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Non med > population health > Flashcards

population health Flashcards

1
Q

what does epidemiology observe and record?

A

outcomes and exposures, and sue statistical techniques to elucidate associations between the two

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2
Q

what are randomised trials?

A

experiments that use intervention to assess effect of exposure and outcome

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3
Q

what are 3 basic study types that are different regarding when data in collected?

A

cross sectional, retrospective, prospective

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4
Q

what is a cross sectional study?

A

Looking at the prevalence of disease in a population to measure the burden of disease

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5
Q

what is a case control study?

A

Retrospective, looks at people with and without a specific disease and explores previous exposures that might have caused the disease

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6
Q

what is a cohort study?

A
  • Usually prospective but can be retrospective
  • Prospective takes a sample of the target population and looks at current level of an exposure that might cause disease and follows up with the patients to see what proportion get or don’t get the disease
  • Retrospective takes a group of individuals with the disease and looks at the proportion that have been exposed to what is thought to be causing the disease
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7
Q

what is the heirarchy of study designs?

A

1) editorials, expert opinion
2) case series, case reports
3) case-control studies
4) cohort studies
5) randomised control trials
6) systematic reviews

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8
Q

what are the stages of a clinical audit?

A

1) Selecting a topic. 2) Agreeing standards of best practice (audit criteria). 3) Collecting data. 4) Analysing data against standards.

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9
Q

what are the principles of the NHS?

A

1) The NHS provides a comprehensive service, available to all
2) Access to NHS services is based on clinical need, not an individual’s ability to pay
3) The NHS aspires to the highest standards of excellence and professionalism
4) The patient will be at the heart of everything the NHS does
5) The NHS works across organisational boundaries
6) The NHS is committed to providing best value for taxpayers’ money
7) The NHS is accountable to the public, communities and patients that it serves

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10
Q

three types of disease prevention?

A

Primary – prevent the disease from occurring
E.g. promoting healthy eating and exercise, immunisation, eliminating environmental risks
Secondary – prevent the disease progressing by detecting and treating the disease early
Screening programs e.g. cervical smear
Tertiary – limiting physical/social consequence of the disease or preventing recurrence of the disease
e.g. stroke rehabilitation

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11
Q

hypothesis testing meaning of H0, H1 and P values?

A

H0 – null hypothesis
-> The aim in statistical analysis is to accept or reject the null hypothesis, the null hypothesis usually meaning there is no difference
H1 – this is your hypothesis, it is true if you reject H0 and false if you accept H0
The P-value is the number where you accept or reject the null hypothesis (normally at a 95% significance level)

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12
Q

how is a confidence interval used?

A
  • If confidence interval spans 1 with RR or 0 in RR reduction then the results are not statistically significant
  • Not all statistically significant results are clinically significant, clinical significance requires it to have enough of an impact to affect clinical practice
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13
Q

what is a confounding factor and how does it effect results of a study?

A
  • A confounding factor is a third variable that influences both the independent and dependent variables
  • Confounding factors impact the results of a study due to being associated with what is being studied, so it appears like what is being studied is causing a disease but in fact it is the confounding factor
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14
Q

what is the iceberg of disease concept?

A

a disease in which, for every visibly affected individual, the population will contain numerous others that are sub-clinically infected, carriers or undiagnosed clinical cases.

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15
Q

equation for incidence

A

incidence rate = number of new cases in given time period/population at risk

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16
Q

equation for prevelance

A

Prevalence = number of cases at that time/total population

given as percentage of total population

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17
Q

What is a randomised controlled trial?

A

Experimental clinical trial in which individuals are allocated to different treatment groups in a randomised fashion

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18
Q

Outline how a randomised controlled trial works (3)

A
  • patients selected based on particular characteristics
  • then randomly assigned to experimental group or control group
  • then followed up over time to compare the effects
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19
Q

How to calculate relative risk from a table

A

(a/a+b) / (c/c+d)

20
Q

Significance of relative risk values

A
  • rr=1 then risk in exposed=risk in not exposed
  • rr>1 then risk in exposed greater than risk in not exposed
  • rr<1 then risk in exposed less than risk in not exposed
21
Q

What are the three types of risk?

A
  • absolute risk
  • relative risk
  • attributable risk
22
Q

What is absolute risk?

A
  • Incidence of disease in any defined population
  • most basic measurement
  • often not very useful index by itself to be meaningful it has to be compared with the risk in an unexposed population
23
Q

What is relative risk?

A
  • ratio of incidence rate in exposed compared to non-exposed
  • measure of the proportionate increase in disease rates
  • makes allowance for frequency of disease in non-exposed group
  • consider relative and absolute together eg. Relative risk of 3 is high but if absolute risk is 1/100,000 then it’s less concerning
24
Q

How do you calculate relative risk?

A

-risk in exposed group/ risk in not exposed group

25
Q

What is absolute risk reduction?

A
  • risk difference

- always subtract the decimals, not the percentages

26
Q

What is absolute risk more useful for?

A

-for communicating the true impact of an intervention, yet often not reported in the research and the news

27
Q

What is the odds ratio?

A
  • the odds than an outcome will occur given a particular exposure, compared to the odds of the outcome occuring in the absence of that exposure
  • no causal direction implied (correlation does not imply causation), a positive OR does not establish that B causes A, or that A causes B
28
Q

How can odds ratios be interpreted?

A
  • OR=1, exposure is not associated w/ the disease
  • OR>1, exposure is positively associated w/ the disease
  • OR<1, exposure is negatively associated w/ the disease
  • the further the OR is from 1, the stronger the association
29
Q

incidence vs prevelance for chronic and acute diseaes

A
  • Acute diseases (e.g. influenza), incidence tends to be large relative to prevalence
  • For chronic diseases (e.g. diabetes), incidence tends to be small relative to prevalence
30
Q

what are the two numerical data types?

A

continuous - data with a full range of fractions, potentially infinite number of possible values along a continuum (e.g. weight, height)

discrete- data without fractions, whole numbers (number of patients)

31
Q

what are the 3 categorical data types?

A
  • binary- 2 options
  • nominal - groups that cannot be arranged in order
  • ordinal - ranked, data consists of labels (non-numeric) or subjective (numeric) that can be arranged in order
32
Q

what is the normal distrubution?

A
  • An arrangement of a data set in which most values cluster in the middle of the range and the rest taper off symmetrically toward either extreme.
  • bell shaped symmetrical curve which is used for continuous data
33
Q

what is standard deviation used for?

A
  • SD used for data which is normally distributed to see how much the data vary around their mean
  • Low SD means that the spread of data is very close to the mean
34
Q

what does standard error mean?

A
  • The standard error is a statistical term that measures the accuracy with which a sample distribution represents a population by using standard deviation.
  • Measures PRECISION of the mean
  • It shows how close the sample mean is to the population mea
35
Q

what does a low SE (standard error) tell you?

A
  • Low SE = variability low, more accurate

- Increasing sample size lowers the SE

36
Q

what is the formula for calculating standard error?

A

by taking the standard deviation and dividing it by the square root of the sample size

37
Q

what is the ‘true value’ ?

A

“True value” is the mean value we would get if we had data for the whole population

38
Q

what is the confidence interval?

A
  • Range of values which the “true” population parameter is found with a given confidence
  • The interval in which the population/true mean is expected to fall in 95% of the time
  • Value which we can be 95% confident that the true value lies
39
Q

what is the difference between standard deviation (SD) and confidence interval (CI)?

A
  • Standard deviation tells the spread around a mean in a sample
  • Confidence interval tells the range in which the true value is likely to be
40
Q

what does correlation coefficent ‘r’ , tell us?

A
  • 1.0 (negative association)/ +1.0 (positive association)

- > If no association, coefficient = 0

41
Q

what is regression analysis?

A

Statistical method where 1 or more variables is predicted on other random variables (best fit curve)

42
Q

what is multi-variant regression analysis?

A

Relationship between several independent variables and a dependent variable

43
Q

what is bradford hill criteria?

A

Temporal relationship - does the cause precede the effect
Plausibility – is the association consistent with other knowledge
Consistency – have similar results been shown in other studies
Strength – what is the strength of the association between the cause and the effect (relative risk)
Dose-response relationship – is increased exposure to the possible cause associated with increased effect
Reversibility - does the removal of a possible cause lead to reduction of disease risk
Study design – is the evidence based on a strong study design
Judging the evidence – how many lines of evidence lead to the conclusion

44
Q

what is a confounding factor?

A

In statistics, a confounder is a variable that influences both the dependent variable and independent variable, causing a spurious association.

45
Q

what is the formula for risk reduction?

A

risk reduction = risk in exposed - risk in unexposed

46
Q

what is number needed to treat (NNT)?

A
  • demonstrates effectiveness of a treatment
  • the number of patients who would have to recieve the intervention in question in order to prevent one adverse event
  • the lower NNT the more effective the treatment

Non med (3 decks)

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