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Ændr 2. linje i overskriften til AU Passata Light 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN AARHUS UNIVERSITY DEPARTMENT OF PUBLIC HEALTH.

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Presentation on theme: "Ændr 2. linje i overskriften til AU Passata Light 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN AARHUS UNIVERSITY DEPARTMENT OF PUBLIC HEALTH."— Presentation transcript:

1 Ændr 2. linje i overskriften til AU Passata Light 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN AARHUS UNIVERSITY DEPARTMENT OF PUBLIC HEALTH AU CAUSATION SEMINAR 20 NOVEMBER 2014 PARADOXES - SOLVED

2 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU For at få punktopstilling på teksten (flere niveauer findes), brug ‘Forøg listeniveau’ For at få venstrestillet tekst uden punktopstilling, brug ‘Formindsk listeniveau’ Ændr 2. linje i overskriften til AU Passata Light A paradox is a statement that apparently contradicts itself and yet may be true. 3 will be addressed The obesity paradox The smoking paradox Simpsons paradox PARADOXES:

3 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular  Obesity paradox – A survival advantage of being obese – in a population diagnosed with a medical condition (Epidemiology 2014; 25: )  Better survival for obese has been demonstrated for diabetes, CVD, hypertension, LC, MI, and more.

4 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular COLLIDER STRATIFICATION BIAS Obesity [Diabetes] Mortality U Obesity is a less ‘dangerous’ cause of death in patients with diabetes than other causes of diabetes. It is better to have obesity as a cause of diabetes than pancreatic cancer! if you did not have diabetes because of a causal field including obesity, you had another causal filed leading to diabetes and mortality in the group may be higher. Diseases have causes.

5 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU This paradox – and the next and many others - is the result of collider stratification bias. By conditioning on the collider you link the causes of the collider. You then compare obese with those having a different cause of diabetes like pancreatic cancer. A Berksonian bias model Dis ADis B [Hospitalization] When studying hospital patients disease A and B will be associated even if they occur independently in the population.

6 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular THE BIRTH WEIGHT PARADOX The Paradox:  Low birth weight children to smoking mothers have lower infant mortality rates than low birth weight children of non smokers (Judea Pearl, unpublished manuscript 2014 – in Lord´s Paradox Revisited.  LBW children have a MRR of 100 and smoking causes LBW.  Smoking is not beneficial but again we see collider stratification bias.

7 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Smoking LBWDeath U

8 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular In counterfactual language:  How would the mortality rate of babies of smoking mothers compare with that of non smokers had there been no pre-existing uncontrolled difference in birth weight?

9 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular SIMPSONS PARADOX more white than black hats Next day All hats fell down on the floornow more black than white hats

10 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU For at få punktopstilling på teksten (flere niveauer findes), brug ‘Forøg listeniveau’ For at få venstrestillet tekst uden punktopstilling, brug ‘Formindsk listeniveau’ Ændr 2. linje i overskriften til AU Passata Light E = treatment, R = recovery, G = gender SIMPSONS´S PARADOX Str ERecoveryN Recovery rate A % % M % % F % %

11 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU Overskrift én linje Bold eller Regular  If you think data speak for themselves, call a shrink not a statistician.  Data are passive vehicles of information that needs to be understood in the context driven by logical reasoning.  It is not surprising that we see a change in association between 2 variables when a third variable is controlled for – we see this all the time – we call this effect measure modification – and even the direction of association can change.

12 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU For at få punktopstilling på teksten (flere niveauer findes), brug ‘Forøg listeniveau’ For at få venstrestillet tekst uden punktopstilling, brug ‘Formindsk listeniveau’ Overskrift MAKS. én linje EGREGR E has a direct effect on R But the E – R association is confounded by G. G has a direct effect on R and E.

13 Ændr 2. linje i overskriften til AU Passata Light 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN AARHUS UNIVERSITY DEPARTMENT OF PUBLIC HEALTH AU ’PARADOXES’ IN ROUTINE EPIDEMIOLOGIC DECISION MAKING – WHAT SHOULD WE ADJUST FOR??

14 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU An example of analytical thinking guided by DAGs (after O. ARAH) Analyses of BW and adult BP. How to deal with current weight (CW). CW BWBP Look at BW – BP association no adjustment. If like this CW BWBP Now adjustment for CW – but cause comes before the effect.

15 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU More likely CW U BWBP Now adjustment for CW. CW U 1 U 2 BWBP No adjustments needed.

16 20 NOVEMBER 2014 CAUSATION SEMINAR. M.D., PHD JØRN OLSEN DEPARTMENT OF PUBLIC HEALTH AARHUS UNIVERSITY AU CW U 1 U 2 BW U 3 BP BW has no effect but will be associated with BP (confounder, U 3 ). CW U BWBP BW BP ass is biased – bias BW – CW – BP + BW – CW – U – BP CW U BWBP Causal ass. BW – BP + BW – CW – BP but CW – U – BP should be closed.

17 AARHUS UNIVERSITY AU


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