Non-Communicable Human Diseases (OCR Gateway GCSE Biology: Combined Science)

• Many non-communicable human diseases are caused by the interaction of a number of factors
• One such group of diseases is given the umbrella term 'cardiovascular disease' (disease of the heart and associated blood vessels)
• Identification and treatment of cardiovascular disease centres around the concept of risk factors
  • These are factors whose effects can be added together to give an estimate of the overall risk of an individual suffering from cardiovascular disease, either now or at some time in the future

The coronary arteries

• The heart is made of muscle cells that need their own supply of blood to deliver oxygen, glucose and other nutrients and remove carbon dioxide and other waste products
• The blood is supplied by the coronary arteries
• If a coronary artery becomes partially or completely blocked by fatty deposits called ‘plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they should be and therefore cannot stretch to accommodate the blood which is being forced through them - leading to coronary heart disease
• Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina
• Complete blockage means cells in that area of the heart will not be able to respire and can no longer contract, leading to a heart attack

Risk factors for Cardiovascular Disease

• Certain risk factors can increase the chance of developing cardiovascular disease
  • Smoking
  • Poor diet
  • Lack of exercise
  • High alcohol consumption
• These risk factors are usually not causative despite the fact that many will show correlations with the incidence of disease
  • This is because interactions between many different factors all contribute towards the overall likelihood that someone will develop a disease
  • For example; a person who eats a lot of fatty red meat isn't guaranteed to develop cardiovascular disease, but their risk compared to an otherwise-similar person who doesn't eat fatty red meat is very much higher
• Risk factors can interact with each other to further increase the likelihood of an individual developing a disease
  • Chemicals in smoke damage the arteries causing atherosclerosis
  • The issue is amplified by a diet that is high in saturated fats and cholesterol which causes the plaques in atherosclerosis to form
  • A consequence of these two effects is that the individual will suffer from high blood pressure and an increased chance of blood clots forming which may lead to a heart attack or a stroke

Buildup of plaque in the coronary arteries

Effect of narrowing of arteries

Risk Factors for Coronary Heart Disease Table

Reducing the risks of developing coronary heart disease

• Quit smoking
• Reduce animal fats in diet and eat more fruits and vegetables - this will reduce cholesterol levels in the blood and help with weight loss if overweight
• Exercise regularly - again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress

Treatment of coronary heart disease

• Aspirin can be taken daily to reduce the risk of blood clots forming in arteries
• Surgical treatments include:
• Angioplasty
  • A narrow catheter (tube) is threaded through the groin up to the blocked vessel
  • A tiny balloon inserted into the catheter is pushed up to the blocked vessel and then inflated
  • This flattens the plaque against the wall of the artery, clearing the blockage
  • To keep the artery clear, a stent (piece of metal / plastic mesh) is also inserted which pushes against the wall of the artery
  • Sometimes the stent is coated with a drug that slowly releases medication to prevent further build-up of plaque

Inserting a stent into a blocked artery

• Coronary bypass surgery
  • A piece of blood vessel is taken from the patient’s leg, arm, or chest and used to create a new passage for the flow of blood to the cardiac muscle, bypassing the blocked area
  • The number of bypass grafts gives rise to the name of the surgery, so a ‘triple heart bypass’ would mean three new bypass grafts being attached

Coronary bypass graft

• A donor's heart
  • This is a good solution, though the supply of suitable donor hearts is low
  • Donor hearts can be rejected by the recipient's immune system
  • The patient might have to take lifelong drug therapy to suppress their immune system
  • So the patient might become more susceptible to infectious diseases
  • There are risks with the surgery e.g. bleeding, infections and the risks of use of anaesthetics

• Many non-communicable human diseases are caused by the interaction of a number of factors
• As well as cardiovascular disease, this applies to the following diseases
  • Many forms of cancer
    • UV light overexposure, carcinogen exposure, asbestos, aspects of diet
  • Some lung diseases e.g. bronchitis
    • Smoking, air pollution, excessive dust exposure
  • Some diseases of the liver e.g. cirrhosis
    • Alcohol abuse
  • Diseases influenced by nutrition, including type 2 diabetes
    • Obesity/excess body fat
    • Inactivity

Summary of Risk Factors for Non-Communicable Diseases Table

• Lifestyle factors can influence levels of non-communicable disease
  • People make choices that have a direct influence on the risk of each person contracting such diseases
• Obesity-related illnesses were calculated to cost the UK taxpayer GBP 6 billion (USD 7.9 billion) in 2021
  • Governments can also intervene at a local and national level to assist in improving

Obesity and malnutrition

• The key risk factors for both obesity and malnutrition are exercise and diet
• Eating more calories than we burn leads to weight gain
• Significant weight gain can lead to obesity
• Obesity increases the risk of other non-communicable diseases such as
  • Type 2 diabetes
  • Cardiovascular disease
• Obesity is a national problem and has led to the introduction of a sugar tax to try and tackle the issue
• Eating fewer calories than we burn, or having an unbalanced diet can lead to malnutrition
• Malnutrition can lead to many different outcomes depending on the nutrient that is lacking, for example
  • Brittle bones may result if calcium levels are low
  • Anaemia may result from low iron levels
• Malnutrition is often associated with developing countries as many individuals do not have access to the necessary nutrients
• Body Mass Index (BMI) is a simplistic measurement which uses data about the weight and height of an individual to determine their health status

Body mass index can be used to assess the weight of an individual

• Cancer is a group of non-communicable diseases that are thought to account for one-third of deaths in the UK in 2021
• Cancer can occur in almost any tissue of the human body; there are approximately 200 cancers
• It is characterised by uncontrolled cell division
  • This can form a clump of cancerous cells called a tumour
  • The cells are not required and have no specialism, but they still consume resources like glucose and oxygen
• Cancer develops via a mutation which can be caused by chemicals called carcinogens, or by radiation such as UV or radioactive decay

Types of tumour

• Benign tumours:
  • Grow slowly
  • Can easily be removed surgically
  • Do not transfer to other parts of the body
• Malignant (cancerous) tumours
  • Grow quickly
  • Invade other tissues and can spread to organs via the circulatory system
  • Cancerous cells detach from a growing tumour and form secondary tumours in other organs
  • This is called metastasis

The stages of cancer development.

Treatment of cancer

• Cancers that are diagnosed early have a much better chance of being treated successfully
  • Diagnosis can be done using X-rays, blood or urine tests or by using monoclonal antibodies
  • The most frequent cancers in the UK are breast, lung and bowel cancers, prostate cancer in men and ovarian cancer in women
• Treatments
  • Chemotherapy
    • Using chemicals to kill cancerous cells
  • Radiotherapy
    • Using X-rays to kill cancerous cells
  • Palliative
    • This helps a person who has fatal cancer to die as comfortably as possible
  • All doctors will advocate that prevention is better than cure
    • Many cancers are less likely to develop if people lead healthy lifestyles
    • Not smoking, exercising regularly and eating a healthy diet
  • The most desirable type of cancer treatment is one that targets cancerous cells only, without doing any damage to normal body cells
    • Chemotherapy patients often lose their hair because the drugs target fast-growing cells, which includes the tumour cells but also, unfortunately, hair follicle cells that produce hair