A doctor is reviewing the health records of two patients. Patient A is a 55-year-old male who exercises regularly, has a healthy body mass index (BMI), does not smoke, and has a blood cholesterol level of 4.2 mmol/L. Patient B is a 55-year-old male who does little exercise, is classified as obese, smokes 20 cigarettes a day, and has a blood cholesterol level of 7.8 mmol/L. Explain why Patient B has a higher risk of developing cardiovascular disease than Patient A.

Pearson Edexcel A-Level Biology A (9BI0) — 1.1 Cardiovascular disease and risk · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A doctor is reviewing the health records of two patients. Patient A is a 55-year-old male who exercises regularly, has a healthy body mass index (BMI), does not smoke, and has a blood cholesterol level of 4.2 mmol/L. Patient B is a 55-year-old male who does little exercise, is classified as obese, smokes 20 cigarettes a day, and has a blood cholesterol level of 7.8 mmol/L.

Model answer (5 marks)

Patient B has a higher blood cholesterol level (7.8 mmol L⁻¹) than Patient A (4.2 mmol L⁻¹). High cholesterol promotes the formation of fatty deposits (plaques) in arterial walls, narrowing the lumen and restricting blood flow.

Smoking in Patient B damages the endothelium and causes platelets to clump, increasing the likelihood of thrombosis.

Patient B is obese and sedentary, which is associated with hypertension. Higher blood pressure puts extra strain on artery walls and accelerates atherogenesis.

In contrast, Patient A’s lower cholesterol, normal BMI, regular exercise and non‑smoking status all reduce these risks.

Therefore, the combination of high cholesterol, smoking, obesity and inactivity makes Patient B’s overall risk of cardiovascular disease much greater than Patient A’s.

Examiner tips

  • Use the exact risk factors listed in the mark scheme; link each factor to a physiological effect.
  • Show the causal chain: risk factor → plaque/arterial damage → disease.
  • Keep each point brief and use exam terminology (e.g., atheroma, thrombosis).

Common mistakes

  • Confusing cholesterol level with LDL/HDL; students may mention LDL without specifying. Failing to mention the effect of smoking on endothelial damage. Over‑expanding the answer with irrelevant details such as diet or genetics.

Mark scheme (5 marks)

  1. Patient B has a higher blood cholesterol level, which increases the risk of fatty deposits (plaques/atheroma) forming in artery walls
  2. These fatty deposits cause the artery lumen to narrow (arteries become narrowed), restricting blood flow
  3. Smoking damages the lining of blood vessels / causes platelets to clump, increasing the risk of a blood clot (thrombosis) forming
  4. Obesity / lack of exercise is linked to higher blood pressure, which puts greater strain on artery walls and increases risk of cardiovascular disease
  5. Patient A's lower cholesterol, healthy weight, exercise and non-smoking status each reduce risk, so the combination of multiple risk factors in Patient B makes his overall risk significantly greater

Key terms in this question

cardiovascular disease · cholesterol

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