Mortality rates - what you really need to know

Summary

This 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

• 📊 Mortality rates are calculated by comparing the number of deaths (numerator) to the total population (denominator).
• 🔍 Absolute numbers of deaths do not indicate mortality risk without knowing the population size.
• 📈 An increase in both the number of deaths and the population proportionally keeps the mortality rate stable.
• 👨‍⚕️ Epidemiologists use mortality rates to understand changes in death risks over time.
• 📚 There are different types of mortality rates: mortality rate, case fatality rate, and proportionate mortality.
• 🌐 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.
• 🏥 Case fatality rate measures the proportion of people dying from a disease within a specific time period and reflects disease severity.
• 💊 Case fatality rates can be used to evaluate the effectiveness of treatments or interventions.
• 📊 Proportionate mortality shows the percentage of all deaths attributed to a specific cause within a certain time period.
• 🏙️ Comparing proportionate mortalities between cities or regions requires knowing the overall mortality rates to assess risk accurately.
• 📊 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

00:00

📊 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.

05:03

💊 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.

Keywords

💡Mortality Rates

Mortality rates refer to the proportion of deaths in a population over a specific period of time. They are crucial for understanding the risk of dying from a particular disease or condition. In the video, mortality rates are discussed in the context of how they are calculated and interpreted. The script mentions that to calculate these rates, one needs both the absolute number of deaths (numerator) and the total population (denominator). The video emphasizes that mortality rates, rather than absolute numbers of deaths, indicate the risk of dying from a disease.

💡Epidemiologists

Epidemiologists are scientists who study the distribution and determinants of diseases in populations. They play a key role in measuring and interpreting mortality rates. The video mentions that epidemiologists use these rates to understand how diseases affect populations over time. They are essential in analyzing the data to determine if the risk of dying from a disease has increased.

💡Death Rates

Death rates are specific types of mortality rates that measure the number of deaths from all causes or specific causes within a population. The video explains that these rates are calculated by dividing the number of deaths by the population size at a certain point in time, often mid-year. Understanding death rates helps in assessing the overall health of a population and the impact of diseases.

💡Numerator

In the context of calculating rates, the numerator is the number of events or occurrences being counted, such as the number of deaths from a specific disease. The video script uses the term to explain that without knowing the population size (denominator), one cannot accurately determine the mortality rate, as the numerator alone does not indicate risk.

💡Denominator

The denominator in rate calculations represents the total number of entities at risk of the event, which in mortality rates is the total population. The video script explains that changes in the denominator can affect the rate, emphasizing the importance of proportional changes in both the numerator and denominator to maintain the same rate.

💡All-Cause Mortality Rate

The all-cause mortality rate is a measure of the total number of deaths from all possible causes within a specific population. The video describes how to calculate this rate by dividing the total annual deaths by the population at mid-year and then multiplying by 1,000 to express it per 1,000 population. This rate provides a broad view of the general health and mortality trends in a population.

💡Case Fatality Rate

The case fatality rate is the proportion of deaths from a particular disease among those who have been diagnosed with that disease over a specified time period. It is a measure of disease severity. The video uses this term to illustrate how this rate can be used to evaluate the effectiveness of treatments or interventions, as it shows the proportion of patients who die from a disease.

💡Proportionate Mortality

Proportionate mortality refers to the percentage of all deaths that are caused by a specific disease. The video script explains that this is calculated by dividing the number of deaths from a particular disease by the total number of deaths and then multiplying by 100. It is used to understand the contribution of different diseases to overall mortality but does not directly indicate the risk of dying from a disease.

💡Risk of Dying

The risk of dying is the likelihood of an individual's death due to a specific cause within a given time frame. The video emphasizes that absolute numbers of deaths do not indicate this risk; instead, rates such as mortality rates are needed. The script provides examples to show that without knowing the overall mortality rates, one cannot determine the risk of dying from a disease just by looking at proportionate mortality.

💡Population

Population in the context of the video refers to the total number of individuals in a given area or group being studied. It is crucial for calculating mortality rates, as it serves as the denominator. The video script explains that changes in population size can affect the interpretation of mortality rates, which is why the population at mid-year is often used for calculations.

💡Fictitious Numbers

Fictitious numbers in the video are hypothetical data used to illustrate concepts. They represent the absolute numbers of deaths from a certain disease over time. The video uses these numbers to demonstrate how one cannot determine if the risk of dying from a disease has increased without knowing the corresponding population data (denominator).

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