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Cohort studies - Coggle Diagram
Cohort studies
Measures of Outcome
Incidence rate
Time period refers to the time an individual remains free of the disease.
Expressed>no. of new cases/total person-years of observation.
No. of people who get the disease (new cases) in a specified period.
Cumulative incidence/Incidence proportion [risk]
Per 1000 people
No. of people at risk
of the disease at the
start of the period
Measures of association btwn exposure & outcome
Absolute Comparison
Measures difference=Risk differences, attributable risk
Attributable risk
Measure the difference in frequency of disease (risk) btwn the exposed and unexposed groups
indicates the risk of disease in an exposed group caused(attributed) by the exposure
Clinic relevance=measure extent of a disease caused by an exposure
Relative Comparison
Measures ratios
=
e.g Risk ratios,relative risk
Relative risk
Clinic relevance=indicates individual risk
compares the risk
among the exposed
to the risk
among the unexposed
Interpretation of Relative Risk
Exposure=Risk factor?
RR<1:Reduces risk factor>Protective=
RR=1:No
RR>1:Increases risk factor
Risk Comparison
RR=1:No Difference btwn exposed & unexposed
RR>1Risk of disease is higher in exposed than in unexposed group
RR<1:risk of disease in exposed group is lower than in unexposed
Attributable Risk interpretation
AR of 0 means no difference so no additional risk caused by that exposure
Predict burden on health services
Relative Risk interpretation
Implications: Significant=no overlapping 1 , non-significant=overlaps 1
Confidence intervals=check precision of Risk estimate