studies Flashcards
studies aim
to give an available source of data that gives an epidemiological picture of the UK society
descriptive studies show
- Amount and distribution of disease in a population
- Insight into aetiology = health service needs
descriptive studies are useful because they
- Identifying health problems + monitoring and surveillance
- Any effects worthy of further investigation
- Assess effectiveness of measures of prevention and control
- Assess needs for health services and planning
- Ideas on disease aetiology
advantages of descriptive studies
cheap, quick, good overview
disadvantages of descriptive studies
no evidence about cause, doesn’t need hypotheses
examples of analytical studies
cross sectional
case control
cohort
cross sectional studies investigate
disease frequency, survey, prevalance
process of cross sectional studies
- Observations made at a specific point in time
- Conclusions made about relationship of disease and variables in a defined population
+ and - of cross sectional studies
- Advantages: Quick and easy
- Disadvantages: gives no cause
case control study process
- Compare two groups of people; a group who have the disease and group who don’t (ie cases and controls)
- Data gathered to see if individuals have been exposed to the suspect aetiological factors
- Results are given as RR
cohort study process
- Collect baseline data from a group of people who don’t have the disease
- Group then followed until a sufficient number have developed the disease to allow analysis.
- Original group separated into subgroups according to original exposure and then compared to see incidence of disease according to exposure.
- Allow calculation of cumulative evidence for follow up over time
study called that involves trials?
randomised controlled trial
point of trials?
Experiments used to test ideas about aetiology or evaluate interventions
RCT used to
assess new treatment
process of RCT
- 2 groups at risk of developing disease are assembled; split into study (intervention) group and control group)
- Study group = new drug and the control = placebo.
- Treatment outcomes are compared.
- Calculate a relative risk (aetiological components)
standardisation?
removal/adjustments of confounding variables (e.g. age) when comparing pops
SMR?
standardised mortality ratio - death rate converted into ratio for easy comparison
quality of data - is a measurement of
trustworthiness
case definition
Purpose is to decide if an individual has the condition or interest or not
coding and classification
data converted into coding via analysis + storage - rules for this
ascertainment
data set complete? missing subjects
Bias is
any trend in the collection, analysis, interpretation, publication or review of data that can
lead to conclusions that are systematically different from the truth.
types of bias x4
selection bias: not representative of whole study pop
information bias: errors in measuring exposure
follow up bias: 1 group followed up more than another
systematic error bias: measurements tend to always fall on one side of the true value