Decades-long research tracks heart health improvements among American Indians

For more than 35 years, University of Oklahoma Health Campus researchers have played a key role in the Strong Heart Study, a landmark project that has uncovered critical insights into cardiovascular disease among American Indian communities. Today, it remains the most extensive and longest-running study of its kind in the United States.

The study has also made a difference in health outcomes. Overall, data show generational declines in the number of new cases of cardiovascular disease. Deaths from cardiovascular disease have decreased more among men, while the prevalence of cardiovascular disease has declined more among women.

To mark the study’s longevity, the journal Preventing Chronic Disease has published a guest editorial and seven papers by OU researchers that capture the breadth and depth of the work.

“For 35 years, the Strong Heart Study has shown what can be achieved when scientists and communities work side by side. The knowledge we’ve gained has directly improved cardiovascular health in American Indian communities and has contributed to a broader understanding of cardiovascular disease across the U.S.,” said Ying Zhang, M.D., M.S., Ph.D., director of the Center for American Indian Health Research at OU Hudson College of Public Health and a professor of biostatistics and epidemiology.

Before the Strong Heart Study, American Indians were largely left out of cardiovascular disease research, and many people believed they had a lower risk. As the study progressed, it quickly became evident that not only was heart disease prevalent among American Indians, but it was also higher than in many other racial and ethnic groups in the United States.

The Strong Heart Study followed participants in 12 tribes and communities in Oklahoma, Arizona, North Dakota and South Dakota. The effort began in 1989 and recently completed seven phases of participant examinations.

The first phase enrolled more than 4,500 participants, aged 45 to 74, from four states. Researchers conducted physical exams, performed laboratory tests and issued questionnaires related to heart health that included a focus on demographics, medical history and psychological and social health. Subsequent phases continued with the same cohort while adding specialized tests such as echocardiography and carotid ultrasound.

Toward the end of the third exam cycle, family members of the original participants were recruited to help researchers better understand the genetic influence on cardiovascular disease, and this inclusion continued in the fourth phase, bringing the total number of participants to more than 7,500. Phases five, six and seven continued follow-up with both the original and family cohorts.

“In addition to demonstrating high rates of cardiovascular disease, the Strong Heart Study identified diabetes as a significant risk factor; developed American Indian-specific risk prediction calculators for cardiovascular disease and hypertension; showed that protein in urine is a unique risk factor for cardiovascular disease in American Indians; and, in American Indian youth, documented lipid disorders and subclinical cardiovascular disease findings (an early stage of disease with no noticeable symptoms),” said Tauqueer Ali, Ph.D., MPH, MBBS, a professor of research in the OU Hudson College of Public Health and vice chair of the Strong Heart Study steering committee.

Jessica Reese, Ph.D., an assistant professor in the OU Hudson College of Public Health and senior biostatistician for the Strong Heart Study, was an author on a study that found that major swings in systolic blood pressure (the top number in a blood pressure reading) are linked to a higher risk of death and serious heart problems among American Indians.

Specifically, researchers found that people with the greatest variability in systolic blood pressure were:

• 35% more likely to die from any cause
• 81% more likely to die from heart disease
• 39% more likely to experience a major heart event compared with those whose blood pressure readings stayed more consistent

Reese was also an author on a study to evaluate the association between vitamin D deficiency and the prevalence of cardiovascular disease risk factors among American Indian adolescents. At the beginning of the study, about half of the adolescents who took part had vitamin D deficiency. They were more likely to be obese, have low HDL cholesterol (the “good” cholesterol) and have metabolic syndrome, a cluster of conditions that increase the risk for diabetes and cardiovascular disease.

“Vitamin D deficiency is an often-overlooked health issue that may contribute to serious long-term consequences,” Reese said. “Our findings show the importance of monitoring vitamin D levels early in life and considering how nutrition and lifestyle factors affect long-term heart health.”

The Strong Heart Study has also served as a platform for a wide range of ancillary studies, both observational and interventional. Observational studies (participants are observed and outcomes are tracked without testing a potential treatment) have examined sleep health, stroke, brain structure and cognitive performance, dementia, resilience, bilingualism, and environmental exposures such as air quality and metals in water.

Interventional studies (in which a treatment is assigned) have focused on cholesterol and blood pressure, healthy diet, physical activity, and rhythm and timing exercises aimed at improving mental and physical functioning.

The Strong Heart Study is considered community-based participatory research, grounded in strong partnerships built on mutual trust with tribal communities. Researchers work in collaboration with community partners, seeking their guidance in both the design and implementation of each phase to ensure the work remains respectful and meaningful.

“The Strong Heart Study is one of the most important contributions to public health in the past three decades,” said Dale Bratzler, D.O., MPH, dean of the OU Hudson College of Public Health.

“By partnering closely with American Indian communities, this research has filled critical gaps in our understanding of heart disease and helped reduce health disparities. Its findings continue to shape prevention strategies, not only for American Indian populations but for public health as a whole.”

For more than 35 years, University of Oklahoma Health Campus researchers have played a key role in the Strong Heart Study, a landmark project that has uncovered critical insights into cardiovascular disease among American Indian communities. Today, it remains the most extensive and longest-running study of its kind in the United States.

The study has also made a difference in health outcomes. Overall, data show generational declines in the number of new cases of cardiovascular disease. Deaths from cardiovascular disease have decreased more among men, while the prevalence of cardiovascular disease has declined more among women.

To mark the study’s longevity, the journal Preventing Chronic Disease has published a guest editorial and seven papers by OU researchers that capture the breadth and depth of the work.

“For 35 years, the Strong Heart Study has shown what can be achieved when scientists and communities work side by side. The knowledge we’ve gained has directly improved cardiovascular health in American Indian communities and has contributed to a broader understanding of cardiovascular disease across the U.S.,” said Ying Zhang, M.D., M.S., Ph.D., director of the Center for American Indian Health Research at OU Hudson College of Public Health and a professor of biostatistics and epidemiology.

Before the Strong Heart Study, American Indians were largely left out of cardiovascular disease research, and many people believed they had a lower risk. As the study progressed, it quickly became evident that not only was heart disease prevalent among American Indians, but it was also higher than in many other racial and ethnic groups in the United States.

The Strong Heart Study followed participants in 12 tribes and communities in Oklahoma, Arizona, North Dakota and South Dakota. The effort began in 1989 and recently completed seven phases of participant examinations.

The first phase enrolled more than 4,500 participants, aged 45 to 74, from four states. Researchers conducted physical exams, performed laboratory tests and issued questionnaires related to heart health that included a focus on demographics, medical history and psychological and social health. Subsequent phases continued with the same cohort while adding specialized tests such as echocardiography and carotid ultrasound.

Toward the end of the third exam cycle, family members of the original participants were recruited to help researchers better understand the genetic influence on cardiovascular disease, and this inclusion continued in the fourth phase, bringing the total number of participants to more than 7,500. Phases five, six and seven continued follow-up with both the original and family cohorts.

“In addition to demonstrating high rates of cardiovascular disease, the Strong Heart Study identified diabetes as a significant risk factor; developed American Indian-specific risk prediction calculators for cardiovascular disease and hypertension; showed that protein in urine is a unique risk factor for cardiovascular disease in American Indians; and, in American Indian youth, documented lipid disorders and subclinical cardiovascular disease findings (an early stage of disease with no noticeable symptoms),” said Tauqueer Ali, Ph.D., MPH, MBBS, a professor of research in the OU Hudson College of Public Health and vice chair of the Strong Heart Study steering committee.

Jessica Reese, Ph.D., an assistant professor in the OU Hudson College of Public Health and senior biostatistician for the Strong Heart Study, was an author on a study that found that major swings in systolic blood pressure (the top number in a blood pressure reading) are linked to a higher risk of death and serious heart problems among American Indians.

Specifically, researchers found that people with the greatest variability in systolic blood pressure were:

• 35% more likely to die from any cause
• 81% more likely to die from heart disease
• 39% more likely to experience a major heart event compared with those whose blood pressure readings stayed more consistent

Reese was also an author on a study to evaluate the association between vitamin D deficiency and the prevalence of cardiovascular disease risk factors among American Indian adolescents. At the beginning of the study, about half of the adolescents who took part had vitamin D deficiency. They were more likely to be obese, have low HDL cholesterol (the “good” cholesterol) and have metabolic syndrome, a cluster of conditions that increase the risk for diabetes and cardiovascular disease.

“Vitamin D deficiency is an often-overlooked health issue that may contribute to serious long-term consequences,” Reese said. “Our findings show the importance of monitoring vitamin D levels early in life and considering how nutrition and lifestyle factors affect long-term heart health.”

The Strong Heart Study has also served as a platform for a wide range of ancillary studies, both observational and interventional. Observational studies (participants are observed and outcomes are tracked without testing a potential treatment) have examined sleep health, stroke, brain structure and cognitive performance, dementia, resilience, bilingualism, and environmental exposures such as air quality and metals in water.

Interventional studies (in which a treatment is assigned) have focused on cholesterol and blood pressure, healthy diet, physical activity, and rhythm and timing exercises aimed at improving mental and physical functioning.

The Strong Heart Study is considered community-based participatory research, grounded in strong partnerships built on mutual trust with tribal communities. Researchers work in collaboration with community partners, seeking their guidance in both the design and implementation of each phase to ensure the work remains respectful and meaningful.

“The Strong Heart Study is one of the most important contributions to public health in the past three decades,” said Dale Bratzler, D.O., MPH, dean of the OU Hudson College of Public Health.

“By partnering closely with American Indian communities, this research has filled critical gaps in our understanding of heart disease and helped reduce health disparities. Its findings continue to shape prevention strategies, not only for American Indian populations but for public health as a whole.”