HL Biology IA, awarded a level 6. research question is 'An investigation into the correlation between the prevalence of obesity and mortality rate due to coronary heart disease in developing and developed countries.'
An investigation into the correlation between the prevalence of obesity and mortality rate due to
coronary heart disease in developing and developed countries.
Candidate Code: jjs506
Research questions
I. What is the correlation between the prevalence of obesity and mortality rate due to coronary heart disease per
100,000 people in accordance with HDI rankings?
II. How does this correlation compare between developing and developed countries?
Introduction
As an aspiring doctor, I am always eager to gain a more in-depth understanding of the human body; I always find myself
being fascinated by anything related to the human body, from the body’s natural reaction mechanism to diseases to simple
processes that are a necessity for our survival. I was provided with the chance to develop my knowledge on numerous
medical complications when I undertook virtual work-experience, that took place in Thailand, which allowed me to expand
my knowledge. This had to be done due to the fact that the COVID-19 lockdowns prevented me from obtaining a
shadowing internship in real life. Throughout the experience, I became very interested in cardiology, specifically coronary
heart disease. This sparked my interest as the mortality rate due to coronary heart disease (CHD), also known as ischemic
heart disease (IHD), coronary artery disease (CAD), and atherosclerotic cardiovascular disease (ACD)1, was 63.1 per
100,000 in Thailand, in 20162. Therefore, I assumed that obesity rates were also high in Thailand, due to the common
presumption that obesity is a major factor in developing coronary heart disease. However, upon further research I found
that only 4.8% of the Thai population were considered obese3, i.e. had a BMI≥30kgm-2. This revelation only further
increased my curiosity, and therefore I decided to base my IA on the correlation between incidences of coronary heart
disease per country and national levels of obesity.
Background information
Coronary Heart Disease
Cardiovascular diseases (CVDs) are one form of non-communicable diseases. They cause approximately one-third of
deaths worldwide4, which is an estimated 17.9 million deaths annually5. Coronary heart disease (CHD) is considered the
most prevailing of cardiovascular diseases6, and its prevalence is expected to increase in the coming years7. The disease is
identified by the occlusion of coronary arteries, which are the arteries that supply blood to the heart8. Atherosclerosis, a
process which causes the narrowing and hardening of the blood vessels, is the main etiopathogenic mechanism that results
in the occlusion of coronary arteries7. It’s progression is said to be related to an interplay between environmental and
genetic factors. The genetic factors usually exert their effects directly or through the cardiovascular risk factors. These
include, but are not limited to, age, sex, family history, high blood pressure, high cholesterol, diabetes mellitus, genetics,
small LDL particles, elevated serum homocystein, elevated serum lipoprotein (a), porthrombotic factors, inflammatory
makers, and others7.
Atherosclerosis is the process characterized by the accumulation of lipids, fibrous elements, and inflammatory molecules in
the walls of the large arteries. Low-density lipoprotein (LDL) cholesterol builds up in the subendothelial space7 of the
blood vessels, which partially or totally blocks the blood flow to the large arteries of the heart9. These LDL cholesterol
molecules can become oxidized and subsequently7 engulfed by macrophages, forming macrophage foam cells. These
localize on blood vessel walls and secrete a variety of substances10 that are responsible for the formation of an initial
atherosclerotic lesion, or fatty streak, in a blood11,12 vessel. This type of lesion is classified as a type III lesion, otherwise
known as an atheroma, a lesion that is potentially symptom-producing13. An illustration depicting the process of plaque
formation is seen in Figure 1.
1
, Figure 1: Animation illustrating the formation of an atheroma in the Figure 2: Diagram illustrating blood flow restriction by atherosclerosis
blood vessel12. and rupture of artherosclerotic lesion14.
The process of atherosclerotic plaque progression is accompanied by calcification, a process in which the atheroma
hardens, and becomes ‘stable’15. However, some plaques evolve to take on a more unstable phenotype with greater degrees
of inflammation. Eventually, a plaque may rupture, and the contact of blood with the exposed subendothelial cells and
plaque content causes the formation of occlusive thrombi16. This can be seen in Figure 2.
Atherosclerosis and coronary thrombosis can lead to many health risks including:
➔ Hypertension:
Hypertension is defined as a condition in which the blood vessels have persistently raised pressure17. As the blood
vessels become narrower and more restricted, the blood pressure increases in order to be able to pump a sufficient
amount of blood around the body;
➔ Angina pectoris18:
Angina pectoris is described as the discomfort experienced when the heart muscle is deprived of adequate oxygen
and is characterized by discomfort in the chest, shoulder, back, or arms. This is typically aggravated by emotional
stress or exertion18;
➔ Shortness of breath/fatigue19:
As the heart is unable to pump a sufficient amount around the body efficiently, shortness of breath or extreme
fatigue is caused due to the fact that cells are not receiving enough oxygen for aerobic respiration to take place.
➔ Myocardial infarction18:
Myocardial infarction, otherwise known as a heart attack, is caused by a complete blockage of blood to the heart
muscle, leading to the death of cardiac muscle cells. This can be either fatal or nonfatal fatal10.
Obesity
Obesity is characterised as an abnormal or excessive fat accumulation that presents a risk to health. A body mass index
(BMI) over 25kgm-2 is considered overweight, and a BMI greater than 30kgm-2 is obese21. Over 4 million people die each
year as a result of being overweight or obese, and the prevalence of obesity continues to increase; worldwide obesity has
nearly tripled since 197521.
The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories that have
been burned; the overconsumption of food is not compensated for through exercising. This is due to two main global
changes:
➔ Easier access to processed foods, which are high in fats and sugars. Therefore there has been an increased intake of
these energy-dense foods21;
➔ An increase in physical inactivity due to the increasingly sedentary nature of many forms of work, changing modes
of transportation and an increase in urbanisation21.
These are directly resulting from the development of countries, which lead to changes in dietary and physical activity. This
is because as a country develops, there is less strain on primary sector employment, which is much more physical. The
improvement in education allows for higher-paying jobs, leading to increases in disposable income, which can be spent on
2
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller christinatziatas. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.49. You're not tied to anything after your purchase.
