The effect of lifestyle on some non-communicable diseases: explain the effect of lifestyle factors including diet, alcohol and smoking on the incidence of non-communicable diseases at local, national and global levels.

The idea

Incidence means the number of new cases in a population over a period. Lifestyle factors change that number. A diet high in saturated fat, salt and sugar raises the risk of obesity, type 2 diabetes, coronary heart disease and some cancers. Alcohol misuse damages the liver, causing cirrhosis, and raises the risk of some cancers and high blood pressure. Smoking damages lung tissue and blood vessels, increasing the risk of lung cancer, chronic obstructive pulmonary disease and coronary heart disease. These effects appear locally, for example in a town with many smokers, nationally in NHS statistics, and globally where tobacco or alcohol marketing is widespread. Explaining means linking the factor to a biological effect and then to a change in incidence, not just naming the disease.

What earns the marks

• Defines incidence as the rate of new cases in a population over time, so the explanation is about changing numbers of cases rather than individual symptoms.
• Links diet to disease through mechanisms such as obesity, raised blood cholesterol, high blood pressure and insulin resistance.
• Links alcohol to liver cirrhosis, some cancers and high blood pressure, and smoking to lung cancer, chronic obstructive pulmonary disease and cardiovascular disease.
• Applies the explanation at local, national and global levels, for example comparing smoking rates in a local area with national trends and global tobacco use.
• Uses data or trends appropriately, such as a fall in national smoking rates followed by a fall in lung cancer incidence, while noting that effects may lag.
• Recognises that risk factors often combine, so a person who smokes, drinks heavily and has a poor diet faces compounded risk.

Common mistakes and how to put them right

• Saying a lifestyle factor causes a disease in every person who experiences it.

  Put it right: It increases risk or incidence in a population, not certainty for an individual.

• Confusing incidence with prevalence.

  Put it right: Incidence counts new cases over a period, while prevalence counts all existing cases at a point in time.

• Treating correlation as proof of cause.

  Put it right: Explain the biological mechanism, such as tar damaging cilia and DNA in lung tissue.

• Ignoring the level asked for; correction: if the question says national, use national data or policy rather than only personal advice.

Exam tips

• State the factor, the biological effect and the resulting disease in one clear chain.
• Name the level you are writing about so the examiner can see local, national or global coverage.
• Use comparative language such as 'higher incidence' or 'lower risk' rather than absolute claims.
• If data are provided, quote a trend and explain what it shows about incidence.