What is health?Spec 5.1
Health is not just about being free from illness. 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.
| Part of health | What it means | Example of it going wrong |
|---|---|---|
| Physical | The body is working properly and is free from disease | Having an infection such as tuberculosis |
| Mental | Being able to think clearly and cope with everyday life | Long-term anxiety or depression |
| Social | Having good relationships and a place in the community | Being isolated or lonely |
Someone can have no disease and still not be healthy by this definition. For example, a person who is physically fit but severely stressed and isolated is not in a state of complete well-being.
Communicable and non-communicable diseasesSpec 5.2
A communicable disease can be passed from one organism to another. It is caused by a pathogen, so it is also called an infectious disease. Cholera, tuberculosis and malaria are communicable.
A non-communicable disease cannot be passed from one person to another. It is not caused by a pathogen. Cardiovascular disease, many cancers and diseases linked to nutrition are non-communicable.
| Communicable | Non-communicable | |
|---|---|---|
| Cause | A pathogen | Not a pathogen; often a mix of several factors |
| Passed on? | Yes, between people (or animals or plants) | No |
| Examples | Cholera, tuberculosis, malaria, HIV | Heart disease, lung cancer, liver disease |
How one disease can lead to anotherSpec 5.3
Having one disease can make you more susceptible (more likely to catch) other diseases. There are several ways this happens.
- A weakened immune system. HIV destroys white blood cells, so the body cannot fight off other pathogens. People with HIV are much more likely to develop infections such as tuberculosis.
- Damaged barriers. A disease that damages the skin or the lining of the airways makes it easier for other pathogens to get in.
- Poor nutrition. Some diseases make it hard to eat or absorb food. A poorly nourished body makes fewer of the cells and chemicals needed for defence.
- Mental health. A long-term physical illness can lead to depression or anxiety. Poor mental health can in turn make physical health worse.
Using data
You may be given a table, graph or scatter diagram linking two diseases. A scatter diagram can show a correlation: as one variable changes, the other changes too. A correlation does not prove that one disease causes the other. Something else could be responsible for both.
Data from a larger, randomly chosen sample is more reliable than data from a small one. Also check that the people sampled are representative of the group the conclusion is about.
Reading a scatter diagram
A scatter diagram shows that in 20 regions, the regions with more people infected with HIV also have more people with tuberculosis. Describe the pattern and state what can be concluded.
- The points slope upwards from left to right.
- As HIV infections increase, tuberculosis cases increase, so there is a positive correlation.
- A correlation does not show cause, but it is consistent with HIV making people more susceptible to tuberculosis.
Answer: Positive correlation between HIV and tuberculosis. It supports, but does not prove, that HIV increases susceptibility to tuberculosis.
Tap to enlargeQuick check
Give the WHO definition of health.
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A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.
What is the main difference between communicable and non-communicable diseases?
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Communicable diseases are caused by pathogens and can be passed on; non-communicable diseases cannot be passed on.
Explain why someone with HIV is more likely to get tuberculosis.
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HIV destroys white blood cells, so the immune system is weakened and cannot fight off other pathogens.
What does a positive correlation on a scatter diagram show?
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As one variable increases, the other also increases.