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Module 1- Epidemology Flashcards

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1
Q

What is Epidemiology?

A

Epidemiology is the study of how much disease occurs in groups and the of the factors that determine differences in disease occurrence between two groups.

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2
Q

What is N/D?

A

n= people from the population with the dis-ease. d= population

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3
Q

Why is Epidemiology studies carried out?

A

determine causes of dis-ease and establish preventative measures and treatments and inequity

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4
Q

Why is Age standardisation carried out?

A

To eliminate confounding caused by the different age distributions(one population may have more older people and older people tend to die faster.

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5
Q

What makes epidemiology studies different from other science studies

A

The starting point

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6
Q

Why is time important?

A

Every person has 1 lifetime with the death rate 100%

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7
Q

What makes crude rates different from standardised rates?

A

Crude rates take into account whole population while standardised rates take into account age

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8
Q

What is a population?

A

A group of people who share a common feature

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9
Q

What is GATE and what is PECOT

A

Gate is the frame that all epidemiological studies can fit into while PECOT represents all the key components.

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10
Q

Can all Epidemiological studies be hanged on the gate frame?

A

Yes

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11
Q

How many EG groups and CG can compose in one study

A

There can be several EG but only ONE CG

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12
Q

What is EGO?

A

Is a measure of disease occurrence. EGO= a/EG

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13
Q

What is CGO?

A

Measure of disease occurrence. CGO=b/CG

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14
Q

Why are CGO and EGO important?

A

The entire purpose of Epi studies is to calculate how much dis-ease occurs in a particular group and why they are different

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15
Q

What is a cohort study?

A

observational study, participates divided into two groups depending their choices. No intervention

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16
Q

Why is cohort studies used rather than RCT?

A

Unethical cases and unpractical

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17
Q

What are the advantages of Cohort studies?

A

1) No recall bias 2) One exposure, multiple outcomes can be measured 3)many exposures, multiple outcomes can be measured

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18
Q

What the weaknesses of Cohort studies?

A

1) Confounding 2) Maintenance error (misclassification) 3) rare diseases not useful 4) Selection bias(findings implications + lost of follow-up) 5) allocation error(especially in diet measurements)

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19
Q

Common design features of cohort study

A

Observational, followered overtime

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20
Q

What is a RCT study

A

participants are randomly allocated to either the Exposure group or the comparison group

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21
Q

What are the advantages of RCT?

A

Less or no confounding

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22
Q

What are the disadvantages of RCT?

A

1) Maintenance error(people stop intervention if they know it’s bad) 2) Recruitment error(highly motivated volunteers) 3) Expensive(cost per participate) = small studies

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23
Q

What makes a RCT study different to a cohort study?

A

Allocation process- RCT allocation is random while in cohort you observe what they have been doing

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24
Q

Why are RCT studies not done always

A

1) Unethical 2)impractical

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25
What impact does small RCT studies have on the CI and R.E
Wide CI= High random error
26
How can random error be reduced?
Meta-analyse- Narrow CI=Low random error
27
What is a cross-sectional study?
Allocation and outcome measurements are done at the same time
28
What are the advantages of cross-sectional studies?
1) no maintenance error
29
What are the disadvantages of cross-sectional studies?
1) recruitment error 2) Confounding 3) reverse causality 4) measurement error
30
What is a meta-analysis?
The results of small studies are combined into one
31
How is allocation bias avoided
Randomisation process-as it makes sure that both groups are as similar as possible
32
confounding possible when participants are randomly assigned to EG or CG?
Yes- when there is tampering with the randomisation process by the investigator and in small study designs(by chance)
33
What are the main 2 methods for adjustment
Age standardisation and strata
34
What are the requirements for a factor to be a confounder
Another factor apart from the exposure is presented which is associated with the outcome
35
Why is confounding bad?
We cannot make a causation conclusion- can't determine whether the exposure caused the difference in EGO or CGO or the confounding factor or both
36
What is recruitment bias?
Participates recruited from the eligible population are not a representative of the eligible population(the responders are different from the non-responders)
37
What is the difference between subjective and objective?
Subjective measurement is influenced by personal interpretation(self-reported) while objective is based on computers and objects that are not influenced by personal interpretation
38
Why is blinding important
Participants and investigators are not able to temper with the allocation process and reduces maintenance bias
39
What are the four main factors that can cause maintenance error?
Contamination, compliance, co-intervention, loss-to-follow-up
40
What is co-intervention?
Intervention by the participator or the inviestator which introduces a confounding factor
41
What is risk ratio(RR)
RR measures the likelihood of a disease occurring in one group compared to another
42
What is risk difference(RD)
The excess risk of dis-ease in the exposure group compared with those in the comparison group
43
How to calculate a RR?
EGO/CGO=
44
How to calculate a RD?
EGO-CGO=
45
Does RR or RD give more information
RD as it contains units, hence context
46
What is RRI? What's the calculation?
1.00- RR=>1 The exposure increases the risk of the outcome
47
What is RRR? What's the calculation?
1.00- RR=<1 The exposure decreases the risk of the outcome
48
What indicates that there is no difference in the EG and CG group?
RR=1 RD=0
49
Does RR or RD have units?
RR has no units as it cancels out in division while RD has units
50
What is Random Error?
Error that occurs by chance
51
What are the four main factors that cause random error?
Random sampling Error, Random measurement error, Randomness inherent in biological phenomena, random allocation error
52
What's the relationship between the confidence interval and random error
Confidence interval measures the amount of random error present in the estimates of EGO, CGO, RR and RD in the whole pop
53
What is regression to the line?
(first trail) extreme values will move closer to the mean on the second trail. Hence, the change in the results is likely to be by chance weather than the intervention
54
What is the effect of a large and small study size on random error?
Small study size= More random error Large study Size= less random error
55
Write a interpretation of a 95% CI?
In 100 identical studies using samples from the same population, 95/100 of the 95% CIs will include the true value.
56
Is the 99% CI better or worse than the 95% CI? if so why?
The 95% CI is better than the 99% CI bc it has less random error
57
What do the different widths of the CI indicate about random error?
Wide CI= poor precision and increase random error Narrow CI= Good precision and decrease random error
58
When can you state that the results are statistically significant?
No overlap between the CI of EGO and CGO, The CI intervals do not cross the no effect line and the width of the CI is a moderate size(with less area for random error)
59
What is the CI called when it touches the no effect line?
Borderline statistically significant
60
How is age specific death rates calculated?
Number of deaths in the age group/ population in that age group
61
How is the expected number of deaths calculated?
Age Specific death rates/1000 x standard population
62
How is Crude Death rate calculated?
Total number of deaths in a group/ Total population of that group
63
Can ecological studies be either cross-sectional or longitudinal?
Yes
64
If there is high amount of random error in the study, is it possible to tell whether there is a difference in the EGO or CGO?
No
65
Which type of error would you be least concerned about in an cohort study?
Random error
66
Is screening for breast cancer an example of primary prevention ?
No
67
What is Te Mana Whakahere?
Autonomy, capacity for self-governanc
68
What are the disadvantage of cross-sectional study?
1- Only correlations can be made- no causal links 2- rare outcomes 3- confounding 4- Reverse causality
69
What are the advantages of a cross sectional study?
1- Cheap 2- Repetitive 3- no maintenance error
70
What are the three main characteristics of a cross sectional study?
1- Allocation 2- Prevelence 3- non-experimental
71
What is prevalence
Measures the amount of disease present at one point in time
72
When measure prevalence
Transition from a non dis-ease state to a dis-ease sate is not easily observable
73
What does p~ IxD mean
Prevalence depends on incidence and the number of deaths and cure rates
74
How can increase incidence result in low prevalence ?
Increase cure rate and death rate
75
The difference between two measures of prevalence at two different points in time is measure of
Incidence
76
What impact would a effective treatment, hence a short duration of disease have on prevalence
Increases cure rate which decreases prevalence
77
Why is incidence a better measure than prevalence
Incidence is a clear measure as it is only impacted by the number of diseases and also includes time, hence context
78
What is period prevalence
Mixture of incidence and prevalence. We ask about the past disease onset’s that have occurred over a period of time at one point in time
79
What is an epidemic
An outbreak- like coronvirsus- | Disease that’s widespread in a short time period
80
Dies prevalence involve time in calculations
No
81
Is prevalence or incidence a easier measure
Prevalence as we can just stop the time and measure with no time interval
82
What study can measure period prevalence
Cross-sectional

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