7.1 Non-Communicable Diseases

A free GCSE Biology lesson for AQA (8461) from OBA School: health and disease, how diseases interact, risk factors, correlation and causation, and the costs of disease. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe health and explain the difference between communicable and non-communicable diseases
• Describe how different types of disease can interact
• Explain what a risk factor is and give examples, including those with a proven causal mechanism
• Tell the difference between a correlation and a cause when reading data
• Discuss the human and financial costs of non-communicable diseases

Key words

• Health: A state of physical and mental well-being, not just the absence of disease.
• Communi- cable disease: A disease caused by a pathogen that can be passed from one person to another.
• Non-communi- cable disease: A disease that cannot be passed from person to person, e.g. heart disease, most cancers, type 2 diabetes.
• Risk factor: Something linked to an increased chance of developing a disease. It may be part of a lifestyle or a substance in the body or environment.
• Correlation: A link between two variables: as one changes, the other tends to change too.
• Causal mechanism: A proven explanation of how one factor actually causes a change, e.g. how chemicals in tobacco smoke cause lung cancer.

Health and disease

Health is a state of physical and mental well-being. Disease is a major cause of ill health, but diet, stress and life situations (for example income, housing and access to healthcare) also affect both physical and mental health.

• Cause; Communicable disease pathogens: bacteria, viruses, fungi, protists; Non-communicable disease not caused by a pathogen; often lifestyle, genes, age, environment
• Spread; Communicable disease can pass from person to person (or animal to person); Non-communicable disease cannot be passed on by contact
• Examples; Communicable disease measles, salmonella food poisoning, malaria; Non-communicable disease coronary heart disease, type 2 diabetes, most cancers, lung and liver diseases

Key fact: Non-communicable diseases cause most deaths worldwide, especially cardiovascular diseases, cancers and lung diseases.

Diseases can interact

A person can have more than one health problem at once, and one problem can make another more likely.

In the same way, severe physical ill health (for example a long illness or a serious injury) can lead to mental illness such as depression.

Exam tip: If asked how diseases interact, give the cause, the effect and a named example, e.g. "HPV infects cells of the cervix and can trigger cervical cancer".

Risk factors, correlation and cause

A risk factor increases the chance of getting a disease; it does not make it certain. Risk factors can be aspects of a person's lifestyle (smoking, diet, exercise, alcohol) or substances in the body or environment (carcinogens, ionising radiation, air pollution). Many diseases are caused by several risk factors acting together.

For some risk factors, scientists have found a causal mechanism, for example:

• smoking and lung disease and lung cancer
• obesity and type 2 diabetes
• alcohol and liver disease and brain function
• smoking and alcohol during pregnancy and harm to the unborn baby
• carcinogens, including ionising radiation, and cancer

A correlation in data only shows a link. It does not prove that one factor causes the other: both might be caused by a third factor, or the link might be chance. A causal mechanism must be found by other studies.

Exam tip: Describe a correlation in words using both variables: "as the percentage of obese adults increases, the percentage with type 2 diabetes also increases". Then say whether it shows cause.

The costs of non-communicable diseases

• Individual and family; Human costs pain, shorter or lower-quality life, early death; family members may become carers; Financial costs lost earnings; cost of care, travel and equipment
• Local community; Human costs fewer people able to work or volunteer; Financial costs local health services and care homes stretched
• Nation and world; Human costs millions of early deaths each year worldwide; Financial costs huge cost to the NHS of treatment; lost working days slow the economy

Worked example: rate per 100 000 people

In a town of 48 000 people there are 36 new cases of a disease in a year. Calculate the rate per 100 000 people.
rate = (cases ÷ population) × 100 000 = (36 ÷ 48 000) × 100 000 = 75

Answer: 75 cases per 100 000 people per year

Key fact: Rates "per 100 000" let you compare places with different population sizes fairly.

Common mistakes

• Saying a risk factor "causes" a disease. It increases the chance of the disease.
• Concluding that a correlation proves cause. You need a causal mechanism.
• Calling cancer communicable. Cancer cannot be caught, even though a few viruses (such as HPV) can trigger it.
• Comparing numbers of cases in places of different size. Compare rates (per 100 000 people) instead.

Revision questions

Try these, then check your answers below each one.

Question 1. Which of these is a non-communicable disease? (Choose from: Coronary heart disease, Measles, Malaria, Salmonella food poisoning.)

Answer: Coronary heart disease

Working: Coronary heart disease cannot be passed from person to person. The others are caused by pathogens.

Question 2. True or false? A correlation between two factors proves that one factor causes the other.

Answer: False

Working: False. A correlation only shows a link. A causal mechanism must be found to show cause.

Question 3. What two-word term means something that is linked to an increased chance of developing a disease?

Answer: risk factor

Working: A risk factor increases the chance of a disease.

Related lessons

• Previous lesson: 6.6 Uses of Monoclonal Antibodies
• Next lesson: 7.2 Cancer
• In this chapter: 7.3 Smoking and the Risk of Disease
• In this chapter: 7.4 Diet, Exercise, and Disease
• In this chapter: 7.5 Alcohol and Other Carcinogens

Continue in the full course

This lesson is section 7.1 (AGCBH0701) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.