according to the American Heart Association, with cardiovascular disease ranking as the number one cause. Alarmingly, in recent years a growing body of research has pointed to a disproportionately increased risk of stroke in American Indians when compared with other racial and ethnic groups in the US.

In a new observational study published online in the March 3 edition of the Journal of the American Heart Association (JAHA), investigators reported a 47 percent higher risk of non-hemorrhagic stroke in American Indians when compared with the other groups studied. Even among individuals without atrial fibrillation (Afib), American Indian adults still had a 59 percent higher risk of stroke than those from other racial and ethnic groups.

This paper builds on the researchers' previous data, which showed the highest rates of Afib in American Indians, study author José M. Sanchez, MD, assistant professor of medicine in the division of cardiology/cardiac electrophysiology at the University of Colorado Anschutz Medical Campus, told Neurology Today.

“Enhanced awareness that American Indians may be especially prone to stroke is a critical first step in prevention by focusing on risk factor modification, guideline-directed therapies (such as anticoagulation in Afib), and the importance of access to high quality health care.”

During the ongoing pandemic, he added, there have been countless challenges to outpatient medicine. “Our vulnerable populations who already struggle navigating our health care system have been further marginalized by the disproportionate risks of COVID-19 in their community as well as worsened access to care. Reinforcing guideline-directed care (especially for Afib), could potentially help providers who manage these vulnerable populations offer solutions, such as telehealth, to provide their patients with better access to care.”

Study Findings

Using the Healthcare Cost and Utilization Project (HCUP) to review records from all adult California residents receiving care in an emergency department, inpatient hospital unit, or ambulatory surgery setting between 2005 and 2011, researchers from the University of California, San Francisco and the Cleveland Clinic Institute of Medicine looked at nearly 17 million adults for a median of four years of follow up.

HCUP data included age, sex, race, income level, and insurance payer at each health care encounter. Hispanic ethnicity was separately reported from race in HCUP and was considered a mutually exclusive category if either White or ‘other’ was selected for race. Only those individuals who solely selected American Indian race were counted in that group. Median household income for the individual's zip code was used to separate individual income level by quartiles.

Overall, nearly 106,000 adults (0.6 percent) identified as American Indian, while 56.7 percent were non-Hispanic White, 25.9 percent were Hispanic, 8.7 percent were of Asian descent, and 8.1 percent were Black. There were nearly 170,000 non-hemorrhagic strokes during the follow-up period, with about 37,000 strokes occurring among patients with Afib.

The investigators found, even after adjusting for age, sex, income level, insurance payer, hypertension, diabetes, coronary artery disease, congestive heart failure, and other risk factors, that American Indians adults still had a 47 percent higher risk of non-hemorrhagic stroke than the rest of the cohort (p<0.0001). American Indians with Afib had a 38 percent higher risk of non-hemorrhagic stroke compared with other groups who also had Afib (p<0.0001).

“This is the first large study investigating the effect of [Afib] on strokes in the American Indian race in a longitudinal analysis,” Dr. Sanchez and colleagues wrote.

“Unfortunately, inadequate access to health care as well as variations in prescribing patterns creates a challenge for these patients and translates into Afib patients not receiving adequate therapy,” Dr. Sanchez told Neurology Today. “It is very likely that if these individuals (especially those at highest risk of stroke) could receive regular preventive care with adequate screening for common ailments such as hypertension and diabetes accompanied by anticoagulation therapy for atrial fibrillation, the observed heightened risk of stroke might be mitigated.”

What Needs to Be Done

These findings, experts told Neurology Today, are yet another reminder of how much work remains to be done in addressing stroke risk in Native American populations around the US.

“This study reveals that the increased stroke risk in Native Americans persists even in the absence of Afib and even after controlling for confounders, suggesting there are additional factors we don't understand or haven't identified possibly responsible for this increased risk,” said Cumara O'Carroll, MD, MPH, an assistant professor of neurology at Mayo Clinic in Scottsdale, AZ, who provides stroke services to patients at Tuba City Regional Health Care through a telestroke network. It also highlights the need for further stroke research in Native American populations and for better representation of Native Americans in national stroke trials, she added.

“As stroke neurologists, it is imperative that we begin to address the disparities in acute ischemic stroke care, especially with the expansion of the therapeutic window to 24 hours in 2018,” Dr. O'Carroll said. “Traditionally, Black, Hispanic, Native American, and low-income patients have had less access to acute stroke care (that is, thrombolysis and endovascular intervention) and patients living in low-income areas have had reduced access to high-volume stroke centers. Care at high-volume stroke hospitals is associated with lower stroke mortality, and part of the disparity may result from the disproportionate number of some underrepresented racial and ethnic groups, i.e. Native Americans, who live in rural regions great distances from large medical centers.”

For instance, one challenge for the stroke patients Mike Stitzer, MD—a neurologist at Winslow Indian Health Care Center in Arizona and chief clinical consultant in neurology for the Indian Health Service (IHS)—sees in the Navajo Area IHS is getting to the location with IV tPA or interventional therapies within the needed timeframe. “If a rurally-living Native American patient presents with a TIA, having a very low threshold to complete the workup inpatient over considering rapid outpatient evaluation is a good idea. The nearest outpatient imaging center for an MRI or cardiologist for an echocardiogram may be harder to get to for a variety of reasons. In rural northern Arizona, it may take a few weeks or more to arrange for such studies. If a patient has already had a stroke, ensuring the less common risks are looked at before discharge when the initial workup for typical risks is unremarkable can help avoid the chance it may not be done at all if left for outpatient care.”

To give the recovery and secondary stroke prevention care the best chance of success, he noted, it is also necessary to create a comprehensive plan for any outpatient follow-up of devices like an implanted loop recorder, and to make sure the location of any rehab or chronic outpatient stroke care will be “readily accessible to the patient, and that any socioeconomic barriers to keeping this follow-up are addressed before they leave the hospital.”

Another potential solution to these access barriers “is the promotion and implementation of a robust telestroke network for IHS facilities and tribal hospitals, which are oftentimes small, rural, and lacking specialty care. A telestroke network would increase the likelihood of the administration of acute stroke treatment (thrombolysis) within a standard treatment window and would also facilitate the transfer of patients to a higher level of care if they require further intervention such as endovascular therapy,” said Dr. O'Carroll.

However, the JAHA study looked at California specifically, where “only 3 percent of Native Americans live on reservations or rancherias. In fact Los Angeles County has the highest percentage of Native Americans in the state,” Dr. Stitzer said, so it would be interesting to see additional data on whether urban, suburban, or rural zip codes had any effect on the findings, as well as whether the results would be consistent in Native American groups in other parts of the country.

“Native American tribes across the country are not one homogenous group. This study was only looking at self-identified tribal members who received care in California. There are over 100 federally recognized tribes in California, out of the more than 570 across the country, but many of them are smaller. The largest tribal populations in California are actually those with traditional lands out-of-state, including Cherokee, Apache, and Navajo. There might be differences in the genetic and environmental risks when looking at different tribes,” he added.

For example, “Does someone from my California tribe, Estom Yumeka Maidu with a population of a little over 1,000 and based out of Oroville, CA, and a Diné (Navajo) with over 300,000 tribal members and who may have grown up in an area of Arizona with uranium mining, have similar stroke risk? Does it matter if the patients assessed in this study were born and raised in California, regardless of tribe, versus if they moved there later in life?”

Salvador Cruz-Flores, MD, MPH, FAAN, a stroke neurologist who is professor and founding chair of the department of neurology at Texas Tech University Health Sciences Center at El Paso, pointed out that while studies like this one reiterate the significant presence of health disparities, many important questions remain unanswered. “Besides true biological factors like hypertension or diabetes, one has to look upstream to understand what structural issues have raised these problems. Race is not and cannot be considered a biological risk factor.” Race needs to be considered in the context of sociocultural environment, he said.

“The study adjusted for some [social and environmental] factors, and yet there was a residual disparity. Here is where the effects of race in the social context, as in racism, will need to be considered. That is to say, the experience of having lived being part of a socially marginalized group with not only less access but also with the allostatic effects or biological effects of racism,” Dr. Cruz-Flores said.

As neurologists and researchers, he continued, “we need to start looking at structural issues in the health system and policies that promote this marginalization. We need to start looking at race not as a biological risk factor but a factor with a sociopolitical and cultural context that needs fixing.”

Public Health Initiatives and Partnerships

“Whether striving for improved screening programs (for stroke risk factors), or implementing primary or secondary stroke prevention measures, or advocating for acute stroke treatment in Native American populations, as stroke neurologists, we should remember the importance of evaluating barriers to care, identifying local resources, developing community partnerships, obtaining tribal support, and promoting cultural competence,” said Cumara O'Carroll, MD, MPH, an assistant professor of neurology at Mayo Clinic in Scottsdale, AZ, who provides stroke services to patients at Tuba City Regional Health Care through a telestroke network.

A number of initiatives have successfully and appropriately targeted stroke and related risk factors in Native American communities, she said, including “the landmark Special Diabetes Program for Indians, which includes two community-based programs (Healthy Heart & Diabetes Prevention Program) with the goal of reducing cardiovascular risk factors such as Diabetes among Native Americans and Alaska Natives. These programs resulted in the development of ‘toolkits,’ which are accessible to the public and assist in the implementation of innovative diabetes prevention programs at the local level.”

The Centers for Disease Control and Prevention's Racial and Ethnic Approaches to Community Health (REACH) program also engaged with communities and resulted in increased medication compliance in Native Americans with hypertension, she said. “Other successful strategies have included community-talking circles, which have been effective in promoting diabetes education, and community-based exercise classes targeting Native American elders, which have improved physical and emotional well-being.”

Mike Stitzer, MD, a neurologist at Winslow Indian Health Care Center in Arizona, who is also chief clinical consultant in neurology for the Indian Health Service, said his health care center engages a nutrition team, community health promotion outreach, a wellness center with exercise classes, and other public education efforts to address some of the underlying stroke risks in the community.

In Wisconsin, Robert Dempsey, MD, the Manucher Javid Professor and chairman of neurological surgery at the University of Wisconsin School of Medicine, told Neurology Today he is currently partnering with the Oneida Nation on a stroke prevention program.

While the university and tribal leadership have already collaborated on a range of initiatives over the years, Dr. Dempsey said this particular project began after the Elder Council of the Oneida Nation identified important concerns in their community to be stroke and premature cognitive decline in their elders.

“After listening to their needs, I was able to say, ‘I've spent most of my life studying stroke and vascular cognitive decline related to silent or mini-stroke, and my research suggests that that is something that is measurable and can be preventable.’ Working with the Tribal Council as well as the elders and their Health Council, our question became how can we develop a stroke prevention program in the tribe that would be a partnership?”

“The elders of the tribe are often the keepers of the traditions and the language, which are essential,” he said. “So we are working with the Oneida Health Council, to grow a program together and have it be culturally appropriate. We are training tribal health coaches in the community, we are involving the elders to talk about the material, and we are working in all age groups, including children where good or bad health habits get started, to educate the population about proper health habits to reduce stroke, as well as identify early warning signs.”

Although COVID-19 has led to some delays, Dr. Dempsey said the collaboration has been continuing virtually until they are able to meet in-person again soon. Dr. Dempsey and his colleagues from both the University of Wisconsin and the Oneida Nation will be measuring the effects of behavioral interventions (exercise, diet, smoking cessation) on stroke risk as well as tracking whether people are developing atherosclerosis—“and whether it's getting worse or better as we try to change the risk factors. We will look at carotid ultrasounds, blood tests, cognitive status, and whether or not individuals are having strokes or TIAs.” The program is meant to be sustainable for stroke prevention in the Oneida Nation in the long term, by training tribal members to continue to educate and recognize signs of stroke as well as make behavioral modifications, and to perhaps extend their knowledge to the other member tribes in Wisconsin—and beyond.

Link Up for More Information

• Breathett K, Sims M, Gross M, et al. Cardiovascular health in American Indians and Alaska Natives: A scientific statement from the American Heart Association https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000773. Circulation 2020;141(25):e948–e959.
    • Sanchez JM, Jolly SE, Dewland TA, et al. Incident strokes among American Indian individuals with atrial fibrillation https://www.ahajournals.org/doi/full/10.1161/JAHA.120.019581?af=R. J Am Heart Assoc 2021; Epub 2021 Mar 2.
      • Sanchez JM, Jolly SE, Dewland TA, et al. Incident atrial fibrillation among American Indians in California http://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.119.042882. Circulation 2019; 140:1605–1606.
        • Stroke prevention with the Oneida: Building successful tribal academic research partnerships: https://ictr.wisc.edu/stroke-prevention-with-the-oneida/. Accessed March 5, 2021.