COHORT

If an obvious source of the contamination is identified

cohort

group or groups of persons are defined on the basis of presence or absence of exposure to a suspected risk factor of a disease

cohort study

it determine and compare the occurrence of outcome among exposed and unexposed

cohort studies

cohort studies is also known as:

• follow-up studies

• incidence studies

• prospective studies

• longitudinal studies

• panel studies

strongest observational design for establishing cause-effect relationship

cohort study

sources of bias:

• selection

• misclassification

• cofounding

patients as subjects

randomized clinical trials

interventions assigned to individual community members

field trials

interventions assigned to whole communities

community intervention trials

recite their counterparts

• therapeutic

• preventive

• between subjects design

• within subject design

• same group of subjects

• secondary prevention

• primary prevention

• parallel group design

• cross-over design

• factorial design

determine the ability of an agent or procedure to diminish symptoms, prevented occurrence or decrease risk of death

secondary prevention

•evaluation of whether an agent or procedure reduces the risk of developing the disease among those free from the disease

primary prevention

effects on the dependent variable for one subject or group of subjects are compared with the effect for another subject or another group of subjects

parallel group design

effects on the dependent variable for an experimental condition and for the controlled condition are compared within one person

cross-over design

used to test two or more hypothesis simultaneously

factorial

Factor that plays an essential role in producing an outcome

cause

Identifiable relationship between exposure and disease

association

Presence of mechanism that leads from exposure to disease

cause

Alteration in the frequency or quality of one event is followed by a change in the other

causal

Association is a result of the relationship of both factor and disease with a third variable

non-causal

it is not due to systematic error

internal validity

it is not due to random error

external validity

non-representative sample

selection bias

inaccurate information

information bias

Mixing the effect of the exposure on the disease with that of a 3rd factor

cofounding

Obtain overall estimate of the association

assessing cofounding

Bradford Hill’s criteria for Causal Inference

• A

• C

• C

• D

• E

• S

• S

• T

• T