The effect of lifestyle on some non-communicable diseases: Risk factors are linked to an increased rate of a disease.

The idea

A risk factor is anything that raises the chance of developing a disease, but it is not a guarantee. In non-communicable diseases, such as type 2 diabetes or coronary heart disease, risk factors act statistically across a population: groups exposed to the factor show a higher rate of disease than groups not exposed. For example, smokers show a higher rate of lung cancer than non-smokers, yet some smokers never develop it. Scientists identify risk factors by comparing disease rates between groups, often using large samples and long follow-up periods. Correlation does not prove causation, so other variables must be controlled. Understanding risk factors allows individuals to reduce risk through lifestyle choices and lets public health bodies target advice and screening.

What earns the marks

• Defines a risk factor as something that increases the probability or chance of a disease developing, not something that definitely causes it.
• Explains that risk factors are linked to an increased rate of disease across a population, shown by comparing disease frequency in exposed and unexposed groups.
• Uses a named example, such as smoking and lung cancer, or a high-sugar diet and type 2 diabetes, to show the statistical link.
• Distinguishes correlation from causation, noting that other factors must be controlled before concluding that a risk factor contributes to a disease.
• Recognises that non-communicable diseases are not passed between people, so risk factors are usually lifestyle, environmental or genetic.
• Applies the idea to reducing risk, for example stopping smoking lowers the chance of developing smoking-related diseases.

Common mistakes and how to put them right

• Saying a risk factor causes a disease.

  Put it right: A risk factor increases the chance or rate of disease; it does not make the disease certain.

• Treating a single case as proof.

  Put it right: Risk is shown by comparing rates in large groups, not by one person who did or did not become ill.

• Assuming correlation proves causation.

  Put it right: A link may be due to another variable, so controlled studies are needed before claiming cause.

Exam tips

• Use the phrase increased chance or increased rate rather than causes when describing risk factors.
• Support your answer with one named disease and one named risk factor, then state the direction of the link.
• If asked to evaluate, mention that data from large populations is stronger evidence than a single anecdote.