6.3.1Global Challenges

Health and Disease: Disease Types — OCR Gateway GCSE Combined Science A J250 - Biology Revision Notes & Topical Questions

5 min read 10 parts Lesson 9 of 18

📚 OCR Gateway GCSE Combined Science A J250 - Biology Hub / Topical Revision

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Part 1 of 8Health and disease

Health is a state of complete physical, mental and social wellbeing, not merely the absence of disease. A disease is a condition in which part of the body or mind does not work properly, causing symptoms. Health is influenced by many factors, including diet, stress, the environment, life situation and the presence of disease.

Diseases are divided into two broad groups.

	Communicable	Non-communicable
Cause	Pathogen (bacterium, virus, fungus, protist)	Not caused by a pathogen
Spread	Can pass from one person (or organism) to another	Cannot be passed on
Examples	Measles, tuberculosis, malaria, athlete's foot	Heart disease, many cancers, type 2 diabetes, asthma, inherited disorders such as cystic fibrosis

Part 2 of 8Types of non-communicable disease

Non-communicable diseases have many different causes, and often several factors act together.

Types of non-communicable disease

Inherited disorders

Inherited disorders result from faulty alleles, for example cystic fibrosis and sickle cell disease.

Lifestyle diseases

Lifestyle diseases are linked to diet, smoking, alcohol and lack of exercise,

such as obesity, type 2 diabetes, coronary heart disease and lung cancer.

Deficiency diseases

Deficiency diseases arise from a lack of a nutrient, such as scurvy (vitamin C) or rickets (vitamin D or calcium).

Environmental diseases

Environmental diseases are linked with pollutants or radiation, for instance asthma triggered by dust, or skin cancer from UV light.

Cancer

Cancer is caused by uncontrolled cell division after mutations in genes that control the cell cycle.

Risk factors increase the probability of getting a disease but do not guarantee it. A correlation between a factor and a disease does not prove that the factor is the cause. Scientists look for a plausible mechanism and repeated results from large, well-designed studies.

Part 3 of 8Interactions between diseases

Diseases can affect each other.

A weakened immune system makes a person more likely to catch communicable diseases.

HIV infection damages certain white blood cells, which makes people prone to infections like tuberculosis.

Some viruses can trigger cancer; human papillomavirus (HPV) can cause cervical cancer.

Poor mental health can reduce the effectiveness of the immune system, and a poor diet can lead to a weak immune system and so more infections.

Physical ill health can also cause depression.

Thus, health in one area often interacts with others.

Part 4 of 8The pattern of disease in populations

The rate of disease differs between regions and over time.

The pattern of disease in populations

In wealthier countries, non-communicable diseases such as heart disease and cancer are the main causes of death, partly because people live longer and partly because of lifestyle; in poorer countries, communicable disease linked to unclean water, poor nutrition and lack of healthcare is more important.

Cost matters too: treating disease costs money to individuals, health services and the economy, and loss of workers harms families and societies.

Data on disease are often shown in bar charts or tables, and you may need to calculate rates per 100 000 people, or percentage change over time.

Part 5 of 8Study design and evidence

When data show a link between a risk factor and a disease, check three things: whether the sample is large and representative, whether other variables have been controlled, and whether the effect has been repeated by other studies. For example, early studies showing that lung cancer rates rose with the number of cigarettes smoked were supported later by laboratory evidence of cancer-causing chemicals in tar, so that smoking is now accepted as a cause rather than just a correlation.

Part 6 of 8Cancer, risk and prevention

Cancer is a good example of a non-communicable disease with several causes.

Normal cells divide only when needed, under the control of genes.

Tumour

A mutation in such a gene can lead to cells dividing without control, forming a mass called a tumour.

Benign

A benign tumour grows in one place and is enclosed by a membrane, so it does not invade other tissues, though it may press on organs.

Malignant

A malignant tumour invades neighbouring tissues, and cells can break off and spread through the blood to form secondary tumours elsewhere,

which is called metastasis.

Malignant tumours are cancers.

Known risk factors include smoking (lung cancer), UV radiation (skin cancer), ionising radiation, some viruses such as HPV, obesity, and inherited alleles such as certain forms of BRCA genes that raise the risk of breast cancer. Reducing risk includes not smoking, using sun protection, eating a balanced diet and screening programmes that catch cancer early, when treatment is most likely to succeed.

Part 7 of 8Measuring the burden of disease

Public health bodies record the number of cases (incidence) and deaths due to a disease.

Measuring the burden of disease

To compare countries of different size, use a rate such as cases per 100 000.

For example, 2 400 cases in a population of 6 000 000 is 2 400 / 6 000 000 x 100 000 = 40 cases per 100 000.
A rise in the rate over time suggests a real increase, whereas a rise in the total number could simply reflect a larger population.

When a graph shows deaths from a communicable disease falling after the introduction of a vaccine, you should state the trend, quote numbers,

and give the likely cause, though other factors such as better sanitation may have also contributed.

Part 8 of 8Exam-style questions

Explain the difference between a communicable and a non-communicable disease, giving one example of each. [4]4 marks
In country A, 340 deaths per 100 000 people are caused by heart disease. In country B the figure is 85. Suggest two reasons for the difference. [2]2 marks
Suggest how HIV infection can lead to the development of tuberculosis. [2]2 marks

Key terms

Term	Meaning
Health	A state of physical, mental and social wellbeing.
Disease	A condition in which part of the body does not function properly.
Communicable disease	A disease caused by a pathogen that can be passed on.
Non-communicable disease	A disease that is not caused by a pathogen and cannot be passed on.
Pathogen	A microorganism that causes disease.
Risk factor	Something that increases the chance of developing a disease.
Deficiency disease	A disease caused by a lack of a nutrient.
Correlation	A relationship between two variables that may not be causal.

Avoid these mistakes

Defining health only as 'not being ill'; it also includes mental and social wellbeing.

Saying all diseases are caused by microorganisms.

Saying that a risk factor always causes the disease. It only raises the probability.

Mixing deficiency diseases (not communicable) with infections.

Concluding that a correlation proves cause, with no further evidence.

Last updated: 20 October 2026