Epidemiology: 8) Cohort Analysis - Measures Of Effect

Front 1

Number needed to treet

Back 1

1/(Po-P1) = -1/RD

Front 2

Utility of Risk Risk Difference

Back 2

RD can have more clinical/public health meaning since is characterizes absolute risk

Front 3

RR vs. RD

Back 3

-RR is less dependent upon the underlying population.
-RD provides incidence information.
-No methods to do multivariate RD.

Front 4

2 reasons to use OR

Back 4

1) Logistic regression for fixed (defined) cohort studies.
2) Case-control estimates

Front 5

OR can estimate RR if

Back 5

D is infrequent in both E+ and E-
min(Po,P1)<0.1 (10%)

Front 6

Major problems with risk, incidence, and odds information

Back 6

They do not measure the health "impact" of a particular exposure.

Front 7

Attributal fraction

Back 7

Proportion of the disease occurence that would be eliminated if exposure to the risk factor were prevented

Front 8

Attributable fraction: Synonyms

Back 8

-Etiologic fraction
-attributable proportion
-attributable risk
-population attributable risk (percent)

Front 9

Who is the Attrubutable fraction calculated for?

Back 9

1) E+ group
2) Entire population

Front 10

Attributable fraction for the exposed (discription)

Back 10

Proportion of cases in the E+ group attributable to E.
Eg. Among NSAID users, what proportion of peptic ulcers are caused by NSAIDS?

Front 11

Attributable fraction for the exposed (Eqn)

Back 11

(P1-Po)/P1 (risk data)
(I1-Io)/I1 (rate data)
(RR-1)/RR (risk data)
(IRR-1)/IRR (rate data)
(OR-1)/OR (rare disease assumption)

Front 12

Attributable fraction for Population (disc)

Back 12

Proportion of cases in the population attributable to E.
Eg. For a given patient population, what proportion of peptic ulcers are caused by NSAIDS? (need strength of the association between E and D and prevalence of E+)

Front 13

Attributable fraction for Population (eqns)

Back 13

(P-Po)/P (risk)
(I-Io)/I (rate)
¶(RR-1)/[1+¶(RR-1)] (risk)
¶(IRR-1)/[1+¶(IRR-1)] (rate)
¶c(OR-1)/OR (Odds)

Front 14

Attributable Fraction for population (¶ and ¶c)

Back 14

¶ = N1/N (proportion exposed in cohort for risk data)
¶ = T1/T (Proportion exposed for person-time for rates)
¶c = a/(a+b) (exposure prevalence in D+ for rare D)

Front 15

Attributable fraction for exposed (protective exposures) (disc)

Back 15

Also called prevented fraction or effictiveness.
Often used in vaccine studies

Front 16

Attributable fraction for exposed (protective exposures)(eqn)

Back 16

1)(Po-P1)/P1
1)1-RR

Front 17

Marginal cost-effecitiveness

Back 17

(Difference in cost)/(Events prevented)
See 8-12