epidemiological studies, analysis of cancer Flashcards
what are the three types of cohort studies
prospective, retrospective and ambi-directional cohort
what is a cohort study
group of people with similar exposures
Usually In a defined POPULATION.
what is a retrospective cohort study
a study in which outcomes have occurred before the start of the investigation
what are ambi-directional cohort?
combines prospective and retrospective, the cohort is identified from past records and assesses the date for the outcome. the same cohort is followed up prospectfully in the future for further assessment of outcomes.
what is the relative risk calculation
incidence risk among an exposed group divided by incidence risk amongst non-exposed group
what are the advantages and disadvanatages of cohort studies
- incidence can be calculated
- several possible outcomes related to exposure can be studied simultaneously
- not suitable for rare diseases
- time consuming and expensive
- study may alter peoples behaviour
what types of bias are common in cohort studies
differential loss, contamination, selection bias, information bias and missclarification bias
what is a case control study
observational study of those with the disease of interest and suitable control group without disease
what are the three distinct features of case-controls
- exposure and outcome have occurred before the start of the study
- study proceeds backwards effect - cause (always retrospective)
- uses control of comparison group
what is a case
a person in the population who have been identified as having the disease under investigation
what is a control
person/persons in a comparison group that differs in disease extreme,e in not having the outcome that is being studied
what are the examples of case-control bias
selection, information and confounding
what is an odds
ration of the number of ways an event can occur to the number of ways an event can’t occur
what is an odds ratio
ratio of the odds that the cases were exposed to the odds that the controls were exposed too
advantages of case-control studies
commonly used in outbreak investigation
relatively inexpensive
important to understand new diseases only realistic study design for uncovering aetiology of rare diseases
disadvantages of case-control study
susceptible to bias, i restricted to a single outcome, especially susceptible to recall bias
cross-sectional studies
an analytical investigation in which subjects are sampled at a fixed point or period of time and the association between the concurrent presence or absence or risk factors and diseases are investigated
what is descriptive cross-section
presence of disease, disability and symptoms of ill-health. measurement of variables
what is analytical cross-sectional
strength of association between disease or risk factors
determinants of predictors of disease
advantages of cross-sectional studies
- less costly
- easy and quick
- provides an estimate of the prevalence of a disease
- used for chronic conditions with low case fatality
disadvantages of cross-sectional studies
- does not provide incidence
- prone to bias
- weak design for providing causality
what are gene interaction studies
the different effects of environmental exposure on disease risk in subjects with different genotypes
what are methods to analyse traditional genetic designs
adoption studies, twin studies, family studies
what are advantages in gene environment interaction study
An understanding of gene- environment Interaction has Important
implications for public health - Alds in predicting disease rates
disadvantages of traditional genetic designs
Lack of replication
Does not account for whether environmental
effects are additive , multiplicative o r interactive
what are genome wide association study
An approach that Involves scanning biomarkers from DNA of many people in order to find genetic variation associated w ith a particular disease field phenotypes
what are the advantages of genome-wide association
can lead to the discovery of biological mechanism s
can study low-frequency and rare variants
successful at identifying novel variant- trait associations
disadvantages of genome wide association
Doesn’t necessarily pinpoint causal variants a n d genes
- Has Lim ited clinical predictive’ value
- cannot identify all genetic determinants.
