Types of Studies in Diabetes Epidemiology

TYPES OF STUDIES IN DIABETES EPIDEMIOLOGY 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 Retrospective PRESENT Cross-sectional Prospective FUTURE Time 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 30 Incidence /100,000 RETROSPECTIVE STUDY Determining differences in: • • • • • • Life style Diet Reproductive on Medication Family Hx Genetics PRESENT Disease PAST Time RETROSPECTIVE STUDY: PROS & CONS PRO CON • • • • • • 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 PROSPECTIVE STUDY Retinopathy+ PRESENT DM Future Risk factors??? Retinopathy- Time PROSPECTIVE STUDY: PROS & CONS PRO CON • • • • 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 TYPES OF STUDIES AND GOALS CROSS-SECTIONAL Understand RETROSPECTIVE Estimate risk factors Validate risk factors PROSPECTVE Prevention-Control-Intervention-Education-Management EXPERIMENTAL STUDY • Animal • Drug trials • Human EXPERIMENTAL STUDY Randomized Clinical Trial:DPP Exercise Outcome evaluation Random Selection Diet Drug EXPERIMENTAL STUDY Cross-over design Outcome evaluation