measures of mortality

Measures of Mortality

International death certificate • The basis of mortality data.• Divided in 2 parts;• 1st is the immediate cause & the

underlying cause which started the whole trend of the events leading to death,

• 2nd records any significant associated disease that contributed to the death but not directly lead to it.

Cause of death

I. Disease or condition (a)… Bronchopneumonia… directly leading to (due to or as a consequent of)

death

Antecedent causes (b)………………….Morbidity conditions, (due to or as a consequent of)

if any, giving rise to (c) …Strangulated hernia.. the above cause

Cause of death

I. .II. Other significant …Diabetes…

conditions contributing …………………to the death, but not …………………related to the disease …………………or condition leading to it ………………….

The underlying cause

• “is the disease or injury which initiated the train of morbid events leading directly to death”, or

• “The circumstances of the accident or violence which produced the fatal injury”.

National death certificate

• Socio-demographic profile.• Cause of death:

a) disease or condition directly leading to death.b) Antecedent causesc) Morbid condition

• Other contributing factors (not related to disease leading to death).

Uses of mortality data

• Explaining trends & differentials in overall mortality,

• Indicating priority for health action and the allocation of resources,

• Designing intervention programs, • Assessment & monitoring of public health

problems and programs, and• Considered as clues for epidem research

Crude death rate:

• The number of deaths (from all causes) per 1000 estimated mid year population in one year, in giving place.

• It measures the rate at which deaths are occurring from various causes in a given population, during a specified period.

Number of deaths during the year *1000Mid year population

Life expectancy:

Longevity, the average length of life of individuals in a population. In poor communities life expectancy at birth is mainly are reflections of infant and child mortality.

Population

Crude death rate

Age -specific death rates per 1000 population

0-11-45-78-4445-6456+

A15.213.50.60.41.510.759.7

B9.922,61.00,53.618.861.1

Summarizes the effect of tow factors. A. population composition

B. age - specific death rate (which reflect the probability of dying(

Specific death rate :a - cause or disease specific e.g., tuberculosis, cancer, accident.

b- Related to specific groups e.g., age-specific, sex-specific, age and sex specific, etc.

Specific death rate :

Can help us to identify particular groups or groups "at risk" for preventive action.

They permit comparisons between different causes within the same population.

Specific death rate due to tuberculosis= Number of deaths from tuberculosis during a calendar year *1000

Mid-year population

Specific death rate for males= Number of deaths among males during calendar year *1000

Mid- year population of males

Specific death rate :

Specific death rate in group 15-20 years= No deaths of persons 15-20 yrs in a year *1000Mid year population of persons aged 15-2

Death rate for January= Deaths in January *12 * 1000 Mid-year population

Weekly death rate= Death in the week * 52 *1000

Mid-year population

Specific death rate :

Case fatality rate: Total number of deaths due to a particular disease *100

Total number of cases due to the same disease • Represents the killing power of the

disease.

• Number of deaths due to particular cause (or in a specific age group) per 100(or 1000) total deaths.

proportional mortality rate (ratio):

proportional mortality rate (ratio):

A-proportional mortality from a specific disease =

No deaths from the specific disease in a year*100 Total deaths from all causes in that year

B - Under 5 proportionate mortality rate=Number of deaths under 5 years of age in the given year *100

Total number of deaths during the same period

C-proportional mortality rate for aged 50 years and above=

Number of deaths of persons aged 50 years and above*100 Total deaths of all age groups in that year

proportional mortality rate (ratio):

Survival rate:

It is the proportion of survivors in a group, (e.g., of patients) studied and followed over a period (e.g., a5-year period).

Total number of patient s alive after 5 years *100=

Total number of patients diagnosed or treated

Adjusted or standardized rates

• To remove the confounding effect of the different factors involved in the comparison and give a single standardized or adjusted rate (age, sex, parity… etc).

• Carried out by two methods; direct or indirect standardization, both begin with selection of the population, not the age structure.

Steps of direct standardization

• The standard population (SP) “is one for which the numbers in each age and sex group are known”

• 1st step: (SP) selection. • 2nd step: To apply to the standard

population, the age-specific rates of the population whose crude death rate is to be adjusted or standardized.

Steps of direct standardization

• 3rd step: Consequently, for each age group, an expected No of deaths or events in the standard popn is obtained. These are added together to all age groups to give the total expected deaths.

• 4th step: Divide the total expected No of deaths by the total of the standard popn; yields the standardized or age adjusted rate

Steps of direct standardization

Calculation of age-specific death rate for city X

Crude death rate per 1000= 8.3

Age Mid year popn

Death in the year

Age-specific death rate

04,0006015.01 - 44,500204.4

5 - 144,000123.015 - 195,000153.020 - 244,000164.025 - 348,000253.135 - 449,000485.345 - 548,00010012.555 - 647,00015021.4

53,500446

Calculation of standardized death rate for city X

Age Standardized Popul

Age-specific death

rate/1000

Expected deaths

02,40015.0361 - 49,6004.442,24

5 - 1419,0003.05715 - 199,0003.02720 - 248,0004.03225 - 3414,0003.143,435 - 4412,0005.363,645 - 5411,00012.5137,555 - 648,00021.4171,2

93,000609,94

Standardized deathRate/1000=609.94*1000=6.6593,000

• Standardizing for age distribution has reduced the crude death rate from 8.3 to 6.56.

• Usually, the national popn is used as standard when inter-regional comparisons between cities within a range is made.

• To make it over a period of yrs, a standard popn can be maintained for that period.

Indirect age standardization

1. Standardized Mortality ratio (SMR)The simplest and most useful form of indirect standardization is (SMR)

2. Other standardization techniques.

Other standardization techniques

1. Indirect adjustment: yields absolute age adjusted rate (calculate the index death rate and a standardizing factor for each popn of interest).

2. Life-table is an age-adjusted summary of current all-causes mortality.

Other standardization techniques

3. Regression techniques (inefficient means of standardization).

4. Multivariate analysis: a computer using regression or similar methodsCan standardize for many variables simultaneously.