4. MEASURES OF FREQUENCY Flashcards
- Fill in the descriptions for the Blocks labelled 1-7.
- Measures of Disease Frequency
- Prevalence
- Point
- Period
- Incidence
- Cumulative
- Rate
- What are Measures of Disease Frequency?
- these are also known as measures of Disease
Occurrence - they asses the frequency and distribution of Health
Conditions and outcomes in populations
- How are Measures of Disease Frequency most often expressed as?
- they are expressed as percentages
- this is because they reflect binary outcomes
- Binary Outcomes are also known as Variables
- What are two examples of Binary Outcomes?
- Presence vs absence of a Health Condition
- Occurrence vs no occurrence of a health outcome
- How do we calculate Prevalence?
- What is Point Prevalence?
- this is the number of existing cases at a specific point
in time - DIVIDED by the population at risk
NB:
- AN EXAMPLE OF A SPECIFIC POINT IN TIME:
- today, yesterday, etc.
- What does the “Population at Risk” refer to?
- this typically excludes the number of individuals who
are immune to the disease - we consider the whole population for practical
purposes
- What is Period Prevalence?
- this is the number of existing cases during a specific
time period - DIVIDED by the population at risk
NB:
- AN EXAMPLE OF A SPECIFIC TIME PERIOD:
- the years of 2019-2020
- When is Period Prevalence more applicable?
- it is more applicable for chronic diseases
- these diseases have no cure or a low mortality
- How do we work out Cumulative Incidence?
- What are two other terms for Cumulative Incidence?
- Incidence Proportion
- Incidence
- What is Cumulative Incidence?
- this is a Cumulative measure
- it quantifies all the cases that appeared during a
specific time period - it relates this to the population at risk
- What is meant by “Population at risk” when it comes to Cumulative Incidence?
- this is a person without the condition currently
- but they could potentially develop it
NB:
- the denominator is the same as for when we work out
Prevalence
- the denominator excludes existing cases that occur at
the beginning of the time period
- What is Cumulative Incidence used for?
- it is used to quantify the risk of the outcome in a
specific population - at a specific time period
- Provide an example of Cumulative Incidence?
- the incidence of cancer in Cyprus during 2014 was two
cases per 1000 persons
- What can Prevalence display?
PREVALENCE CAN DISPLAY:
- local burdens of disease
- regional burdens of disease
- global burdens of disease
IT IS USEFUL IN COMPARING:
- the disease frequency between regions or
subpopulation groups
- What do we use Prevalence and Incidence for?
- they are used to compare disease frequencies in
different population groups
- What is regularly documented incidence useful for?
REGULARLY DOCUMENTED= annual, seasonal etc.
- it can inform us about temporal (time) trends in
disease patterns - this is useful when it comes to diseases that emerge
from projected public health concern
- What is Mortality Rate?
- this is also known as Death Rate
- it is the most important measure of mortality
- it quantifies the number of deaths in a
population during a specified time period
- What is the calculation for working out the Mortality Rate very similar to?
- the calculation for working out Disease Incidence
THE MAIN DIFFERENCE BETWEEN THEM:
- IN THE MORTALITY RATE:
- the numerator has the number of deaths
- INSTEAD of the new disease cases
- How do we calculate All Cause Mortality Rate?
- What is the All Cause Mortality Rate?
- this is also known as the Crude Mortality (Death) Rate
- it takes into account all the deaths from all causes
within a specified point in time
- How do we calculate Cause-Specific Mortality Rate?
- What is Cause-Specific Mortality Rate?
- this is also known as Cause-Specific Death Rate
- it takes into account all deaths from a specific cause
- it does this within a specified time point
- How do we calculate Age Specific Mortality Rate?
- What is Age Specific Mortality Rate?
- this is also known as Age-Specific Death Rate
- this takes into account all the deaths in a specific age
group - it does this within a specified time point
- What are the 2 types of Age-Specific Mortality?
- All Cause
- Cause-Specific
- How do we calculate the Case Fatality Rate (Ratio)?
- What is the relationship between Incidence, Prevalence and Mortality?
- What 2 factors is Prevalence determined by?
- Incidence
- Duration of the disease
(death rate/mortality)
(recovery rate)
- How do we calculate Incidence Rate?
- What is Incidence Rate?
- this is also referred to as: Rate
- it is based on the observation that the population at
risk keeps changing over the follow up - this means that the population at risk is not constant
- this is because people who become ill with the disease
or die from other causes will no longer be at risk
- What is Incidence Rate applicable to?
- it is applicable to Research studies
- it is not as applicable to Population based surveys
- this is because detailed data on the exact follow up
time is required
- What is another term for “Follow up Time”?
- time at risk
- this is calculated for all individuals
- it is then added up
- this gives rise to Person time
- What is the main advantage of Incidence Rate?
- it does not assume that all study participants are
followed up for the whole duration of the study - this differs from Cumulative Incidence
- What is more accurate about using the Incidence Rate?
- it has a more accurate denominator
- this means that is has a more accurate quantification
of risk - this is called the “Rate” in this case
- What is a similarity between Incidence Rate and Cumulative Incidence?
- the two can be interpreted in exactly the same way
- What is the only difference between Incidence Rate and Cumulative Incidence?
- the reporting of the per unit population
- Does this summary make sense?
- yes