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Public Health > Overview of research methodology > Flashcards

Overview of research methodology Flashcards

1
Q

What is research?

A

Old French term “Re-cerchier” meaning to “search intensively”: a process by which we aim to discover new knowledge. Uses a systematic process  Scientific Method

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2
Q

Why is critical appraisal required

A
  • Published research is not always reliable or relevant.
  • We need a systematic framework to conduct research, interpret research and assess quality.
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3
Q

Why is study design important?

A
  1. Specific questions need specific design (feasibility, ethics)
  2. Different designs have different causal strengths
  3. Determines nature of bias and confounding (validity)
  4. Affects resources needed: sample size, staff, expertise, access to records, time!  efficiency
  5. Ethical issues vary
  6. May influence measurement accuracy (e.g. prospective vs retrospective data collection)
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4
Q

Descriptive study

A

No comparison group. Answers who, what, when, where.
E.g. case study, case series, non-analytic cohort

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5
Q

advantages of descriptive study

A

Hypothesis generation
Health service planning & management

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6
Q

disadvantages of descriptive study

A

Cannot establish causality

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7
Q

Cross sectional study

A

Exposure and outcome measured at one point in time
= snap-shot
= prevalence study

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8
Q

Advantages of cross sectional study

A

-Relatively cheap & easy
-Measure multiple variables at the same time

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9
Q

Disadvantages of cross sectional study

A
  • Cannot measure temporality
    -Cannot measure incidence
    -Information bias (recall bias); Selection bias
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10
Q

Cohort study

A

“A group of people who share a common characteristic or experience within a defined period”.

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11
Q

Advantages of cohort study

A

–Temporality
-Can calculate incidence
-Useful for rare exposures
-Can study multiple outcomes (of single exposure

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12
Q

Disadvantages of cohort study

A

-Loss-to-follow-up
-Detection bias
-Time consuming, expensive

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13
Q

retrospective

A

Study begins when outcome has already occurred
Participants grouped on exposure (NOT outcome status)

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14
Q

prospective

A

Outcome has not yet occurred
Participants grouped on basis of exposure
Follow up to see if outcome occurs

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15
Q

case control study

A

Identify cases (those who have the outcome/disease)
Choose controls (those without outcome/disease)
Measure exposure in both cases and controls
Common sources  hospital, neighbourhood, family members. “Matched controls”

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16
Q

Advantages of case control study

A

Efficient
Relatively quick
Good for rare outcomes
Can study multiple exposures

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17
Q

Disadvantages of case control study

A

Selection bias (selection of controls)
Information bias: Recall
Can only calculate odds ratio
No temporality

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18
Q

Randomised Control study

A

Similar to cohort, but exposure
assigned randomly & always prospective

Randomisation is a way to deal with confounders (known & unknown)
Participants have equal chance of receiving exposure/intervention as the control.

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19
Q

Advantages of RCT

A

Minimal bias/confounding
Strong evidence

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20
Q

Disadvantages of RCT

A

Ethical issues
Time-consuming, expensive
Loss-to-follow-up
Not suitable for all research questions

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21
Q

What is blinding or masking in research studies?

A

Blinding or masking involves concealing information about the intervention received (e.g., treatment or placebo) from participants, clinicians, field workers, lab personnel, or statisticians involved in the study. This is done to prevent bias in the assessment of outcomes.

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22
Q

What are the types of blinding?

A

Blinding can be single-blinded, where either participants or researchers are unaware of the intervention received, or double-blinded, where both participants and researchers are unaware. Triple-blinding involves concealing information from participants, researchers, and outcome assessors.

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23
Q

Why is blinding used in research studies?

A

Blinding is used to minimize bias that could result from knowledge of the intervention. It helps ensure that participants behave consistently and that researchers assess outcomes objectively, reducing the risk of bias in study results.

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24
Q

Ecological studies

A

Work with population or group-level variables. Previous examples were all looking at individual level. Study design itself can vary: but mostly cross-sectional ecological study

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25
Advantages ecological studies
Hypothesis generation Relatively quick and cheap
26
Disadvantages of ecological studies
Ecological fallacy Confounding, bias Cannot determine causality
27
What is occurrence?
Describes the burden of disease (how much there is).
28
When do we use measures of occurrence or frequency
Quantify the extent of an outcome(e.g. occurrence of disease) populations in order to motivate for response/ resources. E.g How many cases of diabetes were diagnosed in South Africa in 2022?
29
Measures of occurrence/ frequency
Prevalence Incidence (Incidence Proportion & Incidence Rate) Odds
30
What is association?
Compares the occurrence of disease in different exposure groups. Explores the relationship between exposure(s) and an outcome(s) of interest and whether it could be causal.
31
When do we use measures of association
We want to understand how exposures and outcomes are related, if one causes the other, if we want to modify exposure to increase or decrease the outcome. E.g. How strongly is smoking related to lung cancer?/ How many cases of lung cancer could we prevent by implementing tobacco control measures?
32
measures of disease association
-Relative measures Prevalence ratio Incidence: Risk ratio or rate ratio (RR) Odds ratio (OR) -Absolute measures Proportion / rate and risk differences Number needed to treat etc.
33
cases/ counts
Individuals in a population who have the disease, health disorder, or suffers the event of interest. Usually forms the numerator for measures of disease frequency (A)
34
population at risk (N)
The population from which cases come from. Usually forms the denominator in calculations of disease frequency
35
ratio
Comparison of two groups (numerator and denominator can be related)
36
rate
A rate is a ratio with a time component / change over time
37
proportion
A ratio in which the numerator is included in the denominator (A/N)
38
odds
A ratio in which the numerator is not included in the denominator (A/N-A)
39
prevalence
The number of cases of disease in a population at one point in time, as a proportion of the total number of persons in that population i.e. proportion of a population that has the disease/event at a specific point in time no of disease/ total population at point in time
40
incidence proportion (risk)
no of new cases in a given time period/ no at risk at beginning of time period
41
incidence rate
no of new cases in a given time period/ total person- time of observation or risk during that period Used if incomplete follow-up – i.e. loss to follow-up/open population (participants entering and leaving) IR takes into account the: Size of population (number of individuals in a population that become ill) length of time contributed by all persons during the period they were in the population.
42
aims of measures of association
Measures of association allow us to compare measures of disease frequency Quantify the association
43
relative measures of association
Measures of disease frequency are divided by one another Ratios of two measures of disease frequency
44
Absolute measures of association
Measures of disease frequency are subtracted from one another Tells us about the Public Health Impact
45
relative measures of association: ratio
-prevalence ration - cumulative incidence ratio - incidence rate ration - odds ratio
46
Prevalence ratio
Prevalence of disease in exposed / prevalence of disease in unexposed
47
Cumulative incidence ratio
Risk (incidence proportion) of disease in exposed / risk (incidence proportion) of disease in unexposed Also called risk ratio or relative risk
48
incidence rate ratio
Rate (incidence rate) of disease in exposed / rate (incidence rate) of disease in unexposed Also called rate ratio or relative rate
49
odds ratio
Odds of exposure in disease / odds of exposure in non-diseased*
50
Interpretation of Relative Measures of Association: <1 (less than 1):
The numerator is smaller than the denominator The exposure is “protective”/disease is less likely in the exposed
51
Interpretation of Relative Measures of Association =1
The numerator and denominator are equal There is no difference in disease occurrence between the exposed and unexposed
52
Interpretation of Relative Measures of Association >1 (greater than 1):
The numerator is larger than the denominator The exposure is “harmful”/disease is more likely in the exposed
53
Interpretation of Relative Measures of Association = Significant?
The relative measure of association is an estimate, and should be reported and interpreted with a 95% Confidence Interval (generated by statistical software) If the 95% confidence interval includes the value of 1, then not significant
54
risk ratio
ratio of two probabilities probability of an event occurring in treatment group / probability of the event occurring in control group risk in exposed/ risk in unexposed based on incidence- cohort studies, RCT
55
odds ratio
ratio of two odds odds of exposure occurring in cases group/ odds of exposure occurring in control group odds in cases/ odds in controls case control
56
prevalence ratio
prevalence exposed/ prevalence unexposed for cross sectional studies
57
Absolute measures of association
- prevalence difference - incidence proportion difference - incidence rate difference
58
prevalence difference
Prevalence of disease in exposed - prevalence of disease in unexposed =The number of cases that could be eliminated if the exposure was eliminated
59
incidence proportion difference
Risk (incidence proportion) of disease in exposed - risk (incidence proportion) of disease in unexposed
60
incidence rate difference
Rate (incidence rate) of disease in exposed - rate (incidence rate) of disease in unexposed
61
Population Risk or Rate difference: PRD = Rt – Ru
Population risk difference gives you the excess number of cases in the whole population that is associated with the exposure Can use incidence rate / incidence proportion or prevalence -Rt = Incidence rate OR incidence proportion OR prevalence in the whole population -Ru = Incidence rate OR incidence proportion OR prevalence in the unexposed
62
Attributable Proportion:
This calculates the proportion of disease that is attributable to the exposure, also known as attributable risk (or fraction) Can calculate attributable proportion in the exposed or in the population
63
Attributable Prop in Exposed
APe=[(Re – Ru) / Re] APe is the attributable proportion in the exposed Re is the incidence rate, cumulative incidence or prevalence in the exposed Ru is the incidence rate, cumulative incidence or prevalence in the unexposed APt is the attributable proportion in the total population Rt is the incidence rate, cumulative incidence or prevalence in the total population
64
Attributable Prop in Population
APt=(Rt – Ru) / Rt APe is the attributable proportion in the exposed Re is the incidence rate, cumulative incidence or prevalence in the exposed Ru is the incidence rate, cumulative incidence or prevalence in the unexposed APt is the attributable proportion in the total population Rt is the incidence rate, cumulative incidence or prevalence in the total population
65
Number needed to treat
1 / [risk in exposed) – (risk in unexposed) The number needed to be treated or the exposure to be prevented in order to prevent one case of disease
66
Interpretation of Absolute Measures of Association
If difference=0 there is no association between exposure and disease Difference will lie between -100% and 100%, or -1 and 1 when expressed as proportions. E.g. Prevalence difference = 0.08 “ In this study, smokers had 8 additional cases of TB per 100 people compared to non-smokers”

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