This lecture looks specifically at measures of disease frequency: morbidity and mortality. You will see how morbidity data can be used, how routinely collected mortality data can begin to throw light on very important issues that might determine health. You will review the sources of important, routinely collected population data in Malaysia: demographic data (e.g., population census) and health event data (e.g., mortality, hospital and general practice data).

1. MORBIDITY & MORTALITY,
HEALTH DATA
Halyna Lugova, MD, PhD
September 25, 2014
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400
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2. Epidemiologic Language
“The prevalence rates of HIV and DM amongst TB patients were
7.7 and 30%, respectively. *…+ Diabetic TB patients had a higher
mortality rate (7.5%) compared to the TB only and DM only groups
(1 and 2%, resp.).”
Suleiman, S. et al. (2012). Role of Diabetes in the
Prognosis and Therapeutic Outcome of Tuberculosis.
International Journal Of Endocrinology, 6 p.
“The average annual incidence rate of DF per 100 000 populations
was higher as compared to that of DHF. Conversely, the yearly
mean mortality rate of DHF per 100 000 populations was greater
than that of DF. *…+ The dengue situation in Malaysia has
worsened with an increasing number of reported cases and deaths
during the last decade.”
Mia, M. et al. (2013). Trends of dengue infections in
Malaysia, 2000-2010. Asian Pacific Journal of Tropical
Medicine, 6(6), 462-466. 2

3. Role of Measurement
“The death rate is a fact; anything
beyond this is an inference.”
― William Farr (1807 – 1883), British
epidemiologist, one of the founders of
medical statistics
“What gets measured gets done.”
― Mason Haire (Author of Modern
Organization Theory)
3
Source: http://www.epimonitor.net/Quotable_Quotes.htm
Images from public domain

4. Ratio, Proportion and Rate
• Ratio: one number divided by another number:
4
x/y
often multiplied by k (100; 1,000; 10,000; 100,000)
Examples: 3 hospitals/60,000 people
= 0.00005 hospitals per person
*k (100,000) = 0.00005 * 100,000 = 5 hospitals per
100,000 people
40 observed cases of DM /20 expected cases of DM
= 2 (no units)
OR = odds ratio
SMR = standardized mortality ratio

5. Ratio, Proportion and Rate
• Proportion: a specific ratio in which the numerator is
a subset of the denominator: x/(x+y)
usually multiplied by k (100; 1,000; 10,000)
x – the number of individuals in the population with characteristic C
x+y – the number of individuals in the same population with and without
characteristic C
Example: proportional mortality
no. of TB deaths / total no. of deaths in 2008 in
Malaysia
= 0.03
*k (100) = 3% or3 per 100; *k = 1,000 = 30 per 1,000
5

6. Ratio, Proportion and Rate
• Rate: basic measure in disease occurrences and
vital statistics:
x*/(x+y)
usually multiplied by k (100; 1,000; 10,000)
x* = the frequency of events during a certain time period
x+y = the number at risk of the event during that time period,
i.e. the sum of follow-up time contributed by the people at risk
of the event
Example: incidence rate
6

7. Ratio, Proportion or Rate?
• The number of students who had dental caries divided by the
number of students who did not have dental caries
Ratio
• The number of students who had dental caries divided by the
number of students who had oral health diseases
Proportion (numerator is a subset of denominator)
• The number of dentists divided by the number of population
Ratio
• The number of students newly diagnosed with dental caries from Jan
2013 till Dec 2013 divided by the number of students who had not
been diagnosed with the disease before Jan 2013
Rate (indicates frequency of event over population at risk during
specific time)
7

8. Measures of Morbidity
Incidence:
Rate of Disease Occurrence in Population
• Measures change from non-disease to disease
• Incidence rate is defined as a number of new cases
in the population at risk which occurred over a given
period of time
Incidence =
Number of new cases
X k
Population at risk
• Population-at-risk: all persons in the population who
have not been diagnosed with the disease of interest
at the beginning of the observation period, but who
are capable of developing the disease 8

9. Measures of Morbidity
Prevalence:
Reflects Already Existing Disease
• Proportion of population which has disease
• Prevalence is defined as a number of existing cases
in a population at a specified time:
• Population: Number of persons present in the
population of interest
9
Prevalence =
Number of cases with the
disease/condition at a specified time
X k
Population at a specified time

10. Relationship between Incidence and Prevalence
10
Source: Eric Notebook (1999) Issue 2: Incidence vs. Prevalence. Available at:
http://cphp.sph.unc.edu/trainingpackages/ERIC/eric_notebook_2.pdf
Incidence is a measure of the flow of water into the tub
Prevalence measures the proportion of the tub (the total
population) filled with water (the prevalent cases)
.
Prevalence = Incidence x Duration (approx.)

11. Difference between Incidence & Prevalence
Characteristic
What is
measured
Time of
disease
diagnosis
Period of
time
Denominator
Incidence
Rapidity of
disease
occurrence
Newly
diagnosed
Period of
study that
allows
monitoring
disease
occurrence
Population
at-risk
Prevalence
Proportion of
population
with disease
Surviving
cases
diagnosed at
any time
Specific
time
Whole
population
11

12. Problems with Morbidity Data
 Numerators: difficulties with diagnostics, problems with
data on cases
 Denominators: certain groups in the population may be
underrepresented, problems with defining population-at-risk
 Hospital Data: selective admissions, missing or incomplete
records, problems of comparability between different
hospitals, absence of defined catchment area (problems
with denominator)

13. Measures of Mortality
Mortality data indicate severity of disease, risk of dying from a
disease, and effectiveness of treatment and prevention
programs.
It is useful in comparison between different populations and in
time. Annual mortality rates are calculated by all causes or by
specific diseases; by age, sex, ethnicity.
Most of the countries’ legislation imposes a requirement of
compulsory registration of all deaths. Therefore, mortality
statistics is usually more available than information on morbidity
If the disease does not ordinarily cause death then mortality
rates are useless
13

14. Case Fatality Rate
Case fatality rate (percent)
푁표.표푓 푖푛푑푖푣푖푑푢푙푎푠 푑푦푖푛푔 푑푢푟푖푛푔 푎
푠푝푒푐푖푓푖푒푑 푝푒푟푖표푑 표푓 푡푖푚푒 푎푓푡푒푟 푑푖푠푒푎푠푒 표푛푠푒푡 표푟 푑푖푎푔푛표푠푖푠
푁표. 표푓 푖푛푑푖푣푖푑푢푎푙푠 푤푖푡푕 푡푕푒 푠푝푒푐푖푓푖푒푑 푑푖푠푒푎푠푒
x 100
• Measure of the severity of a disease
• Measure of the benefits of a disease intervention program, new
treatment
In 2008, population of children under 14 years of age in Malaysia was 8 millions of whom
210,000 were sick with TB
2,000 of 210,000 died from TB.
The mortality rate as a result of TB in 2008 =
ퟐ,ퟎퟎퟎ
ퟖ,ퟎퟎퟎ,ퟎퟎퟎ
= 0.00025, or 0.025% or 0.25 per 1,000
children
The case-fatality rate as a result of TB in 2008 =
ퟐ,ퟎퟎퟎ
ퟐퟏퟎ,ퟎퟎퟎ
= 0.0095, or 0.95% or 9.5 per 1,000
children
14

15. Proportionate Mortality
Proportionate Mortality (percent)
푁표.표푓 푑푒푎푡푕푠 푓푟표푚 푎 푝푎푟푡푖푐푢푙푎푟 푑푖푠푒푎푠푒 푖푛 푎 푦푒푎푟
푇표푡푎푙 푑푒푎푡푕푠 푖푛 푎 푦푒푎푟
x 100
• Proportion of deaths in a population caused by a
particular disease
• Shows trends but not risk or cause
• Useful to compare impact of diseases in a population
15

16. Proportionate Mortality
16
Community A Community B
Mortality rate from
all causes
30/1,000 15/1,000
Proportionate
mortality from
disease X
Mortality rate from
disease X
9/1,000 9/1,000

17. Proportionate Mortality
17
Community A Community B
Mortality rate from
all causes
20/1,000 10/1,000
Proportionate
mortality from
disease X
Mortality rate from
disease X
14/1,000 17/1,000

18. Problems with Mortality Data
• Depends on death certification
• Coding of death certificates including
changes related to changes of ICD.
• Errors in diagnosis, counting population or
percentages of population at risk,
identification of age and other demographic
groups
18

19. Commonly Used Health Indicators
Annual crude live birth rate
푁푢푚푏푒푟 표푓 푏푖푟푡푕푠 표푐푐푢푟푖푛푔 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 푖푛 푡푕푎푡 푝표푝푢푙푎푡푖표푛 푎푡 푚푖푑푦푒푎푟 표푓 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual crude death rate
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 표푐푐푢푟푖푛푔 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 푖푛 푡푕푎푡 푝표푝푢푙푎푡푖표푛 푎푡 푚푖푑푦푒푎푟 표푓 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual specific death rate (by age, sex, cause or a combination)
푁푢푚푏푒푟 표푓 푠푝푒푐푖푓푖푒푑 푑푒푎푡푕푠 표푐푐푢푟푖푛푔 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 표푓 푠푝푒푐푖푓푖푒푑 푝표푝푢푙푎푡푖표푛 푎푡 푚푖푑푦푒푎푟 표푓 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual maternal mortality rate
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푓푟표푚 푚푎푡푒푟푛푎푙 푐푎푢푠푒푠 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟 푎푡 푎 푔푖푣푒푛 푡푖푚푒
푁푢푚푏푒푟 표푓 푤표푚푒푛 표푓 푐푕푖푙푑푏푖푟푡푕 푎푔푒 푖푛 푡푕푎푡 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual maternal mortality ratio
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푓푟표푚 푚푎푡푒푟푛푎푙 푐푎푢푠푒푠 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟 푎푡 푎 푔푖푣푒푛 푡푖푚푒
푁푢푚푏푒푟 표푓 푙푖푣푒 푏푖푟푡푕푠 푖푛 푡푕푎푡 푝표푝푢푎푙푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
19

20. Commonly Used Health Indicators (cont.)
Annual infant mortality rate ( = IMR)
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푢푛푑푒푟 1 푦푒푎푟 표푓 푎푔푒 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 표푓 푙푖푣푒 푏푖푟푡푕푠 표푐푐푢푟푖푛푔 푖푛 푡푕푎푡 푝표푝푢푎푙푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual neonatal mortality rate
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푢푛푑푒푟 28 푑푎푦푠 표푓 푎푔푒 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 표푓 푙푖푣푒 푏푖푟푡푕푠 표푐푐푢푟푖푛푔 푖푛 푡푕푎푡 푝표푝푢푎푙푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual post-neonatal mortality rate
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푏푒푡푤푒푒푛 28 푑푎푦푠 푎푛푑 1 푦푒푎푟 표푓 푎푔푒 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 표푓 푙푖푣푒 푏푖푟푡푕푠 표푐푐푢푟푖푛푔 푖푛 푡푕푎푡 푝표푝푢푎푙푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
Annual stillbirth rate (fetal death rate)
푁푢푚푏푒푟 표푓 푑푒푎푡푕푠 푎푡 20 표푟 푚표푟푒 푤푒푒푘푠 푔푒푠푡푎푡푖표푛푎푙 푎푔푒 푖푛 푎 푑푒푓푖푛푒푑 푝표푝푢푙푎푡푖표푛 푑푢푟푖푛푔 푎 푦푒푎푟
푁푢푚푏푒푟 표푓 푙푖푣푒 푏푖푟푡푕푠 표푐푐푢푟푖푛푔 푖푛 푡푕푎푡 푝표푝푢푎푙푡푖표푛 푑푢푟푖푛푔 푡푕푒 푠푎푚푒 푦푒푎푟
x 1.000
20

21. Types of Health Data
• Population data: the number of people in a population
and their attributes
• Vital statistics: live births, deaths, and marriages
• Health statistics: morbidity by type, data on notifiable
diseases, impairment, cancer registries
• Health services statistics: number and types of
facilities, nature of services; costs, payment
mechanisms
• Data on social inequalities in health: rates of poverty,
level of education, and occupational conditions
21

22. Population (age) pyramid
 This population pyramid is wide at the base, which means
there is a large proportion of young people in the
country. It tapers very quickly as you go up into the older
age groups, and is narrow at the top.
22
 This pyramid is
expanding; it shows
that a very small
proportion of
people are elderly.
This shape of
pyramid is typical of
a developing
country
Source: http://www.indexmundi.com

23. Population (age) pyramid
• This shape is typical of a developed country. It is
narrow at the base, wider in the middle, and
stays quite wide until the very top, as there is a
sizable percentage of older people.
23
 This pyramid is
contracting,
showing lower
numbers or
percentages of
younger people.
Source: http://www.indexmundi.com

24. Population (age) pyramid
24
Source: http://www.indexmundi.com

25. Vital and Health Statistics
• Data collection should be fair and complete, therefore
this data is usually collected by governmental agencies
• In Malaysia, there are various agencies that collect
data: the key health data collectors are the
Department of Statistics of Malaysia (DSM) and the
Ministry of Health (MOH)
25

26. Vital and Health Statistics in Malaysia
• DSM gathers data through periodic statements/reports from
government agencies and from the census conducted (Banci
Negara)
• DSM also receives data on births and deaths from the National
Registration Department (JPN)
• Vital Statistics Malaysia, 2012 report presents statistics on
births and deaths for 2011 (final) and 2012 (preliminary) at
state and administrative district levels*.
• The population estimates used in the calculation of these
indicators are based on the Population and Housing Census
2010, which is done every 10 years
*Source: Department of Statistics Malaysia, Official Portal
http://statistics.gov.my/portal/images/stories/files/LatestReleases/vital/Vital_Statistics_Malaysia_
2012.pdf
26

27. Vital and Health Statistics in Malaysia
• MOH collects data through
 Hospital admissions / discharge
 Clinic attendance and diagnosis
 Periodic district health reports
 Monthly reports from Vector Borne Disease Control Program
Notifiable Disease Reports
Health Facts (published annually, 2014 ed. available with
data from 2013)
Health Indicators (annually, currently latest is 2013 data)
Source: Official Portal Ministry of Health Malaysia
http://www.moh.gov.my/english.php/pages/view/56
27

28. SUMMARY
• Rates are an important concept, they allow
measurement and comparison of health data
• By exploring patterns and variations in the health
outcomes we can begin to hypothesize about possible
determinants of population health, and this is the
essence of descriptive epidemiology. Descriptive
epidemiology relates to the study of variations in
population health by time and person and place
28

29. SUMMARY
• Incidence rate is the number of new cases which occur
during a specified time period in a defined at risk
population
• Prevalence is a number of cases in a defined
population at a particular point in time, or during a
specified period
• The relationship between incidence and prevalence is
determined by the duration of disease
29

30. SUMMARY
• Proper collection of vital and health statistics is very
important; Dep of Statistics and MoH are key
collectors in Malaysia
• Mortality data is usually more available than
morbidity data, but it depends on death certification
aspects, diagnostics criteria and other factors
30