No. Biostat - 5Date: 10.08.2008

MEASURES OF MORTALITY

Lecture Series on Lecture Series on BiostatisticsBiostatistics

Dr. Bijaya Bhusan Nanda, Dr. Bijaya Bhusan Nanda, M. Sc (Gold Medalist) Ph. D. (Stat.)M. Sc (Gold Medalist) Ph. D. (Stat.)

Topper Orissa Statistics & Economics Services, 1988Topper Orissa Statistics & Economics Services, 1988

bijayabnanda@yahoo.com

CONTENTSCONTENTS

IntroductionIntroduction Determinants of MortalityDeterminants of Mortality Uses of Mortality dataUses of Mortality data Sources of Mortality dataSources of Mortality data Measures of MortalityMeasures of Mortality Life TableLife Table

LEARNING OBJECTIVELEARNING OBJECTIVE

They will be able to compute They will be able to compute different indices of mortality.different indices of mortality.

They will be able to spell out general They will be able to spell out general determinants of mortality.determinants of mortality.

They will be able to spell out They will be able to spell out usefulness of mortality indicators.usefulness of mortality indicators.

Death:Death: ““the permanent disappearance of all evidences of the permanent disappearance of all evidences of

life at any time after birth” (WHO).life at any time after birth” (WHO).

• MortalityMortality: :

• A demographic event – Average risk of dying of a A demographic event – Average risk of dying of a person in the group during a time span. person in the group during a time span.

• This is one of the three determinants of This is one of the three determinants of population change i.e. fertility, mortality and population change i.e. fertility, mortality and migrationmigration..

• Factors of mortality patternsFactors of mortality patterns::

• Endogenetics (biological):Endogenetics (biological):

• Exogenetic(environmental):Exogenetic(environmental):

INTRODUCTION

VVary over Space and Timeary over Space and Time

DETERMINANTS OF MORTALITY

Classified in to three categories:

Demographic structure- Age, Sex Composition etc.

Social advancement- Age at marriage, Adequacy of medical facilities, General condition of nutrition, Housing and Sanitation, Literacy, Religion, Caste and Community beliefs etc.

Economic development- Occupation, Standard of living/ per capita income , Type of economy etc.

Useful for projecting the future size of the population

Identify population groups that are at high risk and in need of health service

Indicatives of quality of life and expectation of life at birth.

Useful guides to planners

Helpful to insurance companies

USES OF MORTALITY RATE

There are two sources:There are two sources:

I.I. Direct sourceDirect source Registration of vital eventsRegistration of vital events Sample Registration SurveysSample Registration Surveys National Family Health SurveysNational Family Health Surveys

II.II. Indirect sourceIndirect source Age data of two consecutive censuses may be Age data of two consecutive censuses may be

used to estimates death ratesused to estimates death rates Demographic year book: U.N. PublicationDemographic year book: U.N. Publication World Health Organization (WHO) also World Health Organization (WHO) also

provides dataprovides data

SOURCES OF MORTALITY DATA

MEASURES OF MORTALITYMEASURES OF MORTALITY

It is the quantitative and statistical devices It is the quantitative and statistical devices to label the risk of mortality to which a to label the risk of mortality to which a population is exposed over a period of time.population is exposed over a period of time.

Different measures of mortality:-Different measures of mortality:- Crude death rate:Crude death rate:

Crude death rate (d) =( D/P)*1000Crude death rate (d) =( D/P)*1000

D= No. of deaths in a population during a D= No. of deaths in a population during a given calendar yeargiven calendar year

P= average number of persons living in the P= average number of persons living in the population during the yearpopulation during the year

MeritsMerits requires minimum data on mortalityrequires minimum data on mortality Easy to interpretEasy to interpret

DemeritsDemerits Since the risk of death is not uniform for Since the risk of death is not uniform for

different segments of population (age, sex different segments of population (age, sex etc.) CDR is a crude measure and cant be etc.) CDR is a crude measure and cant be used directly for comparing the levels of used directly for comparing the levels of mortality in two or more countries.mortality in two or more countries.

Age specific death rate (ASDR)Age specific death rate (ASDR)

nnDDxx = No. of death between x and x+n in the yr. = No. of death between x and x+n in the yr.

nnPPxx = No. of persons aged between x and x+n in = No. of persons aged between x and x+n in

the middle of yr.the middle of yr.

Note: LNote: Line graph of ASDR at y-axis and age at ine graph of ASDR at y-axis and age at x-axis it shows J-shape pattern for developed x-axis it shows J-shape pattern for developed countries and U-shape pattern for developing countries and U-shape pattern for developing countries because in developing countries countries because in developing countries mortality rates are comparatively higher at mortality rates are comparatively higher at younger ages.younger ages.

Age Specific Death Rates(ASDR)

nDx

nPx

1000==nnMMxx==

No. of infants dying under one year of age in a year No. of infants dying under one year of age in a year per thousand live birth in a given geographical region.per thousand live birth in a given geographical region.

DD0 0 : No. of infants who died before celebrating their : No. of infants who died before celebrating their

first birthday.first birthday.

B : Total No. live births occurring in that year and B : Total No. live births occurring in that year and geographical region.geographical region.

Infant Mortality Rate (IMR)

D0

B1000IMR=IMR=

Defined as the total number of deaths of children aged 1 to 4 Defined as the total number of deaths of children aged 1 to 4 yrs. per 1000 population of the same age in a given year and yrs. per 1000 population of the same age in a given year and geographical region.geographical region.

Child Mortality Rate (CMR)

CDR =

No. of deaths of children aged 1to 4 yr in given yr and region

tot. population aged 1 to 4 in the given yr and a given region

× 1000

No. of infants dying within the first 4 weeks or up to 28 days of life per 1000 live birth in a year and No. of infants dying within the first 4 weeks or up to 28 days of life per 1000 live birth in a year and geographical region.geographical region.

NMR =Deaths of infants up to 4 weeks

No. of live births× 1000

No. of infant deaths during the first seven days of No. of infant deaths during the first seven days of life per 1000 live births in a year and geographical life per 1000 live births in a year and geographical region.region.

ENMR = Deaths of infants in the first week of life

No. of live births× 1000

Neonatal Mortality Rate (NMR):

Early Neonatal Mortality Rate (NMR):

No. of still births/ late foetal deaths (after 28 No. of still births/ late foetal deaths (after 28 weeks of gestation) plus deaths within first weeks of gestation) plus deaths within first week of life in a year and geographical region week of life in a year and geographical region for 1000 births (live and still) in a year and for 1000 births (live and still) in a year and region.region.

Perinatal Mortality Rate (PMR)

PMR=

Foetal deaths after 28weeks of gestation + deaths of newborns within 7days

No. of live births during the same year× 1000

Number of infants deaths after 28 days to less than 1yr (between 4 Number of infants deaths after 28 days to less than 1yr (between 4 weeks to 52 weeks) of age per 1000 live births in a given year.weeks to 52 weeks) of age per 1000 live births in a given year.

Post Neonatal Mortality Rate (PNMR)

PNMR=

No. of deaths of newborns between 4weeks or less than 1yr old in a year

No. of live births during the same yr× 1000

Maternal Mortality Ratio (MMR)

No. of deaths of women while pregnant or No. of deaths of women while pregnant or within 42 days of termination of pregnancy within 42 days of termination of pregnancy from any cause related to pregnancy/ from any cause related to pregnancy/ childbearing and child birth per 100,000 live childbearing and child birth per 100,000 live births in a given year.births in a given year.

No. of live births during the same year × 100000MMR=

Deaths of pregnant women and women after termination of pregnancy within 6 weeks from any cause related to pregnancy

Maternal Mortality Rate (MMRT)

MMRT =

No. of maternal deaths of women in age 15-49

× 1000

Number of maternal deaths while pregnant Number of maternal deaths while pregnant or within 42 days of termination of or within 42 days of termination of pregnancy from any cause related to pregnancy from any cause related to pregnancy/ childbearing and childbirth per pregnancy/ childbearing and childbirth per 100,000 women in reproductive ages 15-49.100,000 women in reproductive ages 15-49.

No. of women in age 15-49 in a given yr

Foetal Death:Foetal Death:

Deaths prior to the complete expulsion or Deaths prior to the complete expulsion or extraction from its mother of a product of extraction from its mother of a product of conception at any time of pregnancy.conception at any time of pregnancy.

Still BirthStill Birth

Death of foetus after completing 28 weeks and Death of foetus after completing 28 weeks and till the time of birth.till the time of birth.

Incidence RateIncidence Rate

Number of NEW cases of specified diseases Number of NEW cases of specified diseases occurring in a defined population during a occurring in a defined population during a specified period of time.specified period of time.

((Continued…………)Continued…………)

Prevalence RatePrevalence RateNumber of all current cases (old and new) of a disease Number of all current cases (old and new) of a disease

at one point in time in relation to defined population.at one point in time in relation to defined population.

Incidence rate =

No. of new cases of specified disease during a given period

Population at risk× 1000

No. of new and old cases of specified disease existing at a given point in time

Prevalence rate =Estimated population at the same point in time

× 1000

28 weeks of gestation completed

Live Birth

7 Days

28 Days

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Time Reference for Mortality in Childhood and Infancy

The risk in a population may vary The risk in a population may vary largely with various socio-economic largely with various socio-economic and biological traits.and biological traits.

The lack of reliable and requisite data The lack of reliable and requisite data presents serious problem sometimes of presents serious problem sometimes of considerable magnitudeconsiderable magnitude..

Limitations of Measures of Mortality

Exercise: Calculate the crude and Age specific death Exercise: Calculate the crude and Age specific death rates of the population from the following data rates of the population from the following data

Age-group Age-group (Years)(Years)

PopulationPopulation DeathsDeaths

Under 10Under 10 20,00020,000 600600

10-2010-20 12,00012,000 240240

20-4020-40 50,00050,000 1,2501,250

40-6040-60 30,00030,000 1,0501,050

Above 60Above 60 10,00010,000 500500

Expectation of LifeExpectation of Life The curate Expectation of life, (eThe curate Expectation of life, (exx) gives the ) gives the

average number of completed years of life average number of completed years of life lived by the cohort lived by the cohort ll00 after age x by each of after age x by each of lx lx persons attaining that age. The complete persons attaining that age. The complete expectation of life, denoted as eexpectation of life, denoted as exx

oo,, measures measures the average number of years a person of given the average number of years a person of given age can be expected to live under the age can be expected to live under the prevailing mortality conditions. It gives the prevailing mortality conditions. It gives the number of years of life entirely completed and number of years of life entirely completed and includes the fraction of the year survived in includes the fraction of the year survived in the year in which death occur, which on the the year in which death occur, which on the average can be taken to be ½ years. eaverage can be taken to be ½ years. exx

o = o = eex x

+1/2+1/2

REFERENCEREFERENCE An Introduction to the Study of An Introduction to the Study of

Population, Bhaskar D. MishraPopulation, Bhaskar D. Mishra Techniques of demographic Analysis, Techniques of demographic Analysis,

K. B Pathak, F. RamK. B Pathak, F. Ram Fundamentals of Applied Statistics, Fundamentals of Applied Statistics,

S.C Gupta and V. K Kapoor.S.C Gupta and V. K Kapoor.

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