Risk Factors

• Non-communicable disease


  Diseases not spread from person to person, instead caused by risk factors
• In the 1930s, rate of lung cancer began to increase sharply and scientists couldn't explain this
• Scientists could not carry out experiments on humans to try to work out what causes lung cancer as that would be unethical
• Epidemiology


  Studying the patterns of disease to determine risk factors
• Lung cancer is much more common among cigarette smokers than among non-smokers


  Scientists look at how many cigarettes people smoked each day and then how many of these people developed lung cancer
• Correlation


  A link between two variables
• A correlation does not prove cause, it simply suggests that two things might be linked
• As the number of cigarettes smoked per day increases


  The risk of developing lung cancer also increases
• As the number of years a person smoked increases


  The risk of developing lung cancer increases
• Causal mechanism


  How a risk factor could scientifically cause a disease
• Cigarette smoke contains chemicals which damage DNA and increase the risk of cancer, called carcinogens
• Smoking increases the risk of lung cancer
• Sampling


  Investigating a group of people to draw conclusions about a whole population
• Ideally we'd look at every single person in a population, but in practice it's not possible so we sample a group of people
• If the sample is not representative of the whole population, it can lead to bias
• To avoid bias, we need to take as large a sample as possible and it must be as random as possible