Transcript types of studies in diabetes epidemiology

TYPES OF STUDIES IN DIABETES
EPIDEMIOLOGY
Nam-Ham Cho, Ajou University
TYPES OF STUDIES BASED ON:
• Purpose
• Time
• Cost
• Feasibility
TYPES OF STUDY
Observational
Descriptive
Analytical
– Cross-sectional
– Retrospective
– Prospective
Experimental
– Clinical Trial
– Community Intervention Trial
– Field Trial
A STUDY DESIGN FOR THE OUTCOMES
OF DIABETES
• Diabetes
• Morbidity (Complications)
• Mortality (Death)
• Economics
• Treatment
• Education
• Prevention & Control
• Intervention
TIME AND TYPES OF STUDY
PAST
PRESENT
Retrospective
Cross-sectional
Time
FUTURE
Prospective
CROSS-SECTIONAL STUDY
PRESENT
Cross-sectional
Time
ANALYTICAL STUDY
A cross-sectional study:
– Privides a snap shot
– Is simple
– Provides associated factor
– Is first line of epidemiologic research
CROSS-SECTIONAL STUDY
What is different about:
• DM
• Morbidity (Complications)
• Mortality (Death)
How is it different about:
• SES
• Age at onset
• Season
CROSS-SECTIONAL STUDY
Korea
Japan
Kuwait
Israel
England
Canada
Netheland
Denmark
Pittsburgh, USA
Scotland
Sweden
Finland
0
10
20
Incidence /100,000
30
RETROSPECTIVE STUDY
Determining differences in:
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Life style
Diet
Reproductive on
Medication
Family Hx
Genetics
PRESENT
PAST
Time
Disease
RETROSPECTIVE STUDY: PROS & CONS
PRO
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Suitable for rare diseases
Inexpensive
Minimal ethical problems
Short study time
Small # of subjects
Subjects need not volunteer
CON
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Susceptable to selection &
memory bias
Inconsistency: definitions of
symptoms or diseases may
have been modified over
time.
Can not determine incidence
Limitations in data
Relative risk approximation
PROSPECTIVE STUDY
Retinopathy+
PRESENT
DM
Risk factors???
Future
Retinopathy-
Time
PROSPECTIVE STUDY: PROS & CONS
PRO
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Less variability to bias
No recall necessary
Incidence determined
Relative risk accurate
CON
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Consistent disease
definitions & symptoms.
Longer time
Common disease only
Expensive
Ethical concern
A high drop-out rate
Volunteers needed
A large # of subjects needed
The Hawthorne-effect
TYPES OF STUDIES AND GOALS
CROSS-SECTIONAL
Understand
RETROSPECTIVE
Estimate risk factors
PROSPECTVE
Validate risk factors
Prevention-Control-Intervention-Education-Management
EXPERIMENTAL STUDY
• Animal
• Drug trials
• Human
EXPERIMENTAL STUDY
Randomized Clinical Trial:DPP
Exercise
Diet
Drug
Outcome evaluation
Random Selection
EXPERIMENTAL STUDY
Cross-over design
Outcome evaluation
Review Questions (Developed by the Supercourse
team)
•
What are the advantages and
disadvantages for retrospective studies?
•What are the advantages and
disadvantages for prospective studies?