Epidemiology Flashcards

1
Q

What is epidemiology ?

A

The study of the distribution and determinants of health-related states or events in specified populations, neighbourhoods, school, city, county, state, country, globe and the application of this study to control of health problems.

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2
Q

Factors that influence disease epidemiology

A

Disease type
Mode of transmission
Genetic composition
Environment
Behaviour
Pathogenic virulence
Vaccination status

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3
Q

Disease type

A

Communicable - infectious (widespread)
Non-communicable - (localised)

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4
Q

Mortality rate

A

Mortality rate is an estimate of the portion of a population that dies during a specified time period.

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5
Q

Statistics needed for mortality rate

A

A denominator population
A time frame

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6
Q

Case fatality rate

A

The proportion of cases of a specified condition that are fatal within a specified time.

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7
Q

Weaknesses of CFR estimation

A

May underestimate (esp in early days) of outbreak / if there are breakdowns in reporting system

May overestimate if the denominator is limited

It assumes all cases have been tested

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8
Q

Infection fatality rate

A

The proportion of cases of a specified condition that die divided by the total infected people.

  • depends on detection and reporting of asymptomatic or mild cases
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9
Q

Infection rate

A

The rate at which the infection spreads within a population

Ro < 1 : spread is less likely
Ro > 1 : spread is more likely

Larger the Ro : the harder it is to control the spread of disease

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10
Q

Denominators

A

Health board
City
Hospital
Disease register
Recruited to a study

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11
Q

Mortality rate

A

No people died / population x 100

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12
Q

Person time

A

The time period (e.g. number of years) that a person is exposed to risk.

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13
Q

N year follow up

A

The time period for which a cohort of people have been followed up for a given condition.

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14
Q

Incidence

A

Number of new cases

Number of new people with outcome over a time / total number of people in the group at risk

Multiplied by the population

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15
Q

Prevalence

A

Proportion of population that has disease at a given time.

Point : at a specified time
Period : over a specified period

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16
Q

Incidence vs Prevalence

A

Incidence : useful for identifying causes of disease
prevalence : identifies disease burden

17
Q

Patterns of outcome occurrence

A

Sporadic
Endemic
Outbreak
Epidemic
Pandemic

18
Q

Outcomes

A

Death
Hospitalisation
Quality of life
Surrogates

19
Q

Exposure

A

Non-modifiable : age, sex, genotype

Modifiable : smoking, weight, diet

Interventions : drug therapy, surgery

20
Q

Risk equation

A

Number of outcomes in a group / number of people in a group x100

21
Q

Relative risk equation

A

Risk in exposed / risk in unexposed

22
Q

Relative risk reduction

A

(1- relative risk) x 100

23
Q

Absolute risk reduction

A

Risk in unexposed - Risk in exposed

24
Q

Number needed to treat

A

1 / Absolute risk reduction

25
Confidence intervals
A range of plausible values Wider interval : greater the uncertainty
26
Hierarchy of evidence
From bottom to top : less prone to confounding and bias Top : more likely to influence clinical practice
27
Cross-sectional study (include objective and time frame of study)
Sample a population Estimate the proportion Use data PREVELENCE PAST
28
Case control study (include objective and time frame of study)
Select cases with an outcome Select controls without the outcome Explore exposures in cases and controls Compare exposures in cases and controls Identify association CAUSE PAST
29
Cohort study (include objective and time frame of study)
Select people without an outcome Classify according to exposure Follow up Compare risk of disease in exposed and unexposed CAUSE, PROGNOSIS, INCIDENCE FUTURE, PAST
30
Randomised control trial (include objective and time frame of study)
Random allocation Compare risk of outcome in intervention and control groups. TREATMENT EFFECT PAST
31
Systematic error
What/How data is collected How data is analysed/interpreted/reported