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2.14 Health, lifestyle and risk factors

What health is, communicable and non-communicable diseases, how diseases interact, the main risk factors (diet, exercise, smoking, alcohol, carcinogens), correlation and causation, BMI and waist:hip ratio, and the costs of disease.

AQA Edexcel OCR 2 min read

What health means

Key terms

  • Health: a state of complete physical, mental and social well-being, and not just the absence of disease.
  • Communicable disease: a disease caused by a pathogen that can be passed from one person to another.
  • Non-communicable disease: a disease that cannot be passed on, such as heart disease, most cancers and type 2 diabetes.
  • Risk factor: something about a person's lifestyle, or a substance in their body or environment, that makes a disease more likely.

How diseases interact

Diseases and other factors affect each other:

  • a defect in the immune system makes a person more likely to catch communicable diseases
  • some viruses living in cells can trigger cancers (for example, HPV can cause cervical cancer)
  • immune reactions to a pathogen can trigger allergies, such as skin rashes or asthma
  • severe physical illness can lead to mental illness, such as depression.

Diet, stress and life situations (such as poverty or where you live) also have a big effect on both physical and mental health.

Risk factors

Risk factors linked to diseases: smoking, poor diet and obesity, lack of exercise, alcohol, and carcinogens and radiation, joined to the diseases they increase the risk of
Risk factors linked to diseases: smoking, poor diet and obesity, lack of exercise, alcohol, and carcinogens and radiation, joined to the diseases they increase the risk of
  • Diet, obesity and lack of exercise increase the risk of cardiovascular disease and type 2 diabetes.
  • Smoking causes lung disease and lung cancer, and damages the heart and blood vessels.
  • Alcohol damages the liver and affects brain function.
  • Smoking and alcohol in pregnancy harm the unborn baby.
  • Carcinogens, including ionising radiation, increase the risk of cancer.

Many diseases are caused by several risk factors acting together.

Correlation and cause

A scatter graph showing a positive correlation between cigarettes smoked and lung cancer deaths, with notes on correlation and cause
A scatter graph showing a positive correlation between cigarettes smoked and lung cancer deaths, with notes on correlation and cause

A correlation means two things change together. It does not prove that one causes the other. A risk factor is only accepted as a cause once scientists find a mechanism: for example, chemicals in tobacco smoke damage the DNA in lung cells.

Measuring obesity (Edexcel)

BMI = mass (kg) / (height (m))^2
BMI categories for adults
BMICategory
Below 18.5Underweight
18.5 to 24.9Normal (healthy) weight
25 to 29.9Overweight
30 to 39.9Obese
40 or moreSeverely obese

Example: mass 80 kg, height 1.75 m. BMI = 80 ÷ 1.752 = 80 ÷ 3.0625 = 26.1, which is overweight. BMI does not tell muscle from fat, so a very muscular athlete can have a high BMI. The waist:hip ratio (waist measurement ÷ hip measurement) shows fat stored around the middle, which is more closely linked to heart disease. A ratio above about 0.9 for men or 0.85 for women means a higher risk.

The cost of non-communicable diseases

Non-communicable diseases cost the NHS and other health services a lot of money for treatment. Families lose income when someone cannot work or needs care, and the whole country loses workers. In poorer countries, they also slow down economic development.

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