Population Health Epidemiology IV Flashcards
What did Clemmensen 1965 say about epidemiology?
- The aim of every epidemiology study in cancer is to prevent it
What is the definition of risk factor?
- An environmental, behavioural or biological factor confirmed by temporal sequence, usually increasing the probability of a disease occurring and if absent or removed, reduces the probability
- They are part of the casual chain, or expose the host to the casual chain.
- Once disease occurs, removal of risk factor may not result in cure
What is the concept of cause?
- Few diseases have single ‘cause’
- Most result from exposure of susceptible individuals to one of more causal agents
- Exposure to causal agent(s) does not inevitably result in disease
- Investigation of cause complex:
- characteristics of susceptible/resistant individual
- types of exposure to external agent
What is the selected Bradford Hill Criteria for Causal association ie Factor under study likely to cause disease?
- Strength of association
- Dose response
- Change in risk factor – reduction
- Time sequence
- Consistency
- Specificity – defined exposures
- Biological plausibility
- Experimental preventive trials
What is a cause?
- External agent which results in disease in susceptible individuals
What are confounding variables in regard to Causes?
- Concept of cause must be distinguished from concept of association
- Not all factors associated with occurrence of disease are causes
- Some factors may be associated independently with a causal agent but do not themselves cause disease or increase risk of developing disease
What is definition of Confounding variable?
- Particular type of extraneous variable which for some reason has been left uncontrolled.
- The result is that on looking at the findings of an experimental study, rather than only one possible variable exerting influence on outcome, there are found to be others, which are said to be confounding the results
What is an example of Confounding variable of Drug trial for control of hypertension?
Test group (drug); Placebo group (control)
Result: test group lower blood pressure than placebo group
Confounding: average age of test group significantly lower than control group. Hypertension age related, therefore result may be due to age difference rather than effect of drug.
What are some negatives of descriptive epidemiology?
- Can only go so far
- Patterns and trends not causes
- Hypothesis generating
- Ecological fallacy
What is a Risk factor hypothesis?
- Suggestion that exposure to a particular agent may cause the development of a particular disease if susceptible individual exposed to agent in question
OR - Suggestion that possession of certain characteristics (e.g. socio-economic status, ethnicity, genetics) may make disease outcome more likely if exposed to certain agents
Gained from descriptive epidemiology, clinical impression, lab studies
What are some examples of examination of descriptive data?
- Decrease in caries levels associated with War-time sweet rationing
- Higher incidence of oral cancer in West of Scotland compared with rest of UK
- Caries more prevalent in children from low socio-economic groups
In each case, ask question why which generates hypothesis
How can you investigate risk factor hypothesis?
- In animals can conduct experiments
- In humans can’t use experimental approach so;
- Start with generation of hypothesis
- Should be biologically plausible
- Use Analytic observational study
What are the three common indices of risk?
- Absolute
- Relative
- Attributable
What is absolute risk?
- Most basic measure
- Incidence rate of disease amongst people exposed to agent
- Not very useful, as assumes no risk incurred by people not exposed to agent
What is Attributable risk?
- Difference between incidence rates in exposed and non-exposed groups
- Represents the risk attributable to factor being investigated
