You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
This lesson covers the concepts of health and disease as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the WHO definition of health, distinguish between communicable and non-communicable diseases, explain risk factors and understand the difference between correlation and causation.
The World Health Organization (WHO) defines health as:
A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.
This definition is important because it recognises that being healthy is not simply about being free from disease. A person can have no identifiable illness yet still not be "healthy" if their mental or social well-being is poor.
There are three components to this definition:
| Component | Meaning | Example |
|---|---|---|
| Physical well-being | The body is functioning correctly, free from disease or injury | No infections, organs working normally |
| Mental well-being | A person can cope with normal stresses of life, think clearly and maintain emotional stability | Feeling positive, managing anxiety |
| Social well-being | A person has good relationships, feels part of a community and is able to participate in society | Supportive friendships, not isolated |
Exam Tip: If asked to define health, you must include all three components (physical, mental and social) and state it is not merely the absence of disease. Leaving out any part may cost marks.
A disease is a condition where part of the body does not function correctly, leading to specific signs and symptoms. Diseases reduce one or more of the three components of health.
Diseases are broadly divided into two categories:
graph TD
A[Disease] --> B[Communicable<br/>Caused by pathogens<br/>Can spread between organisms]
A --> C[Non-communicable<br/>Not caused by pathogens<br/>Cannot spread]
B --> D[Examples:<br/>HIV, tuberculosis,<br/>malaria, cholera]
C --> E[Examples:<br/>cancer, diabetes,<br/>heart disease, asthma]
Communicable diseases are caused by pathogens — organisms that invade the body and cause disease. There are four main types of pathogen:
| Pathogen type | Description | Example diseases |
|---|---|---|
| Bacteria | Single-celled prokaryotes that reproduce rapidly; damage cells or release toxins | Salmonella, tuberculosis (TB), gonorrhoea |
| Viruses | Tiny particles (not cells); invade host cells and use them to replicate | HIV, measles, influenza, tobacco mosaic virus (TMV) |
| Fungi | Can be single-celled or multicellular; some produce spores | Rose black spot, athlete's foot |
| Protists | Eukaryotic organisms, often single-celled; some are parasites | Malaria (Plasmodium) |
Communicable diseases can spread by:
Non-communicable diseases (NCDs) are not caused by pathogens and cannot be transmitted between people. They are often long-lasting (chronic) conditions.
Common non-communicable diseases include:
Non-communicable diseases are the leading cause of death worldwide.
A risk factor is something that increases the likelihood of developing a particular disease. Risk factors can be:
| Type | Description | Examples |
|---|---|---|
| Lifestyle factors | Choices a person makes | Smoking, diet, exercise, alcohol consumption |
| Substances in the body | Chemicals or molecules linked to disease | High blood cholesterol, high blood pressure |
| Genetic factors | Inherited genes that increase susceptibility | Family history of breast cancer, sickle cell disease |
| Risk factor | Associated disease(s) |
|---|---|
| Smoking | Lung cancer, cardiovascular disease, COPD |
| Obesity | Type 2 diabetes, cardiovascular disease, some cancers |
| Excessive alcohol | Liver disease, brain damage, some cancers |
| Lack of exercise | Cardiovascular disease, obesity, type 2 diabetes |
| High-fat diet | Cardiovascular disease (due to high cholesterol and atherosclerosis) |
Exam Tip: Risk factors do not directly cause a disease — they increase the chance of developing it. Always use precise language: "Smoking increases the risk of lung cancer" rather than "Smoking causes lung cancer."
Communicable and non-communicable diseases can interact with each other:
When scientists study diseases and risk factors, they often find correlations — patterns in data where two variables change together. However, a correlation does not prove that one factor causes the other.
| Term | Definition | Example |
|---|---|---|
| Correlation | A statistical relationship between two variables — when one changes, the other tends to change too | Countries with higher ice cream sales have higher rates of drowning |
| Causation | One factor directly causes the other to happen | Smoking damages cells in the lungs, which can directly lead to cancer |
Scientists use controlled experiments, peer review and large sample sizes to establish causation.
graph TD
A[Observation:<br/>Two variables appear linked] --> B{Is there a<br/>direct mechanism?}
B -->|Yes, established by experiments| C[Causation confirmed]
B -->|No, or not yet proven| D[Correlation only]
D --> E[Could be a<br/>confounding variable]
D --> F[More research<br/>needed]
Exam Tip: A very common exam question asks you to explain why a correlation between a risk factor and a disease does not prove the risk factor causes the disease. Always mention confounding variables, the need for controlled experiments and large sample sizes.