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MD1 > Population Health > Flashcards

Population Health Flashcards

1
Q

What is Public Health?

A

Science and art of preventing disease and improving health through the organised efforts of society

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2
Q

What is Population Health

A

The health outcomes of a group of individuals, including the distributions of outcomes within the group

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3
Q

What are the three types of prevention?

A

Primary Prevention- Reduce likelihood of developing disease
Secondary Prevention- Prevents or minimises progress of disease
Tertiary Prevention- Reduces Progression of damage already done

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4
Q

What is Epidemiology?

A

Study of Distribution and Determinants of Disease

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5
Q

What is Incidence?

A

Number of new cases of a disease within a specified time period. Expressed as a rate

Longitudinal studies needed

Poor Survival will have a higher incidence than prevalence

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6
Q

What is Prevalence?

A

Number of existent cases of disease at a particular point of time.

Expressed as a proportion

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7
Q

What is the prevalence if Incidence and Duration are constant over time?

A

P=ID

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8
Q

What is Risk?

A

Probability of disease occurring in a disease free population during a specified time period

Risk= Number new cases/ Population at risk

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9
Q

What is Rate?

A

Probability of disease occurring in a disease free population during the sum of individual follow up periods

Rate = New cases in a defined period total person time / Total person-time of follow up

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10
Q

What is absolute risk/rate

A

isolated measure of risk/rate (specific)

Eg. 5 strokes/10,000 men per year

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11
Q

Formula for Relative Risk?

A

RR= Re/Ru (exposed/unexposed)

Indicates relative magnitude of exposure

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12
Q

Formula for Attributable Risk?

A

AR= Re-Ru

Indicates the absolute of change in risk/rate of outcome

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13
Q

What are the features of a cross sectional study?

A

Sample of population selected at one point in time

Each subject only contributes data once (no follow up)

Mostly descriptive outputs

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14
Q

What are the advantages and disadvantages of cross sectional studies?

A

Relatively cheap and easy

need for representative sample

explore associations among variables, but no explicit data on temporal relationship

weak evidence of causality

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15
Q

What does the attributable risk percentage represent?

A

percentage of incident disease among exposed people that was due to the exposure

AR/Re x100

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16
Q

How is data collected in cross sectional studies?

A

Questionnaires, examinations, investigations. Prevalence mainly looked at

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17
Q

What is a case control study?

A

Comparison of previous exposure status between cases and controls. Looks at the effect of an exposure on an outcome of interst.

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18
Q

What is the purpose of matching during a case control study?

A

Reduce confound variables having a bias.

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19
Q

What are the advantages and disadvantages of case control studies?

A

gives explicit knowledge about temporal relationship between exposure and outcome (exposure came before outcome)

Useful for studying rare outcomes.

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20
Q

What are cohort studies? Does it use OR or RR?

A

Longitudinal studies done with follow up of subjects to collect incidence data. Compares outcomes between those exposed and not exposed to a risk factor and relative risks are derived

21
Q

What are the advantages and disadvantages of cohort studies?

A

Advantages: explicit and detailed knowledge about temporal relationship b/w exposure and outcome.

  • Can include multiple exposures and outcomes
  • cohorts can be established as part of routine clinical care

Disadvantages

  • Difficult for rare outcomes
  • More difficult and expensive
22
Q

Why is retrospective cohort study still considered a longitudinal study?

A

Study is begun at a time where a cohort has already been established and data is available about an exposure in the past

23
Q

What is Bias?

A

An Unintentional error due to a systematic difference between or among groups which leads to under or over-estimaion of true results.

24
Q

What are the two main types of bias?

A

Selection and Information (measurement)

25
Q

What is selection bias?

A

systematic difference in characteristics of people selected for study and those not selected. eg. selecting only people that can speak english.

Systematic diff. within groups also lead to selection bias
-eg. recruiting cases within hospital but controls outside.

26
Q

How is selection bias minimised?

A

careful recruitment (rep. sample of population, and cases and controls from same source)

Maximise response

Minimise subjects lost to follow-up

27
Q

What is information bias?

A

Systematic difference in how information is collected. Arises when variability in methods of collecting data.

28
Q

What is recall bias?

A

Type of information bias where cases are more likely to recall presence of exposure due to already established prejudice about association b/w the risk factor and the outcome.

29
Q

How is information bias minimised?

A

Uniform collection methods of information between or among groups being compared.

30
Q

What is confounding variables? What are two examples?

A

Influences relationship between exporsure and outcome. A third variable that indepenently affects the outcome, and is related to the exposure. Age and sex are examples.

31
Q

How is confounding minmised?

A

Design and execution stages: match by confounder or restriction (eg only select males)

Analysis: Stratification and multivariate analyses

32
Q

How does randomisation help to deal with confounding?

A

Makes treatment groups identical in all aspects other than the intervention in order to reduce the effect of confounders.

33
Q

What is intention to treat analysis and what is it used for?

A

Helps deal with selection bias. People lost to follow up (eg cross over: people started on place start taking drug, or people assigned to drug stop taking it) is a source of selection bias if it is significant. Intention to treat assumes subjects remained in their randomised group, regardless of what the did in real life. Intetnion to treat always under estimates any treatment effect (ie conservative). Cross over introduces overlap in treatment between groups, but ITT ignores this effect, a positive ITT therefore give more confidence.

34
Q

What is Hazard?

A

Continuously updated, instantaneous rate which is measured in longitudinal studies with close follow up.

HR is Similar to OR and RR, except it does not reflect a time unit of the study.

35
Q

What is the survival analysis?

A

During follow, explicitly captures of outcome and their time of occurrence. Survival analysis measure ‘time to event’

36
Q

What is a Hazard ratio of 0.5?

A

at any given point in time within the period of followup, the probability of outcome in the intervention group is half of that of the control group.

37
Q

What is the number needed to treat and how is it calculated?

A

NNT= number of people needed to undergo the intervention in order to prevent outcome in one. It is a marker of efficiency of the intervention.

NNT= 1/(absolute risk or rate reduction)

38
Q

How do internal and external validity differ?

A

Internal refers to how well a trial deals with limitations such as bias confounding.

External validity refers to the applicatbility of the trial results.

39
Q

What does PICOT stand for?

A 
P= population
I= Intervention
C= Comparator/control
O= Outcome
T= Timing
40
Q

What is internal validity?

A

Extent to which the results are valid (accurate, robust etc.) Dependant on study design, data collection and analyses.

41
Q

What is Stratified Randomisation?

A

Randomisation by levels of key confounders= eg dividing groups into male and female then randomising from there.

42
Q

What is the p-value?

A

Probability that the observed result arose from chance.

43
Q

What does the width of the 95% confidence interval measure?

A

Precision of result.

44
Q

How is external validity assessed?

A

Determining the degree of concordance between RCT and the clinical setting in terms of PICOT

45
Q

How do you calculate Odds Ratio

A

(odds of outcome among exposed)/(Odds of outcome among unexposed)

OR= AD/BC

46
Q

What is the difference between phase 1 and 2 in clinical trials?

A

Phase 2 targets a larger, unhealthy population with placebo (safety and efficacy) whereas phase 1 is just to a small healthy group (safety and side effects).

Test whether it works in phase 2.

47
Q

What is clinical trial phase three?

A

Drug given to large group of people, measure effectiveness, monitor side effects

Compare to commonly used treatments

Collect information that allows the drug to be used safely

(Can sometimes be released at 3)

48
Q

What is Phase IV for clinical trials?

A

After drug has been marketed. Long term effectiveness and any side effects with long term use. Can be an observation study (ie. seeing performance in other countries before trialling in own)

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