3.2.9Exchange and Transport
Risk Factor Data — AQA A Level Biology 7402 Revision Notes & Topical Questions
5 min read 9 parts Lesson 18 of 48 1 quiz
3.2.9 Risk Factor Data — AQA A Level Biology 7402 notes: Interpret data on risk factors for lung disease and other conditions, distinguishing risk from certainty and evaluating the quality of evidence.A risk factor is a variable that is associated with an increased probability of…
- Exam-style question 1
- Exam-style question 2
- Exam-style question 3
- Absolute risk
- Relative risk
- Peer review
Section 1 of 9What is a risk factor?
A risk factor is a variable that is associated with an increased probability of developing a disease.
- and a history of infection.
When you describe a risk factor in an answer, always give its direction (increases or decreases the chance), compare with a reference group, and then add the qualification that the factor raises the probability but does not guarantee the outcome. Protective factors, such as regular exercise or vaccination, are described in the same way, with a reduced probability.
Section 2 of 9Expressing risk
| Measure | Meaning | Example |
|---|---|---|
| Absolute risk | Probability of disease in a group | 2 per 1000 per year |
| Relative risk | Risk in exposed ÷ risk in unexposed | Smokers' risk is 10 times higher |
| Odds | Number with disease ÷ number without | Used in case-control studies |
A large relative risk may mean very little if the absolute risk is tiny; for example doubling a risk from 1 in 100 000 to 2 in 100 000 is still very rare. Always consider both.
Section 3 of 9Reading graphs of risk
When asked to compare two sets of figures, always perform a calculation, such as converting to rates per 1000 so that different sample sizes can be compared fairly.
Section 4 of 9Quality of evidence
Evidence is more reliable when it is drawn from a large randomly chosen sample, collected by repeatable, standardised methods, and published in a peer-reviewed journal after checking by other experts. Be cautious about studies funded by an organisation with a vested interest, small samples, short time spans, or self-reported information. Findings gain credibility when they are replicated by independent groups.
Section 5 of 9Social and ethical dimensions
Data on risk influence public policy
- bans on smoking in public places, taxes on tobacco, clean-air zones and labelling.
- Individuals decide on their behaviour by weighing risk against benefit, though perception of risk is often influenced by personal experience rather than numbers.
- Scientists must report uncertainty honestly.
Some questions give a statement of risk in words and ask you to interpret it.
- so most smokers still do not develop lung cancer, although their risk is much greater.
Section 6 of 9Lifestyle, genetic and environmental risk factors
Risk factors are often grouped into categories to help organise answers.
| Category | Examples | Can it be changed? |
|---|---|---|
| Lifestyle | Smoking, diet, exercise, alcohol | Yes, by choice |
| Environmental | Air pollution, radon gas, asbestos at work | Partly, by regulation and protective equipment |
| Genetic | Alpha-1 antitrypsin deficiency, family history | No, but screening can help |
| Biological | Age, sex, previous infections | No |
- A person with a genetic predisposition who smokes is at far greater risk than either factor alone would suggest,
- because the factors interact.
- Alpha-1 antitrypsin normally inhibits the enzyme elastase;
- people lacking it are at an increased risk of emphysema,
- which is worse with smoking.
- Examples include screening for lung cancer in heavy smokers, workplace limits on dust, stop-smoking support and the promotion of vaccination.
- The effectiveness of such measures can be evaluated by comparing the incidence of disease before and after the measure.
- A new treatment may increase the prevalence of a disease because patients live longer, even though incidence has not changed.
Section 7 of 9Exam-style questions
In group A, 45 of 3000 people develop COPD. In group B, 18 of 1500 develop COPD. Calculate the incidence per 1000 for each group and state which has the higher risk. [3]3 marks
A: 45 ÷ 3000 × 1000 = 15 per 1000 (1). B: 18 ÷ 1500 × 1000 = 12 per 1000 (1). Group A has the higher risk (1).
A newspaper claims that a pollutant 'doubles the risk of asthma'. Suggest why this statement may be misleading. [2]2 marks
It gives only relative risk and no absolute figure (1). If the original risk is very low, the doubled risk may still be tiny (1).
Suggest two features of a study that make its findings more reliable. [2]2 marks
Large sample size (1). Groups matched for confounding variables such as age and sex / repeated by other researchers / peer-reviewed (1).
Section 8 of 9Key terms
| Term | Meaning |
|---|---|
| Risk factor | A factor associated with an increased likelihood of disease. |
| Absolute risk | Probability of an event occurring in a group. |
| Relative risk | Ratio of risk in exposed and unexposed groups. |
| Incidence | Number of new cases in a population in a time period. |
| Peer review | Evaluation of research by independent experts before publication. |
| Dose-response | Relationship in which effect changes with exposure level. |
Section 9 of 9Exam technique
Marked practiceQuizzes for this lesson
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