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Study designs, Epidemiological study design, Types of studies
The document provides an overview of various study designs in medical research, including observational and interventional studies, and emphasizes the importance of choosing the appropriate design for specific research questions. It outlines different types of studies such as descriptive, case-control, cohort, and randomized trials, explaining their characteristics, methodologies, and applications. It also discusses the differences between quantitative and qualitative research and highlights systematic reviews and meta-analyses as important tools for synthesizing research findings.
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Introduction to study designs, their types, uses, and a hierarchical overview.
Definition and distinction between quantitative and qualitative research.
Exploration of observational and experimental studies, detailing descriptive studies and case reports.
Focus on analytical study designs including ecological, cross-sectional, case-control, and cohort studies.
Description of cross-sectional studies, their purpose in assessing prevalence and disease burden.
Methodology of case-control studies, comparing cases with controls to assess exposure.
Description of cohort studies, their design, purpose, and examples related to obesity.
Introduction to experimental designs, including randomized controlled trials and their applications.
Comparison of various study types based on their objectives and directions of inquiry.
Discussion of systematic reviews, their methodologies, and the role of meta-analysis in research.
Explanation of qualitative research, its significance, and the questions it addresses.
Examples highlighting the appropriate study designs for various research questions.
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Study designs, Epidemiological study design, Types of studies
- 1. STUDY DESIGNS - AnOverview Dr Lipilekha Patnaik professor, Community Medicine Institute of Medical Sciences & SUM Hospital, Siksha ‘O’ Anusandhan deemed to be University Bhubaneswar, ODISHA, INDIA E mail– drlipilekha@yahoo.co.in 1
- 2. Session Outline Study designsand its types Observational and Interventional studies Uses of different studies Systematic review and metaanalysis Hierarchy of study designs in research An introduction to Qualitative study Ideal study design for different situations 2
- 3. Study Design A studydesign is a specific plan or protocol for conducting the study, which allows the investigator to translate the conceptual hypothesis into an operational one. 3
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- 5. Quantitative vs Qualitative vQuantitativeresearch is used to quantify the problem by way of generating numerical data which can be transformed into useable statistics. It can generalize results from sample to population. vQualitative research is exploratory research. It is used to gain an understanding of underlying reasons, opinions etc. and provides insight into the problem. 5
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- 7. Types of epidemiologicalstudies Types of studies Alternative name Unit of study OBSERVATIONALSTUDIES ◦ Descriptive studies – Case report, case series Individuals ◦ Cross sectional surveys ◦ Analytical studies ◦ Ecological Correlation Populations ◦ Cross-sectional Prevalence Individuals ◦ Case-control Case-reference Individuals ◦ Cohort Follow-up Individuals EXPERIMENTALSTUDIES (Intervention Studies) ◦ Randomized control trials Clinical Trials Patients ◦ Field trials Healthy People ◦ Community trial Community studies Communities 7
- 8. DESCRIPTIVE STUDIES ØDescriptive studyis the first phase of epidemiological investigation. ØObserving the distribution of disease or health related events in human population. ØIdentify the characteristics with which the disease is associated. ØBasically 3 questions are asked when, where and who i.e. Time, place and person distribution. 8
- 9. Case reports Case series Populationstudies (Cross sectional surveys) 9
- 10. Case Reports ØDetailed presentationof a single case. ØGenerally report a new or unique finding üe.g. previous undescribed disease üe.g. unexpected link between diseases üe.g. unexpected new therapeutic effect üe.g. adverse events 10
- 11. Case Series ØExperience ofa group of patients with a similar diagnosis ØCases may be identified from a single or multiple sources ØGenerally report on new/unique condition 11
- 12. Cond. ØAdvantages •Useful for hypothesisgeneration •Informative for very rare disease with few established risk factors ØDisadvantages •Cannot study cause and effect relationships •Cannot assess disease frequency 12
- 13. Case Report Case Series Onecase of unusual findings Multiple cases of findings 13
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- 17. Ecological Study žIt isnot easy to establish links between environmentalexposures and health outcomes using individuallevel data. žEcological study designs provide one way of avoiding these difficulties and studying the effects of environmentalexposures on different health outcomes. žEcological studies look for associations between the occurrenceof disease and exposure to known or suspected causes. žHowever, the unit of analysis is not an individualbut a population / a group of persons 17
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- 19. Cross-sectional Study Data collectedat a single point in time An “observational” design that surveys exposures and disease status at a single point in time (a cross-section of the population) Describes associations Prevalence 19 A “Snapshot”
- 20. 20 time Study only existsat this point in time Study population No Disease Disease factor present factor absent factor present factor absent
- 21. Sample of Population Playing outdoorgames regularly Not playing outdoor games Prevalence of Overweight/ obesity Prevalence of Overweight/ obesity Time Frame = Present 21 Defined Population of school going adolescents Example
- 22. Why we docross-sectional study? ØTo assess the burden of disease in a population and to assess the need for health services. ØTo compare the prevalence of disease in different populations. ØTo examine trends in disease prevalence or severity over time. ØTo find out association 22
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- 25. Case-Control Studies §Start withpeople who have disease (Cases) §Match them with controls that do not have disease §Look back and assess exposures 25
- 26. Other Name RetrospectiveStudy Unit of Study Cases/Control Study QuestionWhat has happened ? Direction of Inquiry= F O Study Design 26
- 27. 27 Study population Cases (disease) Controls (no disease) factor present factorabsent factor present factor absent present past time Study begins here
- 28. 28 Obese adolescents Normal adolescents PresentPast NoOutdoor games No Outdoor games Regular outdoor games Regular outdoor games Cases Controls Example
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- 30. Cohort Study Cohort isdefined a group of people who share a common characteristic or experience within a defined time period (age, occupation, exposure) Birth cohort, exposure cohort 30
- 31. Begin with disease-freeindividuals Classify patients as exposed/unexposed Record outcomes in both groups Compare outcomes using relative risk 31
- 32. Other Name ProspectiveStudy / Follow-up Study/Incidence Study Unit of Study Individual Study Question What is happening ? Directionof Inquiry F O Study Design 32
- 33. 33 time Study begins here Study population freeof disease Factor present Factor absent disease no disease disease no disease present future
- 34. Example 34 Not playing outdoor games Playingoutdoor games regularly Not obese Obesity Obesity Not obese Present Future Cohort of School going adolescents
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- 36. EXPERIMENTAL STUDIES 1. Experimentalstudies are similar in approach to cohort studies excepting that the study condition are under direct control of the investigator. 2. There is some action, intervention or manipulation which are deliberate. AIM OF EXPERIMENTAL STUDY 1. To provide scientific proof of aetiological factor. 2. To provide a method of measuring the effectiveness and efficiency of health services for the prevention control and treatment of diseases. TYPES OF EXPERIMENTAL STUDIES 1. Animal study 2. Human study 36
- 37. Types 1. Randomised controlledtrials 2. Non-randomised trials. 37
- 38. Other Name InterventionStudy Objective To know the effect of intervention Unit of Study Individual meeting entry criteria Study Question What is happening after intervention in both groups ? Direction of Inquiry I E Study Design (Intervention with Standard of care or placebo) 38
- 39. Experimental Design 39 time Study beginshere (baseline point) Study population Intervention Control outcome no outcome outcome no outcome baseline future RANDOMIZATION
- 40. Participants are allocatedin to two groups. 1) study group : To receive preventive and therapeutic manoeuvres. 2) control group : Not to receive any intervention or to receive standard of care. 40 Randomisation
- 41. 41 time Study begins here obesestudents Intervention (Regular exercise &Outdoor games) Control Decrease BMI No change of BMI Decrease BMI No change of BMI Obese students Future (After 2 years) RANDOMIZATION
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- 43. Different studies havedifferent uses Objective Type of study Prevalence Cross-sectional Incidence Cohort Causal association Cohort Case-control Prognosis Cohort Natural history of disease Cohort Treatment effect Randomised Controlled Trial 43
- 44. Did the investigatorassign exposure? Experimental Study Observational Study Yes No Random Allocation? Comparison Group? Yes Yes No No Analytical Study Descriptive Study Randomized Control trial Non- Randomized Control trial Direction? Exposure Outcome Exposure and outcome at the same time Cohort Study Case Control Study Cross- Sectional Study Exposure Outcome 44
- 45. Systematic Review “A reviewthat is conducted according to clearly stated, scientific research methods, and is designed to minimize biases and errors inherent to traditional, narrative reviews.” Margaliot, Zvi, Kevin C. Chung. Systematic Reviews: A Primer for Plastic Surgery Research. PRS Journal. 120/7 (2007) 45
- 46. Meta analysis ØMeta-analysis isa statistical analysis of a collection of studies. ØMeta-analysis methods focus on contrasting and comparing results from different studies in anticipation of identifying consistent patterns and sources of disagreements among these results. Ø“While all meta-analyses are based on systematic review of literature, not all systematic reviews necessarily include meta- analysis.” 46
- 47. Hierarchy of StudyDesign 47
- 48. QUALITATIVE RESEARCH Qualitative researchcan provide insight into the priblem which is not possible with purely quantitative data • A means for exploring and understanding the meaning individuals or groups ascribe to social or human problems • Study human behavior and social world Help us to understand the world in which we live and why things are the way they are 48
- 49. Qualitative research answerquestions on: ◦Why people behave the way they do ◦How opinions and attitudes are formed ◦How people are affected by the events that go on around them ◦How and why cultures have developed ◦The difference between social groups 49
- 50. Which is theideal study design? §A rare case of Dermatomyositis came to the hospital – Case report §Prevalence of Hypertension among adolescents in Bhubaneswar city – Cross sectional §To find out the association of bottle feeding with the incidence of diarrhea – Cohort §Association of Smoking and MI – Case Control §Safety and efficacy of Malaria vaccine – RCT §To explore factors of nonuse of contraceptives in a tribal community – Qualitative study 50
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