Mortality rates - what you really need to know
Summary
TLDRThis video educates viewers on calculating mortality rates, emphasizing the importance of understanding death rates rather than just absolute numbers. It covers three key measures: mortality rate, case fatality rate, and proportionate mortality. The script clarifies that while absolute numbers of deaths may increase, the risk of dying can remain constant if the population grows proportionally. It also explains how to calculate specific rates for age groups and diseases, and discusses the significance of case fatality rates in measuring disease severity and the impact of interventions. Proportionate mortality is highlighted as a way to view the contribution of different causes of death, but not as a direct indicator of risk.
Takeaways
- đ Mortality rates are calculated by comparing the number of deaths (numerator) to the total population (denominator).
- đ Absolute numbers of deaths do not indicate mortality risk without knowing the population size.
- đ An increase in both the number of deaths and the population proportionally keeps the mortality rate stable.
- đšââïž Epidemiologists use mortality rates to understand changes in death risks over time.
- đ There are different types of mortality rates: mortality rate, case fatality rate, and proportionate mortality.
- đ Mortality rate is expressed per 1,000, 10,000, or 100,000 of the population and can be calculated for specific time periods or age groups.
- đ„ Case fatality rate measures the proportion of people dying from a disease within a specific time period and reflects disease severity.
- đ Case fatality rates can be used to evaluate the effectiveness of treatments or interventions.
- đ Proportionate mortality shows the percentage of all deaths attributed to a specific cause within a certain time period.
- đïž Comparing proportionate mortalities between cities or regions requires knowing the overall mortality rates to assess risk accurately.
- đ Proportionate mortality is useful for understanding the relative contribution of different causes of death but does not directly indicate risk.
Q & A
What is the importance of understanding mortality rates?
-Understanding mortality rates is crucial as it helps in assessing the risk of dying from a particular disease over time and allows for comparisons across different populations or time periods.
Why can't we determine the risk of dying from a disease just by looking at the absolute number of deaths?
-The absolute number of deaths does not indicate mortality risk because it does not account for changes in the total population size. The risk can only be determined by comparing the number of deaths (numerator) to the total population (denominator).
What is meant by the 'denominator' in the context of mortality rates?
-The 'denominator' refers to the total population at risk of dying, typically measured at a specific point in time, such as mid-year, to calculate mortality rates.
How is the all-cause mortality rate calculated?
-The all-cause mortality rate is calculated by dividing the total number of deaths from all causes within a specified time period by the total population at mid-year, and then multiplying by 1,000 (or another factor) to express the rate per 1,000 or per 10,000 population.
What is the significance of calculating mortality rates for specific subgroups?
-Calculating mortality rates for specific subgroups, such as age groups, allows for a more detailed understanding of the risk factors and health outcomes within those groups.
How does the case fatality rate differ from the mortality rate?
-The case fatality rate measures the proportion of people who have a specific disease and die from it within a certain time period, reflecting the severity of the disease, whereas the mortality rate considers all deaths in the population.
Why are case fatality rates useful for measuring the benefits of a new drug or intervention?
-Case fatality rates are useful for measuring the benefits of new drugs or interventions because they directly show the impact on reducing deaths among those who have the disease.
What is proportionate mortality and how is it calculated?
-Proportionate mortality is the proportion of all deaths that are due to a specific cause. It is calculated by dividing the number of deaths from that cause by the total number of deaths, and then multiplying by 100 to get a percentage.
Why is proportionate mortality not a direct measure of risk?
-Proportionate mortality is not a direct measure of risk because it does not consider the overall mortality rates in a population. It only shows the relative contribution of different causes of death.
How can you compare the risk of dying from a disease in two different cities using proportionate mortality?
-To compare the risk of dying from a disease in two cities using proportionate mortality, you would need to know both the proportionate mortality and the overall mortality rates for each city. This allows you to calculate the actual number of deaths from the disease per a certain population size.
What is the key takeaway from the discussion on mortality rates in the video script?
-The key takeaway is that while absolute numbers of deaths can be informative, it is the rates (adjusted for population size) that provide a true measure of mortality risk and allow for meaningful comparisons and analyses.
Outlines
đ Understanding Mortality Rates
This paragraph introduces the concept of mortality rates and their calculation. It explains that absolute numbers of deaths do not indicate risk without knowing the population size, which serves as the denominator. The speaker illustrates how death rates remain constant if both the numerator (number of deaths) and the denominator (population) increase proportionally. Three measures of mortality are mentioned: mortality rate, case fatality rate, and proportionate mortality. The paragraph then delves into calculating mortality rates, emphasizing the importance of using the mid-year population to ensure that those counted in the denominator could potentially become part of the numerator. Examples are given for calculating all-cause mortality rates for the general population and for specific age groups and diseases.
đ Case Fatality Rate and Proportionate Mortality
The second paragraph discusses case fatality rates, which measure the proportion of people with a disease who die from it, indicating disease severity. It provides an example of how to calculate this rate using deaths from heart disease. The paragraph then explains proportionate mortality, which is the proportion of all deaths attributed to a specific cause, using heart disease as an example again. The speaker clarifies that proportionate mortality does not measure risk but shows the contribution of different causes of death relative to each other. The paragraph concludes with a cautionary note that proportionate mortality should not be confused with risk and examples are given to demonstrate how comparing proportionate mortalities without knowing the total mortality rates can be misleading.
Mindmap
Keywords
đĄMortality Rates
đĄEpidemiologists
đĄDeath Rates
đĄNumerator
đĄDenominator
đĄAll-Cause Mortality Rate
đĄCase Fatality Rate
đĄProportionate Mortality
đĄRisk of Dying
đĄPopulation
đĄFictitious Numbers
Highlights
Importance of understanding mortality rates and their calculation methods.
Epidemiologists measure mortality by comparing death rates over time.
Risk of dying cannot be determined from absolute numbers alone.
Death rates require both the number of deaths (numerator) and population size (denominator).
If population and death numbers increase proportionally, mortality rates remain the same.
Introduction to three measures of mortality: mortality rate, case fatality rate, and proportion of mortality.
Explanation of all-cause mortality rate calculation.
Mortality rates can be calculated for specific subgroups, such as age groups.
Calculation of mortality rate for specific diseases, like heart disease.
Combining age group and disease to calculate mortality rate.
Case fatality rate measures disease severity by the proportion of deaths among diseased individuals.
Case fatality rates are useful for measuring the benefits of new drugs or interventions.
Proportionate mortality is the percentage of all deaths attributed to a certain disease.
Proportionate mortality does not indicate risk of dying but shows the contribution of different causes of death.
Example of how proportionate mortality can be misleading without knowing total mortality rates.
Total mortality rates are necessary to compare risk between different populations.
Proportionate mortality provides a quick overview of the relative contribution of different causes of death.
Invitation for viewers to share their thoughts and engage in the discussion.
Transcripts
hey everyone in this video we're going
to learn something very very important
and that's mortality rates and how
they're calculated check it out let's
have a quick look at how epidemiologists
measure mortality let's take a look at
some fictitious numbers again here are
the absolute numbers of death for
certain disease over time from looking
at this graph we cannot tell if the risk
of dying from that disease increased
over time for that we would need to know
the death rates and we only have the
numerator for these death rates shown
here we don't have the numbers of the
total population during these time
points or in other words we don't have
the denominator so if the population
would have increased at the same pace
the death rates would have essentially
stayed the same so if the denominator
increases to the same extent as the
numerator the relationship stays the
same and in this case the rates would
stay the same phrase differently the
absolute number of deaths is the
numerator and the population is the
denominator if those two increase
proportionally as in this case the rate
stays the same so you see absolute
numbers are not an indication of
mortality risk but rates are in the
following minutes we're going to cover
three measures of mortality
two of them are rates one is not we're
going to cover the mortality rate the
case fatality rate and the proportion of
mortality let's start out with mortality
rates there are a couple of ways to
approach them the most obvious way would
be to calculate the so called all-cause
mortality rate which can be expressed
per 1,000 population 10,000 population
or 100,000 population that's totally up
to the beholder
the annual all-cause mortality takes the
number of deaths from all causes in a
specified time period let's say in one
year and divides that by the number of
all persons in the population at
mid-year why mid-year well because the
population changes over time remember
everyone who's in the denominator should
be eligible to become part of the
numerator in order to obtain the number
per 1000 population we multiply that by
1,000 we might not be interested in the
entire population but in the mortality
rate of a specific subgroup let's say
we'd like to know the annual all cost
more
tality for adults age 32 for years well
then we take the number of deaths from
all causes in one year that occurred in
the age group of 30 to 40 and we divide
that by the number of persons 30 to 40
years of age at mid-year again we
multiply that by 1,000 in order to get
the number of deaths per 1,000
population similarly we might want to
get the mortality rate for specific
disease like heart disease in other
words the annual mortality for heart
disease per 1000 population we take the
number of deaths from heart disease in
one year divide that by the number of
persons in the population at mid-year
and multiply that by 1,000 I think
you're getting the gist of it
now let's take that a step further and
combine the two previous mortalities and
calculate the annual mortality from
heart disease per year in adults 30 to
40 years of age per 1,000 population we
take the number of deaths from heart
disease in one year that occurred in the
age group of 30 to 40 year olds and
divide that by the number person's 30 to
40 years of age at mid-year and multiply
that by 1,000 now let's turn to case
fatality rate case fatality rates are
defined as the proportion of people who
have a disease and who are dying from it
in a specified time period it's actually
a measure of disease severity it's
calculated as the number of deaths
during a specific time period after its
onset let's say heart disease divided by
the number of persons with heart disease
in that period case fatality rates are a
great way to measure the benefits of a
new drug or intervention now let's turn
to proportionate mortality that's
defined as the proportion of all deaths
that die from a certain disease let's
take heart disease again so the
proportion of mortality from heart
disease in the specific time period
would be calculated as the number of
deaths from heart disease divided by the
total deaths multiplied by 100 in order
to get a percentage let's take a
fictitious example again proportionate
mortality is often displayed in the form
of a bar graph where the entire bar
represents 100 percent of deaths and a
certain proportion of that 100 percent
died of a certain disease let's pick
heart disease again so let's say that
the proportionate mortality was 50% in
the pop
relation in CDA now let's take cdb and
draw the proportionate mortality for it
you see it's also 50 percent so does
that mean that the risk of dying from
heart disease is the same in those two
cities think for a moment pause the
video for 20 to 30 seconds then come
back ok so the solution is that
proportionate mortality in and of itself
is not a measure of risk you would need
to know the total mortality rates in
both cities in order to say anything
about risk however if I told you that
total mortality per 10,000 population
was 10 in CDA and 20 and city be knowing
that the proportion of mortality was 50%
in both cities you'd be able to
calculate that in city a five people
died of heart disease per 10,000 whereas
in city B 10 died of heart disease so
the risk of dying of heart disease was
actually double ncdb you wouldn't have
been able to say that just from looking
at the proportion of mortalities let's
pick another example let's say that the
proportionate mortality from heart
disease was 20 percent in city X and 40
percent in City Y as we've just learned
these numbers are actually not telling
you that there's an increased risk of
dying from heart disease in City why
you'd need at least to know the overall
mortality rates in both cities so let's
say that the overall mortality rate was
10 / 10 thousand in City X and 5 in
10,000 and city Y 20 percent of 10 is 2
and 40 percent of 5 is also 2 so there's
an equal risk of dying in both cities so
proportionate mortality is not an
indicator for risk of dying but what it
provides you with is a quick look at the
relative contribution of the different
causes of death so I hope you found this
useful as always I'd love to hear your
thoughts so please leave a comment below
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