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POPHLTH 111: Module 1-2 > Definitions > Flashcards

Definitions Flashcards

1
Q

A Cross Sectional study

A

measures a disease state in one point in time

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2
Q

Population/group

A

a group of people sharing a common feature – ethnicity, gender, disease

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3
Q

Ecological study

A

rather than studying individuals, it studies whole populations

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4
Q

Purposes of Epidemiology

A

Improve the health of the population by preventing disease.
Identifying differences in frequency – inequity
Determine the causes of the differences
Intervene to reduce difference – prevention or treatment

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5
Q

Disease frequency is also referred to as

A

disease occurrence/ risk/ rate

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6
Q

The definition of health/ disease by epidemiologists can be broad or

A

narrow

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7
Q

Where do epidemiologists start?

A

the living population

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8
Q

categorical data is

A

yes/ no

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9
Q

numerical data is

A

numbers of events

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10
Q

numerical data can be changed to

A

categorical data

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11
Q

P in PECOT

A

population is the top of the triangle, participants is the bottom = Participant population

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12
Q

Prevalence =>

A

is measuring the number of people in a disease state at one point in time

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13
Q

Incidence =>

A

is measuring the occurrences of disease over a specific time frame

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14
Q

Is prevalence or incidence given without a unit of time?

A

prevalence except the time it was measured it mentioned

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15
Q

When is prevalence expressed as a percentage?

A

when numerator is categorical

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16
Q

When is prevalence expressed as a mean?

A

when numerator is numerical

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17
Q

E =

A

exposure group

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18
Q

C =

A

comparison group

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19
Q

O=

A

outcomes

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20
Q

T=

A

time

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21
Q

examples of longitudinal study

A

cohort, RCT

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22
Q

cohort study aka

A

observational follow up study

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23
Q

incidence

A

measures occurrence of disease over time

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24
Q

when is it best to measure prevalence

A

when you want to find out IF something is happening or the thing you’re studying doesn’t have an easily identifiable starting point.

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25
Q

what is prevalence

A

the occurrence of disease in one point in time so T= 1

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26
Q

What type of study can you measure both prevalence and incidence

A

longitudinal

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27
Q

what type of study can you not measure incidence

A

cross sectional

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28
Q

Relative risk is

A

EGO/CGO

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29
Q

Risk difference is

A

EGO- CGO

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30
Q

which method of risk comparison has no context

A

relative risk

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31
Q

which risk comparison has units

A

RD

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32
Q

RD is sometimes called

A

absolute risk difference

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33
Q

RR is a ratio so it has no

A

units

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34
Q

Relative risk reduction is calculated when RR is less than

A

1

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35
Q

If RR is 0.67, RRR is

A

33%

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36
Q

Beware when u see a large RR but a

A

small RD

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37
Q

the true benefit of treatment can only be ascertained when you measure the

A

risk when you don’t treat

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38
Q

only good thing about RCT is that it

A

reduces confounding by making the same amount of confounding factors in both groups.

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39
Q

What is the main goal of epidemiology (IIDI) ?

A

Improve the health of populations by preventing disease
Identify differences in frequency- inequities
Determine the causes of differences
Intervene to reduce difference

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40
Q

What is it epidemiologists job to measure ?

A

the health and disease frequency of populations

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41
Q

Where can the numerator only come from

A

the denominator

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42
Q

What is age standardisation?

A

Age standardisation is converting the age structures of different populations being studied to fit a standard model.

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43
Q

Why age standardise?

A

It reduces confounding by age by comparing CG and EG groups of the same age and predicting age specific death rates

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44
Q

How do you age standardise?

A

First allocate people by age. find the age specific death rate in different age divisions of both populations being studied. Then convert the age structures to a standard age structure and predict the number of dead people/ population/ time.

45
Q

crude death rate

A

total number of deaths / total population (without age standardising)

46
Q

How to do overall age standardisation?

A

all expected age standardised death rates/ total standard population

47
Q

what is the prevalence of disease in a population affected by?

A

the rate of incidence and the rate of people dying/ being cured.

48
Q

if the numerator in prevalence is numerical it is expressed as a

A

mean

49
Q

Study type when you observe a group for a period of time

A

cohort study/ observational follow up

50
Q

what are EGO and CGO

A

measures of occurrence

51
Q

incidence or prevalence involving almost always counting categorical disease events

A

incidence

52
Q

incidence or prevalence involving measuring numerical disease states as well as categorical disease events

A

prevalence

53
Q

what direction is the arrow for cohort study

A

down

54
Q

the numerator of prevalence could be measured when?

A

right now and if it has occurred in a prior period

55
Q

period prevalence is signified by arrow in what direction

A

backwards

56
Q

What is the square grid representing

A

different disease outcomes

57
Q

horizontal arrow represents

A

prevalence

58
Q

when comparing disease rates, it is important to measure both CG and EG because

A

there may be a normal level of disease in both groups already before the exposure is affecting it

59
Q

Relative risk is essentially a

A

ratio of occurences

60
Q

Difference between occurrences is called

A

risk difference

61
Q

risk difference is also called

A

absolute risk difference

62
Q

base all decisions on

A

risk difference

63
Q

If EGO=CGO relative risk is

A

1, meaning no effect

64
Q

When relative risk is less than 1 you can calculate

A

Relative risk reduction

65
Q

When relative risk is more than 1 you can calculate

A

Relative risk increase

66
Q

all measures of risk or occurrence (incidence/prevalence) are

A

absolute

67
Q

‘no effect’ value for risk difference is…. This is when CGO=EGO

A

0

68
Q

The RD is an absolute risk reduction if the risk is

A

lower in the exposure group

69
Q

The RD is an absolute risk increase if the risk is

A

higher in the exposure group

70
Q

If the outcomes are calculated as a mean then the difference between two means is called

A

mean difference

71
Q

Key design features of RCT

A

participants are allocated randomly to CG and EG group

72
Q

Reasons you can’t do an RCT

A

Unethical due to randomising people to something that could cause them harm or randomising them to something that is known to save lives with the others not getting it.

73
Q

When is it ethical to do an RCT

A

When you’re comparing the effectiveness of interventions that is already known not to cause harm. When you don’t know if it increases the risk of death but you know it decreases the risk of disease.

74
Q

What are the four main causes of non random error in epidemiological studies?

A

poor study design, processes, measurement, and analyses

75
Q

Non random errors are often called

A

systemic error / bias

76
Q

Tell me what RAMBOMAN is and what is stands for

A

RAMBOMAN is used to identify where non random errors can occur. It stands for: Recruitment, Allocation, Maintenance, Blind or Objective Measurement and Analyses.

77
Q

What does study validity depend on

A

the amount of NR and R error

78
Q

Recruitment error is sometimes called…

A

external validity error

79
Q

In what order from top to bottom is the P triangle layered

A

Setting, Eligibles, Participants

80
Q

Two types of recruitment error

A

non response bias and non representative error

81
Q

non representative error is what?

A

non representative error is a recruitment error where the participants recruited are non representative of the eligibles.

82
Q

Selection bias makes the most impact on results when the aim of the study is more observational prevalence rather than testing interventions because

A

they want the results to be able to be applied to the populations or group they’re studying

83
Q

define non response bias - when does it happen and what is the risks of it

A

Non response error could happen when only a small part of the eligible population ‘responds’ to participate in the study. If there are differences between the responders and non responders, this could mean that the results may not be representative of the eligible population.

84
Q

Recruitment error can be combated by having: (3 levels)

A

the setting well described, participants representative of the eligible population and risk profile reported?

85
Q

Main question of Recruitment error:

A

Can these results be applied to a particular group/ population

86
Q

Main question of Allocation:

A

Were the study participants correctly and successfully allocated to the Exposure Group (EG) and the Comparison Group (CG)?

87
Q

What are the two ways people can be allocated into EG and CG groups?

A

Randomly or by measurement

88
Q

how participants are allocated to EG and CG has a big effect on the presence of ….- what is this?

A

confounders- they are other factors that, in addition to the exposure, can effect outcomes, therefore if there is an association between them

89
Q

To be a confounder what is the conditions of this

A

they have to have a relationship, but also independently cause deaths so you can’t tell how many deaths were caused by the exposure.

90
Q

In what study are participants randomly allocated to EG and CG groups

A

Random Controlled Trials

91
Q

In what study are participants allocated to EG and CG by measurement

A

Observational study

92
Q

What are allocation measurement errors

A

This is when the measurement of the exposure isn’t accurate so people end up being allocated in the wrong EG or CG group

93
Q

How do you reduce allocation measurement errors?

A

well designed questionnaires, relying on biological measures rather than the memory/honesty of the person

94
Q

What is baseline comparison and when should it be done?

A

baseline comparison is checking for differences in the EG and CG groups. This is done for especially small RCT studies as well as observational studies in case there is still differences in each group due to chance

95
Q

How do you make sure allocation is done properly in large RCTS. Describe?

A

Make sure there is ‘concealment of allocation’. This is stopping doctors tampering with the random allocation of interventions process and giving interventions to patients they think is suitable.

96
Q

Why is it important to collect information about other differences in the EG and CG groups?

A

this can help to adjust for them

97
Q

The ‘M’ question is:

A

Were most of the participants maintained throughout the study in the groups (EG & CG) to which they were initially allocated?

98
Q

When does maintenance error occur

A

when participants change their exposure status - ie by not maintaining their exposure status/ being exposed to other exposures that could skew the results
or
When participants are lost to follow up

99
Q

BOM stands for … and is about

A

Blind or Objective Measurement is about the accuracy of the measurements of disease outcomes

100
Q

The BOM question is

A

were the people doing the measurements unaware of the participants exposure status (blind) and were the measurements made objectively?

101
Q

Making patients and the doctors blind (double blind) helps to reduce what error and why

A

maintenance error because people don’t know that they’re taking something useless

102
Q

If a study isn’t blind what might happen

A

participants might have a bias on their outcome if their trying to test the effectiveness of something

103
Q

Objective measurements help to reduce measurement errors by

A

making sure that patients responses are aligned to a single standard

104
Q

give an example of an objective measure and a subjective measure

A

death, the amount of glucose in blood vs measures of pain or how you feel

105
Q

define AN- analyses

A

Analyses is where known confounders were adjusted for. This can be stratified analysis

106
Q

describe stratified analysis

A

this is like conducting sub studies by splitting the triangle into different circles and comparing EG CG groups from the same strata and then standardising the structures

107
Q

age standardisation is a form of

A

Stratified analysis

108
Q

why does comparing stratas help to reduce confounding

A

people with the same confounders will be compared to each other

109
Q

There will always be confounding that will cause bias to happen but we need to think which

A

direction the bias will lie

POPHLTH 111: Module 1-2 (4 decks)

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