B8: Health and Disease
Health, disease and risk factors for non-communicable diseases
B8 Health And Disease
📋 Key Concepts
Health is a state of physical and mental wellbeing, not just the absence of disease. Diseases can be communicable (can be passed between individuals) or non-communicable (cannot be passed on). Risk factors increase the likelihood of developing a non-communicable disease.
Key Terms
- Health - a state of physical and mental wellbeing
- Communicable disease - a disease that can be passed from person to person (caused by pathogens)
- Non-communicable disease - a disease that cannot be passed between people
- Risk factor - something that increases the chance of developing a disease
- Causation - when a factor directly causes a disease
- Correlation - when two things are linked but one does not necessarily cause the other
- Benign tumour - a tumour that stays in one place and does not spread
- Malignant tumour - a tumour that spreads to other parts of the body (cancer)
📝 What Is Health?
Health is defined by the WHO as "a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity." This means health is about more than just not being ill - it includes mental health, social wellbeing and physical fitness.
Factors Affecting Health
- Diet - a poor diet (too much or too little food, or lack of key nutrients) can lead to malnutrition, obesity, or deficiency diseases
- Stress - long-term stress can cause physical illness (e.g. high blood pressure, heart disease) and mental health problems (e.g. anxiety, depression)
- Life situations - access to healthcare, income, education, housing and employment all affect health
- Infectious diseases - communicable diseases can damage health directly and also weaken the immune system
Physical and mental health are linked. A person with a long-term physical illness is more likely to suffer from depression. A person with a mental health condition may neglect their physical health, leading to further problems.
📝 Communicable vs Non-Communicable Diseases
Communicable diseases can be passed from person to person (they are infectious, caused by pathogens such as bacteria, viruses, fungi and protists). Non-communicable diseases cannot be passed between people - they develop over time and are often linked to lifestyle or genetic factors.
| Feature | Communicable Diseases | Non-Communicable Diseases |
|---|---|---|
| Can be passed on? | Yes - from person to person | No - cannot be passed between people |
| Cause | Pathogens (bacteria, viruses, fungi, protists) | Lifestyle factors, genetics, environmental factors |
| Duration | Usually short-term (though some can be chronic) | Usually long-term or lifelong |
| Examples | Flu, COVID-19, measles, malaria, HIV | Cancer, cardiovascular disease, type 2 diabetes, asthma |
| Treatment | Antibiotics (bacteria), vaccines (prevention), antivirals | Lifestyle changes, medication, surgery |
Example 1
Question: Classify the following diseases as communicable or non-communicable: measles, type 2 diabetes, malaria, lung cancer.
Answer: Measles - communicable (caused by a virus, can be passed between people). Type 2 diabetes - non-communicable (cannot be passed on, linked to lifestyle factors). Malaria - communicable (caused by a protist, transmitted by mosquitoes). Lung cancer - non-communicable (cannot be passed between people, linked to risk factors like smoking).
📝 Non-Communicable Diseases
Non-communicable diseases are the leading cause of death globally. They develop over a long time and are often caused by a combination of genetic and lifestyle factors. The three main non-communicable diseases at GCSE level are cancer, cardiovascular disease and diabetes.
Cancer
- Cancer is caused by uncontrolled cell division forming tumours
- Tumours can be benign or malignant (see section below)
- Risk factors include smoking, UV exposure, alcohol, obesity and genetic factors
Cardiovascular Disease
- Diseases of the heart and blood vessels, including coronary heart disease
- Caused by build-up of fatty deposits in arteries (atherosclerosis)
- Risk factors include smoking, high blood pressure, high cholesterol, obesity, lack of exercise
Type 2 Diabetes
- The body becomes resistant to insulin or does not produce enough insulin
- This leads to high blood sugar levels that can damage organs
- Risk factors include obesity (especially excess weight around the abdomen), lack of exercise, family history and age
📝 Risk Factors
A risk factor is something that increases the chance of developing a disease. Having a risk factor does NOT mean you will definitely get the disease - it only increases the probability. Some risk factors are lifestyle choices; others are beyond our control.
| Risk Factor | Diseases Linked To | How It Increases Risk |
|---|---|---|
| Smoking | Lung cancer, cardiovascular disease, COPD | Carcinogens in tobacco smoke damage DNA in lung cells, leading to cancer; chemicals damage blood vessels and increase blood pressure |
| Obesity | Type 2 diabetes, cardiovascular disease, some cancers | Excess body fat causes insulin resistance; increases blood pressure and cholesterol; fat cells can produce hormones that promote cell division |
| Alcohol | Liver disease, liver cancer, cardiovascular disease | Alcohol damages liver cells causing cirrhosis; is a carcinogen; raises blood pressure |
| Lack of exercise | Cardiovascular disease, type 2 diabetes, obesity | Inactivity leads to weight gain, higher blood pressure, higher cholesterol and reduced insulin sensitivity |
| UV exposure | Skin cancer (melanoma and non-melanoma) | UV radiation damages DNA in skin cells, which can lead to mutations and uncontrolled cell division |
Some risk factors are NOT lifestyle choices: Age, gender, genetics and family history can all be risk factors that you cannot change. For example, a family history of breast cancer increases your risk regardless of lifestyle.
📝 Causation vs Correlation
Correlation means two things are linked statistically - when one goes up, the other goes up (or down). Causation means one thing directly causes the other. A correlation does NOT prove causation.
Correlation ≠ Causation
If factor A and disease B are correlated, it could mean:
1. Factor A causes disease B (causation)
2. Disease B causes factor A (reverse causation)
3. A third factor C causes both A and B (confounding factor)
If factor A and disease B are correlated, it could mean:
1. Factor A causes disease B (causation)
2. Disease B causes factor A (reverse causation)
3. A third factor C causes both A and B (confounding factor)
Examples
- Causation proven: Smoking causes lung cancer - the carcinogens in smoke directly damage DNA in lung cells. This is a proven causal link, not just a correlation.
- Correlation only: People who carry lighters are more likely to get lung cancer. This is a correlation - the lighter does NOT cause cancer. The real cause is smoking, and carrying a lighter is just associated with smoking (a confounding factor).
Example 2
Question: A study shows that people who drink more coffee have a higher rate of heart disease. Does this prove that coffee causes heart disease? Explain your answer.
Answer: No, this does not prove causation. The study shows a correlation between coffee drinking and heart disease, but there could be a confounding factor. For example, people who drink a lot of coffee may also smoke more, have more stress, or eat less healthily - these could be the actual causes of the heart disease, not the coffee itself. Further research would be needed to determine whether coffee directly causes heart disease.
📝 Cancer: Benign and Malignant Tumours
Cancer is caused by uncontrolled cell division. When cells divide uncontrollably, they form a mass of abnormal cells called a tumour. Tumours can be benign (not cancer) or malignant (cancer).
| Feature | Benign Tumour | Malignant Tumour |
|---|---|---|
| Growth rate | Usually slow-growing | Often fast-growing |
| Spread | Stays in one place; does NOT spread to other parts of the body | Spreads to other parts of the body (metastasis) |
| Encapsulated? | Usually contained within a fibrous capsule | Not contained; cells break away and travel in the blood or lymph |
| Danger | Usually not life-threatening (unless pressing on vital organs) | Life-threatening if left untreated |
| Treatment | Often removed by surgery alone | Requires surgery, chemotherapy, radiotherapy or a combination |
| Recurrence | Unlikely to return after removal | Can return after treatment |
Metastasis: Malignant tumour cells can break off from the original tumour and travel through the bloodstream or lymphatic system to other parts of the body. There, they form new (secondary) tumours. This is why malignant tumours are so dangerous - they can affect multiple organs.
Example 3
Question: Explain the difference between a benign tumour and a malignant tumour. (3 marks)
Answer: A benign tumour stays in one place and does not spread to other parts of the body. It is usually contained within a fibrous capsule and grows slowly. A malignant tumour can spread to other parts of the body (metastasis) - cells break away from the original tumour and travel through the blood or lymph to form secondary tumours elsewhere. Malignant tumours are cancer and are life-threatening.
Example 4
Question: Explain how smoking increases the risk of developing lung cancer. (3 marks)
Answer: Tobacco smoke contains carcinogens (cancer-causing chemicals). These carcinogens damage the DNA in the cells lining the lungs. If the DNA damage affects the genes that control cell division, the cells may begin to divide uncontrollably. This uncontrolled cell division forms a tumour, which can be malignant (cancer) and spread to other parts of the body.
📝 Interactions Between Diseases
Diseases can interact with each other. Having one disease can make a person more susceptible to another. The immune system, mental health and physical damage caused by one disease can all affect the risk of developing other conditions.
Examples of Disease Interactions
- Immune system suppression: HIV damages the immune system, making the person more vulnerable to other communicable diseases (like tuberculosis) that a healthy immune system could fight off
- Physical damage: Severe communicable diseases can damage body organs, increasing the risk of non-communicable diseases. For example, some viruses that cause hepatitis can lead to liver cancer
- Mental health: People with long-term physical health problems (e.g. severe arthritis, cancer) are more likely to develop depression. Depression can then lead to a weakened immune response and poorer physical health
- Lifestyle effects: A person with severe depression may neglect diet and exercise, increasing their risk of cardiovascular disease and type 2 diabetes
Example 5
Question: Explain how having HIV can make a person more likely to develop other diseases. (3 marks)
Answer: HIV infects and destroys white blood cells, which are part of the immune system. This weakens the person's immune system so it cannot effectively fight off pathogens. As a result, the person becomes much more susceptible to other communicable diseases (opportunistic infections like tuberculosis) that a healthy immune system would normally destroy. The person is also less able to fight off cancer cells, increasing the risk of certain cancers.
📝 Effects of Lifestyle on Disease
Lifestyle choices have a major impact on the risk of developing non-communicable diseases. Making healthy choices can significantly reduce the risk, while unhealthy choices increase it. However, even healthy people can develop diseases due to genetic or other factors.
Reducing Risk Through Lifestyle
- Stop smoking - the single most effective way to reduce the risk of lung cancer and cardiovascular disease
- Healthy diet - eat a balanced diet rich in fruit and vegetables, low in saturated fat, salt and sugar
- Regular exercise - at least 150 minutes per week reduces the risk of cardiovascular disease, type 2 diabetes and obesity
- Limit alcohol - reducing alcohol intake lowers the risk of liver disease and some cancers
- UV protection - use sunscreen and avoid sunbeds to reduce the risk of skin cancer
Important: Lifestyle changes reduce risk but cannot eliminate it entirely. Genetic factors and age also play a role. Someone with a very healthy lifestyle can still develop cancer or heart disease.
❓ Practice Questions
Q1: Define the term "health." (1 mark)
Q2: Explain the difference between a communicable disease and a non-communicable disease. Give one example of each. (3 marks)
Q3: Explain the difference between a benign tumour and a malignant tumour. (3 marks)
Q4: A study finds that people who eat more ice cream have higher rates of sunburn. Does ice cream cause sunburn? Explain your answer using the terms "correlation" and "causation." (3 marks)
Q5: Describe two ways in which diseases can interact with each other. Use examples. (4 marks)
Q6: Explain how obesity is a risk factor for type 2 diabetes and cardiovascular disease. (4 marks)
✅ Answers
- Health is a state of physical and mental wellbeing, not just the absence of disease or infirmity.
- A communicable disease can be passed from person to person and is caused by pathogens (e.g. flu, caused by a virus). A non-communicable disease cannot be passed between people and is caused by lifestyle or genetic factors (e.g. cancer or type 2 diabetes).
- A benign tumour stays in one place, does not spread to other parts of the body, and is usually contained within a fibrous capsule. A malignant tumour can spread to other parts of the body through the blood or lymph (metastasis), is not contained by a capsule, and is cancer - it is life-threatening if untreated.
- No, this is a correlation, not causation. Eating ice cream does not cause sunburn. The link is likely due to a confounding factor: both ice cream consumption and sunburn increase during hot, sunny weather. The actual cause of sunburn is UV exposure from the sun, not ice cream. This example shows that correlation does not prove causation.
- 1) Immune system interactions: HIV weakens the immune system by destroying white blood cells, making the person more vulnerable to other communicable diseases (e.g. tuberculosis) that a healthy immune system would fight off. 2) Physical and mental health interactions: A person with a long-term physical illness (e.g. cancer) is more likely to develop depression. Depression can then affect physical health by causing poor diet, lack of exercise and weakened immune response, creating a cycle of worsening health.
- Obesity is a risk factor for type 2 diabetes because excess body fat causes cells to become resistant to insulin, meaning the body cannot properly control blood sugar levels. The pancreas cannot produce enough insulin to overcome this resistance, leading to type 2 diabetes. Obesity is a risk factor for cardiovascular disease because excess body fat raises blood pressure and increases blood cholesterol levels, leading to fatty deposits building up in arteries (atherosclerosis). This narrows the arteries, reducing blood flow to the heart muscle and increasing the risk of heart attacks.
🎯 Exam Tips
- The WHO definition of health includes "physical, mental and social wellbeing" - learn all three parts
- Never say a risk factor "causes" a disease - say it "increases the risk of" or "is linked to" the disease
- For causation vs correlation, always explain that correlation does NOT prove causation and suggest a possible confounding factor
- Benign = stays in one place; malignant = spreads (metastasis) - this is the key difference examiners look for
- When asked about cancer, mention uncontrolled cell division AND the formation of tumours
- For disease interactions, the HIV/immune system example is the most common one on exams
- Lifestyle factors are choices you CAN change; genetic and age factors you CANNOT change - distinguish between these in answers
- Remember that having a risk factor does NOT mean you will definitely get the disease - it only increases the probability
🔢 Maths Skills
Mathematical Skills
You need to interpret epidemiological data — this means reading graphs, tables and charts showing the incidence of diseases and their risk factors. Focus on: calculating percentage change in disease rates; reading data from bar charts and scatter graphs; identifying correlations in data.
Maths Example
Lung cancer cases in a country rose from 12,000 to 15,600 over 10 years. Calculate the percentage increase.
Increase = 15,600 − 12,000 = 3,600. % increase = (3,600 ÷ 12,000) × 100 = 30%
⚠️ Common Misconceptions
Watch Out!
1. Wrong: Risk factors always cause the disease Correct: A risk factor increases the probability of a disease — it is a correlation, not necessarily causation
2. Wrong: Non-communicable diseases cannot be prevented Correct: Many non-communicable diseases can be reduced by lifestyle changes — e.g. stopping smoking reduces lung cancer risk, exercise reduces cardiovascular disease risk
✍️ 6-Mark Question
Extended Answer
6 marks: Explain the difference between correlation and causation using smoking and lung cancer as an example.
Correlation means two variables are linked — when one changes, the other changes too. Causation means one variable directly causes the other. A correlation does not prove causation — there could be a confounding factor. In the case of smoking and lung cancer, there is a strong correlation: as smoking rates increase, lung cancer rates increase. However, correlation alone does not prove that smoking causes lung cancer. Scientists established causation through additional evidence: they identified carcinogens in tobacco smoke that directly damage DNA in lung cells; they showed that the more a person smokes, the greater their risk (a dose-response relationship); they found that stopping smoking reduces risk; and they demonstrated the biological mechanism by which carcinogens cause mutations leading to uncontrolled cell division. This combination of epidemiological correlation and biological evidence proves causation, not just correlation.
Mark scheme: 1 mark for defining correlation; 1 mark for defining causation; 1 mark for explaining that correlation ≠ causation; 1 mark for the smoking–cancer correlation; 1 mark for additional evidence needed (carcinogens/mechanism); 1 mark for concluding how causation was established
📊 AO3: Analyse & Evaluate
Analysis and Evaluation
A study found that countries with higher chocolate consumption have more Nobel Prize winners per capita.
(a) Is this a correlation or causation? Explain.
(b) Suggest a confounding factor that could explain this link.
Answers: (a) This is a correlation — the data shows a statistical link but does not prove chocolate causes Nobel Prizes. (b) Confounding factor: wealthier countries can afford more chocolate AND have better education/research funding, which leads to more Nobel Prizes. The real driver is national wealth, not chocolate.
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