Hadpop2 Flashcards by SN K

What is a census

simultaneous recording of demographic data to all persons in a defined area

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What is a census useful for

allocation of resources
trends in populations, eg ethnicity
projections of populations (how many people living in this area with this defined problem)

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3 ways to measure Birth rates

Crude BR: # of live births per 1000 population
General fertility rate: # of live births per 1000 fertile women between 15-44 - more accurate but not always possible
Total period fertility rate: average # of children born to a hypothetical woman in her lifetime

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How can death rates be measured

Crude mortality rate

2. age-specific mortality rate

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Define incidence

Number of new cases per year in a set population, per 1000 people/per year

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Define prevalence

Number of people with the disease in a set population

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What is SMR

Standardized Mortality Rate
calculated by: observed # of deaths x 100/expected # of deaths

SMR>100 suggests excess mortality and <100 suggests less mortality with confounders accounted for

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What is the p-value

indicates the percentage of the study due to chance, based around 5%

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State 3 types of selection bias

allocating
healthy worker effect
non-response bias

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State 4 types of information bias

instrument
interviewer
recall bias
publication bias

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Define a cohort study

Recruiting disease-free individuals and following up with them for an extended period of time, and classify them according to their exposure status

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State 2 types of cohort studies, and define each one

Prospective: disease-free individuals recruited and followed up
Retrospective: choosing disease-free individuals based on a common past exposure and following up

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What’s an internal comparison

Occurs when you have sub-cohorts within your original group and compare the exposed to the unexposed

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What’s an external comparison

Comparing your exposed group to a reference population

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What is the only study design that allows you to calculate odds ratio?

How would you do it?

Case-control studies
Case: diseased individuals, control: disease-free individuals. Want them as similar as possible

a: exposed cases
b: exposed controls (disease-free individuals)
c: unexposed cases
d: unexposed controls

a/c over b/d
A crazy big dick:)

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List 4 advantages for Case-Control

used for rare diseases
temporal sequencing
can look at multiple exposures at once
Fast and inexpensive (relatively)

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Define temporal sequencing

Confidently say that exposure came before the outcome

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What is intention to treat

Treating everyone the same regardless if they are given the real drug or placebo in an RCT

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Why is it important to keep non-compliars in a study

If non-compliars (those non-compliant) with the drug are removed, loss of randomization also occurs from the trial

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What is the purpose of the Bradford Hill Criteria

To determine whether the causal-effect relationship has been established
Can you directly say this exposure caused the outcome?

List the 9 Bradford Hill Criteria

STD-C-CRABS
Strength of association: stronger the association between exposure and outcome, less likely due to chance, confounding or bias

Temporal sequencing

Dose-response: does the outcome change with increasing/decreasing dosage

Consistency of association; does same association occur in other studies

Coherence of Theory: does the observed observation confirm your scientific thinking

Reversibility: if you remove the causal factor, would you get a reduced risk of the outcome

Analogy: does a similar disease have similar outcomes

Biological Plausibility: is there a plausible biological mechanism to support the theory

Specificity of association: the outcome is associated with a specific factor

Three ways losses can be minimized by, aka three ways to minimize loss to follow up

Follow up appointments
No coercion or inducements
Honesty

What is loss to follow up and when is it significant?

When a patient stops participating in the study before its completion.

A weakness of RCTs and cohort studies, since your results depend on the future results, so you don’t want your patients to drop out of the study

Three ways to maximize compliance of patients

Simplified instructions
Patient allowed to ask lots of questions
Made simple and accessible for patient

How and when would you calculate RR

For RCTs: risk of exposed with disease/total = x risk of unexposed with disease/total = y x/y= "Value", Risk of the exposed getting the disease is "Value" times as likely as a nonexposed individual.

List the 4 pillars of medicine

Principle of... 1. Beneficence (do good) 2. Non-maleficence (do no harm) 3. Autonomy (let the patient decide) 4. Justice (be fair)

What is a systemative review?

Compilation of all primary studies (many RCTS), you narrow them down the most relevant and credible

List 3 characteristics that a study used in a systemative review should have

1. Transparency - nothing hidden 2. Reproducible - can you reproduce the exact same study again 3. Explicit - clear

What's a meta-analysis and when is it used

Within a systemative review that provides an overall value with associated CI. Used in a forest plot

In a forest plot, what does... a) The square represents b) the horizontal lines c) the size of the square d) the diamond e) solid vertical line

a) The odds ratio value b) the CI c) the amount of weight on the study d) The pooled estimate: the average of the studies, the width of the diamond represents the overall 95% CI e) The Null Hypothesis

List the two types of models that can be used in a meta-analysis

1. Fixed effects model - assumes the studies used are homogenous, they're so similar that any variation between data comes from within the study 2. Random effects model - assumes studies are heterogeneous and variation between data comes from in the study and between separate studies

What is a funnel plot

Publication bias can be determined using a funnel plot... Publication Bias: whereby studies are only likely to be published if results are statistically significant or have a large sample size The more funnel-shaped, the less publication bias

List 3 advantages of RCTs

1. You can introduce blinding 2. eliminates confounders 3. you can actually test the intervention

How is Prevalence calculated

of cases at a given time/population # at the time

How is Cumulative Incidence calculated and expressed in units, and what does the value mean?

of new cases of a disease in a period of time/# of people at risk of developing the disease at the start of the same time period As a percentage How many people at risk actually got the disease

How would you calculate Incidence Density and what does that value show?

of new cases of a disease/Total person-time at risk of developing the disease Shows how many people who were at risk for x amount of time actually got the disease

List the general steps for a Cohort study

1. recruit a population of disease-free individuals 2. classify them based on their exposure status, e.g; How many of them have had the BCG 3. Follow up with them for an extended period of time

What does Internal Validity measure

Are the finding of the study valid for the population in the study

What does external validity measure

can the findings be generalizable to other populations outside of the study?

3 advantages for a cohort study

1. temporal sequencing 2. can examine multiple outcomes (the final results) from one exposure 3. Good for rare exposures (but bad for rare outcomes)

What three disadvantages do RCTs and cohort studies have in common

1. Time 2. Expensive 3. risk of loss to follow up

List two disadvantages for a case-control

1. Difficult to select the appropriate control groups as you want them to be as characteristically similar to the case group, (asides from lack of exposure) e. g; similar age, gender, height, etc.

Define a confounding factor and list 5 examples

Is independently associated with the exposure and the outcome but is not on the causal pathway age, gender, genetics, height, smoking (when it's not the exposure being examined)

If a CI value includes the null Hypothesis it is...

Not statistically significant, therefore we accept the Null Hypothesis

If a CI value doesn't include the null hypothesis it is...

statistically significant, therefore we accept the alternate hypothesis

What's a case series?

The absolute fcking worst type of study design, based on reports

What does the incidence rate ratio show

It compares the incidence rates between groups with different levels of exposure

What does the relative risk show

Compares cumulative incidence (a proportion) between groups with different levels of exposure

List in order from top --> bottom the study design triangle

1. Systemative review 2. RCT 3. Cohort studies 4. Case control 5. Cross sectional 6. Case series