Submit Search
Upload
EPI546_Lecture_8.ppt
ā¢
Download as PPT, PDF
ā¢
0 likes
ā¢
3 views
L
LawalBelloDanchadi
Follow
Cohort study design
Read less
Read more
Data & Analytics
Report
Share
Report
Share
1 of 44
Download now
Recommended
Screening_Dwloaded.ppt
Screening_Dwloaded.ppt
Yogi157241
Ā
2010-Epidemiology (Dr. Sameem) basics and priciples.ppt
2010-Epidemiology (Dr. Sameem) basics and priciples.ppt
AmirRaziq1
Ā
Types of clinical studies
Types of clinical studies
Samir Haffar
Ā
STUDY DESIGN.pptx
STUDY DESIGN.pptx
GauravPurohit56
Ā
General epidemiology
General epidemiology
Dr.Shahzad A. Daula
Ā
Quantitative Methods.pptx
Quantitative Methods.pptx
Khem21
Ā
Cross sectional studies
Cross sectional studies
soudfaiza
Ā
Epidemiology an introduction
Epidemiology an introduction
Bhoj Raj Singh
Ā
Recommended
Screening_Dwloaded.ppt
Screening_Dwloaded.ppt
Yogi157241
Ā
2010-Epidemiology (Dr. Sameem) basics and priciples.ppt
2010-Epidemiology (Dr. Sameem) basics and priciples.ppt
AmirRaziq1
Ā
Types of clinical studies
Types of clinical studies
Samir Haffar
Ā
STUDY DESIGN.pptx
STUDY DESIGN.pptx
GauravPurohit56
Ā
General epidemiology
General epidemiology
Dr.Shahzad A. Daula
Ā
Quantitative Methods.pptx
Quantitative Methods.pptx
Khem21
Ā
Cross sectional studies
Cross sectional studies
soudfaiza
Ā
Epidemiology an introduction
Epidemiology an introduction
Bhoj Raj Singh
Ā
Epidemiology methods, approaches and tools of measurement
Epidemiology methods, approaches and tools of measurement
Swapnilsalve1998
Ā
Types of studies 2016
Types of studies 2016
Ahmed Elfaitury
Ā
COHORT STUDIES.pptx
COHORT STUDIES.pptx
reshmasu
Ā
ANALYTICAL STUDIES.pptx
ANALYTICAL STUDIES.pptx
payalrathod14
Ā
Epidemiological Studies
Epidemiological Studies
INAAMUL HAQ
Ā
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Graham Colditz
Ā
Amia tb-review-15
Amia tb-review-15
Russ Altman
Ā
STUDY DESIGN in health and medical research .pptx
STUDY DESIGN in health and medical research .pptx
Abubakar Hammadama
Ā
3. epidem research designs
3. epidem research designs
Chanda Jabeen
Ā
Cohort studies..NIKHNA JAYAN
Cohort studies..NIKHNA JAYAN
Nikhna jayan
Ā
Lecture 1
Lecture 1
Nouf AlKusayer
Ā
Biostatistics general introduction central tendency
Biostatistics general introduction central tendency
Mohmmad Amil Rahman
Ā
Lemeshow samplesize
Lemeshow samplesize
1joanenab
Ā
Crossectional studies 2
Crossectional studies 2
Bruno Mmassy
Ā
Epidemiological study designs
Epidemiological study designs
jarati
Ā
Research Designs
Research Designs
Aravind L R
Ā
chapter2-191105204556.pdf
chapter2-191105204556.pdf
Soujannya Kundu Chowdhury
Ā
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Cecile Janssens
Ā
Case control study
Case control study
Saleh Alhashim
Ā
Cohort Study.pptx
Cohort Study.pptx
Mostaque Ahmed
Ā
Genetic Counseling in the field of medicine.pptx
Genetic Counseling in the field of medicine.pptx
LawalBelloDanchadi
Ā
Disinfection_and_sterilisation of laboratory materials.ppt
Disinfection_and_sterilisation of laboratory materials.ppt
LawalBelloDanchadi
Ā
More Related Content
Similar to EPI546_Lecture_8.ppt
Epidemiology methods, approaches and tools of measurement
Epidemiology methods, approaches and tools of measurement
Swapnilsalve1998
Ā
Types of studies 2016
Types of studies 2016
Ahmed Elfaitury
Ā
COHORT STUDIES.pptx
COHORT STUDIES.pptx
reshmasu
Ā
ANALYTICAL STUDIES.pptx
ANALYTICAL STUDIES.pptx
payalrathod14
Ā
Epidemiological Studies
Epidemiological Studies
INAAMUL HAQ
Ā
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Graham Colditz
Ā
Amia tb-review-15
Amia tb-review-15
Russ Altman
Ā
STUDY DESIGN in health and medical research .pptx
STUDY DESIGN in health and medical research .pptx
Abubakar Hammadama
Ā
3. epidem research designs
3. epidem research designs
Chanda Jabeen
Ā
Cohort studies..NIKHNA JAYAN
Cohort studies..NIKHNA JAYAN
Nikhna jayan
Ā
Lecture 1
Lecture 1
Nouf AlKusayer
Ā
Biostatistics general introduction central tendency
Biostatistics general introduction central tendency
Mohmmad Amil Rahman
Ā
Lemeshow samplesize
Lemeshow samplesize
1joanenab
Ā
Crossectional studies 2
Crossectional studies 2
Bruno Mmassy
Ā
Epidemiological study designs
Epidemiological study designs
jarati
Ā
Research Designs
Research Designs
Aravind L R
Ā
chapter2-191105204556.pdf
chapter2-191105204556.pdf
Soujannya Kundu Chowdhury
Ā
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Cecile Janssens
Ā
Case control study
Case control study
Saleh Alhashim
Ā
Cohort Study.pptx
Cohort Study.pptx
Mostaque Ahmed
Ā
Similar to EPI546_Lecture_8.ppt
(20)
Epidemiology methods, approaches and tools of measurement
Epidemiology methods, approaches and tools of measurement
Ā
Types of studies 2016
Types of studies 2016
Ā
COHORT STUDIES.pptx
COHORT STUDIES.pptx
Ā
ANALYTICAL STUDIES.pptx
ANALYTICAL STUDIES.pptx
Ā
Epidemiological Studies
Epidemiological Studies
Ā
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Precision Prevention: Let's Avoid Exacerbating Cancer Disparities
Ā
Amia tb-review-15
Amia tb-review-15
Ā
STUDY DESIGN in health and medical research .pptx
STUDY DESIGN in health and medical research .pptx
Ā
3. epidem research designs
3. epidem research designs
Ā
Cohort studies..NIKHNA JAYAN
Cohort studies..NIKHNA JAYAN
Ā
Lecture 1
Lecture 1
Ā
Biostatistics general introduction central tendency
Biostatistics general introduction central tendency
Ā
Lemeshow samplesize
Lemeshow samplesize
Ā
Crossectional studies 2
Crossectional studies 2
Ā
Epidemiological study designs
Epidemiological study designs
Ā
Research Designs
Research Designs
Ā
chapter2-191105204556.pdf
chapter2-191105204556.pdf
Ā
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Lessons learned in polygenic risk research | Grand Rapids, MI 2019
Ā
Case control study
Case control study
Ā
Cohort Study.pptx
Cohort Study.pptx
Ā
More from LawalBelloDanchadi
Genetic Counseling in the field of medicine.pptx
Genetic Counseling in the field of medicine.pptx
LawalBelloDanchadi
Ā
Disinfection_and_sterilisation of laboratory materials.ppt
Disinfection_and_sterilisation of laboratory materials.ppt
LawalBelloDanchadi
Ā
14 Disorders_of_endocrine_system and possible causes.ppt
14 Disorders_of_endocrine_system and possible causes.ppt
LawalBelloDanchadi
Ā
Laboratory Techniques in immunology practice.
Laboratory Techniques in immunology practice.
LawalBelloDanchadi
Ā
Introduction to karyotyping examination.
Introduction to karyotyping examination.
LawalBelloDanchadi
Ā
Stages Involved in Research Project.pptx
Stages Involved in Research Project.pptx
LawalBelloDanchadi
Ā
bitai.pdf
bitai.pdf
LawalBelloDanchadi
Ā
publication_11_17171_1196.pdf
publication_11_17171_1196.pdf
LawalBelloDanchadi
Ā
9392189.ppt
9392189.ppt
LawalBelloDanchadi
Ā
TUMOR_MARKERS-naglaa.ppt
TUMOR_MARKERS-naglaa.ppt
LawalBelloDanchadi
Ā
5784787.ppt
5784787.ppt
LawalBelloDanchadi
Ā
simmyaas-121115000851-phpapp02.pdf
simmyaas-121115000851-phpapp02.pdf
LawalBelloDanchadi
Ā
LinkedIn-Marketing-.pptx.pdf
LinkedIn-Marketing-.pptx.pdf
LawalBelloDanchadi
Ā
Management & Entrepreneurship.ppt
Management & Entrepreneurship.ppt
LawalBelloDanchadi
Ā
AAS.ppt
AAS.ppt
LawalBelloDanchadi
Ā
SAMPLING TECHNIQUES.pptx
SAMPLING TECHNIQUES.pptx
LawalBelloDanchadi
Ā
unit-i-entrepreneurshipdevelopmentbbasemiv-230315145423-fe50b247.pdf
unit-i-entrepreneurshipdevelopmentbbasemiv-230315145423-fe50b247.pdf
LawalBelloDanchadi
Ā
2-4StudyDesign_slides.ppt
2-4StudyDesign_slides.ppt
LawalBelloDanchadi
Ā
entrepreneurshipandinnovation-091206034558-phpapp02.pdf
entrepreneurshipandinnovation-091206034558-phpapp02.pdf
LawalBelloDanchadi
Ā
4253047.ppt
4253047.ppt
LawalBelloDanchadi
Ā
More from LawalBelloDanchadi
(20)
Genetic Counseling in the field of medicine.pptx
Genetic Counseling in the field of medicine.pptx
Ā
Disinfection_and_sterilisation of laboratory materials.ppt
Disinfection_and_sterilisation of laboratory materials.ppt
Ā
14 Disorders_of_endocrine_system and possible causes.ppt
14 Disorders_of_endocrine_system and possible causes.ppt
Ā
Laboratory Techniques in immunology practice.
Laboratory Techniques in immunology practice.
Ā
Introduction to karyotyping examination.
Introduction to karyotyping examination.
Ā
Stages Involved in Research Project.pptx
Stages Involved in Research Project.pptx
Ā
bitai.pdf
bitai.pdf
Ā
publication_11_17171_1196.pdf
publication_11_17171_1196.pdf
Ā
9392189.ppt
9392189.ppt
Ā
TUMOR_MARKERS-naglaa.ppt
TUMOR_MARKERS-naglaa.ppt
Ā
5784787.ppt
5784787.ppt
Ā
simmyaas-121115000851-phpapp02.pdf
simmyaas-121115000851-phpapp02.pdf
Ā
LinkedIn-Marketing-.pptx.pdf
LinkedIn-Marketing-.pptx.pdf
Ā
Management & Entrepreneurship.ppt
Management & Entrepreneurship.ppt
Ā
AAS.ppt
AAS.ppt
Ā
SAMPLING TECHNIQUES.pptx
SAMPLING TECHNIQUES.pptx
Ā
unit-i-entrepreneurshipdevelopmentbbasemiv-230315145423-fe50b247.pdf
unit-i-entrepreneurshipdevelopmentbbasemiv-230315145423-fe50b247.pdf
Ā
2-4StudyDesign_slides.ppt
2-4StudyDesign_slides.ppt
Ā
entrepreneurshipandinnovation-091206034558-phpapp02.pdf
entrepreneurshipandinnovation-091206034558-phpapp02.pdf
Ā
4253047.ppt
4253047.ppt
Ā
Recently uploaded
(PARI) Call Girls Wanowrie ( 7001035870 ) HI-Fi Pune Escorts Service
(PARI) Call Girls Wanowrie ( 7001035870 ) HI-Fi Pune Escorts Service
ranjana rawat
Ā
BigBuy dropshipping via API with DroFx.pptx
BigBuy dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
Carero dropshipping via API with DroFx.pptx
Carero dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
Call Girls š«¤ Dwarka ā”ļø 9711199171 ā”ļø Delhi š«¦ Two shot with one girl
Call Girls š«¤ Dwarka ā”ļø 9711199171 ā”ļø Delhi š«¦ Two shot with one girl
kumarajju5765
Ā
Week-01-2.ppt BBB human Computer interaction
Week-01-2.ppt BBB human Computer interaction
fulawalesam
Ā
100-Concepts-of-AI by Anupama Kate .pptx
100-Concepts-of-AI by Anupama Kate .pptx
Anupama Kate
Ā
ź§ā¤ Greater Noida Call Girls Delhi ā¤ź§ 9711199171 āļø Hard And Sexy Vip Call
ź§ā¤ Greater Noida Call Girls Delhi ā¤ź§ 9711199171 āļø Hard And Sexy Vip Call
shivangimorya083
Ā
Call Girls in Sarai Kale Khan Delhi šÆ Call Us š9205541914 š( Delhi) Escorts S...
Call Girls in Sarai Kale Khan Delhi šÆ Call Us š9205541914 š( Delhi) Escorts S...
Delhi Call girls
Ā
Ravak dropshipping via API with DroFx.pptx
Ravak dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
FESE Capital Markets Fact Sheet 2024 Q1.pdf
FESE Capital Markets Fact Sheet 2024 Q1.pdf
MarinCaroMartnezBerg
Ā
Vip Model Call Girls (Delhi) Karol Bagh 9711199171āļøBody to body massage wit...
Vip Model Call Girls (Delhi) Karol Bagh 9711199171āļøBody to body massage wit...
shivangimorya083
Ā
Sampling (random) method and Non random.ppt
Sampling (random) method and Non random.ppt
Dr. Soumendra Kumar Patra
Ā
Generative AI on Enterprise Cloud with NiFi and Milvus
Generative AI on Enterprise Cloud with NiFi and Milvus
Timothy Spann
Ā
CebaBaby dropshipping via API with DroFX.pptx
CebaBaby dropshipping via API with DroFX.pptx
olyaivanovalion
Ā
Mature dropshipping via API with DroFx.pptx
Mature dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
Smarteg dropshipping via API with DroFx.pptx
Smarteg dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
VidaXL dropshipping via API with DroFx.pptx
VidaXL dropshipping via API with DroFx.pptx
olyaivanovalion
Ā
Delhi Call Girls CP 9711199171 āāšā Whatsapp Hard And Sexy Vip Call
Delhi Call Girls CP 9711199171 āāšā Whatsapp Hard And Sexy Vip Call
shivangimorya083
Ā
Al Barsha Escorts $#$ O565212860 $#$ Escort Service In Al Barsha
Al Barsha Escorts $#$ O565212860 $#$ Escort Service In Al Barsha
AroojKhan71
Ā
Chintamani Call Girls: š 7737669865 š High Profile Model Escorts | Bangalore ...
Chintamani Call Girls: š 7737669865 š High Profile Model Escorts | Bangalore ...
amitlee9823
Ā
Recently uploaded
(20)
(PARI) Call Girls Wanowrie ( 7001035870 ) HI-Fi Pune Escorts Service
(PARI) Call Girls Wanowrie ( 7001035870 ) HI-Fi Pune Escorts Service
Ā
BigBuy dropshipping via API with DroFx.pptx
BigBuy dropshipping via API with DroFx.pptx
Ā
Carero dropshipping via API with DroFx.pptx
Carero dropshipping via API with DroFx.pptx
Ā
Call Girls š«¤ Dwarka ā”ļø 9711199171 ā”ļø Delhi š«¦ Two shot with one girl
Call Girls š«¤ Dwarka ā”ļø 9711199171 ā”ļø Delhi š«¦ Two shot with one girl
Ā
Week-01-2.ppt BBB human Computer interaction
Week-01-2.ppt BBB human Computer interaction
Ā
100-Concepts-of-AI by Anupama Kate .pptx
100-Concepts-of-AI by Anupama Kate .pptx
Ā
ź§ā¤ Greater Noida Call Girls Delhi ā¤ź§ 9711199171 āļø Hard And Sexy Vip Call
ź§ā¤ Greater Noida Call Girls Delhi ā¤ź§ 9711199171 āļø Hard And Sexy Vip Call
Ā
Call Girls in Sarai Kale Khan Delhi šÆ Call Us š9205541914 š( Delhi) Escorts S...
Call Girls in Sarai Kale Khan Delhi šÆ Call Us š9205541914 š( Delhi) Escorts S...
Ā
Ravak dropshipping via API with DroFx.pptx
Ravak dropshipping via API with DroFx.pptx
Ā
FESE Capital Markets Fact Sheet 2024 Q1.pdf
FESE Capital Markets Fact Sheet 2024 Q1.pdf
Ā
Vip Model Call Girls (Delhi) Karol Bagh 9711199171āļøBody to body massage wit...
Vip Model Call Girls (Delhi) Karol Bagh 9711199171āļøBody to body massage wit...
Ā
Sampling (random) method and Non random.ppt
Sampling (random) method and Non random.ppt
Ā
Generative AI on Enterprise Cloud with NiFi and Milvus
Generative AI on Enterprise Cloud with NiFi and Milvus
Ā
CebaBaby dropshipping via API with DroFX.pptx
CebaBaby dropshipping via API with DroFX.pptx
Ā
Mature dropshipping via API with DroFx.pptx
Mature dropshipping via API with DroFx.pptx
Ā
Smarteg dropshipping via API with DroFx.pptx
Smarteg dropshipping via API with DroFx.pptx
Ā
VidaXL dropshipping via API with DroFx.pptx
VidaXL dropshipping via API with DroFx.pptx
Ā
Delhi Call Girls CP 9711199171 āāšā Whatsapp Hard And Sexy Vip Call
Delhi Call Girls CP 9711199171 āāšā Whatsapp Hard And Sexy Vip Call
Ā
Al Barsha Escorts $#$ O565212860 $#$ Escort Service In Al Barsha
Al Barsha Escorts $#$ O565212860 $#$ Escort Service In Al Barsha
Ā
Chintamani Call Girls: š 7737669865 š High Profile Model Escorts | Bangalore ...
Chintamani Call Girls: š 7737669865 š High Profile Model Escorts | Bangalore ...
Ā
EPI546_Lecture_8.ppt
1.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 1 Lecture 8 ā Study Design I XS and Cohort Studies Mathew J. Reeves BVSc, PhD Associate Professor, Epidemiology EPI-546 Block I
2.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 2 Objectives - Concepts ā¢ Uses of risk factor information ā¢ Association vs. causation ā¢ Architecture of study designs (Grimes I) ā¢ Cross sectional (XS) studies ā¢ Cohort studies (Grimes II) ā¢ Measures of association ā RR, PAR, PARF ā¢ Selection and confounding bias ā¢ Advantages and disadvantages of cohort studies
3.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 3 Objectives - Skills ā¢ Recognize different study designs ā¢ Define a cohort study ā¢ Explain the organization of a cohort study ā¢ Distinguish prospective from retrospective ā¢ Define, calculate, interpret RR, PAR and PARF ā¢ Understand and detect selection and confounding bias
4.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 4 āRisk Factorā ā heard almost daily Cholesterol and heart disease HPV infection and cervical CA Cell phones and brain cancer TV watching and childhood obesity However, āassociation does not mean causationā!
5.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 5 Why care about risk factors? Fletcher lists the ways risk factors can be used: ā¢ Identifying individuals/groups āat-riskā ā¢ But ability to predict future disease in individual patients is very limited even for well established risk factors ā¢ e.g., cholesterol and CHD ā¢ Causation (causative agent vs. marker) ā¢ Establish pretest probability (Bayesā theorem) ā¢ Risk stratification to identify target population ā¢ Example: Age > 40 for mammography screening ā¢ Prevention ā¢ Remove causative agent & prevent disease
6.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 6 Predicting disease in individual patients Fig. Percentage distribution of serum cholesterol levels (mg/dl) in men aged 50-62 who did or did not subsequently develop coronary heart disease (Framingham Study)
7.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 7 Causation vs. Association ā¢ An association between a risk factor and disease can be due to: ā¢ the risk factor being a cause of the disease (= a causative agent) OR ā¢ the risk factor is NOT a cause but is merely associated with the disease (= a marker) ā¢ Must guard against thinking that A causes B when really B causes A (reverse causation). ā¢ e.g. sedentariness and obesity.
8.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 8 A B A B A B C A B
9.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 9 Prevention ā¢ Removing a true cause ā ā disease incidence. ā¢ Decrease aspirin use ā ā Reyeās Syndrome ā¢ Discourage prone position āBack to Sleepā ā ā SIDS
10.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 10 Back-To-Sleep Campaign Began in 1992
11.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 11 Architecture of study designs ā¢ Experimental vs. observational ā¢ Experimental studies ā¢ Randomization? ā RCT vs. quasi-randomized or natural experiments ā¢ Observational studies ā¢ Analytical vs. descriptive ā¢ Analytical ā XS, Cohort, CCS ā¢ Descriptive ā Case report, case series
12.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 12 Grimes DA and Schulz KF 2002. An overview of clinical research. Lancet 359:57-61.
13.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 13 Grimes DA and Schulz KF 2002. An overview of clinical research. Lancet 359:57-61.
14.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 14 Cross-sectional studies ā¢ Also called a prevalence study ā¢ Prevalence measured by conducting a survey of the population of interest e.g., ā¢ Interview of clinic patients ā¢ Random-digit-dialing telephone survey ā¢ Mainstay of descriptive epidemiology ā¢ patterns of occurrence by time, place and person ā¢ estimate disease frequency (prevalence) and time trends ā¢ Useful for: ā¢ program planning ā¢ resource allocation ā¢ generate hypotheses
15.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 15 Cross-sectional Studies ā¢ Select sample of individual subjects and report disease prevalence (%) ā¢ Can also simultaneously classify subjects according to exposure and disease status to draw inferences ā¢ Describe association between exposure and disease prevalence using the Odds Ratio (OR)
16.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 16 Cross-sectional Studies ā¢ Examples: ā¢ Prevalence of Asthma in School-aged Children in Michigan ā¢ Trends and changing epidemiology of hepatitis in Italy ā¢ Characteristics of teenage smokers in Michigan ā¢ Prevalence of stroke in Olmstead County, MN
17.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 17 Concept of the Prevalence āPoolā New cases Death Recovery
18.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 18 Cross-sectional Studies ā¢ Advantages: ā¢ quick, inexpensive, useful ā¢ Disadvantages: ā¢ uncertain temporal relationships ā¢ survivor effect ā¢ low prevalence due to ā rare disease ā short duration
19.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 19 Cohort Studies ā¢ A cohort is a group with something in common e.g., an exposure ā¢ Start with disease-free āat-riskā population ā¢ i.e., susceptible to the disease of interest ā¢ Determine eligibility and exposure status ā¢ Follow-up and count incident events ā¢ a.k.a prospective, follow-up, incidence or longitudinal ā¢ Similar in many ways to the RCT except that exposures are chosen by ānatureā rather than by randomization
20.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 20 Types of Cohort Studies ā¢ Population-based (one-sample) ā¢ select entire popl (N) or known fraction of popl (n) ā¢ p (Exposed) in population can be determined ā¢ Multi-sample ā¢ select subgroups with known exposures ā e.g., smokers and non-smokers ā e.g., coal miners and uranium miners ā¢ p (Exposed) in population cannot be determined
21.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 21 Disease + - Exp + a b n 1 Exp - c d n 0 N Prospective Cohort Study ā Population- based Design (select entire pop)
22.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 22 Disease + - Exp + a b n 1 Exp - c d n 0 Prospective Cohort Study ā Multi-sample Design (select specific exposure groups) Rate= c/ n 0 Rate= a/ n 1
23.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 23 Exposed Eligible subjects Unexposed Disease Disease No disease No disease FUTURE NOW
24.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 24 Relative Risk ā Cohort Study ā¢ RR = Incidence rate in exposed Incidence rate in non-exposed ā¢ The RR is the standard measure of association for cohort studies ā¢ RR describes magnitude and direction of the association ā¢ Incidence can be measured as the IDR or CIR ā¢ RR = a / ni or a / (a + b) c / no c / (c + d)
25.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 25 Example - Smoking and Myocardial Infarction (MI) MI + - Smk + 30 970 Rate = 30 / 1000 Smk - 10 990 Rate = 10 / 1000 RR= 3 Study: Desert island, pop= 2,000 people, smoking prevalence= 50% Population-based cohort study. Followed for one year. What is the risk of MI among smokers compared to non-smokers?
26.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 26 RR - Interpretation ā¢ RR = 1.0 ā¢ indicates the rate (risk) of disease among exposed and non- exposed (= referent category) are identical (= null value) ā¢ RR = 2.0 ā¢ rate (risk) is twice as high in exposed versus non-exposed ā¢ RR = 0.5 ā¢ rate (risk) in exposed is half that in non-exposed
27.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 27 RR - Interpretation ā¢ RR = > 5.0 or < 0.2 ā¢ BIG ā¢ RR = 2.0 ā 5.0 or 0.5 ā 0.2 ā¢ MODERATE ā¢ RR = <2.0 or >0.5 ā¢ SMALL
28.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 28 Sources of Cohorts ā¢ Geographically defined groups: ā¢ Framingham, MA (sampled 6,500 of 28,000, 30-50 yrs of age) ā¢ Tecumseh, MI (8,641 persons, 88% of population) ā¢ Special resource groups ā¢ Medical plans e.g., Kaiser Permanente ā¢ Medical professionals e.g., ā¢ Physicians Health Study, Nurses Health Study ā¢ Veterans ā¢ College graduates e.g., Harvard Alumni
29.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 29 Sources of Cohorts ā¢ Special exposure groups ā¢ Occupational exposures ā e.g., pb workers, U miners ā If everyone exposed then need an external cohort non-exposed cohort for comparison purposes ā e.g., compare pb workers to car assembly workers ā¢ Specific risk factor groups ā e.g., smokers, IV drug users, HIV+
30.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 30 Cohort Design Options ā¢ variation in timing of E and D measurement Design Past Prospective Retrospective Historical/pros. E D E E D D E Present Future
31.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 31 Disease + - Exp + a b n 1 Exp - c d n 0 Retrospective Cohort Study ā Design Go back and determine exposure status based on historical information and then classify subjects according to their current disease status Rate= c/ n 0 Rate= a/ n 1
32.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 32 Exposed Eligible subjects Unexposed Disease Disease No disease No disease NOW PAST RECORDS
33.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 33 Examples retrospective cohort ā¢ Aware of cases of fibromyalgia in women in a large HMO. Go back and determine who had silicone breast implants (past exposure). Compare incidence of disease in exposed and non-exposed. ā¢ Framingham study: use frozen blood bank to determine baseline level of hs-CRP and then measure incidence of CHD by risk groups (quartile)
34.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 34 PAR and PARF ā¢ Important question for public health ā¢ How much can we lower disease incidence if we intervene to remove this risk factor? ā¢ Want to know how much disease an exposure causes in a population. ā¢ PAR and PARF assume that the risk factor in question is causal ā¢ See Lecture 3 course notes
35.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 35 Venous thromboemolic disease (VTE) and oral contraceptives (OC) in woman of reproductive age ā¢ Incidence of VTE: ā¢ OC users: 16 per 10,000 person-years ā¢ non-OC users: 4 per 10,000 person-years ā¢ Total population: 7 per 10,000 person-years ā¢ RR = 16/4 = 4 ā¢ Prevalence of exposure to OC: ā¢ 25% of woman of reproductive age
36.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 36 Population attributable risk (PAR) ā¢ The incidence of disease in a population that is associated with a risk factor. ā¢ Calculated from the Attributable risk (or RD) and the prevalence (P) of the risk factor in the population ā¢ PAR = Attributable risk x P ā¢ PAR = (16-4) x 0.25 ā¢ PAR = 3 per 10,000 person years ā¢ Equals the excess incidence of VTE in the population due to OC use
37.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 37 Population attributable risk fraction (PARF) ā¢ The fraction of disease in a population that is attributed to a risk factor. ā¢ PARF = PAR/Total incidence ā¢ PARF = 3/7per 10,000 person years ā¢ PARF = 43% ā¢ Represents the maximum potential impact on disease incidence if risk factor was removed ā¢ So, remove OCās and incidence of VTE drops 43% in women of repro age (assuming OC is a cause of VTE)
38.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 38 Exposed Eligible subjects Unexposed Disease Disease No disease No disease FUTURE NOW PARF = -
39.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 39 PARF Calculation ā¢ PARF = P(RR-1)/ [1 + P(RR-1)] where: ā¢ P = prevalence, RR = relative risk ā¢ PARF = 0.25(4-1)/ [1 + 0.25(4-1)] ā¢ PARF = 43% ā¢ Note that a factor with a small RR but a large P can cause more disease in a population than a factor with a big RR and a small P.
40.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 40 Selection Bias ā¢ Selection bias can occur at the time the cohort is first assembled: ā¢ Patients assembled for the study differ in ways other than the exposure under study and these factors may determine the outcome ā e.g., Only the Uranium miners at highest risk of lung cancer (i.e., smokers, prior family history) agree to participate ā¢ Selection bias can occur during the study ā¢ e.g., differential loss to follow-up in exposed and un-exposed groups (same issue as per RCT design) ā¢ Loss to follow-up does not occur at random ā¢ To some degree selection bias is almost inevitable.
41.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 41 Confounding Bias ā¢ Confounding bias can occur in cohort studies because the exposure of interest is not assigned at random and other risk factors may be associated with both the exposure and disease. ā¢ Example: cohort study of lecture attendance Attendance Exam success Baseline epi proficiency - - +
42.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 42 Cohort Studies - Advantages ā¢ Can measure disease incidence ā¢ Can study the natural history ā¢ Provides strong evidence of casual association between E and D (time order is known) ā¢ Provides information on time lag between E and D ā¢ Multiple diseases can be examined ā¢ Good choice if exposure is rare (assemble special exposure cohort) ā¢ Generally less susceptible to bias vs. CCS
43.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 43 Cohort Studies - Disadvantages ā¢ Takes time, need large samples, expensive ā¢ Complicated to implement and conduct ā¢ Not useful for rare diseases/outcomes ā¢ Problems of selection bias ā¢ At start = assembling the cohort ā¢ During study = loss to follow-up ā¢ With prolonged time period: ā¢ loss-to-follow up ā¢ exposures change (misclassification) ā¢ Confounding ā¢ Exposures not assigned at random
44.
Mathew J. Reeves,
PhD Ā© Dept. of Epidemiology, MSU 44 Prognostic Studies - predicting outcomes in those with disease ā¢ Also measured using a cohort design (of affected individuals) ā¢ Factors that predict outcomes among those with disease are called prognostic factors and may be different from risk factors. ā¢ Discussed further in Epi-547
Download now