Morbidity + Mortality Measurements

Question 1

How are mortality data used?

Answer 1

• to explain trends and differences in overall mortality
• indicate priorities for health actions/allocation of resources
• provides data for use in designing interventions
• in assessments an dmonitoring of public health programs - are public health programs working?
• Provide clues in epidemiological investigations

Question 2

Limitations to capturing mortality data?

Answer 2

We do not have a great system for parsing out actual cause of death
* surveillance
* death certificates
* innacurate reporting due to stigma
* compounded causes of death

Question 3

Describe the history of methods of capturing mortality data

Answer 3

1. Bills of mortality (london annual register of death 1665) = unable to accurately capture death (didnt capture those who were not buried), did not capture dissenters, catholics, criminals, etc
2. in 1836 was replaced with the modern death registration system by W. farr (father of modern epidemiology)
3. Now WHO manages this: ICD-10 (still limited to 1 absolute cause of death

Question 4

Mortality Rate =

Answer 4

deaths occurring during a given time period/size of the population in which they occurred (x10^10)

Question 5

Case Fatality Rate (CFR) =

What is it usually used for?

What type of diseases is it normally used for?

Answer 5

Number of deaths from a specific disease during a given time/ number of acses of that dieseas during the same time (x100)

CFR usually used to determine the ‘killing power’ of a disease… how deadly does it appear to be?
Primarily used with highly infectious diseases

Question 6

Proportionate Mortality Rate (PMR) =

What is PMR used to decide?

Answer 6

Number of deahts from a specific cause during a given time / total number of deahts from all causes in the same time (x100)

What is killing people the most? (Where to allocate resources)

The simplest measure of estimating the burden of a disease in the community

Question 7

Cause Specific Mortality Rate (CSMR) =

Answer 7

Number of deaths from a specific cause during given time / total population (x100)

Question 8

Crude Mortality Rate (Crude Death Rate) =

Answer 8

All deaths during a calendar year / the total midyear population (x1000)

The crude death rate gives an estimate as to the rate at which people seem to be dying

Question 9

Infant Mortality Rate (IMR) =

Answer 9

Number of infant deaths less than 1 year of age / Total number of live births during the same year (x1000)

usually expressed per 1000 live births

a death doesnt cound if no birth certificate…

Question 10

Neonatal Mortality Rate =

Answer 10

Number of neonatal deaths (under 28 days) / total number of live births during the same year (x1000)

measures risk of dying among infants under 28 days

the most vulnerable point in human life

Question 11

Post-neonatal mortality rate =

Answer 11

Number of deaths 29-365 days / Total live births during the same year (x1000)

measures risk of dying among older infants (28 days to 12 months)

Question 12

Causes of neonatal deaths developed vs developing countries

Answer 12

Developed: LBW, Congenital anomalies, maternal complications
Developing: LBW, Trauma, tetanus, pneumonia

Question 13

Causes of Postneonatal deaths in developing vs developed countries

Answer 13

developed: Congenital abmomilies, injuries, infection
Developing: infection, malnutrition, injury

Question 14

Maternal Mortality

MMR =

Answer 14

Maternal Death = the death of a woman while pregnant or within 42 days of termination of a pregnancy (irrespective of the duration) from any cause related to or aggravated by the pregnancy or its management (not from accidental causes)

MMR = # of female deaths from pregnancy, childbirth, puerperal causes in a year / # of life births in that same year (x1000)

*usually reflects maternal health in a particular region

MMR is one of the best indicators of overall health of a population: reflects quality of maternal health care and overall other factors such as access to adequate nutrition, gender discrimintation, and power

Question 15

How does the WHO define the periods of fetal death?

Answer 15

Early = under 20 weeks
Intermediate = 20-27 weeks
Late = 27 weeks and over

Question 16

Late Fetal Death Rate =

Answer 16

number of fetal deaths (28 + weeks) during 1 year / number of live births that year

usually expressed per 1,000

Question 17

Still Birth Rate =

Answer 17

Number of fetal deaths (28+ weeks of gestation) during 1year / (# total births)

usually expressed per 1000

Question 18

Child Death Rate (or under 5 mortality rate)

Answer 18

Defined as the numbers of death at age 1-4 years in a given year per 1000 children in that age group at the midpoint of the year (therefore excludes the IMR as infants are not included)

A child survival rate per 1000 births ca be simply calculated by subtracting the U5 mortality rate from 1000 and dividing by 10

Shows the percentage of those who survive to age 5 (a milestone measure of population health)

Tells us child health status & conditions related to malnutrition, injuries, infectious diseases

Question 19

What three types of mortality measures when combined are good indicators of social inequality?

Answer 19

Infant & Child mortality coupled w data on maternal health

Question 20

Developed vs developing countries rates of neonatal mortality to post-neonatal mortality

Answer 20

Developed: Ratio NM:PNM = 3-4:1
Developing: Ratio NM:PNM = 1: 1-2

Question 21

Still Birth Rate =

Answer 21

Number of deaths after the 28 weeks of pregnancy occuring during one year per 1000 total births (still and live births)

Question 22

Perinatal Mortality Rate =

Typical causes?

Answer 22

(# still births + deaths <7days)/total births (x1000)

Perinatal = death of a fetus/baby between 28 weeks of gestation and within the first 7 days after birth
- it is a more specific measure and description of that vulnerable time
Typical causes: infection, hypertension, and intrapartum asphyxia
- typically termed ‘stillbirth’

Essential because it measures the risk of dying between 28 weeks gestation and first week of life = indicates the status of delivery and …

Question 23

Why is it misleading to describe health solely in terms of mortality?

Answer 23

• Because mortality indicators do not reveal the true burden of ill health in a community
• ex: mental illness, infertility, rheumatoid arthrities (invisible illness, those grounded in health inequities, etc)
• Therefore we use those earlier morbidity measures to describe the health status of a population (incidence, prevalence, notification rates, attendance rate at outpatient clinic, admission, readmission, and discharge rates, hospital durations, school absences, sick days from work)

Question 24

Types of Morbidity Rates:

Answer 24

1. Incidence
   - cumulative incidence
   - attack rate
2. Prevalence
   - point prevalence
   - period prevalence

Question 25

What is morbidity?

Answer 25

Morbidity is the state of having a specific illness or conditions. While morbidity can refer to an acute condition, it often refers to a condition that is chronic

Question 26

Incidence proportion (attack rate or risk) =

Answer 26

Number of new cases of disease during specified time interval / Population at middle of time interval

Incidence is a measure ofthe frequency with which an event, such as new cases of illness, occurs in a populatin over a period of time

Is a measure of risk - the probability of developing disease

Question 27

Secondary Attack Rate =

Answer 27

number of new cases among contact / total number of contacts

can provide indication of how social interaction relates to transmissible risk

Question 28

Incidence rate (or person-time rate) =

Answer 28

Number of new cases of disease during specified time interval / summed person-years of observation or average population during time interval

Question 29

Point Prevalence =

Answer 29

Number of current cases (new and preexisting) at a specified point in time / population at the same tine

Question 30

Period Prevalence =

Answer 30

Number of current cases (new and preexisting) over a specified period of time / average or mid-interval population

In chronic disease, we think in terms of periods of time

Question 31

What are the two assumptions when calculating cumulative incidence?

Answer 31

1. Entire population at risk has been followed at beginning of study till the end
2. all participatns are at risk of the outcome of interest

Question 32

Cumulative Incidence (CI) =

When do we use this measure?

Answer 32

the proportion of people in a population who became diseased or ill or experienced an event during the specified period of time
CI = No. new cases of disease or events during time period / total population at risk at the beginning of the time period

We use this measure when we don’t necessarily know the susceptibility

Question 33

What is incidence?

Answer 33

A measure of the frequency with which an event, such as new cases of illness, occurs in a population over a period of time
Incidence is a measure of risk - or the probability of developing disease

The appropriate denominator for IR is the population at risk (susceptibility component)… think about who this is for each case

Question 34

Attack Rate =

When is it most often used?

Answer 34

Number of new cases among the population during the period / population at risk at the beginning of the period (x100)

another measure of morbidity, often synonymous with CI, used most often with short term outbreaks

Question 35

Prevalence: What is it useful for?

Answer 35

Includes both new and old cases
Prevalence indicates the probability that a member of the population has a given condition at a point in time. A way of assessing the overall burden of disease in the population, so it is a useful measure for administrators when assessing the need for services or treatment facilities

Two types of prevalence rates: point and period

Question 36

Point vs period prevalence:

Answer 36

Point: a single point in time – to get a kind of “stop action” or “snapshot” (can be an event rather than a distinct calendar time)
Period: to know how much of a particular disease is present in a populatin over a relatively longer period (used when you want to know how much of a particular disease is present in a population over a relatively longer period)

Question 37

What can we also use prevalence to assess?

Answer 37

Frequency (prevalence) of behaviors or characteristics that might be risk factors for disease.
Smoking isnt a disease per se; however, it relevant to assess the prevalence of this behavior

Example:
many elderly men are found to have prostate cancer on autopsy, even though they were unaware of it and died for other reasons
- It is appropriate to hink of the frequency of prostate cancer at the time of autopsy as prevalence, even though men are having autopsies performed at many different points in calendar time