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Introduction to Case-crossover
design
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 2: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/2.jpg)
Brief introduction to case-crossover design
unusual just before
The simple part of the questionThe challenging part
We need controls to determine what unusual meant. However, using different individuals for comparison is not rationale since everyone is different and has different response to the same exposure.
Brief introduction to case-crossover design
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 3: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/3.jpg)
Feel the design…
Feel the design…
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Time is passing
I am so sick…Why??
Did I do something unusual right before
the illness?????
In comparison to my usual???
Have you experienced?Of course you have.
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 4: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/4.jpg)
Why call it Case-Crossover?
each case is its own controlviewed retrospectively
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 5: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/5.jpg)
Starting example
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 6: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/6.jpg)
Starting example
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Exposure to a hazard
Higher or lower hazard exposures triggers the event? Depends on the relationship.
Case-control design needs different control in the same time
Case crossover needs the same control at different time
Car with accident
Car without accident
Time
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 7: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/7.jpg)
the control is the same person at a different time rather than a different person at the same time.
Starting example
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 8: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/8.jpg)
Matched pair case-control 2*2:
Q: are exposures are differentin cases and controls?
Case-crossover 2*2:
Q: are exposures are differentin hazard and control periods?
Starting example
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Control period
Expo Unexpo
Hazard period
Exposed a b
Unexpo c d
Controls
Expo Unexpo
CasesExposed a b
Unexpo c d
All subjects are cases.
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 9: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/9.jpg)
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Despite being similar, previous experience in conducting case-control studies
does not fully prepare you for doing case-crossover study.
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 10: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/10.jpg)
Terminology used in case-crossover
design
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 11: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/11.jpg)
- Case window, or current period, or effect period:
Example
Terminology
✍Exposure A
Effect period
Exposure B Effect period
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 12: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/12.jpg)
-Hazard period:
Usually the length of hazard period is the same as the length of effect period.
Terminology
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Event onset
Hazard period
Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 13: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/13.jpg)
The length of this period is very important
Terminology
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 14: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/14.jpg)
- Control window, or reference period, or control period:
There are 2 types of control data or information:Exposure information from comparable time period
Exposure information according to individual usual exposure frequency
Terminology
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 15: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/15.jpg)
Suitable study cases
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 16: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/16.jpg)
Study subjects suitable for case-crossover?1- Acute cases2- Crossing over3- Transience of the effect
Study subjects suitable for case crossover?
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 17: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/17.jpg)
Pros and Cons
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 18: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/18.jpg)
Pros:
Pros and cons
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 19: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/19.jpg)
Cons:- Not suitable for chronic diseases:
- Not able to assess long term effects:
- Recall bias:
- Requires careful selection of the length and timing of the windows
Pros and cons
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 20: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/20.jpg)
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 21: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/21.jpg)
A case-crossover study of alcohol consumption, meals and the risk of road traffic crashes
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 22: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/22.jpg)
The role of alcohol and drugs in triggering criminal violence: a case-crossover study
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 23: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/23.jpg)
Risk of new acute myocardial infarction hospitalization associated with use of oral andparenteral non-steroidal anti-inflammation drugs
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 24: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/24.jpg)
Alcohol and risk of admission to hospital for unintentional cutting or piercing injuries at home: a population-based case-crossover study
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari
![Page 25: Introduction to Case-crossover design · Expo Unexpo Hazard period Exposed a b Unexpo c d Controls Expo Unexpo Cases Exposed a b Unexpo c d All subjects are cases. Isfahan- CSC: Clinical](https://reader030.vdocuments.net/reader030/viewer/2022040600/5e88e0153ea1c514e609bdbb/html5/thumbnails/25.jpg)
Clinical features and risk factors for upper gastrointestinal bleeding in children: a case-crossover study
Applications in articles
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Isfahan- CSC: Clinical Studies CenterBy: Tohid Jafari