The Strong Heart Study is an ongoing

cohort study A cohort study is a particular form of longitudinal study that samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation), performing ...

cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...

(CVD) and its risk factors among American Indian men and women. The original cohort began in 1984 with 4,549 participants ages 35–74 from 13 tribal nations and communities in

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

North Dakota North Dakota () is a U.S. state in the Upper Midwest, named after the Native Americans in the United States, indigenous Dakota people, Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north a ...

, and

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

. The need for specific ethnic and cultural understanding and sensitivities was recognized from the onset, so the study has a

community-based participatory research Community-based participatory research (CBPR) is a partnership approach to research that equitably involves community members, organizational representatives, researchers, and others in all aspects of the research process, with all partners in the p ...

(CBPR) model. Community members were involved in all stages of conception, design, and implementation of the research. Now in its seventh phase, the extensive research has led to many important findings about heart disease and unique risk factors in native populations. It is a project funded by the

National Heart, Lung, and Blood Institute The National Heart, Lung, and Blood Institute (NHLBI) is the third largest Institute of the National Institutes of Health, located in Bethesda, Maryland, United States. It is tasked with allocating about $3.6 billion in FY 2020 in tax revenue to ...

(NHLBI). The study maintains field centers in Oklahoma, North and South Dakota, and Arizona and a coordinating center at the

University of Oklahoma Health Sciences Center The University of Oklahoma Health Sciences Center is a public medical school in Oklahoma City, Oklahoma. It is the health sciences branch of the University of Oklahoma and serves as the primary place of instruction for many of Oklahoma's health p ...

History

Prior to 1980,

Indian Health Service The Indian Health Service (IHS) is an operating division (OPDIV) within the U.S. Department of Health and Human Services (HHS). IHS is responsible for providing direct medical and public health services to members of federally-recognized Nativ ...

(IHS) data showed low

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...

s from CVD. After 1980, CVD became the leading cause of death in American Indians. However, the Secretary of Health and Human Service's Task Force on Black and Minority Health determined that information on cardiovascular disease in American Indians was inadequate. The Strong Heart Study was designed to respond to the recommendation. Initial research began in 1984 and the first research manuscript was published in 1990.

Phases

Phase I

Phase I of the study was conducted among adult tribal members from 1984 to 1988 and consisted of three parts: a mortality survey to estimate cardiovascular disease mortality rates, a

morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

survey to estimate incidence of

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...

and

stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...

, and a comprehensive clinical examination of 4,549 tribal members to estimate the

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

of cardiovascular disease and its associations with

risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...

s. Data was collected from a physical examination, electrocardiogram,

blood analysis A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a hypodermic needle, or via fingerprick. Multiple tests for specific blood components, such as a glucose test or a cholester ...

, and

urine analysis A urine test is any medical test performed on a urine specimen. The analysis of urine is a valuable diagnostic tool because its composition reflects the functioning of many body systems, particularly the kidneys and urinary system, and specimens a ...

. DNA was isolated and stored for future genetic studies.

Phase II

Phase II continued the mortality and morbidity surveillance into 1988 to 1994 but added comparative analysis among the three centers. It repeated and expanded the clinical examination from Phase I, in order to monitor changes in risk factor prevalence over time and expand incidence rates beyond CVD to include

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

and

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

Phase III and Family Study

In 1997, Phase III launched the Strong Heart Family Study (SHFS) with 900

first-degree relative A first-degree relative (FDR) is a person's parent (father or mother), full sibling (brother or sister) or child. It constitutes a category of family members that largely overlaps with the term nuclear family, but without spouses. If the persons ...

s and grandchildren of members of the original cohort. The SHFS participants provided clinical examinations matching earlier phases, as well as DNA samples for

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...

-wide

linkage analysis Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separ ...

of cardiovascular disease

biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, ...

s. A sub-sample of Phase III participants were selected to establish accurate

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

prevalence in SHS populations, which Phase II may have underdiagnosed.

Phase IV-VI

Phase IV expanded the SHFS, bringing the total number of participants to 3,776 and continuing the ongoing morbidity and mortality surveillance of the original cohort. At the end of Phase V, a community withdrew their consent to participate, reducing the total number of tribal nations represented in Phase VI from 13 to 12. Phase V and VI continued the mortality and morbidity surveillance of the original SHS cohort and of the SHFS participants to better understand cardiovascular disease,

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

liver disease Liver disease, or hepatic disease, is any of many diseases of the liver. If long-lasting it is termed chronic liver disease. Although the diseases differ in detail, liver diseases often have features in common. Signs and symptoms Some of the sig ...

, and

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

Community-based participatory research

The Strong Heart Study was the first research funded by the NHLBI focusing on specific

ethnic group An ethnic group or an ethnicity is a grouping of people who identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancestry, language, history, ...

s in

rural communities Sociologists have identified a number of different types of rural communities, which have arisen as a result of changing economic trends within rural regions of industrial nations. The basic trend seems to be one in which communities are requir ...

.National Institutes of Health, National Heart, Lung, and Blood Institute Division of Epidemiology and Clinical Applications. (2001-11-01). ''Strong Heart Study Data Book: A Report to American Indian Communities'' (NIH Publication No. 01-3285), p. 47. Bethesda, MD: U.S. Government Printing Office. Retrieved April 4, 2021 from https://www.nhlbi.nih.gov/health-topics/all-publications-and-resources/strong-heart-study-data-book-report-american-indians The 13 American Indian communities were involved in partnership with investigators in all aspects of the study design to ensure the recruitment of participants and conduct of examinations was culturally appropriate and relevant. Community members were part of the steering committee and helped select appropriate locations for examination sites. Community members were the major drivers of participation recruitment. Questionnaires were pilot tested and community members were employed in clinics in a variety of roles."Protocal Planning Phase Complete." Strong Heart Study: Cardiovascular Disease in American Indians. Strong Heart Study Coordinating Center, Oklahoma Health Sciences Center, 01-07-1989, Volume 1, Number 1. https://strongheartstudy.org/portals/1288/Assets/Newsletters/1989%20July.pdf?ver=2018-04-04-110817-460 Data and major findings were continually presented and discussed with communities and aided them in community health planning.

Study design

The study is a longitudinal

observational study In fields such as epidemiology, social sciences, psychology and statistics, an observational study draws inferences from a sample (statistics), sample to a statistical population, population where the dependent and independent variables, independ ...

. In its initial stages, it included three components: The first was a community mortality study to determine CVD mortality rates from 1984 to 1994 among tribal members aged 35–74 years of age residing in the three study areas. The second was the clinical examination of 4,549 eligible tribal members. The third component was the morbidity and mortality surveillance of the participants. Due to the importance of genetics in the occurrence of CVD, the SHS expanded genetic research in later phases. Phase III launched a pilot study which recruited approximately 30 families consisting of more than 900 family members. The pilot SHFS expanded into a fullblown SHFS conducted in Phase IV to investigate the

heritability Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of h ...

of CVD and its risk factors and perform linkage analysis to localize

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s that contribute to CVD risk.

Major findings

The study found the incidence of CVD to be increasing among American Indians. The study confirmed that similar to the general population, the key risk factors for heart disease are

type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...

high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

, high

cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...

, and

smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...

. The research shows that for American Indian populations, type 2 diabetes was the strongest risk factor for heart disease. In young adults, diabetes and prediabetes was found to be independently associated with early adverse effects of heart structure and function. The study also examined environmental exposure to toxic metals and CVD. It found that

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...

and

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

exposures are prospectively associated with higher cardiovascular risk.

Risk calculators

Findings from the SHS have led to risk calculators for American Indians to estimate personal risk of developing coronary heart disease, hypertension, and diabetes.

References

External links

* {{Official website, https://strongheartstudy.org/
Strong Heart Study Risk Calculators

NHLBI Strong Heart Study
Cohort studies Cardiovascular diseases Native American health