The exam consists of 20 questions that include true/false, matching, fill in the blank, and multiple choice questions. The exam time will be exactly 40 mins. The slides that we will be tested on are attached below.Introduction to Epidemiology
and Public Health
Khaled Bahjri, MD, DrPH, MPH
January 13, 2021
Learning Objectives
»Introduction to public health and epidemiology
»Identify core functions of public health
»Public health prevention
»The role of pharmacists in public heath
»Historical perspectives
Definition of Disease, Health and
Public Health
»Disease: A condition of the body or some part or organ
of the body in which its functions are deranged.
»Health: The state of complete physical, mental and
social well-being and not merely the absence of disease
or infirmity (WHO, 1947).
»Public Health: The science and art of preventing
disease, prolonging life and promoting health and
efficiency through organized community effort assuring
conditions in which people can be healthy.
Institute of Medicine (IOM), 1988
Public Health Key Terms
» Clinical care: prevention, treatment, and management of illness
and the preservation of mental and physical well-being through the
services offered by medical and allied health professions; also
known as health care.
» Determinant: factor that contributes to the generation of a trait.
» Cases: Individuals with disease.
» Epidemic or outbreak: occurrence in a community or region of
cases of an illness, specific health-related behavior, or other healthrelated event clearly in excess of normal expectancy. Both terms
are used interchangeably; however, epidemic usually refers to a
larger geographic distribution of illness or health-related events.
» Health outcome: result of a medical condition that directly affects
the length or quality of a person’s life.
Public Health and Clinical Medicine
»The biggest difference between public
health and medicine is that public health deals
with health from the perspective of populations,
while medicine deals with health from the perspective
of individuals.
»In medicine, the patient is the individual person.
»In public health, the patient is the entire community.
The Role of Pharmacists in Public
Health
»Assessing health trends to identify health risk factors
specific to communities.
»Assigning priorities for health-related interventions in
order to provide the greatest benefit.
»Advocacy with local, state and federal authorities in
improving the access to health services in
underserved communities.
»Design and implement health education campaigns
and activities for disease prevention.
»Provide information on local health programs and
services that are available to improve access to care.
Public Health Approach
Ten Achievements of Public Health of
the 20thCentury
»Vaccination
»Motor-vehicle safety
»Safer workplaces
»Control of infectious diseases
»Decline in deaths from coronary heart disease & stroke
»Safer and healthier foods
»Healthier mothers and babies
»Family planning
»Fluoridation of drinking water
»Recognition of tobacco use as a health hazard
Disciplines Associated with Public
Health
»Health promotion
»Health education
»Maternal & child health
»Nutrition
»Preventive care
»Medicine
»Nursing
»Environmental Health
»Biostatistics
»Epidemiology
»Pharmacy
What Is Epidemiology?
» Epidemiology has been characterized as the basic science of
public health.
» Epidemiology is defined as the field that helps to study how
disease is distributed in populations and the factors that
influence or determine this distribution.
» It attempts to answer the question of why disease(s) develop in
some people and not in others.
» The premise underlying epidemiology is that disease, illness, ill
health, and excellent health status are not randomly distributed
in human populations.
» Another definition:
~ “the study of the distribution and determinants of healthrelated states or events in specified populations and the
application of this study to control of health problems.”
What Is The Unique Skill Of
Epidemiologists?
In short, the primary goal of epidemiology is
to measure relationships between
“exposures” and health outcomes – these
may provide a basis for public health
initiatives and policies.
Changing Patterns of Community
Health Problems
» A major role of epidemiology is to provide a clue to changes that take place
over time in the health problems presenting in the community.
Prevention: A Cornerstone of
Epidemiology and Public Health
»“Avoiding preventable diseases, injuries and
premature deaths is a cornerstone of public health
philosophy and action”.
Spectrum of Disease
Occurrence
Levels of
Prevention
Primary:
Reducing the risk of
exposure to diseasecausing agents
Secondary:
Early detection of
disease while
asymptomatic
Tertiary:
Treatment of existing
cases to reduce
complications
Levels of Disease Prevention
Pharmacists and Prevention – Primary
»Although tertiary prevention is the most form, some
primary prevention of diseases done by pharmacists
include: Vaccination
»Educational campaigns (at both community and national
levels) e.g. the “Poison Prevention week” done via
school programs and public service announcements.
Pharmacists and Prevention – Secondary
»Secondary prevention includes:
~ Provision of screening services and devices that facilitate early
detection of disease or exposure. These have gone from being
individual on-demand to community-wide screening or health
fairs.
~ At the national level, professional organizations support these
interventions via continuing professional development and
training programs. These organizations also assist with
promoting reimbursement to ensure pharmacies can afford to
offer the services.
Pharmacists and Prevention – Tertiary
»Pharmacists have long been involved in disease
prevention.
»Most interventions are conducted at the individual level
and are best categorized as tertiary. These include:
Treating patients to restore health or reduce impact of
disease.
»Ensuring patients understand safe medication use
thereby preventing medication errors.
»Monitoring patients to ensure the medications are
working and not causing any new adverse reactions.
Pharmacists and Prevention – Tertiary
»At the community level, pharmacists involvement in
health boards or other policy-making groups that seek to
improve access to services and helping to identify the
treatment services most needed in the community.
»At the national level, pharmacists contribute to tertiary
prevention via sharing of their innovative practice ideas.
»Participating in clinical research.
»Advocating better access to care for patients.
»Developing best evidenced-based practice guidelines.
From Observations to Preventive
Actions –Three Examples
» Example #1, Ignaz Semmelweis and Childbed Fever
~ Pregnant women were admitted for childbirth to one of
two clinic in Vienna.
~ The First Clinic was staffed by physicians and medical
students and the Second Clinic by midwives.
~ Physicians and medical students began their days
performing autopsies on women who had died from
childbed fever; they then proceeded to provide clinical
care for women hospitalized in the First Clinic for
childbirth.
~ The midwives staffing the Second Clinic did not
perform autopsies. Semmelweis had been impressed by
mortality rates in the two clinics in 1842.
~ Mortality in the First Clinic was more than twice as
high as in the Second Clinic-16% compared with 7%.
From Observations to Preventive
Actions –Three Examples
» Example #1, Ignaz Semmelweis and Childbed Fever
~ After Semmelweis insisted that students and physicians clean their
hands with a chlorine solution between each patient, the maternal
mortality rate in the First Clinic dropped.
From Observations to Preventive
Actions
» Example #2, Edward Jenner and Smallpox
~ People were terrified of a horrible disease called smallpox.
~ As a doctor, Edward Jenner decided to carry out an experiment. In 1796 a
milk maid came to Jenner complaining of a cowpox rash on her hand.
~ Jenner took some of the pus from the cowpox rash. He scratched some of the
pus into the hand of an 8 year old boy. The boy fell ill with cowpox but soon
recovered.
~ Jenner then took some pus from someone with the dangerous disease,
smallpox, and scratched this into the boy’s arm.
~ The boy developed a scab but did not develop smallpox.
~ Jenner’s discovery came to be known as vaccination from the Latin word for
a cow: vacca.
From Observations to Preventive
Actions
» Example #3, John Snow and Cholera
~ John Snow was a famous anaesthetist and he carried out his work in
London during the third large epidemic of cholera in England.
~ John Snow identified that workers at a local brewery did not get cholera they had their own water supply and a free beer allowance!
~ Mapping of cases led John snow to suspect water from the Broad street
pump as a cause of cholera.
~ He found that those who were affected had drunk water from the pump.
~ He identified that a child at number 40 Broad street had been ill with
cholera and that sewage had probably contaminated the well.
Snow’s
map
Map shows high
concentration of
cases near Broad
Street pump
After the handle was removed the
outbreak subsided.
The Dynamics of Disease
Transmission
Learning Objectives
»To introduce concepts related to disease transmission
using the epidemiologic approach to communicable
diseases as a model.
»To define important terms related to the occurrence of
disease in a population.
»To calculate an attack rate and illustrate how it may be
used to measure person-to-person transmission of a
disease.
»To describe the steps in an outbreak investigation and
introduce how cross-tabulation may be used to identify
the source.
Two Broad Types of Epidemiology
DESCRIPTIVE EPIDEMIOLOGY
ANALYTIC EPIDEMIOLOGY
»Examining the distribution of a
disease in a population, and
observing the basic features of
its distribution in terms of time,
place, and person.
» Testing a specific hypothesis
about the relationship of a
disease to a putative cause,
by conducting an
epidemiologic study that
relates the exposure of
interest to the disease of
interest.
What is Infectious Disease Epidemiology?
Infection in one person can be transmitted to others
Person with disease
Asymptomatic Person
Treated Person
Infectious Epidemiology
»Human disease does not arise in a vacuum.
»It results from an interaction of the host (a person), the
agent (e.g., a bacterium), and the environment (e.g.,
polluted air).
Modes of transmission
An infectious agent may be
transmitted from its natural reservoir
to a susceptible host in different ways.
Reservoir
The reservoir of an infectious
agent is the habitat in which the
agent normally lives, grows, and
multiplies.
Host
The final link in the chain of
infection is a susceptible host.
Susceptibility of a host depends
on genetic or constitutional
factors, specific immunity, and
nonspecific factors that affect an
individual’s ability to resist
infection or to limit pathogenicity.
The Basic Triad Of Infectious Epidemiology
The Basic Triad Of Infectious Epidemiology
Routes of Transmission
Direct
»Skin-skin
~ Herpes type 1
» Mucous-mucous
~ STD
» Across placenta
~ Toxoplasmosis
» Through breast milk
~ HIV
» Sneeze-cough
~ Influenza
Indirect
» Food-borne
~ Salmonella
» Water-borne
~ Hepatitis A
» Vector-borne
~ Malaria
» Droplets
~ COVID-19
»Air-borne
~ Measles
Interventions
» Interventions are directed at:
~ Protecting portals of entry
• Sanitizing
• Hand washing
• Masking
• Bed nets
~ Increasing host’s defenses
• Vaccinations promote development of specific antibodies that protect
against infection.
• Prophylactic use of drugs. For example, antimalarial medication.
• Treatment with antibiotics to eliminate the infection.
~ Herd immunity suggests that if a high enough proportion (70 to 90%)
of individuals in a population are resistant to an agent, then those few
who are susceptible will be protected by the resistant majority, since the
pathogen will be unlikely to “find” those few susceptible individuals.
Epidemiologic Curve
Describing Disease Occurrence
» Endemic: persistent occurrence with a low to moderate level
» Epidemic or outbreak: occurrence clearly in excess of the
expected level for a given time period
» Pandemic: epidemic spread over several countries or
continents, affecting a large number of people
Exploring Occurrence of Disease
»When a disease appears to have occurred at more
than an endemic (usual) level and we wish to
investigate its occurrence, we ask:
~ Who was attacked by the disease?
~ When did the disease occur?
~ Where did the cases arise?
Who
»The characteristics of the human host are clearly
related to disease risk. Factors such as sex, age, and
race as well as behavioral risk factors (e.g., smoking)
may have major effects.
Pertussis
Gonorrhea
When
»Certain diseases occur with a certain periodicity.
Aseptic meningitis
Where
»Disease is not randomly distributed in time or place.
Lyme disease
West Nile virus
Outbreak Investigation
»When confronted with several possible causal agents,
as is often the case in a food-borne disease outbreak,
a very helpful method for determining which of the
possible agents is suspected to be the cause is
called cross-tabulation.
Attack rate =
ill
exposed
Incubation Period
»The incubation period is defined as the interval from
receipt of infection to the time of onset of clinical
illness (the onset of recognizable symptoms).
Factors Affecting Incubation Period
»Dose of infection.
»Site of entry.
»Rate of multiplication.
»Host defense mechanism.
Factors Affecting The Gradient of an
Infection
»Infectivity is the ability of a pathogen to establish an
infection.
»Pathogenicity is the property of causing disease.
»Virulence is the ability to infect damage a host.
Outbreak Investigation
QUESTIONS? COMMENTS?
Measuring the Occurrence
of Disease Morbidity
Khaled Bahjri, MD, DrPH, MPH
January 13, 2021
Learning Objectives
»To describe the important role of epidemiology in
disease surveillance.
»Define Morbidity
»Describe and distinguish the different Measures of
Morbidity
»Describe and distinguish the following, including how to
measure each: Incidence Rate, Prevalence and
Surveillance
»Describe the relationship between incidence and
prevalence
Basic Question in Research
Is there an association between Exposure and Disease?
Exposure
Independent
variable
Disease / Health Outcome
Dependent
variable
Surveillance
» The “ongoing systematic collection, analysis, and
interpretation of health data essential to the planning,
implementation, and evaluation of public health practice
closely integrated with the timely dissemination of these data
to those who need to know.
» Surveillance was commonly conducted for infectious diseases,
but in recent years it has become increasingly important in
monitoring changes in other types of conditions such as
congenital malformations, noncommunicable diseases, and
environmental toxins, and for injuries and illnesses after
natural disasters such as hurricanes or earthquakes.
Types of Surveillance
» Passive surveillance denotes surveillance in which
either available data on reportable diseases are used or
reporting is mandated or requested with the
responsibility for the reporting often falling on the health
care provider or district health officer.
~ When passive surveillance is used, existing staff
members (commonly physicians) are often asked to
report new cases. However, they are often
overburdened by their primary responsibilities of
providing health care and administering health
services.
» Active surveillance denotes a system in which project
staff make periodic field visits to health care facilities
such as clinics and hospitals to identify new cases of a
disease or diseases or deaths from the disease that
have occurred (case finding).
Why Assess Morbidity?
• In order to examine the transmission of disease in human populations, we
need to be able to measure the frequency of disease occurrence
• We will begin this discussion by considering the development and course
of a disease in an individual over a period of time along with the sources
of data as seen below
Measuring of Diseases Occurrence
In order to examine the transmission of disease in human
populations, we need to be able to measure the frequency of
disease occurrence.
Measuring
Parameters
Mean/Median
s
Counts
Prevalenc
e
Incidence
Incidence
Rate
Ratio
Measures of Morbidity:
Mean and Median
▪
▪
▪
Health outcomes are sometimes not always measured by
presence or absence, but rather as a continuous
measure.
Examples: Body Mass Index, blood pressure,
cholesterol, birth weight, metabolic markers.
In these cases, we need measures of centrality and
spread.
Measures of Morbidity:
Counts
» Number of events to represent number of persons with disease.
» Numerator without a denominator.
» Diagnosed cases that are reported to the department of health.
» Count of No. cases of a disease, is used for surveillance of
infectious disease for early detection of outbreaks.
• Number of cases
“we have 2 cases of tetanus”
On its own very little informative!!
Measures of Morbidity:
Counts
Example:
» 165 in Texas ~ 169 in Missouri ~ 182 in Mississippi
» The numbers of cases may be similar, but the number of
people in each state is not
» We need Proportions and Rates!
Measures of Morbidity:
Proportions
» A proportion is the expression of one part to the whole.
» It is in the form of (a/a+b) x k.
» K is an appropriate constant (i.e., 100; 1,000; 100,000) to
make the result a whole number.
» Numerator is always included in the denominator.
Example:
» From 7,999 females aged 16 – 45 y, 2,496 use modern
contraceptive methods.
» The proportion of those who use modern contraceptive
methods = 2,496 / 7,999 x 1000 = 312 per 1000.
Measures of Morbidity:
Prevalence
» The proportion of people who have the disease out of the
total population.
» Also known as the “Burden of the disease”.
» For prevalence, we need a numerator that represents the
number of existing cases (new and old), and denominator
(total population).
3
— = 0.6
5
= 60%
= 60 per 100
New case
Old case
Measures of Morbidity:
Incidence
» The proportion of people who newly acquire the
disease over the population at risk for a given time
period.
» For incidence, we need a numerator (number of new
cases), and denominator (population at risk).
» Also known as the “risk of the disease”.
1
— = 0.33 = 33%
3
New case
Old case
(removed from
denominator)
Identifying New Cases to Calculate
Incidence
Relationship between Incidence and
Prevalence
Incidence
Prevalence =
Incidence X Duration
Loose criteria,
Immigration of cases
New cases
Duration
Prevalence
Increased death due to
disease,
More cure,
Lost…
Problems with Incidence and Prevalence
Measurements
Problems with Numerators
• The first problem is defining who
has the disease.
• Example: Rheumatoid arthritis (RA)
graph below shows the results of a
survey conducted in Sudbury,
Massachusetts, using two sets of
criteria for diagnosing the disease.
• The next issue relating to
numerators is that of ascertaining
which persons should be included
in the numerator (sources of data).
Measures of Disease – Incidence
Rate
» Rate is a measure when the numerator is part of the
denominator but measured over time): (a/a + b) x k.
» The proportion of people who newly acquire the disease over
the number of years of follow-up for a given time period.
» For incidence rate, we need a numerator (number of new
cases), and denominator (person-years at risk), and a time
period of interest.
IR = 2 / 35.5 person years
= 0.056 cases / person year
= 5.6 cases / 100 person years
Sum of observation
person-time at risk
= 56 cases / 1000 person years
Measures of Disease – Odds/Risk
Ratio
»Measures used to compare groups with each other.
»Risk is number of events over population at risk.
»Odds is defined as the number of events to the number of nonevents.
»Example:
Exposed + (n=100) >>>>>>>>>>>>>>>>> 5 New cases
Exposed – (n=100) >>>>>>>>>>>>>>>>> 2 New cases
Both exposed and non-exposed groups have 10 old cases
Odds Ratio =
(15/85)/(12/88)
= 1.29
Risk
Ratio
= (15/90)/(12/90)
= 1.25
Example
New Cases
of Disease
Existing Cases
Location
City A
City B
of Disease
20
100
5
10
Year Person-years
2008
45
2008
90
Population
100
1000
» Calculate the prevalence, incidence, incidence rate in each population as
well as odds and risk ratio:
1.Prevalence City A: (20+5)/100 = 25%
Prevalence City B: (100+10)/1000 = 11%
2.Incidence City A: 5/80 = 6.3%
Incidence City B: 10/900 = 1.1%
3.Incidence Rate City A: 5/45 = 1.1%
Incidence Rate City B: 10/90 = 1.1%
4.Odds Ratio City A vs City B: (25/75)/(110/890) = 2.69
5.Risk Ratio City A vs City B: (25/80)/(110/900) = 2.56
Exampl
e2
1. What is the
prevalence from Jan
2003 to Jan 2004?
2. What is the incidence
from the beginning of
2003 to the end of
2010?
Legends:
—- Cases
___ Free of disease
Censored – Lost to follow-up
3. What is the incidence
rate from the
beginning of 2003 to
the end of 2009?
Measuring the Occurrence of
Mortality
Learning Objectives
» Describe and distinguish the different Measures of Mortality
» Identify problems with Mortality data
» Measures of disease mortality among children.
Measuring Mortality
» Expressing mortality in quantitative terms can pinpoint differences
in the risk of dying from a disease between people in different
geographic areas and subgroups in the population.
» Mortality rates can serve as measures of disease severity (health
outcomes), and can help us to determine whether the treatment for
a disease has become more effective over time.
» In addition, given the problem that often arises in identifying new
cases of a disease, mortality rates may serve as surrogates for
incidence rates when the disease being studied is a severe and
lethal one.
Problems with Mortality Data
• Most of our information about deaths comes from death
certificates.
• By international agreement, deaths are coded according to
the underlying cause.
• The underlying cause of death is defined as “the disease or
injury which initiated the train of morbid events leading directly
or indirectly to death or the circumstances of the accident or
violence which produced the fatal injury.“
• The underlying cause of death therefore “excludes information
pertaining to the immediate cause of death, contributory causes
and those causes that intervene between the underlying and
immediate causes of death.“
• Countries and regions vary greatly in the quality of the data
provided on their death certificates.
Measures of Mortality:
Number of Death
• This is only numerator data and so does not measure risk of
death. Risk requires denominator data.
• If, for example, the size of the U.S. population is also
increasing in the graph below the risk of dying from cancer
does not change.
Measures of Mortality:
Crude Mortality
• Annual death rate, or mortality rate, from all causes.
• Death from all causes in the total population.
• The crude mortality rate is a very general indicator/index of the health
status of a geographic area or population.
• This type of crude rate is not appropriate for comparison of different
populations.
Crude
Mortality =
Number of deaths from all causes
Total population or Mid-year population
Example:
15,231 total deaths in New Mexico during calendar year 2006.
2,010,787 = estimated 2006 mid-year population for New Mexico.
Crude Mortality = 15,231/2,010,787 = 0.00757 = 76 per 10,000
Measures of Mortality:
Cause-specific Mortality
• Death due to specific cause or subgroup of a
population.
• Commonly used measure for comparison of different
populations.
Cause-specific Number of deaths from a specific disease or subgroup
Mortality
=
Total population or Mid-year population
Example:
In the United States in 2003, a total of 108,256 deaths were attributed to
accidents (unintentional injuries). The estimated population was
290,809,777.
Cause-specific Mortality = 108,256/290,890,777 = 37 per 100,000
Age Specific Death Rate
Age-specific Mortality = # of deaths in specified age/group
Total population in same specified age/group
What is the death rate for children ages 1-14 in 2006?
37 = deaths among children ages 1 -14 during 2006
381,910 = estimated 2006 mid-year population for population aged 1-14
37 X 1,000,000 = 97 per 1,000,000
Age-specific Mortality = 381,910
Measures of Mortality:
Proportionate Mortality
• Proportion of all deaths that is caused by a specific disease
Proportionate Number of deaths from a specific disease or subgroup
Mortality
=
Total death
Example:
In the Caribbean countries in 2000, there
were 6,764 deaths attributed to heart
disease, out of a total of 43,036 deaths.
Proportionate Mortality = 6,764/43,036 =
157 per 1000
Measures of Mortality:
Case Fatality
• Death due to specific cause among those diagnosed with a specific
disease.
• Case Fatality is a measure of the severity of the disease.
Case Fatality =
Number of people who die due to a specific disease
Number of people with the specific disease
Example:
Assume 9 deaths among 100 people in a
community all diagnosed with the same
disease.
Case Fatality = 9/100 = 9%
Measures of Mortality:
Years of Potential Life Lost
• Years of potential life lost (YPLL) is a Mortality index that is used
for setting health priorities.
• YPLL is a measure of premature mortality, or early death before
the age of 75
Vital Feto-Infancy Mortality
Measures
Conception
1st Birthday
Live Birth
Gestatio
Early Fetal
nPerinatal Death
Death
20 wks
6
Days
Infancy
28 days
Fetal Death
Infant Death
Neonatal Death
Postneonatal Death
0 Weeks
28 Weeks
Birth 28 Days
1 Year
Fetal Death Measures
“Death prior to the complete expulsion or extraction from its mother
of a product of human conception, irrespective of the duration of
pregnancy and which is not an induced termination of pregnancy”
Perinatal Mortality
Perinatal =
# fetal deaths >28 weeks
gestation + infant deaths 28 days but <
1 year after birth
-------------Live births in same time
period
Maternal Mortality
» Deaths of pregnant women and women after
termination of pregnancy within 6 weeks from any
cause related to pregnancy.
Maternal Mortality =
# of maternal deaths
within 42 days of
pregnancy termination
-------------Live births in same time
period
Measures of Mortality:
Early Life
The Natural History of
Disease:
Ways of Expressing
Prognosis
Learning Objectives
» Describe and distinguish the different approaches to measuring the
prognosis of diseases.
» Sources of epidemiologic data.
» Interactive tool to obtain local, national and global epidemiologic data.
What is the “Natural History” of
Disease?
•
•
•
•
•
•
A ; Biologic onset of disease
P ; Pathologic evidence of disease if Sought
S ; Signs and symptoms of disease
M ; Medical care sought
D ; Diagnosis
T ; Treatment
Definition - Prognosis
» Prognosis refers to the probability of an individual patient
developing a particular outcome over time, based on his
clinical and non-clinical characteristics and on their
combination with disease specific characteristics
Prognosis
» A person who was just diagnosed with a disease would be interested in the
prognosis of the disease
» Prognosis is predicting the progress or outcome of the disease
» Prognosis may be expressed as:
~ Deaths from the disease; or
~ Survivors with the disease
Five Approaches to Expressing
Prognosis
» Case-fatality
» Observed survival
» Five-year survival
» Median survival time
» Relative survival
» Note: Any measures used to quantify prognosis must be
case-based
~ That is, the denominator is the number of people with
the specified disease
Case‐Fatality
Case-fatality = number of people who die of
a disease
number of people who have
the disease
Example:
200 people with the disease
20 deaths from the disease
Prognosis = CF = 20/200
U.S. Department of Health and Human
Services, Centers for Disease Control and
Prevention
Observed Survival Rate
• The observed survival (rate) is an estimate of the probability
of surviving.
• Survival curve plots percent survival (cumulative probability
of survival) by time (time since the beginning of study).
• Cumulative probability of surviving can be calculated using
the technique of life table or Kaplan-Meier.
Survival curves according to risk groups as defined by prognostic
score for Chronic Lymphocytic Leukemia
Five‐year Survival Rate
• The percentage of patients who are alive 5 years after
treatment begins or 5 years after diagnosis
5-year survival =
Number of persons with the specified disease surviving 5 years
--------------------------------------------------------------total number of persons with the specified disease
Interpreting 5-year Survival Rate
» Increased five-year survival for cancer patients over time is generally
inferred to mean that cancer treatment has improved and that fewer
patients die of cancer.
» Increased five-year survival, however, may also reflect diagnosing
early-stage cancer and/or finding people who would never have become
symptomatic from their cancer.
Interpreting 5-year Survival Rate
» Overall survival rates are at times misleading
» Although survival at 5 years is the same in both groups (10%), most of
the deaths in group A did not occur until the fifth year, whereas most of
the deaths in group B occurred in the first year.
Median Survival Time
• Defined as the length of time that half of the study population survives
• Why should we use median survival time rather than mean survival
time, which is an average of the survival times?
• Two advantages of median survival time over mean survival
• ◦ Less affected by extremes
• ◦ Need not observe all of the deaths
Median Survival time is 1 Year
Relative Survival Time
» What would we expect the 5-year survival of 30 years old males to be if they
were compared to the same age group that did not have colorectal cancer?
» So for any group of people with a disease, we want to compare their survival to
the survival we would expect in this age group even if they did not have the
disease. This is known as the relative survival rate.
In-class Exercise
1. What is the proportionate
mortality from Jan 2003 to
Jan 2007?
2. What is the prevalence from
Jan 2003 to Jan 2004?
3. What is the case fatality from
the beginning of 2003 to the
end of 2010?
4. What is the crude mortality from
the beginning of 2003 to the
end of 2009?
Legends:
---- Cases
___ Free of disease
Censored - Lost to follow-up
5. What is the disease-specific
mortality from the beginning of
2003 to the end of 2009?
In-class Exercise II
Calculate the following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Total 1-year population
Population of women 15-44 years of age
Population of women 55 years and older
Number of live births
Number of deaths within 6 days after birth
Number of fetal deaths
Number of deaths within the first 28 weeks of gestation
Number of maternal deaths
Total deaths
Number of deaths below 1 year after birth
Number of deaths below 28 days after birth
Number of deaths 55 years and older
Number of deaths due to heart disease
Number of people diagnosed with heart disease
Crude mortality
Maternal mortality
Infant mortality
Neonatal mortality
Fetal mortality
Perinatal mortality
Post-neonatal mortality
Proportionate mortality of heart disease
Heart disease case fatality
Mortality specific to heart disease
Age specific (55 years and older) mortality
Prevalence of heart disease
160,000
40,000
44,000
3,300
2
66
32
5
1,444
88
4
848
133
5,600
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