D. Research questions. This study will be guided by the following three research questions:
1. Can high cholesterol levels be genetically related?
2. Can high cholesterol levels be anatomically induced?
3. Do high cholesterol levels always result from poor eating choices?
E. Assumptions and Limitations. For the purposes of this study, it will be assumed that a chi-square analysis represents a superior methodology for the investigation of the above-stated general hypothesis.
F. Definition of terms.
1. Coronary heart disease (CHD).
1. High-density lipoprotein (HDL). This is the so-called "good" cholesterol (Griffith & Wood, 1997).
This term refers to an elevation of cholesterol in blood plasma (Albertine, 2001).
3. Low-density lipoprotein (LDL). This is the so-called "bad" cholesterol; these are the particles that contribute to atherosclerosis (e.g., the hardening and narrowing of the arteries) (Ulrich, 2002).
Chapter 2: Review of the Literature
Overview. As noted above, there are two types of lipoproteins in the blood; their relative quantities in the blood are main factors in heart disease risk (Henkel, 1999).
1. Low-density lipoprotein (LDL). This is the so-called "bad" cholesterol; LDLs are the form in which cholesterol is communicated into the blood and represent the primary cause of harmful fatty buildup in arteries. Henkel notes that the higher the LDL cholesterol level in the blood, the higher the risk of contracting heart disease.
2. High-density lipoprotein (HDL). By contrast, HDLs are the so-called "good" form of cholesterol, HDLs carry blood cholesterol back to the liver, where it can be eliminated. According to Henkel, HDL serves to prevent cholesterol accumulations in blood vessels; therefore, low HDL levels tend to increase the associated risk of heart disease.
One of the basic ways LDL cholesterol levels can reach dangerous levels is through eating too much of two nutrients: 1) saturated fat (commonly found mostly in animal products, and 2) cholesterol (found only in animal products); saturated fat increases LDL levels more than anything else in the diet. A wide range of other factors, though, also affect blood cholesterol levels including:
1. Genetic. According to Henkel, high cholesterol levels can frequently be found in families. "Even though specific genetic causes have been identified in only a minority of cases, genes still play a role in influencing blood cholesterol levels," he says (p. 23).
2. Overweight and Obesity. The author reports that excess weight tends to increase blood cholesterol levels; therefore, reducing weight may help to lower levels (Henkel, 1999).
3. Sedentary or Active Lifestyles. Henkel points out that regular physical activity may not only lower LDL cholesterol, but it may increase the levels of desirable HDL.
4. Age and Gender. Prior to experiencing menopause, Henkel points out that women tend to have total cholesterol levels that are lower than men of the same age; however, as shown in Figure 1 below, cholesterol levels naturally increase as both men and women age. According to Henkel, menopause has been associated with increases in LDL cholesterol in women in a number of studies.
5. Stress. Finally, although clinical studies have not demonstrated any direct connection between cholesterol levels and stress, clinicians advise that because people sometimes eat fatty foods to console themselves when under stress, this can result in higher blood cholesterol (Henkel, 1999).
While high total and LDL cholesterol levels, together with low HDL cholesterol, can tend to increase heart disease risk, these are just some of a wider range of other risk factors that include cigarette smoking, high blood pressure, diabetes, obesity, and physical inactivity. "If any of these is present in addition to high blood cholesterol, the risk of heart disease is even greater" (Henkel, p. 23).
Etiology. Total serum cholesterol levels gradually rise from childhood through adulthood. Cross-sectional studies indicate that cholesterol tends to peak in both sexes at around age 60 years; in fact, after a certain age, cholesterol levels tend to decline (see Figure 1 below) (Baum et al., 2000). According to Baum and his colleagues, "Prospective data corroborate these age and gender patterns, and the data further reveal that body mass index changes in parallel with cholesterol levels. Therefore, the rise in cholesterol during adulthood and the fall after age 60 may be attributable, in part, to weight change" (p. 227). While there is some evidence that the incidence of hypocholesterolemia (cholesterol < mg/dl) tends to increase in prevalence between the ages of 65 and 85 years, Baum et al. point out that other evidence suggests that individuals who manage to reach age 80 years in otherwise good health tend to enjoy "normal" cholesterol levels, without an overrepresentation of either hypo- or hypercholesterolemia (Baum et al., 2000).
Figure 1. Mean serum cholesterol levels by sex and age.
Source: Baum et al., 2000 p. 227.
Review of Selected Studies to Date. A public health demonstration project by Greenblatt-Ives, Kuller, & Traven (1993) evaluated the efficacy of community-based cholesterol-lowering interventions in elderly individuals. In this study, approximately 1,200 ambulatory, noninstitutionalized men and women 65 to 79 years of age suffering from serum cholesterol levels over 240 mg/dl were randomly assigned to health screenings and promotion services at local hospitals and clinics, or to a control group. According to Baum and his colleagues, the intervention developed by Greenblatt et al. was provided through scheduled appointments that were free of charge; approximately half of the intervention group subjects completed their appointments. The results revealed of this study showed that after 2 to 3 years, neither of these groups (the intervention group as a whole nor those actually attending the intervention sessions) experienced reduced cholesterol levels that were lower than those of the control group. In fact, only active drug treatment significantly was shown to reduce serum cholesterol concentrations in this study. The authors concluded that aggressive treatment (i.e., with drugs) is therefore required to in order to achieve any substantive reduction in cholesterol among elderly, hypercholesterolemic individuals (Baum et al., 2000).
In their study, "Baseline Assessment of the Health Status and Health Behaviors of African-Americans Participating in the Activities-for-Life Program: A Community-Based Health Intervention Program," Paschal, Lewis, Martin, Dennis-Shipp, and Simpson (2004) report that, "Obesity is a major contributor to the high rates of hypertension and diabetes among Americans, particularly African-Americans. For instance, African-Americans have a higher prevalence of being overweight than their Caucasian counterparts" (p. 305). Furthermore, the authors emphasize that today, 30% of African-Americans are categorized as being obese compared to 28% of Caucasians.
Further exacerbating the already high rate of obesity and related conditions among African-Americans is the widespread problem of poor nutrition and inactivity. Although national figures suggest that 23% of the adult population has a sedentary lifestyle, a disproportionate number of African-Americans seem to have such, with 55-75% of African-American women rarely exercising, and 30 to 66% of men not exercising (Bronner, 2001). In addition, general nutrition and eating habits are poor for this population. For instance, approximately 76% of the African-American population do not currently meet minimum recommendations for daily fruit servings, and less than half (42%) currently meet the minimum daily requirements for vegetables per day (Bronner, 2001).
Purpose and Goal of Study. The purpose of the study by Dennis-Shipp and his colleagues was to determine the baseline results from a 9-month "Activities-for-Life" program; this regimen provided financial incentives, nutrition education, and physical fitness activities for African-American men and women. According to the authors, "This was a culturally relevant health education and physical fitness program that was community-based and easily accessible to its predominantly African-American community" (p. 306). The goal of the intervention program was to reduce those risk factors commonly associated with obesity and related health problems such as diabetes and hypertension in the sample population (Dennis-Shipp et al., 2004).
Methods and Participants. The Activities-for-Life initiative was implemented in 2002, by the Center for Health & Wellness, a primary health care and prevention and wellness center located in Wichita, Kansas; the participants in the program were provided formal education about life-threatening conditions (obesity, poor nutrition, hypertension, and diabetes) and were required to participate in physical fitness activities each week at the Center for Health & Wellness for a period of nine months (Dennis-Shipp et al., 2004).
The study sample was comprised of 134 African-Americans who resided in northeast Wichita, Kansas; 94 (or 70%) of the participants were females and 40 (30%) were males. The authors report that the age of the participants ranged from 20-74 years of age with the majority (52%) being between the ages of 35 and 54 years; in addition, 55% of the subjects were employed or self-employed, and 15% were unemployed (not including those that were retired or students) and 40% of the subjects were married. The authors also report that 83% of the subjects had some type of medical or health insurance. The amount of formal education achieved by the participants ranged from one year of schooling…