(1) Introduction to non-communicable diseases

Reminders

Communicable/transmissible diseases are those in which the pathogen is passed from one host to another.

A non-communicable/non-transmissible disease cannot be passed from one host to another.

 

Non-communicable diseases by their nature cannot be transmitted between individual organisms e.g. cancer, diabetes, heart diseases (eg cardiovascular) or respiratory diseases of the lung.

 

Health is the state of an organism's well-being - physical or mental, but ill health is where there is a problem including suffering from some disease.

The World Health Organisation (WHO) defines good heath as "a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity".

So, even if you are a very fit person, you are not necessarily healthy e.g. if you had mental health issues and/or lonely.

 

A disease is a medical condition where part of an organism (plant or animal) isn't functioning properly - in some way the organism is not as it should be.

The disease may take the form of cell damage to the host (plant or animal) which in some way impairs the healthy ('normal') structures or functions of the organism.

Most organisms, including ourselves, experience ill health at some point in their life.

If you have an increased chance of contracting a disease you are described as susceptible.

 

There are many causes of ill health in plants and animals from a non-communicable disease e.g.

mutation in an organism's genes (DNA) eg cancers,

an organism might suffer some deficiency eg lack of vitamins in human diet, lack of light on plant growth

an organism may experience mental or physical trauma triggered by some event eg depression, bereavement, serious accident,

the lifestyle of an organism can have consequences on your health eg links between: smoking and lung cancer, too much sugary/fatty food and obesity and/or diabetes,

 

All diseases show symptoms at some point in their development.

Symptoms are indications of disease in an organism - usually observable eg cough, rash, diarrhoea, leaf discolouration etc.

Sometimes symptoms do not show up immediately after infection - the virus or bacteria may multiply for days or weeks when sufficient of the pathogen is present to create visible symptoms.

This period of infection without symptoms is called the incubation period and may last hours, days, weeks or months - which is a bit scary, because you can't apply medical treatment to a medical condition you don't know you've got!

 

So, diseases can be classified as communicable and non-communicable.

See  communicable diseases  and  plant diseases

Non-communicable diseases cannot be transmitted between individual organisms e.g. cancer, diabetes, heart diseases (eg cardiovascular) or respiratory diseases of the lung.

These cannot be spread from person to person or between other animals and people.

They tend to last for a long time and slowly get worse over time, in the case of 'humans' they can be often linked to our lifestyles.

Examples are asthma, cancer and heart diseases.

If you are suffering from one non-communicable disease, your bodies defences may be weakened by it making you more susceptible to another disease - a 'knock on' effect reducing your body's ability to fight off a second disease.

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Key points Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Revision notes on non-communicable diseases and good health, tailored for IGCSE/GCSE Biology students:

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Introduction to Non-Communicable Diseases and Good Health

1. What Is Good Health?

• Definition: Good health is a state of physical and mental well-being, not just the absence of disease.

• It includes:

  • A functioning immune system

  • Balanced mental health

  • Proper nutrition and exercise

  • Healthy social relationships

Good health is dynamic — it can change over time due to lifestyle, environment, or genetics.

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2. What Are Non-Communicable Diseases (NCDs)?

• Definition: Diseases that cannot be passed from person to person.

• They are not caused by pathogens (like bacteria or viruses).

• Usually chronic (long-lasting) and develop slowly over time.

Examples of NCDs:

• Cardiovascular diseases (e.g. heart disease, stroke)

• Cancers

• Type 2 diabetes

• Chronic respiratory diseases (e.g. asthma, COPD)

• Neurological disorders (e.g. Alzheimer’s)

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3. Causes and Risk Factors

Non-communicable diseases are often caused by a combination of factors:

A. Lifestyle Factors:

• Poor diet (high in fat, sugar, salt)

• Lack of exercise

• Smoking

• Excessive alcohol consumption

• Stress

B. Environmental Factors:

• Air pollution

• Exposure to harmful chemicals (e.g. asbestos, radiation)

C. Genetic Factors:

• Inherited conditions (e.g. some cancers, diabetes)

🔍 Risk Factor: Anything that increases the chance of developing a disease. Some are controllable (diet), others are not (genetics).

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4. Effects of Non-Communicable Diseases

• Can lead to long-term disability, reduced quality of life, or death.

• May affect mental health (e.g. depression from chronic illness).

• Often require ongoing treatment or lifestyle changes.

• Can place a financial burden on individuals and healthcare systems.

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5. Importance in Understanding Human Biology

• Helps explain how lifestyle choices affect health.

• Reinforces the link between body systems (e.g. circulatory, endocrine) and disease.

• Encourages preventative healthcare and early detection.

• Supports understanding of public health strategies (e.g. anti-smoking campaigns, dietary guidelines).

• Promotes scientific literacy — understanding risk, correlation vs. causation, and health data.

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Quick Summary Table

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Keywords, phrases and learning objectives for this part on introducing non-communicable diseases

Be able to define and describe examples of  non-communicable diseases.

Know the WHO definition of good health and definition of disease.

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