relative risk estimation with examples and their interpretation
TRANSCRIPT
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
1/15
Roll no. 73, 74, 79, 80.
RELATIVERISK
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
2/15
Cohort Study
Cohort Study or Panel Study is a type ofanalytical (observational) study usually
undertaken to obtain additional evidenceto prove or disprove the existence of anassociation between suspected cause and
disease.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
3/15
Elements of a Cohort Study
1. Selection of study subjects.
2. Obtaining data on exposure.
3. Selection of comparisongroups.
4. Follow-up.5. Analysis.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
4/15
Analysis
Data analyzed in terms of:
Incidence Rates.
Estimation of risk.
Relative Risk
Attributable Risk.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
5/15
2 X 2 Table
DISEASERISKFACTOR
PRESENT ABSENT
PRESENT a b
ABSENT c d
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
6/15
Relative Risk (RR)
Relative Risk is the ratio of theincidence of the disease among exposed
and the incidence among the non-exposed.
Aka riskratio.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
7/15
=
Note:
Numerator is not a part of the Denominator.
= +
=
+
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
8/15
Interpretation
In a simple comparison between anexperimental group and a control group:
A relative risk of 1 means there is no
difference in risk between the two groups.RR of < 1 means the event is less likely tooccur in the experimental group than in thecontrol group.
RR of > 1 means the event is more likely tooccur in the experimental group than in thecontrol group.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
9/15
Examples
And their Interpretations
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
10/15
Cigarette Smoking and Lung Cancer
DEVELOPEDLUNG
CANCERSMOKER
YES NO
YES 70 6930
NO 3 2997
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
11/15
RR Estimation and Interpretation
Lung cancer incidence among smokers =70
70+6930=
70
7000= 10 per 1000
Lung cancer incidence among non-smokers=
3
3+2997=
3
3000= 1 per 1000
RR =
= 10
Smokers are 10 times at greater risk ofdeveloping lung cancer than non-smokers.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
12/15
Radiation Exposure and Cancer
CANCER
RADIATIONYES NO
YES 30 20
NO 10 90
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
13/15
RR Estimation and Interpretation
Cancer incidence among those exposed to radiation =
30
30+20=
30
50= 60 per 100
Cancer incidence among those not exposed to radiation =
10
10+90=
10
100= 10 per 100
RR =
= 6
Those exposed to radiation are 6 times at greaterrisk of developing cancer than those not exposed.
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
14/15
Conclusion
Thus, Relative Risk (RR) is a good measure todetermine if a factor leads to an increase, decrease orno effect on the development of some diseasesymptom.
RR=1No effect
RR1Leads to development of the disease
-
8/11/2019 Relative Risk Estimation With Examples and Their Interpretation
15/15