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SPINE > Stroke Epidemiology DNF > Flashcards

Stroke Epidemiology DNF Flashcards

1
Q

Define stroke

A

Clinical syndrome of focal or general neurological deficit of vascular cause that persists beyond 24hrs or is interrupted by death within 24hrs.

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2
Q

Define TIA

A

A transient (less than 24 hours) neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without evidence of acute infarction.

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3
Q

What are the different types of stroke?

A

Ischaemic stroke - blockage off blood supply to the brain.
Haemorrhagic stroke - bleeding in or around the brain
TIA - symptoms only last for less than 24hrs, temporary blockage.

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4
Q

What are the different types of ischaemic stroke?

A

Large artery atherosclerosis
Cardioembolism
Small vessel occlusion
Stroke of other (un)determined aetiology.

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5
Q

What are the different types of haemorrhagic stroke?

A

Intracerebral haemorrhage
Subarachnoid haemorrhage

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6
Q

What is the global burden of stroke?

A

1 in 4 people over 25yrs will have a stroke in their lifetime.
62% in under 70s.
53% of all strokes are in women
High levels of stroke related death and disability
£26billlion societal cost annually, including £8.6 for the NHS and social care - UK

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7
Q

What health inequalities exist in stroke nationality?

A

Higher prevalence in controal and NE and North Cumbria - both double the prevalence in London.
Higher ageing population, smoking, alcohol, more deprivation.

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8
Q

How does deprivation levels affect the prevalence of stroke?

A

More deprived - higher rates of ischemic and intracerebral haemorrhage - more drastic effect for ischemic.

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9
Q

What are the most common long term impacts of stroke?

A

77% - upper limb weakness
72% - lower limb weaknesss
60% visual impairement
54% facial weaknesss
50% - speech impairment, reduced bladder control
Others - impaired swallowing, aphasia, sensory loss, depression, impaired bowel control.

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10
Q

What are some unmodifiable risk factors for stroke?

A

Previous stroke or TIA
Age
Family history
Ethnicity
Gender
Pregnancy

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11
Q

What are some modifiable risk factors for stroke?

A

Hypertension
SMoking
Diabetes
Diet
Physical inactivity
Obesity
High cholesterol
Alcohol
Heart disease.

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12
Q

Are strokes prevantable?

A

WHO - 90% could be prevented - reducing HTN, diet, smoking and exercise
Would reduced cardiovascular disease, cancer, diabetes and other sign death and suffering.

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13
Q

How has the prevalence of stroke changed over time?

A

Occurring at an earlier age- now over a third between 40-69yrs, the average dropped by 1/2 years.
Males - median age of stroke in younger than women.

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14
Q

What is the public health campaign to improve stroke outcomes?**

A

FAST
Face - unilater drooping
Arms - weakness
Speech - slurred
Time - faster admission to hospital, able to receive treatment

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15
Q

What population-wide strategies can be used to prevent stroke?

A

Smoking ban - reduce tobacco, salt, sugar and alcohol consumption
Affordable healthy food, PA and actvity facilities
Reducing deprivation by improving socio-economic conditions.
Regular stroke awareness and risk factors campaign.
Encouraging healthy lifestyle.

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16
Q

What can be done on a community level to reduce the risk of a stroke?

A

Community park runs
Community health centres - free blood pressure/weight checks
Community green space and exercise classes.

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17
Q

What factors can be done at the individual level to reduce stroke burden?

A

Screening for vascular risk factors.
Rapid CVD identification and management
Management of co-morbidities.

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18
Q

Why is it important to understand disease frequency?

A

Understand the size of the problem
Spotting outbreaks of a disease
Assess risk and management of condition
Aids planning of resources - over time, areas of healthcare failing, do they require more focus.

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19
Q

What factors should be included in the definition of a case definition and population at risk?

A

Place
Time
Demographics
Defininy event, signs,symptoms.

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20
Q

What is the most basic epidemiological measure?

A

Count - integers
Often a numerator of many measures
Important to distinguish between incidence and prevalence.

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21
Q

What is the difference between rate, ratio and proportion?

A

Ratio - one number divided by another - apples to oranges
Proportion - type of ratio, when all of numerator is included in denominator - red apples to all apples
rate - contain a measure of time eg 60km per hour.

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22
Q

What is the prevalence proportion?

A

The number of disease in pop /total pop
No time component
Looks at existing disease in a population in a given time
“ Snapshot”
Dimensionless, positive number 0 to 1

23
Q

What is point prevalence?
How to calculate it?

A

Proportion of a population who have disease at any one time
Number of cases of disease / total population
At a particular point in time.

24
Q

What is period prevalence?

A

The proportion of a population who have a disease during a specified time period (multiple weeks over years etc)

Number of cases of disease /total population (cases and non-cases)
During a period of time.

25
Q

What is incidence as a measure of disease frequency?

A

Occurrence of new cases in a population at risk over a specific time period.
Can be count of new cases, proportion o newly infected to population or rate at which new infection has occurred (force of morbidity).
Measures conversion of health status (proportion/rate)

26
Q

How do you calculate incidence proportion?

A

Total population at risk during that time period

27
Q

What is incidence rate and how do you calculate it?

A

Measures the speed that new cases develop during the specified time period
Cases per person time
Synonyms: incidence, incidence density and rate
Risk period may not the same for all subjects.

28
Q

What is meant by person time and total person-time?

A

Person-time = the amount of time that each person is in the population at risk
Total person time - sum of person times for al participants in the study.

29
Q

How do you calculate incidence rate?

A

Person-time at risk during study period (follow-p)

30
Q

What is the difference between absolute and relative risk?

A

Asbolute - the true risk of an event occurring, number of cases/total population
Relative - compares risk of one group to risk in another group

31
Q

How do you calculate the attributable risk?

A

The risk of x in condition /the risk of x in control population.

32
Q

How do you calculate the number needed to treat to prevent one additional bad outcomes?

A

1/attributable risk reduction.

33
Q

Why is stroke an important public health issue?

A

High frequency (incidence and prevalence) of stroke
High impact on the individual (disability, quality of life, mortality)
High impact on society (cost, social services demand)
Health inequalities

34
Q

What prevention services should be improved for stroke?

A

Prevention of stroke is a role for all clinicians and public health stakeholders.
Focus on improved identification and management of risk factors
Health promotion should encourage self-management of risk factors and health and advise in lifestyle, activity, diet etc.

35
Q

A case definition in research should be?

A

Must be explained and justified
Definitions should be reproducible, clear, specific and measurable.

36
Q

How to calculate absolute risk reduction?

A

AR of events in control - AR in the treatment group.

37
Q

What is a case-control study?

A

Observational study (investigator does not sign exposure)
Analytical study (as comparison group)
Looks at outcome and works back to find the exposure.
Looks to identify potential associations between causes and outcomes

38
Q

How to calculate absolute risk reduction?

A

AR of events in control - AR ins treatment.

39
Q

How do you calculate the relative risk?

A

AR treatment / AR control

40
Q

How do you calculate relative risk reduction?**

A

1 - RR
or
ARc-ARt/ARc

41
Q

What are the strengths of case control studies?

A

Informative - investigate multiple potential casual exposure in one study
Efficient - well suited to rare disease, start with people with disease then work backwards
Ideal when long latency between exposure and disease
Can be carried out relatively quickly and inexpensively

42
Q

What are the limitations of case control studies?

A

Susceptible to biases: recall bias, interviewer bias, selection bias.
Information on exposure may rely on inaccurate and incomplete historical records.

43
Q

How to calculate an odds ration?

A

Odds of event in exposed /odds in non-exposed
(Ye/Ne)/(Yc/Nc)

44
Q

What is meant by an odds ratio?

A

Measures the association between an exposure and an outcome
Compares the relative odds of the occurrence of the outcome of interest given exposure to the variable of interest
Determines if a variable is a risk factor
Most commonly used in

45
Q

How should you interpret an Odds ratio?

A

OR =1 - exposure not associated with an outcome
OR >1 = exposure increases risk of outcome
OR < 1 = exposure decreases risk of outcome.

46
Q

How does the interpretation of confidence intervals relate to odds ratio?

A

If the CI do not include the null OR valve (which is always OR=1) is taken to mean statistical significance.
Narrower confidence intervals indicate less precision.

47
Q

How to calculate the population-attributable fraction?

A

Proportion of cases exposed to risk x (1 - (1/AOR))

48
Q

What are the key features of a case-control study?

A

Data is collected retrospectively.
Look at both cases and non cases, then look to identify previous exposure to potential risks/protective factors.
Outcome measuric tends to be an odds ratio
Are vulnerable to recall bias and difficulty selecting an appropriate control group.

49
Q

What would a Population Attributable Factor of 19% mean?

A

Is risk factor aka smoking was eradicated in the whole population then the incidence of stroke in the population would be reduced by 18%.

50
Q

What is the population-attributable risk factor?

A

Combines the strength of association with the prevalence in the population.
Represents the percentage of cases that would not happen if the risk factor exposure was reduced to the ideal amount.

51
Q

What is the difference between primary, secondary and tertiary prevention?

A

Primary = prevent onset of disease
Secondary = seeks to halt progression of disease once it is established
Tertiary = minimise further progression to disabilities and complications, improve quality of life even if the disease course itself cannot be altered.

52
Q

What is the difference between a high risk v population based prevention strategy?

A

High risk - focused on individuals at greatest risk, aims to reduce the number of individuals with a higher risk of disease

Prevention - aims to reduce the absolute risk for every person in the population by the same amount

53
Q

What is meant by the prevention paradox?

A

Many prevention stratergies target high risk population
However - larger populations at a lower risk can actually have a higher incidence of a disease than a small number of people at a high risk.

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