Diabetes and Heart Disease Risk in Blacks

  • STATUS
    Recruiting
  • participants needed
    2000
  • sponsor
    National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Updated on 22 October 2022
diabetes
cardiovascular disease
insulin
electrocardiogram
body mass index
heart disease
myocardial infarction
infarct
low density lipoprotein
fats
glucose intolerance
hdl cholesterol
Accepts healthy volunteers

Summary

It is unknown if obesity contributes to the development of heart disease in African American men and women.

This study was created to determine whether there is a relationship between sex and body size and the incidence of heart disease in African American men and women. Researchers will attempt to associate obesity with the presence of heart disease risk factors. Risk factors that will be studied include; total body fat, body fat distribution, fat content of the blood (triglyceride concentration, low density lipoproteins [LDL], and high density lipoproteins [HDL]), how fast fat is removed from the blood, and how well insulin works in the body.

Scientific studies have shown that obesity and increased levels of fat content in the blood are important risk factors for heart disease in Caucasian women. However, similar studies in African American women have failed to show the same correlation. In fact, it appears that African American women in all three body weight groupings, nonobese, overweight, and obese experience high death rates due to heart disease. In addition, prior research has shown that obese African American men tend to have elevated levels of fat in the blood while African American women have normal blood fat levels. Therefore, if high levels of triglycerides (fat found in the blood) are not seen in non-diabetic obese African American women, it cannot be considered a risk factor in this population. This suggests that studies conducted on Caucasian women may not provide insight into heart disease risk factors in African American women.

The study will take 2000 healthy non-diabetic African American men and women (ages 18-70) and body mass index 3 subgroups; nonobese, overweight and obese. Diabetes undeniably increases the risk of heart disease. Therefore patients suffering from diabetes will not be included in the study. Candidates for the study will undergo a series of tests and examinations over 2 outpatient visits. Subjects will have body fat analyses, resting energy expenditure measurements, an EKG (electrocardiogram), and specific blood tests.

Researchers believe this study will provide significant insight into the causes of obesity and heart disease in African Americans.

Description

This study is designed to investigate in blacks the relationship of risk for diabetes and heart disease from obesity plasma glucose and triglyceride concentrations and the triglyceride related risk factors of small dense low density lipoprotein (LDL), high density lipoprotein (HDL) and central obesity.

The Framingham Study demonstrated that obesity and elevated glucose and triglyceride levels are important risk factors for coronary artery disease in white women. However, studies that have had significant participation of black women such as the Charleston Heart Study, failed to show a relationship of obesity or triglyceride to coronary artery disease mortality in black women. In fact, black women independent of body weight or triglyceride levels experience high mortality from coronary artery disease. Our earlier research has demonstrated that obese black men have elevated triglyceride levels but obese black women have normal triglyceride levels. Consequently if elevated triglyceride levels do not occur in obese nondiabetic black women, then elevated triglyceride levels may not represent a major cardiovascular risk for black women.

The study, Diabetes and Heart Disease Risk in Blacks, is designed to determine the role of obesity, glucose and triglyceride on risk for heart disease in blacks. For this study of blacks, we will study 2 groups, African Americans and Black Africans living in the United States. African Americans must self-identify as African American, be born in the United States and have parents who self-identify as African American and were born in the United States. The second group will be blacks living in the United States but were born in Africa and whose parents were born in Africa.

We will recruit 2000 healthy, non-diabetic individuals (), age range 18- 70, and body mass index (3 subgroups: nonobese, overweight and obese). In 2 outpatient visits to the Clinical Center, participants will have body fat analyses, an electrocardiogram, an oral glucose tolerance test, questionnaires about sleep, stress, discrimination, resilience, etc. and an intravenous glucose tolerance test or a beverage tolerance test. This study has the potential to provide significant insight and lead to the development of programs that help

decrease diabetes and cardiovascular risk in blacks.

Details
Condition Cardiovascular Diseases, Diabetes, Obesity, Hypertension
Clinical Study IdentifierNCT00001853
SponsorNational Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Last Modified on22 October 2022

Eligibility

Yes No Not Sure

Inclusion Criteria

Ethnicity: Black
This is a study of adult African Americans and Blacks that were born in Africa but are now
living in the United States. As African American people are multi-ethnic, we will in this
initial investigation, study two different groups of African American. To enroll
participants must self-identify as African Americans and be born in the United States, with
American born parents or be born in Africa with African born parents. In both groups we
will study sex differences in the role of obesity and TG levels on cardiovascular disease
Medical History: To participate in the study subjects should identify themselves as
In the future, we plan to expand the study to include other groups which self-identify as
African Americans (i.e.AfroCarribeans and Hispanic blacks)
Only blacks are included in this study because the focus of this study is on gender
differences in blacks in risk factors for CAD, specifically obesity, TG levels and TG
related CAD risk factors. Unlike Caucasian women, premenopausal black women do not appear
to be as protected from heart disease as a result of their gender. One model to study this
apparent decrease in gender
related cardioprotection in black women is to compare black men to black women. An
alternative model would be to compare black women to Caucasian women. However, since the
primary focus of this work is on gender differences rather than racial differences
comparing black women to men is a superior model. Other racial groups do not share the loss
of gender-related cardioprotection found in blacks, and have been excluded. Further the
advantage of comparing black men and women is that this comparison provides a better
control of dietary, cultural and genetic factors
Age: The age range of the participants will be between 18 and 70 years. As stated in the
original protocol on page 14: Future investigations are planned which will involve similar
comparisons between premenopausal and postmenopausal black women and between whites and
blacks. To investigate risk for glucose intolerance, diabetes and cardiovascular risk
factors, it is no longer sufficient to maintain the age range between 18 and 50 years. We
need to expand to an age range with an increased prevalence of these risk factors
healthy. This is important so the broadest possible sample of people will enroll. The fact
that people are healthy will be confirmed by the history, physical and laboratory tests
done as part of the screening visit. People with established coronary artery as evidenced
by history of myocardial infarction, coronary artery bypass surgery or PTCA will be allowed
to participate if they are not currently having angina

Exclusion Criteria

Medications: People who take medications that are known to alter the parameters which are
under investigation in this study will be excluded. People taking medications to treat
hyperlipidemia will be included but analyses will be adjusted to take this into account
Subjects on thyroid hormone replacement will be included if their TSH is normal
Diabetes: Because diabetes affects insulin sensitivity and TG levels all people with
diabetes even if the diabetes is controlled with diet alone will not be enrolled in the
study
Pregnant or Breastfeeding: Women who are pregnant, breastfeeding, or have an infant that is
less than four months of age will be excluded. This is because the physiologic changes
associated with pregnancy, breastfeeding or recent childbirth affect the parameters under
study
Black Ethnicity other than American or African
As stated in the inclusion criteria black people are a multi-ethnic group. In this initial
investigation we are focusing on African Americans who are American born and Africans
living in the United States who are African born. In the future, we will expand the study
to include other groups of blacks such as individuals of Afro-Caribbean and Hispanic
blacks
Menstrual History: Now that postmenopausal women are included, menstrual history will be
taken but women with irregular menses and hysterectomy will not be excluded. Women between
the ages of 40 and 55 years will have FSH checked for proper characterization. Women 56
years of age and older will be assumed to be postmenopausal. However, women on any type of
injectable hormonal contraception will be excluded because hormonal contraception affects
both TG levels and glucose metabolism
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