Computation and Measurement of Risk - Mathematics and Statistics for the Environment - page 194

TABLE 8.4
Frequently Used Measures of Mortality

Measure Numerator Denominator 10 n

Crude death rate Total numerator of deaths during a given

time interval

Mid-interval population 1000 or

100,000

Cause-specific death rate Number of deaths assigned to a specific

cause during a given time interval

Mid-interval population 100,000

Proportionate mortality Number of deaths assigned to a specific

cause during a given time interval

Total number of deaths from
all causes during the same
time interval

100 or
1000

Death-to-case ratio
interval

Number of deaths assigned to a specific
cause during a given time interval

Number of new cases of same
disease reported during the
same time interval

100

Neonatal mortality rate Number of deaths among children < 28

days of age during a given time interval

Number of live births during
the same time interval

1000

Postneonatal mortality rate Number of deaths among children 28-364

days of age during a given time interval

Number of live births during
the same time interval

1000

Infant mortality rate Number of deaths among children < 1 year

of age during a given time interval

Number of live births during
the same time interval

1000

Maternal mortality rate Number of deaths assigned to pregnancy-

related causes during a given time interval

Number of live births during
the same time interval

100,000

8.4 MORTALITY FREQUENCY MEASURES

8.4.1 m ortality r ate
A mortality rate is a measure of the frequency of occurrence of death in a defined population during
a specified interval. Morbidity and mortality measures are often the same mathematically; it's just
a matter of what we choose to measure, illness or death. The formula for the mortality of a defined
population, over a specified period of time, is

Deaths occurring duringgiven time period
Size of the populationamong whichthe deathssoccurred

×10 n

When mortality rates are based on vital statistics (e.g., counts of death certificates), the denominator
most commonly used is the size of the population at the middle of the time period. In the United
States, values of 1000 and 100,000 are both used for 10 n for most types of mortality rates. Table 8.4
summarizes the formulas of frequently used mortality measures.

8.4.1.1 Crude Mortality Rate (Crude Death Rate)
The crude mortality rate is the mortality rate from all causes of death for a population. In the United
States in 2003, a total of 2,419,921 deaths occurred. The estimated population was 290,809,777. The
crude mortality rate in 2003 was, therefore, (2,419,921/290,809,777) × 100,000, or 832.1 deaths per
100,000 population (WISQARS, 2012).

8.4.1.2 Cause-Specific Mortality Rate
The cause-specific mortality rate is the mortality rate from a specified cause for a population. The
numerator is the number of deaths attributed to a specific cause. The denominator remains the
size of the population at the midpoint of the time period. The fraction is usually expressed per