Epidemiological Study Design Basic of epidemoplogy

Epidemiology

1. STUDY DESIGNS - An Overview 1 Dr Lipilekha Patnaik professor, Community Medicine Institute o f Medical Sciences & SUM Hospital, Siksha ‘O’ Anusandhan deemed to be University Bhubaneswar, ODISHA, INDIA E mail– [email protected]

2. Session Outline 2 Study designs and 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

3. Study Design A study design is a specific plan or protocol for conducting the study, which allows the investigator to translate the conceptual hypothesis into an operational one. 3

4. TYPES Q UAN T I T A T I V E 4 QUALITATIVE

5. Quantitative vs Qualitative 5 Quantitative research is used to quantify the p r oble m b y wa y o f gene r a t in g nu m e r i c a l da t a which can be transformed into useable statistics. It can generalize results from sample to population. Qualitative research is exploratory research. It is used to gain an understanding of unde r l y in g r ea s on s, opinion s e t c. an d p r o v ide s insight into the problem.

6. Types of epidemiological studies U ni t o f s t ud y T y p e s o f s t udi e s A l t e r n a t i v e n a me O B SE R V A TIO NA L S T UD I E S Descriptive studies – Case report, case series Cross sectional surveys Analytical studies 7 Individuals Ecological Correlation Populations Cross-sectional Prevalence Individuals Case-control Case-reference Individuals Cohort Follow-up Individuals EXPERIMENTAL STUDIES (Intervention Studies) Randomized control trials Clinical Trials Field trials Patients Healthy People Communities Community trial Community studies

7. DESCRIPTIVE STUDIES 8 Descriptive study is the first phase of epidemiological investigation. Observing the distribution of disease or health related events in human population. Identify the characteristics with which the disease is associated. Basically 3 questions are asked when, where and who i.e. Time, place and person distribution.

8. Case reports Case series Population studies (Cross sectional surveys) 9

9. Case Reports 10 Detailed presentation of a single case. Generally report a new or unique finding e.g. previous undescribed disease e.g. unexpected link between diseases e . g . un ex p ec t e d n e w t h e r a p e u t i c e f f ect e.g. adverse events

10. Case Series 11 E x p er i e n c e o f a g r ou p o f p a t i e n ts wi t h a similar diagnosis Cas e s ma y b e id e n t i f i e d f r o m a s in g l e or multiple sources Generally report on new/unique condition

11. C o n d . Advantages Useful for hypothesis generation I n f o r m a t i v e f o r v e r y r a r e d i s e a s e established risk factors w i t h f e w Disadvantages Cannot study cause and effect relationships Cannot assess disease frequency 12

12. Case Report Case Series One case of unusual findings Multiple cases of findings 13

13. Us e s 14 Hypothesis generation Suggesting associations

14. ANALYTICAL STUDIES 15 Ecological study C r o ss - sec t i on al Case-control Cohort

15. Ecological Study 16 ⦿ It i s not ea s y t o e s ta b li s h li nks b et w ee n e nv i ro n m e n t a l e xpo s ur e s a nd h ealt h ou tc o m e s u s i ng i nd i v i du a l le v e l d ata . ⦿ Ec o l og ic a l s t udy d e s i gns prov i de one w a y of a vo i d i ng t h e s e difficulties and studying the effects of environmental exposures on d i ff e r e nt h eal t h ou tc o m e s . ⦿ Ec o l og ic a l s t ud ie s l ook for a ss o ciati o ns b et w ee n t he o cc urr e n c e of d i s ea s e a nd e xpo s ure t o kno w n or s u s p ecte d ca u s e s . ⦿ H o w e v e r , t he un i t of a n al y s i s i s not a n i nd i v i du a l but a popu lati on / a group of persons

16. Cross-sectional Study D a ta c oll ec t e d a t a s ingl e poin t i n t i me An “observational” design that surveys exposures and disease status at a single point in time (a cross-section of the population) D esc r ib e s ass o c i a t ion s Prevalence A “ Snapshot ” 17

17. time S t ud y o n l y e x i s t s at t h i s p o i n t i n t i m e factor present No Disease factor absent Study popu l a t i on factor present Disease factor absent 18

18. S a m p l e of P opu l a t i o n Playing ou t doo r g a m e s regularly Prevalence of Overweight/ obesity Not playing ou t doo r g a m e s Prevalence of Overweight/ obesity Time Frame = Present Defined Population of school going adolescents E xa m p l e 19

19. Why we do cross-sectional study? 20 To assess the burden of disease in a population and to assess the need for health services. To compare the prevalence of disease in different populations. To examine trends in disease prevalence or severity over time. To find out association

20. Case-Control Studies 21 Start with people who have disease (Cases) Match them with controls that do not have disease Look back and assess exposures

21. Other Name Unit of Study Retrospective Study Cases/Control Study QuestionWhat has happened  Direction of Inquiry= F O Study Design 22

22. Study popu l a t i on Cases ( d i sease ) Controls (no disease) factor present factor absent factor present factor absent p re s e nt past time Study begins here 23

23. Obese adolescents Normal adolescents Present Past N o O u t doo r g a m e s N o O u t doo r g a m e s R e gu l a r ou t doo r g a m e s R e gu l a r ou t doo r g a m e s C ase s 24 C on t r o l s E xa m p l e

24. Cohort Study 25 Cohort is defined a group of people who share a common characteristic or experience within a defined time period (age, occupation, exposure) Birth cohort, exposure cohort

25. Begin with disease-free individuals Classify patients as exposed/unexposed Record outcomes in both groups Compare outcomes using relative risk 26

26. Other Name Prospective Study / Follow-up Study/Incidence Study Individual What is happening  Unit of Study Study Question D i rec t i on of I nqu i r y F O Study Design 27

27. time Study begins here Study popu l a t i on free of disease Factor p r ese nt Factor a b se n t disease no disease disease no disease p re s e nt f u t u r e 28

28. Example Not playing outdoor games Cohort of School going adolescents Playing outdoor g a m e s r e gu l a r l y Not obese Obesity Obesity Not obese Present Future 29

29. E X P E R I M E N T A L S T U DI ES 30 Experimental studies are similar in approach to cohort studies excepting that the study condition are under direct control of the investigator. There is some action, intervention or manipulation which are deliberate. AIM OF EXPERIMENTAL STUDY To provide scientific proof of aetiological factor. 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 Animal study Human study

30. T y p e s 31 Randomised controlled trials Non-randomised trials .

31. Other Name Objective Unit of Study Intervention Study To know the effect of intervention Individual meeting entry criteria What is happening after intervention in both groups  Study Question D i r ec t io n o f Inqui r y I E Study Design (Intervention with Standard of care or placebo) 32

32. e r i m e n t t i me Study begins here (baseline point) ou t c o m e Intervention no outcome Study popu l a t i on outcome Control no outcome baseline f u t u r e E x p RAND O M I Z A T I O N a l D e s i g n 33

33. Participants are allocated in to two groups. study group : To receive preventive and therapeutic manoeuvres. control group : Not to receive any in t e rv en t io n o r t o r e c ei ve s t anda rd o f c a r e . 34 Randomisation

34. t i me Study begins here obese students Intervention (Regular exercise &Outdoor games) C on t r o l Decrease BMI No change of BMI D ec r eas e B M I No change of BMI Obese s t ud e n t s Future (After 2 years ) RANDOMIZATION 35

35. Different studies have different uses 36 Objective Type of study Prevalence Cross-sectional Incidence Cohort Causal association Cohort Case-control P r ogno s i s C oho r t N a t u r a l h i s t o r y o f disease C oho r t Treatment effect R a ndo m i se d C on t r o ll e d Trial

36. Did the investigator assign exposure? Experimental Study Observational Study Y e s No R a ndo m A l l o ca t i on ? Y e s No Comparison Group? Yes No A n a l y t i ca l Study D esc r i p t i v e Study R a ndo m i z e d Control trial Non- R a ndo m i z e d Control trial Di r e c t i on ? E x po s u r e O u t c o m e Exposure and outcome at the same time C oho r t Study Case C on t r o l Study C r o ss - S ec t i on a l Study E x po s u r e 37 O u t c o m e

37. Systematic Review 38 “A review that is conducted according to clearly stated, scientific research methods, and is designed to minimize biases and errors inhe r en t t o t r adi t ional , na rr a t i v e r e v ie w s . ” Margaliot, Zvi, Kevin C. Chung. Systematic Reviews: A Primer for Plastic Surgery Research. PRS Journal. 120/7 (2007)

38. Meta analysis 39 Meta-analysis is a statistical analysis of a collection of studies. Meta-analysis methods focus on contrasting and comparing results from different studies in anticipation of identifying consistent patterns and sources of disagreements among these results. “While all meta-analyses are based on systematic review of literature, not all systematic reviews necessarily include meta- analysis.”

39. Hierarchy of Study Design 40

40. QUALITATIVE RESEARCH 41 Qualitative research can provide insight into t h e p r ible m whi ch i s no t po ss ibl e wi t h pu r el y quantitative data A m ean s f o r e x p l o r i n g an d unde r s t an d i n g t h e meaning individuals or groups ascribe to social or human problems S t ud y hu m a n beha v i o r an d s o c i a l w o r l d Help us to understand the world in which we live and why things are the way they are

41. Qualitative research answer questions on: 42 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

42. Which is the ideal study design? 43 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

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