Mortality dr.wah

Measures of Mortality
Dr. Win Aye Hlaing
Lecturer
Department of Epidemiology
University of Public Health, Yangon
1Monday, June 26, 2017

Mortality
• Death is the foundation of all vital statistics
– The early work on vital statistics was done by John Graunt
(1620–1674), a British demographer
– His work on the Bills of Mortality led to development of statistical
methods to analyze mortality data
• In most countries, laws require registration of deaths
– In the U.S., physicians or medical examiners must certify all
deaths and provide diagnosis for causes of death
– All deaths are recorded and reported to local and state health
departments and finally to the National Center for Health
Statistics (NCHS)
• NCHS developed a Standard Certificate of Death to be used by all
states
• It followed the format recommended by WHO

Sources of Mortality Statistics
• National Center for Health Statistics National
Death Index (NDI)
• Centers for Disease Control and Prevention
(CDC) Morbidity and Mortality Weekly Report
• State vital records
• Tumor registries

Figure 4-1 Trend in numbers of cancer deaths observed in the United States in the early and mid 20th
century and forecast to the year 2000. (Data from the American Cancer Society.)
Downloaded from: StudentConsult (on 2 January 2012 10:38 AM)
© 2005 Elsevier
MEASURES OF MORTALITY
Absolute number
RISK?

• Clearly, the number of people dying from
cancer is seen increasing significantly through
the year 2000,
• but from this graph, we cannot say that the
risk of dying from cancer is increasing,
• because the only data that we have in this
graph are numbers of deaths (numerators)
• we do not have denominators (populations at
risk)
Monday, June 26, 2017 5

Figure 4-2 Cancer death rates for males, United States, 1930-2003 (age-adjusted to the 2000 U.S.
standard population). (From Jemal A, Siegel R, Ward E, et al: Cancer statistics, 2007. CA Cancer J Clin
57:43-66, 2007.)
Downloaded from: StudentConsult (on 2 January 2012 10:38 AM)
© 2005 Elsevier

• Figure 4-2 shows mortality rates for several types
of cancer in men from 1930 to 2003
• The most dramatic increase is in deaths from lung
cancer
• This increase is clearly of epidemic proportions
and, tragically, lung cancer is a preventable cause
of death
• Fortunately, since the mid 1990s, lung cancer
mortality has declined
• Other cancers are also of interest
• Mortality from prostate cancer also peaked in the
mid 1990s, and has declined

• Cancers of the colon and rectum have
declined over many years
• The rate of death from stomach cancer has
declined dramatically since 1930, although the
precise explanation is not known

• The decline may be the result of the increased
availability of refrigeration, which decreased the need
to smoke foods and thereby decreased human
exposure to carcinogens produced in the smoking
process
• Another possible cause is improved hygiene, which
may have reduced the incidence of Helicobacter pylori
infections (cause of stomach cancer)

Calculation of Mortality Rate
• it is usually calculated on an annual basis
• Numerator is the number of deaths
• For vital statistics purpose, the midpoint
(midyear) population is used with the
assumption that:
• Addition and subtraction of population occur
uniformly throughout the year

I. Annual Mortality Rate

Example: Mortality Rate
• 20 deaths from all causes in one year
• 12,000 persons in the population at
midyear
• Annual mortality rate from all causes (per
1,000 population)=?
• (20/12000)*1000
• 1.7 per 1,000 pop

II. Age-Specific Mortality Rate

III.Cause Specific Mortality Rate
E.g. lung cancer (per 1000 Population)

IV. Age and Cause Specific Mortality Rate
E.g. leukemia for children under age 10 (per 1,000
population)

V. Proportionate Mortality Rate

Proportionate Mortality Rate

Comparison: Mortality Rate and
Proportionate Mortality
• Deaths from heart disease in two
communities, “A”and “B”
A B
Mortality rate from all
causes
20/1,000 10/1,000
Proportionate mortality
from heart disease
30% 30%
Mortality rate from heart
disease
6/1,000 3/1,000

Proportionate Mortality
• Deaths from hypertension in two
communities, “C” and “D”
C D
Mortality rate from all
causes
30/1,000 15/1,000
Proportionate mortality
from heart disease
10% 20%
Mortality rate from heart
disease
3/1,000 3/1,000

VI. Case Fatality Rate
• Difference between CFR and PMR-Denominator
• PMR – Total deaths
• CFR – specified disease persons
• CFR measures severity of disease

Case Fatality Rate
• Assume a population of 100,000 people, 20 are
sick with disease “X”
• In one year, 18 die from disease “X”
• The mortality rate in that year from disease
“X”=?
• Case fatality rate from “X”= ?
• MR = 18/100,000 = 0.00018 or 0.018%
• CFR = 18/20 = 0.9 or 90%

Years of Potential Life Lost (YPLL)
Measures the impact of mortality on society
• a measure of premature mortality, or early death
• calculated by summing the years that individuals would have
lived had they experienced normal life expectancy and had not
died from the particular disease
• Often, age 65 (or 75) is used in the calculation
• For example, a person who died at age 30 from heart disease---
65 – 30 = 35 YPLL

Years of potential life lost (YPLL) before age 75, all
races, both sexes, all deaths, United States, 2008

YPLL
• Can assist in three important public health
functions:
1. Establishing research and resource priorities
2. Surveillance of temporal trends in premature
mortality
3. Evaluating effectiveness of program
interventions

Why Look at Mortality?
• Mortality is clearly an index of the severity of a
disease from both clinical and public health
standpoints
• Also used as an index of the risk of disease
• In general, mortality data are easier to obtain
than incidence data for a given disease
• Therefore, it may be more feasible to use
mortality data as an index of incidence
• However, when a disease is mild and not fatal,
mortality is not a good index of incidence

• A mortality rate is a good reflection of the
incidence rate under two conditions:
• First, when the case-fatality rate is high (as in
untreated rabies) and
• Second, when the duration of disease
(survival) is short
• Under these conditions, mortality is a good
measure of incidence, and thus a measure of
the risk of disease

Problems with mortality data
• Death certificates
• International Classification of Disease (ICD)
• Changes in definition of disease (Case
Definition)

Example of a Death Certificate

Example of a completed cause-of-death section on a death
certificate, including immediate and underlying causes
and other significant conditions

i. the immediate cause of death
ii. Underlying cause and
iii. contributory causes
• that intervene between the underlying and immediate
causes of death
• The underlying cause of death is the disease or injury
that initiated the set of events leading to death
• validity of death certificates compared with hospital and
autopsy records

• Deaths are coded according to the International
Classification of Diseases (ICD)
• ICD-9 first used in 1979
• ICD-10 first used in 1999
• now in its tenth revision
• Rules for selection of the underlying cause of death
can be found in ICD

Some causes of death reported
in early 1900s
• Died suddenly without the aid of a physician
• Died suddenly, nothing serious
• Went to bed feeling well, but woke up dead

WHO international Classification of
Definition
• Impairment: : any loss or abnormality of psychological,
physiological or anatomical structure or function
• Disability: : any restriction or lack (resulting from an
impairment) of ability to perform an activity in the
manner or within the range considered normal for a
human being
• Handicap: : a disadvantage for a given individual,
resulting from an impairment or a disability, that limits
or prevents the fulfillment of a role that is normal
(depending on age, sex, social and cultural factors) for
that individual

THANK YOU

Mortality dr.wah

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