Lecture-8 (Demographic Studies and Health Services Statistics).ppt

Demographic and Health
Services Statistics
University of Gondar
College of medicine and health science
Institute of public health
Department of Epidemiology and
Biostatistics
Lemma Derseh (BSc., MPH)

Demographic and Health Services
Statistics
 Demography is the study of human population in its static and
dynamic aspects
 The static aspects of population to be studied could include
characteristics at a point in time such as composition by: age,
sex, race, marital status, economic characteristics
 Whereas the dynamic aspects are: Fertility, mortality, nuptiality
(marriage), migration and growth.

DEMOGRAPHIC AND HEALTH CONT…
 The three elements of demography are the:
 Size,
 Composition and,
 Distribution
of human population
 These elements are affected by three main
demographic processes namely,
 fertility,
 mortality and
 migration

SOURCES OF DEMOGRAPHIC DATA
 Demographic data can be produced mainly through:
 Census
 Continuous vital events registration
 Sample survey
 The choice to carry out among the above sources is
influenced by several factors including: resource (time, man
power, finance), accuracy needed, etc

SOURCES OF DEMOGRAPHIC DATA CONT…
 A census is the enumeration at specific time of
individuals comprising the population within an
area
 There are two methods of making a census:
 1- De fact
 2- De jure

CENSUS CONT…
De facto census
 Counting individuals wherever they actually are on the
day the census is conducted.
Advantage
 The de facto census is much easy, less expensive and
more economic to apply than de-jure type.
The disadvantages include
 Persons in transit may not be included
 Provision of incorrect picture of the population
 Vital rates may be distorted

Census cont…
The de jure census
 Counting individuals at their legal permanent residence
regardless to whether or not they are physically present
at the time of the census.
Advantage
 It gives a true figure.
The disadvantages include
 Expensive in time and money
 Some individuals may be counted twice
 Information may be incomplete

CENSUS CONT….
o
oCharacteristics and essential features of census
o Individual enumeration-implies that each individual is enumerated
and his/her characteristics recorded separately
o Universality within a defined territory- census should cover the entire
country or well defined territory and include every person living
therein
o Simultaneity-data collected should refer to the same well defined
reference period – generally the census day with specific time
o Defined periodicity-census should be taken at regular intervals so
that comparable information is made available in a fixed sequence
o Accuracy and reliability of information

CONTINUOUS VITAL REGISTRATION
 Continuous vital registration consists of the following
component parts:
Live birth
o Extraction or expulsion
o Product of conception
o Breathes or shows evidence of life
o Duration of pregnancy irrelevant
Fetal death
o Death prior to the complete expulsion
o “early fetal deaths” – less than 20 weeks
o “intermediate fetal deaths” – 20 – 28 weeks
o “late fetal deaths” – 28 weeks or more

CONTINUOUS VITAL REGISTRATION CONT…
Death
 Permanent disappearance of life
Marriage
 Act, ceremony, process
 Legal relationship
 Civil, religious or other
Divorce
 Final dissolution of a marriage

SAMPLE SURVEYS
 Though the above sources (census, and vital registration) can be
the major sources of demographic data, it may be difficult to conduct
them in a stuffiest degree in developing countries like Ethiopia
 Census can be done only once in ten years
 Continuous vital registration hasn’t started till now in
Ethiopia
 Sample surveys are thus the feasible alternatives to fill this gap
 This is because sample surveys are based on only some
representative members of the population which may request a
huge resource
 Can be made also in a reasonably short time intervals or
sporadically
 A few survey examples which can give demographic data are DHS,
household consumption and expenditure surveys, etc

DEMOGRAPHIC TRANSITION
 It is occurrence of major demographic changes/trends of
the past two centuries.
Stages of demographic transition
Pre-transitional:- high mortality and high fertility, with low
population growth (young population).
 Triangular, broad based pattern of population pyramid.
 Seen in primitive societies and is sometimes known as
expansive (type I).
Transitional:- high birth rate and reduced death rate, with
high (rapid) growth rate (“young population”).
 triangular pyramid characterizing a developing society
(sometimes known as expansive (type II).

STAGES OF DEMOGRAPHIC TRANSITION
Post –transitional:- low birth and death rates with stable,
moderate growth rate.
 Narrow based pyramid and steeper sides.
 Typical of advanced or developed countries and is
sometimes known as stationary (Type III).
 Life expectancy is higher and a high proportion of the
population survives in to the old age (“old population”).
Stage – IV: low mortality but very low birth rates giving
negative growth rate

POPULATION PYRAMIDS
 Population Pyramids are a useful tool for understanding the
structure, composition and size of populations because they
graphically portray many aspects of a population, such as
sex ratios and age structure.
 The following points are facts about population pyramids:
Normally males are on the left and females are on the
right;
Age categories are in 5 year increasing intervals
labeled up the center axis;
The horizontal axis is measured in millions.

CALCIFICATION OF POPULATION PYRAMIDS
Expansive or expanding
 Characterized by wide base indicating a high-
birth rate & the narrow top indicates a high death rate.
 It is a characteristic of a lower standard of living:
 High birth rate due to poor access to birth control, lack of education
etc.;
 High death rate due to poor medical care & nutrition.

CALCIFICATION OF POPULATION PYRAMIDS CONT…
Stationary or Stable Population
 It has a half ellipse shape.
 The base of the pyramid is similar in width to the population of the
reproductive ages which indicates a stable population.
 It is the characteristic of a high standard of living due to:
 Low birth rate due to good family planning, access to birth control,
financial planning, education, etc.;
 Low death rate due to good medical care, nutrition, education etc.

CALCIFICATION OF POPULATION PYRAMIDS
Contractive or contracting
 Contractive or contracting population pyramids have a
narrower base than the reproductive age population.
 This indicates a decreasing population trend.
 The low birth rate is indicative of a well developed country.

POPULATION PYRAMID
Exercise
 How do you categorize the urban and the country level
population pyramids of Ethiopia into one of the above three
types of pyramids?

VITAL STATISTICS
Ratio
It is the occurrence of one event in relation to the other (x/y)
where x and y are completely independent
 Sex Ratio is measured as the ratio of males relative to females in
a population
 General formula: Sex Ratio = (Number of males/Number of
females) x100%
 Beyond the simple ratio of sexes (males to females), we can add
other variables to it for further analysis like sex ratio by: age, birth,
death, migration, etc.
 W can have other types of ratios like: dependency ratio,
child to women ratio, maternal mortality ratio, etc.

VITAL STATISTICS CONT...
Proportions
 A specific type of ratio in which the numerator is
included in the denominator, usually presented as a
percentage. (x is included in y in the ratio x/y).
 Example: Female/Both sexes, or
(proportion of female in a community)

RATES
 Rate measures the occurrence of an event in a population
over time.
 The time component is important in the definition.
 Generally rates can be broadly categorized as:
Crude rates
Category specific rates
Adjusted rates

RATES
Crude rates
Example:
Crude death rate
Crude Birth Rate
1000
year
same
in the
population
year
-
Mid
year
a
in
birth
live
of
Number
Total
CBR
*



RATES CONT…
Category/specific rates
Examples on mortality rates:

RATES CONT…
Adjusted/standardized rates
 A standardized death rate is a crude death rate that has
been adjusted for differences in age composition between
the region under study and a standard population.
 Standardization allows for comparisons when the
population structures differ and is key in assessing the
potential influence of environmental or cultural factors on
death rates in a region.
 Two methods of standardization
 Direct standardization
 Indirect standardization

FERTILITY RATES
Crude Birth rate (CBR)
It indicates the number of live births per 1000 population
in a given year.
= Number of births per year
Total Mid-year population
The information required to calculate CBR usually obtained
from a complete and accurate vital registration system or
census
However, CBR has limitations like:
It gives only a crude estimate of fertility.
All the population included in the denominator is not
exposed to the risk of pregnancy
It is not good for comparing fertility across populations,
as variations in age distribution of the populations being
compared will affect the birth rate

FERTILITY RATES CONT…
 General Fertility rate
 Number of live births per 1000 women ages 15-49
in a given year or is the same as:
 It relates births to the age-sex group at risk of giving
births (usually defined as women ages 15-49 years)
 It is more refined measure than crude birth rate to
compare fertility across populations

Age Specific Fertility Rate (ASFR)
 ASFR is the ratio of the number of births per year per 1000
women of a specific age (group)
 Example

TOTAL FERTILITY RATE
 It estimates the number of children a hypothetical cohort of
1,000 females in the specified population would bear if they
all went through their childbearing years experiencing the
same age-specific birth rates for a specified time period.
 Or it can be defined as the average number of children that
would be born to a woman by the time she ended
childbearing if she were to pass through all her childbearing
years conforming to the age-specific fertility rates of a given
year

 TFR = (ΣASBR) x 5, where ASBR is each five-year age-specific
birth rate defined as
 Where Bx is the number of live births to mothers age x and Px is
the number of resident women age x.
 The sum of these ASBRs is multiplied by 5 because each ASBR
represents a five-year cohort of women
 Sometimes TFR is expressed per woman instead of per 1,000
women.
 For example, the theoretical replacement rate would be
expressed as 2.1 live births per woman.

Example:
 TFR = 419.7 X 5 = 2,098.5 live births per 1,000 female who
live through their reproductive years
 Note that sometimes the age group 10-15 may be ignored from the calculation of
TFR.

Gross Reproduction Rate (GRR)
 The average number of daughters that would be born to a
woman during her lifetime if she passed through her child-
bearing years conforming to the age specific fertility rates of a
given year
 GRR is exactly like TFR, except that it counts only daughters,
and literally measures “reproduction”–a woman reproducing
herself in the next generation by having a daughter.
GRR = ∑ASFRx(Bf/Bf+m) = TFRx(Proportion of female births)
 Where, Bf= Number of female births and Bm+f= Number of male
and female births i.e. all births

 Example: Let the TFR and Sex Ratio at birth for a certain
country were 6.7 and 1.03 respectively. Then the GRR can
be calculated as:

Net Reproduction Rate (NRR):
 Average number of daughters that would be born to a woman
if she passed through her life-time from birth to the end of her
reproductive years conforming to the age-specific fertility
and mortality rates of a given year
 NRR is always lower than GRR, because it takes into
account the fact that some women will die before entering
and completing their child-bearing years.
 Correspondingly NRR will be less than half the magnitude of
the TFR

Reproduction of population when NRR = 3

Replacement Fertility
 Replacement Level of Fertility is said to have been reached
when NRR=1.0.
 This will occur when surviving women in the hypothetical
cohort have exactly enough daughters (on average) to
replace themselves in the population.
 It is the same as when GRR>1 and TFR>2. Roughly, this is
when couple has an average of two children.
 However, when NRR=1.00 it does not imply that CBR= CDR
or Population growth rate = 0

MEASURES OF MORTALITY
 Crude Death Rate:
 Age-Specific Death Rate (ASDR):
1000
year
given
in the
area
same
in the
population
year
Mid
year
given
a
in
area
an
a
in
occurring
causes
all
to
due
deaths
of
number
Total
CDR 

1000
a
group
age
or
age
at
population
year
Mid
a
group
age
or
age
at
deaths
Total
ASDRa 


 Infant Mortality Rate (IMR):
1000
births
live
Total
age
of
year
one
under
children
of
Deaths
IMR 

MEASURES OF MORTALITY CONT…

POPULATION PROJECTIONS
 There are different types of population projection
methods. The most important once are:
 The exponential method
 The logistic method
 The cohort component method

The exponential growth model
 It is the simplest type of population growth model.
 Exponential growth occurs when a population is not limited by
other competitors, resources are not limited, and the environment
is constant.
 These conditions called an ‘ecological vacuum’, and this does not
often occur (for long) in nature

THE EXPONENTIAL GROWTH MODEL CONT…
P(t) = P0(1 + r)t , where:
Where, P(t) is the population at time t,
 r = CBR-CDR, which is the rate of natural increase or intrinsic rate
of increase. Therefore, r is the theoretical maximum rate of
increase of a population per individual
 P0 is the initial population
 t is the time on which projection is to be made
Equivalently we can use the formula (mathematically same):
P(t) = P0ekt
Where, k = ln(1 + r)

THE EXPONENTIAL GROWTH MODEL CONT…
 Example: Consider the population of a certain minority group
of size 5000 in an island. If this population is increasing by
5% each year, by how many individuals will the population
increase after 30 months?
 Let P(t) be the population after t years. Then
P0 = P(0) = 5000 is the initial population size in the island.
Let r = 0.05 be the percentage increase each year.
 Therefore, the population size after 30 months = 5/2 years is
given by:
P(5/2) = 5000(1.05)5/2 = 5649
 Therefore, the population in the island will increase by 5649 -
5000= 649 individuals after 30 months.

THE LOGISTIC GROWTH MODELS
 Exponential models have a flaw since they assume
population can grow without bound.
 In many situations, growth begins exponentially but then
slows and approaches zero. The population approaches a
maximum sustainable population.
 Logistic models incorporate an upper bound on the
population. It is one of the most important population growth
models.
 P(t) = 1/(1+ae-kt ), where a and k are positive constants in the
model and t is the time.

LOGISTIC GROWTH MODEL CONT…
 Example: The number of students infected with flu at a high
school after t days is modeled by the function:
P(t) = 800/(1 + 49e−0.2t) .
(a) What is the initial number of infected students?
(b) When will the number of infected students be 200?
(c) The school be will closed when 300 students are
infected. When does the school be closed?
(a) At t = 0, we have P(0) = 800/(1 + 49e−0.2t) = 800/(1 + 49) =
800/50 =16. There are initially 16 students infected.
(b) The number of infected students is equal to 200 when P(t)
= 200 = 800/(1 + 49e−0.2t), implying that t ≈14 days

THE COHORT-COMPONENT METHOD
 The cohort component technique uses the components of
demographic change including births, deaths, and migration to
project population .
 It projects the population by age groups, in addition to other
demographic attributes such as sex and ethnicity.
Formula:
P t+n = Survived population + births + net migrant
 Assumption: the components of demographic change, mortality,
fertility, and migration, will remain constant throughout the
projection period.
 Use the cohort component method when population projections by
age and sex are needed for 5 years, 10 years or longer periods of
time

HEALTH SERVICE STATISTICS
 Major limitations of morbidity and mortality data
from health institutions in Ethiopia
 Lack of completeness:
 Lack of representativeness:
 Lack of denominator: The underlying population
served by a health institution is difficult to define
 Lack of uniformity in quality:
 Lack of compliance with reporting:

HEALTH SERVICE UTILIZATION RATES
1. Admission rate (AR): The number of (hospital)
admissions per 1000 of the population per year
1000
area
Catchment
the
of
n
Populatio
Total
year
the
in
Admissions
of
Number
AR 

2. Average length of stay (ALS): the average period in hospital (in
days) per patient admitted.
Deaths
and
s
Discharge
of
Number
ays
Patient D
zed
Hospitali
of
Number
Annual
The
ALS 

 Bed-occupancy rate (BOR): the average
percentage occupancy of hospital beds.
 Turnover interval (TI): the average period, in
days, that a bed remains empty( the average time
elapsing between the discharge of one patient
and the admission of the next).
365
1
Beds
of
Number
Total
ays
Patient D
zed
Hospitali
of
Number
Annual
The
BOR 

Deaths
and
s
Discharge
of
Number
ays
Patient D
zed
Hospitali
of
Number
-
Beds)
of
Number
(365
TI


HEALTH SERVICE UTILIZATION RATES…

HOSPITAL DEATH RATE (HDR)
1000
Period
Given
the
in
s
Discharge
of
Number
Period
Given
a
in
Deaths
Hospital
of
Number
Total
HDR 


EXERCISE
a) Calculate the population doubling time of a given country with annual
rate of
growth ( r) = 1% .
b) The following summary table was taken from the annual (1988) health
profile of
district Z.
Year Total population of the
district
No of health institutions in the district Total number of
hospital beds
Health Station Health Center Hospital
1988 400,000 14 2 1 80
1. The health service coverage of the district
2. The average length of stay
3. Bed occupancy rate
4. Turnover interval

Lecture-8 (Demographic Studies and Health Services Statistics).ppt

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Lecture-8 (Demographic Studies and Health Services Statistics).ppt