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poplhlth 111 > Rod Jackson > Flashcards

Rod Jackson Flashcards

1
Q

What is the study if epidemiology

A

Frequency or occurence of disease in populations

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2
Q

Why do epidemiologists measure the frequency of health + disease in different populatuions

A

Find out the causes of poor health and how to improve it

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3
Q

What is the goal of epidemiology

A

Measure the frequency of health and disease in different populations to find out the causes of poor health and how to improve it.

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4
Q

What is the numerator

A

Cases of disease

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5
Q

What is the denominator

A

The population

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6
Q

Why do we measure the frequency of disease in different populations?

A

If frq of disease is different between two populations (or in same population at different times, can help identify the causes

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7
Q

What is age standardisation

A

Adjust or standardise the age structures of each population so they can be meaningfully compared, and take into account the differences between the denominators.

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8
Q

What is the equation of epidemiology

A

Epidemiology = N/D

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9
Q

What are EGO and CGO

A

The occurence of risk of dis-ease in populations

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10
Q

Equation for EGO and CGO

A

EGO = a/EG
CGO = b/CG

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11
Q

What are the design features of a cohort study

A
  1. start with a group pf participants
  2. allocate them into at least two groups by measuring things
  3. follow over time
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12
Q

What is incidence

A

If the number of dis-ease events that occur are counted forward from a starting point, over a period of time

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13
Q

What is prevalence

A

If the number of people with dis-ease are counted at one point in time, then T = 1

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14
Q

Does incidence or prevalence have a numerical outcome

A

Incidence

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15
Q

What are the two ways to define prevalence

A
  1. Categorical measure (categories): Prevalence of fast heart rates/people in population
  2. Numeral measure (numbers): average heart race = sum of every persons heart rate/people in population
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16
Q

What study allows incidence and prevalence to be measured at the same time

A

Cross-sectional

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17
Q

What are the different ways to measure numerator when measuring prevalence

A

If its difficult to measure when a disease event occurs or it occurs frequently, often measure if (yes/no) it has occured during a prior period but not the total occurences.

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18
Q

What are the strengths of incidence

A
  • Determined by only dis-ease risk in population (clean measures)
  • includes events (N) population (D) and time (T)
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19
Q

What is the weakness of using incidence

A

Difficult to observe events over time

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20
Q

What is the strength of prevalence

A

Relatively easy to measure as you ‘stop time’ and count

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21
Q

What are the weaknesses of prevalence

A
  • Determined only by incidence, cure and death rate (dirty measure)
  • includes only events (N) and population (D) - less info
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22
Q

What are RCT’s

A

Like cohort studies, but participants are randomly allocated to EG and CG.

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23
Q

What is the best study to answer effects of treatments

A

RCTs but only if its ethical and practical

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24
Q

How to calculate risk difference

A

EGO - CGO

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25
Q

What happens if RD = CGO

A

Risk difference = 0

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26
Q

How to calculate risk ratio

A

EGO/CGO

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27
Q

What happens if EGO = CGO

A

Risk difference = 0

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28
Q

What happnes if RR < 1

A

This is relative risk reduction (RRR)

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29
Q

How to calculate relative risk reduction

A

Calculated by subtracting relative risk from 1.0 and multipluing by 100

30
Q

What happens if RR >1

A

This is relative risk increase

31
Q

How is relative risk calcualated

A

By subtracting from 1.0 from RR and multiplying by 100

32
Q

What are the differences between RR and RD

A
  • RD has units but RR does not
  • RD also called absolute risk differene, RR also called relative risk
33
Q

Strength and weakness of RR and RD

A
  • Most people understand RR better than RD but relative measures of risks and benefits are deceptive and provide less information than absolute risk differences
  • all decisions should be based on RD
34
Q

Where does error occur

A

Wrong people are recruited into a study (GATE) or the right people are put in the wrong GATE frame category.

35
Q

What are non-random error due to

A
  • poor study design
  • poor study process
  • poor study measurements
36
Q

What is study validity

A

Study with only a small amount of random or non-random eorror considered valid study

37
Q

Randomised control studies

A
  • Cohort study except how to get into CG and EG
  • allocated randomly
  • called experimental
  • always longitudinal
38
Q

Whats the main problem with allocation

A

Confounding: when exposure mixed with another factor that is also associated with the outcome, has ‘confounding’ error. A potential problem in all observational studies

39
Q

How to deal with confoundment

A

Divide ‘stratify’ the study into sub-studies so participants with the confounders are all in one sub-stratified analysis

40
Q

What does adjustment do when dealing with confoundment

A

Adjustment involves dividing the participants into strata and comparing heavy and moderate drinking in each strata. This reduces the effect of the confounders.

41
Q

Where does non random error occur (4)

A
  • Recruitment errors
  • allocation errors cause confounding
  • maintenance errors
  • (BO) measurement of exposures and outcome errors
42
Q

The differences of allocations in ecological studies and individual studies

A

Ecological: allocated populations to EG and CG.
Individual: allocate individuals to EG and CG

43
Q

Is confounding common in ecological studies, and explain why

A

Yes, because there are a lot of differences between countries and it is difficult to measure these differenes and adjust for them

44
Q

Does an ecological rct increase or reduce chance of confounding

A

Reduce

45
Q

What does it mean by measuring the exact ‘truth’

A

The study of participants are moving targets, so….

Identical measurements of exposures and outcomes in the same or similar people can change from moment to moment

46
Q

What is random measurement error

A

Identical measurements of exposures and outcomes in the same or similar people can change from moment to moment

47
Q

Major causes of random errors

A
  • only using a sample of all the people in population
  • even identically designed and implemented studies include participants with identical characteristics, so could still produce different studies
  • these differences are random errors
48
Q

What does a smaller sample mean

A

Smaller the sample, the greater the chance the sample will be different from the whole population

49
Q

What is the 95% interval

A

A measure of the amount of random error in our estimates of EGO and CGO, RR and RD in the whole population, when you have only done one study

50
Q

What is the 95% interval

A

A measure of the amount of random error in our estimates of EGO and CGO, RR and RD in the whole population, when you have only done one study

51
Q

95% confidence interval defintion

A

There is about a 95% chance that the true value in a population lies within the 95% confidence interval

In 100 studies using samples from the same population, 95/100 of the 95% CI;s will include the true value for the population

52
Q

Confidence interval describes…

A

the range of results likely to include the true result in the population

53
Q

What study design measures incidence and prevalence at the same time

A

Cross-sectional

54
Q

What is the most useful study application of an ecological study

A

Investigating international trends and causes of dis-ease incidence and prevalence

55
Q

True or false, an ecological study can be either an RCT, CS or a CSS

A

True

56
Q

What is the most useful application of a cohort study

A

Investigating the caues of dis-ease incidence

57
Q

What is the most useful application of a cross-sectional study

A

Measuring the prevalence of disease in different groups and population

58
Q

Main strength of an RCT

A

Randomisation minimises confounding

59
Q

Main strength of a cohort study

A
  • Few ethical issues
  • Cheaper than RCT’s
  • Measured before outcome so avoid recall bias with clear time sequence between exposure and dis-ease outcomes
  • Participants more likely a represensative of general populations
60
Q

Main strength of a cross-sectional study

A
  • Cheaper and completed quickly than RCT’s or cohort studies
  • Best desing for assessing prevalence of disease in a population
  • No maintenance error as no follow-up
61
Q

Main strengths of ecological studies

A
  • Usually cheaper and quicker than all other studies because uses already collected data
  • Random error low
62
Q

When is it useful to conduct an ecological study

A
  • When the majority of populations are exposed but others are not.
  • Efficient for rare outcomes
63
Q

Main weaknesses of a RCT

A
  • Ethical limitations
  • Logistically difficult: follow up difficult and costly
  • Usually small as large studies expensive
  • Participants often not represensative of general populations
  • Maintenace error common
64
Q

Main weaknesses of a cohort study

A
  • Confounding common
  • Maintenance error common because exposure not controlled by investigators
65
Q

Main weaknesses of a cross-sectional study

A
  • Uncertain time sequence, limits interpretation of cause and effect
  • Confounding common
66
Q

Main weaknesses of an ecological study

A
  • Confouding common
  • Maintenance error common
67
Q

Difference between the three study types

A

RCT randomised randomly, while the other two allocated by measurement.
RCT and Cohort both have vertical time arrow going down, cross sectional has a horizontal time arrow going right to left

68
Q

A similarity individual participant studies

A

Every person in P is identified and individually allocated to EG or CG

69
Q

What studies meausure incidence, prevalence, or both

A
  • RCT’s and cohort studies measure both icnidene and prevalence
  • Cross sectional only measures prevalence
70
Q

Which study types combine multiple stduies in a meta-analysis

A

RCT’s and cohort (only when sample size is too small)

71
Q

Which study types combine multiple stduies in a meta-analysis

A

RCT’s and cohort (only when sample size is too small)

72
Q

Why are cross-sectional studies never combined using systematic reviews and meta-analyses

A
  • Cross-sectional: prevalence studies are not usually combined because it does not make sense to estimate aerage prevalence
  • Ecological: not combined because generally very large with low random error

poplhlth 111 (4 decks)

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