epidemiology lecture

1. Basic measures of epidemiology
Mr. Afsar Ali
Assistant Professor
MSN, BScN
Foundation University College of Nursing FUCN

2. OBJECTIVES
• At the end of this session, the learners will be
to:
• Understand the concept Mortality, Morbidity
• Discuss the Rate, Ratio, Incidence, and
Prevalence
• Identify the Maternal and Infant rates in the
specific community
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3. Proportion
• A proportion is the number (a) observations with a
given characteristic divided by the total number of
observations (a+b) in a given group, i.e.
Proportion =a/a+b

4. Ratio
• A Ratio is the number (a) of observations in a given
group with a given characteristic divided by the
number (b) of observations without the given
characteristic, i. e.
Ratio=a/b

5. Rate
• Rate is defined as the ratio between two
measurement of different unites, which is
computed over a specified period of time.
Rate= a/a+b*Base
• The multiplier of proportion is called base

6. • A rate is a measure of some event, disease, or
Condition in relation to a unit of population, along
with some specification of time.
• Facilitates comparison of disease frequency
across different groups of people, places, and
time periods
RATE

7. • Most commonly used in epidemiology because it
most clearly expresses probability or risk of
disease or other events in a defined population
Over a specified period of time
RATE

8. COMPONENTS OF CALCULATION
Number of events x Unit of Population
Population "at risk" of experiencing the
event
(Factor or Multiplier (k) is known & constant and used to
denote
the units of such 100, 1000 or per 100,000)
Denominator
Numerator
Factor Multiplier
(k)

9. Example
• 5 children in community with diarrhea X 100
• 5000 children in community
• 5/5000 = .001x100= 0.1%
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10. BASIC HEALTH STATUS INDICATORS
• Mortality (Death) rates
– Crude rates
– Specific rates
• Morbidity (Disease) rates
• Prevalence
• Incidence

11. BASIC HEALTH STATUS INDICATORS
• Births rate
• Fertility rates
•
• Growth rates
• Life expectancy
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Demographic
indicator

12. Morbidity
• Morbidity is the percentage of people in a
population that gets sick of a particular disease.
• Definition: Morbidity refers to the state of being
diseased or unhealthy.
• Demographic reference: Morbidity refers an
incidence of ill health in a population.
•

13. Morbidity Rates
• Morbidity rates refers to the number of people
within a certain unit of the general population, who
have a certain disease or condition. The unit of
population is usually 100, 000. although this may
vary depending on location and the condition in
question.

14. Cont…
• Morbidity rates are used to help determine the
overall prevalence of a specific illness, as well as
where the most instances of the condition occurs
when compare to the population as a whole.
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15. Cont…
• Researchers use morbidity rates as general
statistical data in determining how common, a
particular condition is, as well as in
determining which members of the population
are more likely to become afflicted.

16. Incidence
Measure of new cases of disease (or other
events of interest) that develop in a population
during a specified period of time.
MORBIDITY
INDICATORS

17. Formula # of new cases of disease reported during
a certain period of time in certain geographical
area x 1000
Estimated mid year of an area at risk of
same time
Example: 70 new cases of breast cancer in a 5 year
period
3,000 women at risk
= (2.3100 OR = 23/1,000 women during 5 years)
MORBIDITY
INDICATORS

18. PREVALENCE
Measures the number of people in a given
population who have a specific (existing) condition
at a given point in time.
MORBIDITY
INDICATORS

19. Formula :# Of existing cases (NEW + OLD) of disease
at at given point in time in certain
geographical area
Estimated mid year of an area at risk in same
geographical area population
Example: 2176 client encounter with Asthma =
0.7
31005 patients
= 7asthamatic per 100 patients = 7% OR (70/1000)
OR (7,000/100,000)
MORBIDITY
INDICATORS

20. Mortality
• Mortality is the percentage of those who die
in that population from that disease.
• Mortality is the term used for the number of
people who died within a population
• Mortality refers to the incidence of death or
the number of deaths in a population.

21. Mortality Rates
• A mortality rate is the amount of deaths in a given
population during a given period of time. The rate is
commonly expressed in deaths out of 100 or 1000
individuals. For instance, if in a town of 10,000 inhabitants,
10 people die of the flu, the flu mortality rate would be one
in 1000. Mortality rates can be based on simply how many
die of any cause in a population, or can be used to describe
the death rate of a certain illness or condition.

22. Cont…
• Mortality rates have many uses, but are often utilized to describe
the increase or decrease in a cause of death over a lengthy time
period. For instance, the Center for Disease Control (CDC) used
mortality rates to show that the mortality rate for car-accident
deaths in the United States dropped from almost 25 per 100,000
to nearly 15 per 100,000 between 1979-2006, while during the
same period poisoning deaths rose from five to 15 per 100,000.
Looking at the mortality rates over time can help health officials
understand where to focus prevention and safety efforts, and
indicate possible trends in death due to factors affecting the
measured population.

23. • Rates presented for individuals in specific categories
e.g.
1. Deaths by Age
• Deaths among 1-5 years age persons
2. Death by cause
• Cancer deaths in the year of 1999
3. Death by age and cause
• Cancer deaths among 45-54 years age persons
CATEGORY SPECIFIC
RATES

24. • Maternal Mortality Rate (MMR)
• = # of deaths occurring due to pregnancy during 1 year X
100,000
Total births in same year
• Perinatal Mortality Rate :
= # of fetal (still births) & infants deaths <7days of life
X 1000
Total # births in same year
Examples of category specific rates

25. Examples of category specific rates
• Neonatal Mortality Rate (NMR) : =
• # of infants deaths < 28 days of life X
1000
• Total # births in same year
• Infant Mortality Rate (IMR) :
• = # of infants deaths < one year
of life X 1000
• Total # births in same year
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27. Crude Death Rate
• Death rate: 6.8 deaths/1,000 population (July
2012 est.)
• Definition: This entry gives the average annual
number of deaths during a year per 1,000
population at midyear; also known as crude
death rate. The death rate, while only a rough
indicator of the mortality situation in a
country, accurately indicates the current
mortality impact on population growth.

28. Crude Death Rate
• This indicator is significantly affected by age
distribution, and most countries will eventually show
a rise in the overall death rate, in spite of continued
decline in mortality at all ages, as declining fertility
results in an aging population
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29. Infant mortality Rates
• Definition: the number of deaths of infants
under one year old in a given year per 1,000
live births in the same year; included is the
total death rate, and deaths by sex, male and
female. This rate is often used as an indicator
of the level of health in a country.

31. MMR
• Definition: The maternal mortality rate (MMR) is the
annual number of female deaths per 100,000 live
births from any cause related to or aggravated by
pregnancy or its management (excluding accidental or
incidental causes). The MMR includes deaths during
pregnancy, childbirth, or within 42 days of termination
of pregnancy, irrespective of the duration and site of
the pregnancy, for a specified year.
• MMR 2010 for Pakistan 260/100,000

33. IMPORTANCE/SIGNIFICANCE
• Measure changes over period of time
• Help to analyze health situation (past, present)
• Determine magnitude of health problems
• Allow to make meaning full comparison

34. Reference
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36. THANK YOU