Tutorial 1: Population Data to Benefit Individual People Flashcards
What needs to be clarified in epidemiology and why?
Time, place, people involved
Disease can vary between different periods in time, in different parts of the world and different types of people
What are the 3 aims of epidemiology?
Description - To describe the amount and distribution of disease in human populations
Explanation - To elucidate the natural history and identify aetiological factors for disease usually by combining epidemiological data with data from other disciplines such as biochemistry, occupational health and genetics
Disease Control - To provide the basis on which preventative measures, public health practices and therapeutic strategies can be developed, implemented, monitored and evaluated for the purpose of disease control
What do epidemiological studies aim to find?
Aetiological clues
The scope for prevention
The identification of high risk or priority groups in society
What has to be clarified when discussing epidemiology with patients?
Epidemiology deals with large populations whilst clinical medicine deals with individual patients
Epidemiology is done in ratios - it is describing risk
What is the incidence of a disease?
The number of new cases of a disease in a population in a specific period of time
What is the prevalence of a disease?
The number of people in a population with a specific disease at a single point in time or at a defined period in time
What does incidence tell us?
Something about the trends in causation and aetiology of a disease
What does prevalence tell us?
Something about the amount of disease in a population
What is relative risk?
The measure of the strength of an association between a suspected risk factor and the disease under study
What is the equation for relative risk?
Relative Risk = Incidence of disease in exposed group/Incidence of disease in unexposed group
What sources can be used to collect data for epidemiological studies?
Mortality data Hospital activity statistics Reproductive health statistics Cancer statistics Accident statistics General practice morbidity Health and household surveys Social security statistics Drug misuse databases Expenditure data from the NHS
What different types of epidemiological studies exist?
Descriptive Studies Analytic Studies: - Cross-sectional studies - Case control studies - Cohort Studies
What are descriptive studies?
Studies that attempt to describe the amount and distribution of disease in a given population
Does not provide definitive conclusions about disease causation but may give clues to possible risk factors and candidate aetiology
Usually quick, cheap and and give a valuable initial overview of a problem
When are descriptive epidemiological studies effective?
Identifying emerging public health problems through monitoring and surveillance of disease patterns
Signalling the presence of effects worthy of further investigation
Assessing needs for health services and service planning
Generating hypotheses about disease aetiology
What are cross-sectional studies?
Observations are made at a single point in time.
Conclusions are drawn about the relationship between diseases and other variables of interest in a defined population
What is useful about cross-sectional studies?
Results can be provided quickly
It is usually impossible to infer causation though
What is a case-control study?
A group of individuals with a disease are identified and compared with a group of individuals without the disease
Data is gathered on each individual to determine whether or not they have been exposed to the suspected aetiological factor. Average exposure between the two groups is compared to identify significant differences and give clues as to what factors elevate or reduce the risk of disease
The results are expressed as relative risks
What are cohort studies?
Baseline data is collected from people who do not have the disease. The group is followed until a sufficient number of the group have developed the disease to allow analysis
The original group is arranged into subgroups according to original exposure status which are compared against each other to determine the incidence of the disease according to exposure.
Allow for the calculation of cumulative incidence, allowing for differences in follow-up time
Results expressed as relative risks with confidence intervals
What are trials?
Experiments used to test ideas about aetiology or to evaluate interventions
What is the definitive method for assessing any new treatment?
Randomised control trial
