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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
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
0 10 20 30
Denmark
Pittsburgh, USAScotlandSweden
Finland
KoreaJapan
KuwaitIsrael
EnglandCanada
Netheland
Incidence /100,000
RETROSPECTIVE STUDY
Time
PAST
• Life style
• Diet
• Reproductive on
• Medication
• Family Hx
• Genetics
PRESENT
Disease
Determining differences in:
RETROSPECTIVE STUDY: PROS & CONS
• Suitable for rare diseases
• Inexpensive
• Minimal ethical problems
• Short study time
• Small # of subjects
• Subjects need not volunteer
• 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
PRO CON
PROSPECTIVE STUDY: PROS & CONS
• Less variability to bias
• No recall necessary
• Incidence determined
• Relative risk accurate
• 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
PRO CON
TYPES OF STUDIES AND GOALS
CROSS-SECTIONAL Understand
RETROSPECTIVE Estimate risk factors
PROSPECTVE Validate risk factors
Prevention-Control-Intervention-Education-Management
EXPERIMENTAL STUDYRandomized Clinical Trial:DPP
Random Selection
Exercise
Diet
Drug
Ou
tcome evalu
ation