unit 10 pt 2 - Unit 10: Measures of Public H lth I Health...

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Unformatted text preview: Unit 10: Measures of Public H lth I Health Impact Absolute Measures of Comparison Dr. A. Sanchez-Anguiano Epidemiology 6000 Measures of Public Health Impac Measures of Public Health Impact z Absolute Measures of Comparison Cohort Case/Control » Attributable Risk. √ √ (difficult) » Attributable Risk % √ √ » Attributable Risk %. √ √ » Population Attributable Risk. √ √ (difficult) » Population Attributable Risk %. √ √ » Population Attributable Risk %. √ √ Risk or Rate Difference/ Attributable Risk or Rate Incidence rate difference Cumulative incidence difference/Risk Difference Prevalence difference Note: Some authors consider the name Attributable risk or rate inappropriate because it may imply a definite causa rate inappropriate because it may imply a definite causal relationship. Risk Difference/Attributable Risk Risk Difference/Attributable Risk z Can be calculated either for exposed group or tota z Can be calculated either for exposed group or total population z Can be based on incidence or prevalence - incidence most common and used in lecture examples z The excess risk in those exposed compared to those unexposed z Can calculate for cohort studies-more complex for case control studies as no incidence/prevalence data is available Risk Difference/Attributable Risk Risk Difference/Attributable Risk Difference between the cumulative incidence in the exposed Difference between the cumulative incidence in the exposed and in unexposed groups z RD = R E – R u or AR=I e- I u z RD R E R u or AR I e I u z You have the risk in the exposed group due to exposure X, and the risk in unexposed to X z subtracting the risk in unexposed to X, removes other causes or z R E – R u represents the increase in risk that is due or attributable to the exposure attributable to the exposure. Risk Difference/Attributable Risk Risk Difference/Attributable Risk z A measure of public health impact of an exposure If no association between exposure and disease z If no association between exposure and disease incidence in exposed and unexposed should be the same and RD = same and RD = 0 If there is association RD is >0 z If there is association RD is >0 Cohort Study of OC Use & Bacteriuria Bacteriuria OC use: Urinary infection: Yes No Total Yes 27 455 482 No 77 1831 1908 Total 104 2286 2390 Risk Difference/Attributable Risk Risk Difference/Attributable Risk z Cumulative Incidence in Exposed R E ( or I e ) = ? z Cumulative Incidence z Cumulative Incidence in Unexposed R u ( or I u ) =? Risk Difference Calculation Risk Difference Calculation z R E ( or I e ) = 27/482 = 0.05602 z R u ( or I u ) = 77/1908 = 0.040356 z RD/AR = R E- R u or I E- I u = 0.05602 - 0.040356 = 0.01566 z RD/AR = 1566/100,000 or 1.56 per 100 Interpretation of Risk Difference Difference The excess occurrence of infection among OC users z The excess occurrence of infection among OC users (attributable to their OC use) is 1566 per 100,000 or 1 56 cases of each 100 infections can be attributed to...
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unit 10 pt 2 - Unit 10: Measures of Public H lth I Health...

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