AQA A Level Biology复习笔记3.2.10 Evaluating Data on Lung Disease

Investigating Risk Factors & the Incidence of Lung Disease


  • A risk factor is any factor that correlates with (is linked to) an increased chance of suffering from a particular condition or disease
    • Example of risk factors for the incidence of lung disease is exposure to smoking and pollution


  • The incidence of disease describes the number of cases of a disease that occur in within a particular group of people within a given time

Collecting Data for Studies

  • There are different types of studies that have been done to investigate the effect of risk factors on the incidence of lung disease in humans
  • Prospective studies involve collecting data as it becomes available
    • It can be beneficial in that more accurate data can be obtained
    • It can be highly time-consuming


  • Retrospective studies involve collecting data from the past
    • The data collected may be unreliable as people forget details or alter them
    • Results can be obtained more rapidly


  • Collecting data for studies from the population can be very difficult for a number of reasons
    • Controlled experiments where only one variable is investigated can’t be carried out on humans due to ethical implications. For example, it would be immoral to ask a random group of people to smoke exactly 10 cigarettes every day for 10 years, while the control group is banned from smoking
    • Finding people with sufficiently similar lifestyles can be difficult
    • Long term studies with multiple follow-ups take a lot of time and money
    • It is important to remember that those that make one healthy life choices that is being monitored (e.g. don't smoke) may be more likely to live generally healthier lives (e.g. regularly exercise) which also may have an effect on their risk of disease compared to others that chose other lifestyles


Evaluating Data Linked to Risk Factors

  • There are several things that should be taken into consideration when analysing data from studies on health risk factors
  • Sample size: the number of people involved in the study is very important. A study with a large sample size will have more reliable results
  • Individuals in the sample: if the study only has women aged 20-40 this data is not able to suggest the effect on a male or an older woman, it is therefore important to state the who the data is referring to when evaluating it
  • Levels of exposure: make sure to pay attention to the different levels of exposure to the risk factor that has been included in the study. Eg. 10 cigarettes a day, 20 cigarettes a day, no cigarettes and for how long
  • Control group: identify if the control group matches the other groups closely enough. The people in the control group should be of a similar age and background to those in the other groups
  • Statistical significance: try to determine if the differences between groups are sufficiently large and whether any statistical tests have been carried out to test the significance of the results
  • The influence of other factors/variables: bear in mind that there are many variables that have not been controlled due to moral reason. This means there may be a combination of factors that are interacting with each other to influence the results:
    • Genetics
    • Secondary exposure to smoking
    • Other factors that have not been controlled that has an effect on lung health (e.g. exercise)


Calculating the Relative Risk

  • If the incidence or mortality rate of the disease for different groups has been provided, it can be helpful to calculate the relative risk of each group for comparison
  • For example, the percentage chance of a person developing the disease could be calculated for each group and then compared

Exam Tip

Remember that some diseases developed slowly so there may be a delay between exposure to a risk factor and the disease becoming visible in the population. For example, in a UK study they found there was a delay between the increasing number of men smoking cigarettes during the 1900s and the increasing number of lung cancer cases in men. Cancer can develop at a much slower rate than other diseases, meaning it could be 20 years or more before a smoker shows any sign of the disease.