Cancer Epidemiology Flashcards
What is epidemiology?
The study of the distribution and determinants of disease frequency in specified populations
What is cancer epidemiology concerned with?
The frequencies of cancer in groups of people
Also studies factors that influence cancer frequency in a group of people
The focus is not on the individual
What are the fundamental assumptions in cancer epidemiology?
Cancer does not occur at random
Cancer has causal and preventative factors
Consequently epidemiological studies aim to identify causal and preventative factors for cancer development in groups of people
What are the aims of epidemiology?
To search for a relationship between association between a particular exposure and an outcome
What are the measures of disease frequency?
Incidence which is the number of new cases of cancer that develop in a specific population during a specified period of time
And Prevalence which is the proportion of a population that has a disease at a specific timepoint including both new and previously diagnosed cases of a disease
What is the difference between incidence, incidence rate, incidence rate per person time and age-standardised incidence rate?
The incidence rate takes into account the population size by dividing the number of new cases by the number of people at risk
The incidence rate per person time takes into account how long people lived in the area during the time of study
Cancer rates increase with Age which allows age standardised rates to provide a more valid comparison
What can influence prevalence?
This is a function of both incidence rate and mortality rate so if a disease is long in duration prevalence will be high in relation to incidence however if the disease is of short duration prevalence will be low in relation to incidence
What are the types of epidemiological studies?
Experimental studies like randomized clinical trials and observational studies which may contain a control group and be analytical or may not and be descriptive
What are the types of observational studies?
Cohort studies Case-control studies Cross sectional studies Ecological studies Family studies Case reports
What is a cohort study?
One where there is a study population where the intervention is not allocated by the investigator
The study population is divided up into those who have had exposure to the risk factor being investigated and those who have not (to serve as controls)
And the disease outcomes of both groups are measured
What are the advantages of cohort studies?
They can accurately estimate relative risk of disease development
The magnitude of a risk factors effect can be quantified
Multiple outcomes can be studied
A temporal relationship between exposure and disease may be able to be studied to provide a time-to-event analysis
What are the disadvantages of cohort studies?
They are lengthy and expensive
May require a very large number of participants
Not suitable for rare diseases
Not good for diseases with long term latency
Unexpected factors may influence the association
Loss to follow up due to migration of non-response is a problem
What is a case control study?
A study population is selected retrospectively and then grouped into cases and controls and factors to which individuals in both groups have been exposed to are investigated
What are the advantages of case control studies?
There is no need to recruit large number of subjects or wait for some to develop the disease
Making them quick, cheap and easy to perform
Rare diseases with long term latency can be studied
What are the disadvantages of case control studies?
The selection of cases and controls can be problematic leading to selection bias where there may be a bias to select patients with restricted disease characteristics or controls that do not adequately match the patients
Assessment of exposure is retrospective making it subject to recall bias particularly as people with disease have a greater sensitivity for recalling exposures
