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Public Health > Overview of Epidemiological Studies > Flashcards

Overview of Epidemiological Studies Flashcards

1
Q

Lecture Objectives

A

1) recall the definitions and understand the assumptions underlying epidemiology and epidemiological research
2) understand the differences between experimental research and observational research
3) differentiate between association and causation
4) understand the purpose, characteristics, and measures of associations (if applicable) pertinent to each epidemiological study design
5) identify the advantages, disadvantages, and relative strength of each epidemiological study design

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2
Q

Old definition of epidemiology

A

study of the distribution and determinants of disease frequency in man

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3
Q

New definition of epidemiology

A

the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control health problems

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4
Q

Distribution

A

Who, where, when “descriptive”

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5
Q

Determinants

A

What, why, how “analytical”

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6
Q

Population

A

inhabitants of a given area/region/group

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7
Q

Practical goal of epidemiology

A

to be used as a tool to improve the health conditions of the public

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8
Q

Names of US population studies

A

Framingham Eye, Beaver Dam, Baltimore, Los Angeles Latino Eye, Chesapeake Bay Waterman , Wisconsin Epidemiologic study of diabetic retinopathy

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9
Q

Names of Non-US population studies

A

Barbados, Blue Mountain, Rotterdam, Shihpau, Beijing

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10
Q

Incidence

A

the number of new problems or cases that develop in a population at risk during a given time period; often quantified as a rate

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11
Q

Prevalence

A

the proportion of a given population with a problem at a designated time; quantified as a proportion

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12
Q

What are examples of exposure?

A

actual exposure (toxic chemical or microorganism), a behavior or an individual attribute

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13
Q

The exposure of interest may be associated with…

A

either an increased or a decreased occurrence of disease or other specified health outcome, and may relate to the environment, lifestyle or inherited characteristics

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14
Q

What are examples of outcome?

A

the disease state, event, behavior, or condition associated with health that is under investigation

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15
Q

What are epidemiologic assumptions?

A

disease (and/or risk factors) don’t occur at random; disease is not randomly distributed throughout a population

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16
Q

What are epidemiologic shortcomings?

A

difficulty in measuring exposure, separating causal contributions of exposure from other exposures, difficulty in assessing role of multiple small risks

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17
Q

What is the impractical goal of epidemiology aka the big epidemiological question?

A

does exposure A cause outcome B

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18
Q

What are Hill’s causal criteria?

A

temporality, strength, biological gradient (dose-response), consistency (replication), specificity, plausibility, coherence (compatible), experimental evidence, analogy (alternate explanations

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19
Q

What is the ideal model?

A

counterfactual model

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20
Q

How does the counterfactual model work?

A

ideally the population exposed/treated and the population not exposed/treated are the same subjects; you then follow-up and measure incidence

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21
Q

What is the real design?

A

the two populations are comparable subjects after adjustments, still follow-up and measure incidence

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22
Q

What are the overarching categories of epidemiological studies?

A

experimental and observational

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23
Q

What is an experimental study?

A

randomized controlled trial or individual or community

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24
Q

What is the breakdown of observational studies?

A

analytic and descriptive

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25
Q

What are analytic studies?

A

case-control and cohort

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26
Q

What are descriptive studies?

A

case report and ecological and cross-sectional

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27
Q

Experimental

A

exposure status assigned by researcher; generally described as clinical investigations

28
Q

Observational

A

exposure status not assigned by researcher; primarily involves monitoring people in their natural environments

29
Q

Characteristics of randomized controlled trial

A

experimental design; population is people w/o the outcome; assign treatment and check for outcome; subjects given standard treatment compared to subjects given experimental treatment; compare outcomes vs no outcome for each group

30
Q

Randomized control trial of individual/community

A

measure the disease frequency or exposed/treated vs unexposed/control

31
Q

Why is randomized control trial the gold standard?

A

random group assignment, blinded (preferably double), placebo group, treatment only difference between groups

32
Q

Advantages of randomized control trials?

A

standard approach to test new treatments, prospective, exposure assigned

33
Q

Disadvantages of randomized control trial?

A

time consuming, expensive, same effectivity in real world, non-compliance, ethical issue

34
Q

Examples of random control trials

A

DRS, ETDRS, UK prospective DS, DCT, DRCR.net

35
Q

What are optometry randomized control trials?

A

CITT and vision in preschoolers study

36
Q

Analytic

A

used to help establish cause or risk factors for outcome (what, why, how)

37
Q

Descriptive

A

identify patterns among cases and in populations by time, place, person (when, where, who)

38
Q

What is a cohort study?

A

a forward or prospective study onset in the present with the future evaluated

39
Q

Characteristics of a cohort study

A

observational and analytic; population is people without the outcome; start with exposure and check for outcome; subjects exposed compared to subjects not exposed; compare outcome vs no outcome for each group

40
Q

Cohort advantages

A

comparison group, prospective, suitable for rare exposures, can examine a range of outcomes, temporality: exposure before outcome, establish relative risk, measure incidence

41
Q

Cohort disadvantages

A

relatively expensive, time consuming (study subject drop-out, prolonged follow-up), not suitable for rare outcomes (disease)

42
Q

What is a 2x2 contingency table?

A

compares exposure and outcome

43
Q

What is an example of a cohort study?

A

Orinda vision screening study

44
Q

What is a case-control study?

A

a backwards or retrospective study; onset in the present with analysis of the past

45
Q

What are characteristics of the case-control study?

A

observational, analytic; population: people with the outcome and people without the outcome (control); start with outcome and check for exposure; subjects who have outcome compared to subjects who do not have outcome; compare exposed vs not exposed for each group

46
Q

Advantages of case-control

A

comparison group, relatively inexpensive, quick, can study rare diseases, can test multiple hypotheses for a single outcome, generate exposure odds ratio

47
Q

Disadvantages of case-control

A

retrospective, recall bias, no temporality: which came first, the outcome or the exposure

48
Q

Eye related case control study

A

the lens opacities case-control study; risk factors for cataract

49
Q

Cross-sectional characteristics

A

observational, descriptive; populationL people with the outcome and people without the outcome; exposure and outcome are measured simultaneously; measure and compare subjects with exposure and subjects with exposure and outcome

50
Q

Advantages of cross-sectional study

A

relatively, inexpensive, quick, establish prevalence

51
Q

Disadvantages of cross-sectional study

A

no cause and effect, no temporality, can miss rare exposures/outcomes (diseases), can miss outcomes (diseases) of short duration, not useful for rapidly emerging outcomes

52
Q

Cross-sectional eye studies

A

framingham, baltimore, multi-ethnic pediatric eye disease, baltimore pediatric eye disease

53
Q

Characteristics of ecological study

A

observational, descriptive; aka correlational study, analyzes groups/populations instead of individuals, try and determine relationship between exposure and outcome variables

54
Q

Advantages of ecological studies

A

relatively inexpensive, quick (can sometimes use existing data), big picture (population trends, broad social processes)

55
Q

Disadvantages of ecological studies

A

usually cannot establish causation, unable to control for confounding variable, ecological fallacy: can’t extrapolate population data to individual subjects

56
Q

Example of ecological eye related study

A

an ecologic study of trends in the prevalence of myopia in chinese adults in singapore born from the 1920s to 1980s

57
Q

Characteristics of case report

A

observational, descriptive; case report: documents an unusual medical occurrence, case series: collections of individual case reports

58
Q

Advantage of case report

A

first clue/early warning of a potential problem

59
Q

Disadvantage of case report

A

anecdotal, non-scientific, the plural of anecdote is not data, no comparison group

60
Q

Case report eye example

A

fusarium keratitis outbreak

61
Q

T/F there are hybrid studies combining study types

A

true

62
Q

What is the hierarchy of study strength from basic to scientific?

A

animal research, case series/case reports, case control study, cohort study, randomized controlled trial, systematic review, meta-analysis

63
Q

What are grade A study types?

A

meta-analysis, systematic review, randomized clinical trial, diagnostic studies

64
Q

What are grade B study types?

A

weak randomized clinical trial, cohort study, diagnostic study

65
Q

What are grade C study types?

A

case control studies, diagnostic studies, studies of strong design, nonrandomized trials

66
Q

What are grade D study types?

A

cross sectional studies, case reports/series, reviews, position papers, expert opinion, reasoning from principle

67
Q

Example of action statement strength of evidence A

A

individuals should be advised by their health care providers of the risks of smoking and encouraged to quit smoking and/or seek smoking cessation assistance. Evidence grade: A, strong recommendation

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