Download MEASURING DISEASE FREQUENCY

VITAL STATISTICS
FAJAR AWALIA YULIANTO
COMMUNITY RESEARCH PROGRAM1


There is no complete agreement for all
epidemiologists for the term used in this field
What will be described afterward is common
term that usually used, taken from Last’s
Dictionary of Epidemiology
POPULATION AT RISK
An important factor in calculating measures of
disease frequency is the correct estimate of
the numbers of people under study
0-24
yrs
male
25-69
yrs
0-24
yrs
25-69
yrs
70+yrs
70+yrs
a study of carcinoma of the
cervix
female
POPULATION AT RISK


The people who are susceptible to a given
disease are called the population at risk, and
can be defined by demographic, geographic
or environmental factors
Examples: Occupational injuries occur only
among working people, avian influenza
occurs only among people handling cattle
INCIDENCE AND PREVALENCE


Incidence represents the rate of occurence of
the new cases arising in a given period in a
specified population
Prevalence is the frequency of existing
cases in a defined population at a given point
in time
DIFFERENCES BETWEEN
INCIDENCE AND PREVALENCE
INCIDENCE
PREVALENCE
NUMERATOR
Number of new cases of diseases
during a specified period of time
Number of existing cases of
disease ar a given point of time
DENOMINATOR
Population at risk
Population at risk
FOCUS
Whether the event is a new case
Time of onset of the disease
Presence or absence of a
disease
Time period is arbitrary; rather
a “snapshot” in time
USES
Expresses the risk of becoming ill
The main measure of acute
diseases or conditions, but also
used for chronic diseases
More useful for studies of
causation
Estimates the probability of the
population being ill at the
period of time being studied
Useful in the study of the
burden of chronic diseases and
implication for health services

If the incident cases are not resolved, but
continue over time, then they become
existing (prevalent) cases,
prevalence=incidence x duration
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

If the population at risk undefined, the case
numbers still useful to express the magnitude
of the health events, e.g during epidemic
Attack rate ~ Incidence, used during the
disease outbreak in a narrowly-defined
popilation over a short period of time
Attack rate can be calculated as the number
of people affected divided by the number
exposed
PREVALENCE


P = (Number of people with the disease or
condition at a specified time / Number of
people in the popilation at risk at the specified
time) X 10n
Factors determine prevalence:
The severity of illness
 The duration of illness
 The numberof new cases
That’s why prevalence study do not usually provide
strong evidence of casuality

INCIDENCE


I = (number of new events in a specified
period / Number of persons exposed to risk
during this period) X 10n
The numerator strictly tefers only to first
events of disease
CUMULATIVE INCIDENCE


Unlike incidence, it measures the
denominator only at the beginning of a study
CI = Number of people who get a disease
during a specified period / Number of people
free of the disease in the population at risk at
the beginnig of the period X 10n
CASE FATALITY


Is a measure of the disease severity and is
defined as the proportion of cases with a
specified disease or condition who die within
a specified time
CF = (Number of deaths from diagnosed
cases in a given period / Number of
diagnosed cases of the disease in the same
period) X 100
USING AVAILABLE
INFORMATION TO MEASURE
HEALTH AND DISEASE
DEATH RATE (CRUDE MORTALITY
RATE)
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CMR = (Number of deaths during a specified
period/ number of persons at risk of dying
during the same period) X 10n
The main disadvantage that it does not take
into account the fact that the chance of dying
varies according to age, sex, race,
socioeconomic class and other factors
The following formulation will be diminishing
the limitation of CMR
STUDY QUESTION

The crude death rate for all cancers in Japan
is 241.7 per 100 000 population and the
crude death rate for all cancers in Cote
d’Ivoire is 70.5 per 100 000 population. Is the
death rate in Japan higher than in Cote
d’Ivoire?
AGE SPECIFIC DEATH RATES
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
Can be expressed for specific groups in a
population which are defined by age, race,
sec, occipation or geographical location, or
for specific causes of death
Total number of deaths occuring in a specific
age and sex group f the population in a
defined area during a specified period
10
Estimated total population of the same age
and sex group of the population in the same
area during the same period
n
PROPORTIONATE MORTALITY


The number of deaths from a given cause per
100 or 1000 total deaths on the same period
Proportionate mortality does not express the
risk of members of a population contracting
or dying from a disease
INFANT MORTALITY*
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
It measures the rate of death in children
during the first year of life, the denominator
being the number of live births in the same
year
Number of deaths in a year of children less
than 1 year of age
1000
Number of live births in the same year
CHILD MORTALITY RATE*
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

Is based on deaths of children aged 1-4
years
Injuries, malnutrition and infectious diseases
are common causes of death in this age
group
Describes the probability (expressed per
1000 live births) of a child dying before
reaching 5 years of age
Child mortality rate in selected
countries,2003 (per 1000 live births)
MALES
FEMALES
High income countries
Japan
France
Canada
USA
4
5
6
9
4
5
5
7
Middle income countries
Chile
Argentina
Peru
Indonesia
10
19
36
45
9
16
32
37
Low-income countries
Cuba
Sri Lanka
Angola
Sierra Leone
8
17
276
297
6
13
243
270
MATERNAL MORTALITY RATE
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
Refers to the risk of mothers dying from
causes associated with delivering babies,
complications of pregnancy or childbirth
Number of maternal deaths from puerperal
causes in a given geographic area in a given
year
10
Number of live births that occured among the
population of the given geographic area
during the same year
n
ADULT MORTALITY RATE

Define as the probability of dying between the
ages of 15 and 60 years per 1000 population
Adult mortality rates in selected countries,
2004 (per 1000 population)
Males
Females
High income countries
Japan
Canada
France
USA
92
91
132
137
45
57
60
81
Middle income countries
Chile
Argentina
Peru
Indonesia
133
173
184
239
66
90
134
200
Low income countries
Cuba
Sri Lanka
Angola
Sierra Leone
131
232
591
579
85
119
504
497
LIFE EXPECTANCY*

Defined as the average number of years an
individual given age is expected to live if
current mortality rate continue
Life expectancy atbirth for men and
women in selected countries
Zimbabwe
Russian Fed
Egypt
China
Mexico
USA
Japan
Women
34
72
70
74
77
80
86
Men
37
59
66
70
72
75
79
ALHAMDULILLAH
Wish every science become virtue, and every
mistake become the lesson