Basic measurement

1. Social determinants of Health
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2. Social determinants of Health
 Health and health problems result from a complex
interplay of a number of forces.
 An individual‘s health-related behaviors , particularly
diet, exercise, smoking,
 Surrounding, the physical environment,
 Health care( access and quality)
All contribute significantly to how long and how well
we live.
 These factors are collectively known as Social
determinants of Health.
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3. Components of the SDH
There are four major components of SDH
1. Physical environment
2. social environment
3. life style and behaviors
4. economic environment
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4. Components of the SDH
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5. Core determinants of health
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6. SDH…
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7. Health disparity
Difference in health that is closely linked with social
or economic disadvantage.
It negatively affects groups of people who have
systematically experienced greater social or economic
obstacles to health.
These obstacles stem from characteristics linked to:
 discrimination or exclusion such as race or ethnicity, religion,
 socioeconomic status, gender, mental health,
 sexual orientation, or geographic location.
 Other characteristics physical disabilities,…etc.
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8. WHO commission reports on the SDH
components contribution
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9. SDH contribution in early death
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Source: Schroeder SA. N Engl J Med 2007;357:1221-1228.

10. SDH/lifestyle and behaviors contribution in
death
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11. SDH vs health outcome
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12. Brain storming?
Why is the life expectancy scored 80 years
in some countries and less than 50/45 in
other countries?
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13. Examples of Health Inequalities
Between the countries
 the infant mortality rate is 2/1000 live births in
Iceland and over 120/1000 live births in
Mozambique.
 The lifetime risk of maternal death during or
shortly after pregnancy is only 1 in 17400 in
Sweden, but 1 in 8 in Afghanistan.
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14. …Health Inequalities
within the countries
 In Bolivia, babies born to women with no education have infant
mortality greater than 100/1000 live births vs babies born to
mothers with at least secondary education is under 40/1000
 Life expectancy at birth among indigenous Australians (59.4 for
males and 64.8 for females) vs non-indigenous Australians (76.6
and 82.0, respectively).
 Prevalence of long-term disabilities among European men aged
80+ years is 58.8% among the lower educated vs. 40.2% among
the higher educated.
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15. Why such a huge gap? Reasons for health
inequalities
 Variation in degrees of social disadvantages.
 The circumstances in which people grow, live, work,
and age, and the systems put in place to deal with
illness.
 The unequal distribution of power, income, goods, and
services, globally and nationally,
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16. Reasons for health inequalities…
 consequent unfairness in the immediate, visible
circumstances of peoples lives
 Inaccessibility of health care, schools, and
education
 work condition, leisure, living house, communities,
towns, or cities
 urban environments that has a major impact on
behavior and safety.
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17. Reasons for health inequalities…
 Urbanization poses significant environmental
challenges, particularly climate change
greater in low-income countries and among
vulnerable subpopulations.
 The disruption and depletion of the climate system
Greenhouse gas emissions (…transport and
buildings, agricultural activity)
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18. Why is the healthy society needed?
 The development of a society, rich or poor, can be
judged by the quality of its population‘s health.
 how fairly health is distributed across the social
spectrum and the degree of protection provided from
disadvantage as a result of ill-health.
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19. Why is the healthy society needed?...
 The poorest of the poor have high levels of illness
and premature mortality.
 In countries at all levels of income, health and
illness follow a social gradient,
othe lower the socioeconomic position, the worse
the health conditions.
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20. R/ship between income and Health
Higher income buys better quality healthcare
 More resources for goods/ services that results
in better health care outcomes.
 Parents adopt better health care practices also
tend to be ―more productive‖ resulting in better
outcomes for their children.
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21. Universal Health Care as a social determinants of health
 Access to and utilization of health care is vital to good and
equitable health.
 The health-care system itself is a social determinant of health,
influenced by other social determinants.
 Gender, education, occupation, income, ethnicity, and place of
residence are all closely linked to people‘s access to,
experiences of, and benefits from health care.
 Leaders in health care have an important stewardship role
across all branches of society to ensure that policies and
actions in other sectors improve health equity.
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22. Recommendations for health inequalities
1. Ensuring the access to basic goods, and creating
community that are socially cohesive and protective of the
natural environment are essential for health equity.
2. Build health-care systems based on principles of equity,
disease prevention, and health promotion.
3. Build and strengthen the health workforce, and expand
capabilities to act on the social determinants of health.
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23. Recommendation…
4. Establish and strengthen universal comprehensive social protection
policies that support a level of income sufficient for healthy living for
all.
5. Tackle the inequitable distribution of Power, Money, and
Resources
6. Place responsibility for action on health and health equity at the
highest level of government, and ensure its coherent consideration
across all policies.
7. Strengthen public finance for action on the social
determinants of health
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24. Recommendation…
8. Address gender biases in the structures of society – in
laws and their enforcement.
9. Ensuring the routine monitoring systems for health
equity and the social determinants of health at all level.
10. Provide training on the social determinants of health
to policy actors, stakeholders, and practitioners and invest
in raising public awareness.
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25. Basic measurements in Epidemiology
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26. Learning objectives
After completing this session, students should
be able to:
 Describe the principles of measurement in
epidemiology
 Explain measures of disease frequency
 Calculate measure of disease occurrence
 Calculate measure of mortality
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27. Measurement of health
 Epidemiology is mainly a quantitative science.
 Measures of disease frequency are the basic tools of
the epidemiological approach.
 Health status of a community is assessed by the
collection, compilation, analysis and interpretation of
data on illness (morbidity), on death (mortality),
disability and utilization of health services.
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28.  The most basic measure of disease frequency is a simple count of affected
individuals/people with the event.
 Such information is useful for public health planners and administrators for the
allocation of health care resources in a particular community.
 However, to investigate distributions and determinants of disease, it is also
necessary to know the size of the source population from which affected
individuals were counted.
 One of the central concerns of epidemiology is to find and enumerate
appropriate denominators in order to describe and to compare groups in a
meaningful and useful way.
 Such measures allow direct comparisons of disease frequencies in two or more
groups of individuals.
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29. Measures of …..
….frequency
– Count
– Ratio
– Proportion
– Rate
Disease occurrence
– Prevalence
– Incidence
• Cumulative incidence
( CI), (Incidence
proportion)
• Incidence density
(ID),
• Attack rate (AR)
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30. I. Measuring Disease frequency
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31. 5/19/2022 32
Ratio
 Ratio: relating two completely independent parameters
 A ratio is the relative size of two quantities
 It quantifies the magnitude of occurrence of something in relation to
another.
 One character divided by another (the value of x and y are independent)
◦ Example:
 The ratio of males to females in Ethiopia
 The ratio of male to female birth in ‗X‘ community
 No specific relationship is necessary between the numerator and
denominator (numerator NOT necessarily included in the denominato
 Either the numerator or denominator is set to 1
 n:y or
 n/n: y/n or 1 to y/n

32. example
 # beds per doctor
120 beds/10 doctors
120/10 : 10/10
12 beds for a doctor
 Odds ratio
 Rate ratio
 Maternal mortality rate
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33. 5/19/2022 34
Proportion
 Proportion: relating two dependent parameters
 It is a specific type of ratio in which the numerator is
included in the denominator and the result is expressed
as a percentage.
Example: proportion of female in a community
Female/ Female + male *100
 It is comparison of a part to the whole population
 Numerator MUST BE INCLUDED in the
denominator
 It‘s result ranges between 0 and 1 or(0–100%)

34. 4. RATE
Rate is a special form of proportion that includes the
dimension of time.
Rate: measures the occurrence of an event in a population
over time.
It is the measure that most clearly expresses probability
or risk of disease in a defined population over a specified
period of time, it is considered to be a basic measure of
disease occurrence.
Accurate count of all events of interest that occur in a
defined population during a specified period is essential
for the calculation of rate.
Rate = Number of events in a specific period X k
Pop. at risk of these events in a specified period
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35. Types of rates
There are three types of rate:
 Crude rates
 Specific rates
 Adjusted rates
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36. Summary (Ratio, proportion, and Rate)
♦ All rates are proportions!
♦ All rates are ratios too!
♦ All proportions are ratios!
♦ But all proportions are not rates!
♦ All ratios are not proportions!
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37. II. Measures of Disease Occurrence
1. Incidence
 The incidence of a disease is defined as the number of new
cases of a disease that occur during a specified period of
time in a population at risk for developing the disease.
Incidence rate =Number of new cases of a disease over a period of time X
1000
Population at risk during the given period of time
 The critical element in the definition of incidence is new cases of
disease.
 Because incidence is a measure of new events (i.e. transition from a non-
diseased to a diseased state), incidence is a measure of risk.
 The appropriate denominator for incidence rate is population at risk.
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38. Cont…
 Another important issue in regard to the denominator is
the issue of time.
 For incidence to be a measure of risk we must specify a
period of time and we must know that all of the
individuals in the group represented by the
denominator have been followed up for that entire
period.
Nevertheless the determination of population at risk is a
major problem in the study of disease incidences.
It may require a detailed study based on:
 Interviews
 medical records
 or serology for antibodies, which are very expensive
and time consuming.
 Population fluctuation due to births, deaths, and
migration is another problem in the calculation of the
denominator.
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39. Types of incidence
1. Cumulative Incidence(CI)
An incidence rate which is calculated from a
population that is more or less stable (little fluctuation
over the interval considered), by taking the population
at the beginning of the time period as denominator.
The cumulative incidence assumes that the entire
population at risk at the beginning of the study period
has been followed for the specified time interval for the
development of the outcome under investigation.
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40. 5/19/2022 41
Cumulative Incidence cont…
Cumulative incidence relates occurrences of new cases to the population in
the follow up period
It provides an estimate of the probability, or risk, that an individual will
develop a disease/event during a specified period of time.
CI = Number of new cases of a disease during a given period of time/ Total
population at risk X 1000
1000 persons
at risk
How many
people develop
the outcome?
What
proportion
develop the
outcome?
Time 0 Time 1

41. Incidence density…
An incidence rate whose denominator is calculated using person-time units.
Similar to other measure of incidence, the numerator of the incidence density is
the number of new cases in the population.
The denominator, however, is the sum of each individual‘s time at risk or the
sum of the time that each person remained under observation, i.e., person - time
denominator.
 This is particularly when one is studying a group whose members are
observed for different lengths of time.
 In presenting incidence density, it is essential to specify the time units - that is,
whether the rate represents the number of cases per person - day, person -
month or person - year
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42. Incidence
density =Number of new cases during a given period
x1000
sum of the time each person was observed
Incidence density is often used in study like cohort
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43. 5/19/2022 44
Person -time
Time in months
Each line represents a duration of follow up.
Person-time of follow-up should also not start until the individual is
first at risk. (If a group of workers is followed to assess work-related
risks, generation of person-time could not start before first
employment).
1 2 3 4 5 6 7 8 9 10 11 12

44. Example
No. people Period at risk Person-year
contribution
50 1 year 50
40 6 months 20
20 3 months 5
110 75
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45. Basic requirements for calculating incidence rates
1. Knowledge of the health status of the study
population
2. Time of onset
3. Specification of numerator
4. Specification of denominator:
5. Period of observation
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46. PREVALENCE
 The prevalence rate measures the number of people
in a population who have a disease at a given time.
 It includes both new and old cases.
 Measures disease burden
There are two types of prevalence rates.
1. Point prevalence.
2. Period prevalence
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47. CONT…
 Point prevalence rate measures the proportion of a population
with a certain condition at a given point in time.
 This is not a true rate; rather it is a simple proportion.
Point prevalence rate = condition at one point in time X 100
Total population
 Period prevalence rate measures the proportion of a population
that is affected with a certain condition during a specified
period of time.
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48. Generally prevalence:-
 It is simply defined as the proportion of the total
population that is diseased.
 Unlike the numerator for the two incidence measures,
the prevalence numerator includes all currently living
cases regardless of when they first developed.
 Prevalence denominator includes everyone in the
population— sick, healthy, at risk, and not at risk.
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49. Relationship between incidence and prevalence
 Prevalence depends on the rate at which new cases
of disease develop (the incidence rate), as well as
the duration or length of time that individuals have
the disease.
 Mathematically, the relationship between
prevalence and incidence is as follows:
 prevalence rate ~ IR x D
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50. 5/19/2022 51
Relationships: incidence, prevalence and duration
P≅ I · D

51. Illustrations of incidence and prevalence
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Case 1
Case 2 Case 3
Case 4
Case 5
Case 6
Case 7
Case 8
Incidence would include case 3,4, 5 and 8
Point prevalence (Jan1) case 1, 2 and 7
Point prevalence De. 31) Case 1, 3, 5 and 8
Period prevalence( Jan -Dec) Cases, 1,2,3,4,5, 7 and 8
Key
Start of illness
__Duration of
illness
Key
- On set of illness
- Duration of illness
Dec, 31
Jan, 1

52. Uses
Prevalence rates are important particularly for:
 Chronic disease studies
 Planning health facilities and manpower
 Monitoring disease control programs
 Tracing changes in disease patterns over time.
Incidence rates are important particularly for
 A fundamental tool for etiologic studies
 A direct measure of risk.
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53. Generally
 High prevalence may reflect an increase in
survival due to change in virulence or in host
factors or improvement in medical care or high
incidence
 Low prevalence may reflect:
◦ A rapidly fatal process
◦ Rapid cure of disease
◦ Low incidence.
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54. Increased By
 By longer duration of
the disease
 Prolongation of life of
patients without cure
 Increase in new cases
(increase in incidence)
 In-migration of cases
 Out-migration of
healthy people
 In-migration of
susceptible people
 Improved diagnostic
facilities (better
reporting)
Decreased By
Shorter duration of the disease
High case fatality
Decrease in new cases (decrease
in incidence)
In-migration of health people
Out-migration of cases
Out-migration of susceptible people
Improved cure rate of cases)
Factors influencing Prevalence
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55. Limitations of prevalence studies
 Prevalence studies favor inclusion of
chronic over acute cases
 Disease status and attribute are measured
at the same time; hence, temporal
relations cannot be established.
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56. III. Measurements of Mortality
 Mortality rates and ratios measure the occurrence of
deaths in a population using different ways.
 Rates whose denominators are the total population
are commonly calculated using either the mid-
interval population or the average population.
 This is done because population size fluctuates over
time due to births, deaths and migration.
 Below are given some formulas for the commonly
used mortality rates and ratios.
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57. Total no. of deaths reported
 Crude death rate (CDR) = during a given time interval X 1000
Estimated mid interval population
No. of deaths in a specific age
 Age-specific mortality rate =group during a given time X 1000
Estimated mid interval population of
specific age group
No. of deaths in a specific sex
 Sex-specific mortality rate = during a given time X 1000
Estimated mid interval population of same sex
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58. No. of deaths from a specific cause
 Cause-specific mortality rate = during a given time X 100,000
Estimated mid interval population
No. of deaths from a sp. cause
 Proportionate mortality ratio = during a given time x 100
Total no. of deaths from all causes in the same time
No. of deaths from a sp. disease
 Case fatality rate (CFR) = during a given time x 100
No. of cases of that disease during the same time
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59. No. of fetal deaths of 28 wks or more
Fetal death rate = gestation reported during a given time
No. of fetal deaths of 28 wks or more gestation
and live births in the same time
No. of fetal deaths of 28 wks or more gestation
Per natal Mortality Rate =. Plus no. of infant deaths under 7 days
No. of fetal deaths of 28 wks or more gestation
plus the no. of live births during the same time
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60. No. of deaths under 28 days of age
Neonatal Mortality rate = reported during a given time x 1000
Number. of live births reported during the same
time
No. of deaths under 1 yr of age
Infant mortality rate (IMR) = during a given time X 1000
No. of live births reported during the
same time interval
No. of deaths of 1-4 yrs of age
Child mortality rate (CMR) = during a given time X 1000
Average (mid-interval) population of same
age at same time
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61. No. of deaths of 0-4 yrs of age
Under- five mortality rate = during a given time X 1000
Average (mid-interval) population of the same
age at same time
No. of pregnancy associated deaths
Maternal mortality ratio = of mothers in a given time x 100,000
No. of live births in the same time
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62. Other commonly used indices of health
No. of live births reported
Crude Birth Rate (CBR) = during a time interval X 1000
Estimated mid-interval population
No. of live births reported during a
General fertility rate (GFR)= given time interval X 1000
Estimated no. of women 15-44
years of age at mid interval
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63. No. of live births of weight less than
Proportion of LBW = 2500 gms during a given time x 100
No. of live births reported during the same
time interval
No. of new cases of a sp. disease
Attack rate = reported during an epidemic x k
Total population at risk during the same time
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64.  .
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