This document provides an introduction to basic epidemiology concepts. It defines epidemiology as the study of disease patterns in populations and the factors influencing these patterns. The document outlines key epidemiology concepts like prevalence, incidence, risk factors, exposures and outcomes. It discusses the history of epidemiology and different epidemiological study designs. Important epidemiology measures are also introduced, including various ways to define and calculate disease occurrence and frequency in populations.
Concept and definitions
Health education
Beliefs and approaches in health promotion
Health promotion strategies and priority actions
Public health, social movement, health inequity and millennium goals
Canadian experience in health promotion
Conclusion
Concept and definitions
Health education
Beliefs and approaches in health promotion
Health promotion strategies and priority actions
Public health, social movement, health inequity and millennium goals
Canadian experience in health promotion
Conclusion
Community diagnosis is vital in health planning, evaluation and needs assessment, several types of indicators are valid to be used for community diagnosis including Socio-economic, demographics, health system, and living arrangements.
Epidemiology is the study and analysis of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences
Evidence for Public Health Decision MakingVineetha K
The presentation gives an overview of evidence based public health with emphasis on the seven steps of EBPH Framework. It also includes the data sources to search for evidence and relevant articles explaining the current trend in decision making. One of the sources of the presentation is from EBPH training series by Rocky Mountain foundation. The link is provided in the end slide. Do contact me if you need any help with the resources.
The Burden of Disease ( BOD) analysis describes in details the uses and effects of BOD. How to measure it. Special emphasis has been given in understanding HALY, DALY and QALY.
N.B: 1. Please download the ppt first, as the animations will act better then
2. There are few hidden slides in the presentation, which you may explore too.
Epidemiology is the study of the distribution of health related events. It is concerned with epidemic of communicable disease, non communicable infectious disease, chronic disease,maternal-child health, occupational health, environment health etc.
Community diagnosis is vital in health planning, evaluation and needs assessment, several types of indicators are valid to be used for community diagnosis including Socio-economic, demographics, health system, and living arrangements.
Epidemiology is the study and analysis of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences
Evidence for Public Health Decision MakingVineetha K
The presentation gives an overview of evidence based public health with emphasis on the seven steps of EBPH Framework. It also includes the data sources to search for evidence and relevant articles explaining the current trend in decision making. One of the sources of the presentation is from EBPH training series by Rocky Mountain foundation. The link is provided in the end slide. Do contact me if you need any help with the resources.
The Burden of Disease ( BOD) analysis describes in details the uses and effects of BOD. How to measure it. Special emphasis has been given in understanding HALY, DALY and QALY.
N.B: 1. Please download the ppt first, as the animations will act better then
2. There are few hidden slides in the presentation, which you may explore too.
Epidemiology is the study of the distribution of health related events. It is concerned with epidemic of communicable disease, non communicable infectious disease, chronic disease,maternal-child health, occupational health, environment health etc.
Define epidemiology.
Understand historical milestones Epidemiology pass through before attaining its current level.
Importance of epidemiology public health professionals and its aspec.
Epidemiology is: a) a quantitative basic science based on a working knowledge of statistics, probability, and sound research methods; b) a causal reasoning method based on the development and testing of morbidity and mortality hypotheses; and c) a tool for promoting and protecting public health action based on science, causal reasoning, and practical common sense.
The most ambitious definition of health is that proposed by WHO in 1948: “health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” but,
Practical definitions of health and disease are needed in epidemiology, which concentrates on aspects of health that are easily measurable and amenable to improvement.
Definitions of health states used by epidemiologists tend to be simple, for example, “disease present” or “disease absent”
Introduction to Epidemiology
History of Epidemiology.
Definition of Epidemiology and its components.
Epidemiological Basic concepts.
Aims of Epidemiology.
Ten Uses of Epidemiology.
Scope or The Areas of Application .
Types of Epidemiological Studies.
CHAPTER 1 ITRODUCTION TO EPIDEMIOLOGICAL METHODS.pptxjohnsniky
Technique:
The needle is held with the needle holder and it should enter the tissues at right angles and be no less than 2-3mm from the incision.
The needle is then carried through the tissue where it follows the needle’s curvature.
Sutures of any type that are placed in the interdental papilae should enter and exit the tissue at a point located below the imaginary line that forms the base of the triangle of the interdental papilla.
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
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New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
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Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
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The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
1. Somali International University(SIU)
Faculty Of Health Sciences
Department Of Public Health
Introduction to Basic Epidemiology(1)
Semester 3
Dr.Ahmed Ayna,MS.c PTH-UMST-Sudan
5/10/2021 1
2. At the end of this course, the students should be able to
demonstrate knowledge of:
• Conceptualize the meaning of Epidemiology
• the nature and uses of epidemiology
• the epidemiological approach to defining and measuring the
occurrence of health related states in populations
• Be Familiar with Measuring of Disease Occurrence.
• the contribution of epidemiology to the prevention of disease, the
promotion of health and the development of health policy
• the contribution of epidemiology to good clinical practice and the
role of epidemiology in evaluating the effectiveness and efficiency
of health care.
Learning Objectives
5/10/2021 2
3. • Originates from the Greek words:
– Prefix – epi (upon, on, befall)+
– Root – demos (people, population, man)+
– Suffix – logy (study of)
• Literal translation: “That which befalls man”
(epidemics)
Epidemiology
5/10/2021 3
4. • It is the study of the nature, cause, control and
determinants of the frequency and distribution of
disease, disability and death in human
populations. (Timreck, 1994).
• Epidemiology is an investigative method used to
detect the cause or source of diseases, disorders,
syndromes, conditions or perils that cause pain,
illnesses, injury, disability or death in human
populations or groups. (Timreck, 1994)
Definitions of Epidemiology
5/10/2021 4
5. • It is the study of the distribution and
determinants of disease frequency in human
populations. (MacMahon and Trichopoulos,
1996)
• Epidemiology is a discipline that describes,
quantifies and postulates causal mechanisms
for health phenomena in the population. (Friis
and Sellers, 1996)
5/10/2021 5
6. • Epidemiology:-A study of the distribution and
determinants of health-related states or
events in specified populations, and the
application of this study to control of health
problems. (Last, 1988).
-Key terms in this definition reflect some of the
important principles of epidemiology.
5/10/2021 6
7. • Population of interest are human populations
• Describes distribution of health and disease
(by person, place and time variables). Here
described frequency and patterns.
• Identifies determinants of health and disease
(risk factors, causes)
• Health and disease (injury, illness, disability or
death)
Anatomy of the Definition
5/10/2021 7
8. Hippocrates’ in 400 BC in his “On Airs, Waters
and Place” – the role of the environment in
health and disease among men(Assignment for
further reading)
John Graunt, in 1662, published Natural and
Political Observations Made Upon the Bills of
Mortality which recorded descriptive
characteristics of birth and death data, including
seasonal variations, infant mortality, excess of
male over female deaths, and other findings. He
was the first to employ quantitative methods in
describing population vital statistics.
Highlights in the History of
Epidemiology
5/10/2021 8
9. John Snow investigated a cholera epidemic in
mid-19th century in London. His work featured
various techniques in epidemiologic inquiry such
as spot map of cases, tabulations of cases and
deaths, development and testing of hypotheses
that contaminated water may be associated with
cholera outbreaks. (Assignment for further
reading and writing)
• Koch in late 1800s espoused the concept that
diseases are caused by living organisms and made
possible more refined classification of disease by
specific causal organisms through his postulates
for disease causation. (Assignment for further
reading and writing postulates)
5/10/2021 9
10. • The history of epidemiologic methodology is
largely the history of the development of five
ideas:
1) Human disease is related to the environment in
which we live;
2) Counting of natural phenomena may even be more
instructive than just observing them;
3) “natural experiments” can be utilized to investigate
disease etiology;
4) Natural experiments occur more frequently than we
think and reflect the tremendous heterogeneity of
human experience;
5) “true experiments” may be conducted in human
populations in some circumstances.
5/10/2021 10
11. • Universal political commitment
• Clear and specific goal with precise timetable
• Well-trained and committed staff
• Flexible strategy
• Features of the disease that made its
elimination possible
• Availability of an effective and stable vaccine
Factors that contributed to the success
of eradication:
5/10/2021 11
12. Elucidate disease etiology
◦ May also identify the determinants of outcomes of
illness
◦ Other outcomes of interest – biologic processes like
growth, multiple pregnancy, intelligence and fertility
Explain local disease patterns
◦ By utilizing what is already known about the etiology of
a particular health problem, epidemiologist may be
able to explain and deal, for example, with a particular
outbreak, and formulate preventive measures suitable
to a specific community
Uses of Epidemiology
5/10/2021 12
13. Describe the natural history of disease
– To identify factors related to the course of the
disease once the disease is established
– It is useful to know how the duration of a disease
and the probability of various outcomes (recovery,
death, complications) vary by age, gender,
geography, etc.
5/10/2021 13
14. Provide guidance in the administration and
evaluation of health services(Planning to
Evaluation):-
– Estimation of number of hospital beds required for
patients with specific disease (e.g. mental illness)
or for given segments of the population (e.g.
prematurely born infants, disabled elderly) will
require knowledge of the frequency and natural
history of particular diseases or of all diseases in
the affected segments of the population
5/10/2021 14
15. – The planning of efficient research (diagnostic,
therapeutic, preventive) will require knowledge of
how many cases of a particular disease are likely
to be found in a given population during a given
period
– Knowledge of the relative frequency of disease in
population subgroups is useful if it enables
intervention programs to target these populations
(e.g. screening programs)
5/10/2021 15
16. • Causation
• Natural
History
• Description of
health status
of populations
• Evaluation of
intervention
Uses of Epidemiology
Genetic Factors
Good health
Ill health
Environmental factors
(including lifestyle)
Genetic Factors
Subclinical
changes
Death
Clinical Disease
Recovery
Proportion with ill
health, change over
time, change with
age, etc.
Good health
Ill
health
Time
Ill health
Good health
Health promotion
Preventive measures
Public health services
Treatment, Medical care
5/10/2021 16
17. • Prevention of Disease
• Maintenance of Health
Ultimate Goal of Epidemiology
5/10/2021 17
18. • It is interdisciplinary
– Draws from biostatistics and other social and
behavioral sciences as well as from medically-
related fields of toxicology, pathology, virology,
genetics, microbiology, parasitology and clinical
medicine.
• Use of population research techniques and
requires quantification of relevant factors
– E.g. the presence or absence (or the amount) of
exposure and the magnitude of the outcome
Features of Epidemiology
5/10/2021 18
19. • Key Terms in Epidemiology:-
Definition of epidemic:
– “Attacking many people at the same time”, “widely
diffused and rapidly spreading”, “excessive
occurrence of disease”
– The occurrence in a community or region of cases
of illness clearly in excess of normal expectancy
(Benenson, 2000)
– (Outbreak,Endemic,pnadamic and sporadic)
5/10/2021 19
20. Exposures and Outcomes
The two key elements that we measure in most epidemiological
studies are.
1. The exposure is the process by which an agent comes into
contact with a person or animal in such a way that the person
or animal may develop the relevant outcome, such as a disease
2. The outcome is the disease, or event, or health-related state,
that we are interested in.
3. An exposure can be any factor that may influence the outcome
5/10/2021 20
21. Exposures and Outcomes continued
• An exposure can be any factor that may influence the
outcome
• The outcome can be any health-related event or state - or it
can be a risk factor for, or a precursor to, a disease.
• The risk factor an aspect of personal behavior or lifestyle, an
environmental exposure, or an inborn or inherited
characteristic, that, on the basis of epidemiological evidence,
is known to be associated with health-related condition(s)
considered important to prevent.
5/10/2021 21
22. The Role of Epidemiology?
Epidemiology has major functions:
1. to describe patterns of health and disease within
populations
2. to interpret these differences
3. to apply our results to public health practice, and
4. to evaluate the effect of health-related interventions
5/10/2021 22
23. Observational and Interventional
Epidemiology
• Observational epidemiology (Also called non-experimental
studies). Studies in which the distribution or determinants of
an outcome are examined without any attempt by the
investigator to influence them. Observational epidemiology
includes both descriptive and analytical studies.
• Interventional epidemiology (Also called experimental studies)
Studies designed to test a hypothesis by modifying an exposure
within the study population.
5/10/2021 23
24. Types of Epidemiological Investigation
Epidemiological study
Observational
Aggregated data
Analytic
Ecological
study
Descriptive
Disease
mapping
Individual based
data
Analytic
Cross-
sectional
study Case-
control
study
Cohort
study
Descriptive
Cross-
sectional
study
Case
report
Case
series
Interventional
RCT Quasi Exp.
5/10/2021 24
25. Sequence of Epidemiological Studies
Evaluation of Public Health Intervention
Change in Public Health Policy
Intervention Studies
Individual-Based Analysis
Population-Based Analysis
Descriptive Studies
5/10/2021 25
27. Objectives
1. Explain how cases and population are defined in
epidemiology
2. Define and calculate measures of occurrence
3. Explain how to select the proper measure of
occurrence
4. Define the assumptions behind the use of these
measure
5/10/2021 27
28. Seven measure of disease
occurrence and frequency
1. Counts
2. Prevalence
3. Incidence/risk
4. Mean/variance
5. Median
6. Mode
7. Rates
28
5/10/2021
29. Issues in Defining a Case
Case definition is a set of standardized criteria used
to identify cases and should usually contain
information about the following factors:
1. The method(s) used to identify a case
2. The boundaries of a case
3. The unit of analysis
5/10/2021 29
30. Case definition
The method(s)
used to identify
a case
• The procedures
or instruments
that have been
used to identify
a case.
The boundaries
of a case
• The dividing line
is drawn
between cases
and non-cases
The unit of
analysis
• Household , a
person, an
episode of an
event, a
diseased organ
or tissue.
5/10/2021 30
31. Issues in Defining a Case continued
Example
In a study of the frequency of acute
diarrhoea in a primary school. A child with
an episode that should last at least 48 hours
but less than 14 days in which reports at
least 3 loose stools per day
5/10/2021 31
32. Developing Case Definitions
Factors should be
considered
The question
we want to
answer
Comparison Hypothesis
Testing
Disease
Outbreak
Investigation
Lay
Definitions
The
resources
available
Ethical Issues
5/10/2021 32
33. Issues in Defining the Study population
• The study population is the population of subjects who
potentially could become cases.
• How we define a case, influences how we define the study
population.
• The study population is usually limited by location: e.g. in a
particular hospital, village or district.
• Often the study population is called the population at
risk because it is at risk of developing the outcome of
interest.
5/10/2021 33
34. Issues in Defining the Study population
continued
Examples
• A study of the uptake of measles vaccination,
in which a case was defined as a child between
the ages of 1 and 5 years who was given at
least one dose of measles vaccine in 1998.“,
Study population?
5/10/2021 34
35. Issues in Defining the Study population
continued
Examples
• "A study of the frequency of severe
depression in women aged 65 and over, in which
a case was defined as a woman aged 65 and
over who is diagnosed as having severe
depression, according to the WHO ICD-10, in
1998.“, Study population?
5/10/2021 35
36. Measures of occurrence
• Once we have developed a clear case
definition and defined the study population, we
can go on to quantify the occurrence of the
outcome of interest.
5/10/2021 36
37. Measures of occurrence
Measures of
occurrence
Prevalence
Point
prevalence
Period
prevalence
Incidence
Incidence
risk
Incidence
rate
Odds
5/10/2021 37
38. Measures of occurrence
Two main types of measure of occurrence
1. Prevalence is concerned with quantifying the
number of existing cases in a population at
a designated point of time.
2. Incidence is concerned with quantifying the
frequency of occurrence of new cases in a
defined population, arising during a
given time period.
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39. Measures of occurrence continued
Measures of prevalence and incidence are
meaningless unless we define:
1. What we mean by a case
2. The population at risk of becoming cases
3. The time frame, where this is:
a. A specific point in time (for prevalence)
b. An interval of time (for incidence)
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40. Measures of occurrence continued
There are two types of prevalence
1. Point prevalence is the proportion of persons in a
defined population that has the outcome under study
at a specific point in time. So: Point Prevalence =
Number of Cases at time (t)
Study Population at time (t)
• The prevalence depends on the incidence of the
condition and the duration of each case.
• Prevalence provides a useful measure of the state of
health of a community at a particular point in time.
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41. Measures of occurrence continued
2. Period prevalence measures the number
of cases in a population over a defined
period of time. The numerator for period
prevalence includes cases present at the
start, as well as incident cases which
arose during the period of interest.
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42. The two measures of incidence, incidence risk and rate
1. The incidence risk :
is the proportion of new cases which occur in a population
initially free of the condition during a specified period of time.
So, Incidence risk =
Number of new cases in a defined time period
Population at risk at the beginning of the period
• The incidence risk provides information about the risk of
becoming a case in a given time period.
• It is useful for studying the determinants of a condition which
is relatively uncommon in a static population
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43. • Example: in 1980 the annual mortality
rate (risk of dying) was 26 per 1000 in
Malawi and Yemen, 14 per 1000 in Kenya
and India, 10 per 1000 in Belgium and
France, and 4 per 1000 in Costa Rica.
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44. 2. The incidence rate
relates the number of new cases in a specified time period to
the total person-time at risk.
Incidence rate = Number of new cases in a defined time period
Total person-time at risk
• The incidence rate is used for studying the determinants of a
condition that is relatively common and/or occurring in a dynamic
population. Here, the population at risk at the start is not a good
approximation of the total person-time at risk where many people
are likely to become diseased, or where people frequently enter
and/or leave the population
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45. • Example During a follow-up survey
among 350 female inmates in Sao
Paulo, Brazil, the incidence of
pulmonary tuberculosis among HIV
positive women was 9.92 per 100
person-years
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46. Measures of occurrence continued
• The odds of becoming a case is a measure of the number of cases
in a defined population and time period, divided by the number of
people who did not become a case in the same time period.
• Odds = number of cases
number of non-cases
• In a stable population of 100 school children, 20 children had at
least one episode of conjunctivitis during a one year study period.
The odds of developing conjunctivitis in the school during the study
period was:
Odds = cases / non-cases = 20(100-20) = 20 / 80 Odds =0.25
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47. Measures of occurrence continued
• The prevalence (P) is influenced by the
occurrence of new cases (incidence, I)
and the duration of each case (D):
P= I x D.
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48. • Example 1: If all other factors were kept equal,
what would happen to the prevalence of AIDS in a
specified population following the introduction of a
new treatment that prolongs life but does not cure
the disease?
• Example 2: If all other factors were kept equal,
what would happen to the prevalence of asthma in a
specified population following the introduction of a
new treatment that cures the disease?
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49. Measures of occurrence continued
• The prevalence used to evaluate the impact of
preventative measures aimed at reducing the
burden of a disease or condition in a
community.
• Any comparative results need to be
interpreted with caution because of the
number of factors that influence prevalence
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50. • The incidence risk is also used for evaluating the
impact of preventative measures that aim to reduce
the number of new cases of a condition.
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51. Tuberculosis in Benadir districts
Tuberculosis is a reportable condition
All diagnosed cases must be reported to the
department of health.
In 2011, there were 689 new cases of
tuberculosis in Benadir districts
51
Is this
information
useful?
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52. 1. Counts
Provide an absolute number of the burden of disease
However counts has limited utility for two reasons
The burden of disease in the population is very
different if the population size is 100,000 versus
1,000,000
Some people are not at risk for developing a new
onset of tuberculosis in 2011 (due to pre-existing
infection), thus we need to know not only the size of
the total population, but the size of the total
population at risk
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53. Incidence and prevalence
Two measures overcome many of the limitations
of a simple count of cases - incidence and
prevalence
Prevalence tells us about the proportion of cases
among the total population at any given time
Incidence tells us the probability of a new onset
of disease among those at risk for developing the
illness
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54. 2. Prevalence
The proportion of people who have the disease
(existing cases plus new cases) over the total
population for a given time period
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55. Disease occurrence in a sample of Benadir districts over time
Year 1, 5 individuals
developed the outcome
Year 2, an additional 7
people developed the
outcome
Year 3, an additional 4
people developed the
outcome
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56. What is the prevalence of disease in Year 2?
What is the numerator?
5 cases in Year 1 + 7 cases in Year 2 = 12
What is the denominator?
Total sample size = 30
Prevalence = 12/30 = 0.4
The prevalence of disease in Year 2 is 40%
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57. What is the numerator?
5 cases in Year 1 + 7 cases in Year 2 + 4 cases in Year
3 = 16
What is the denominator?
Total sample size = 30
Prevalence = 16/30 = 0.533
The prevalence of disease in Year 3 is 53.3%
57
What is the prevalence of disease in Year 3?
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58. Summary: Prevalence
For prevalence, we need a numerator (number of
existing cases), and denominator (total sample
size), and a time period of interest
The time period should be specified as much as
possible
For example, when we say “in Year 2” we mean
over the duration of time that spanned up to Year
2
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59. 3. Incidence
Perhaps the most widely used tool in
epidemiology
Goes by many names - most common alternative
name is “risk,” and less commonly, “incidence
proportion”
Numerator = number of new cases
Denominator = population at risk of becoming a
new case
Specified over a specific time period
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60. What is the incidence of disease in Year 2?
What is the numerator?
7 new cases in Year 2
What is the denominator?
25 people at risk (5 people already developed
the disease in Year 1 and are thus not at risk)
Incidence = 7/25 = 0.28
The incidence (risk) of disease in Year 2 is 28%
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61. What is the incidence of disease in Years 2 and 3?
What is the numerator?
7 new cases in Year 2 + 4 new cases in Year 3 = 11
What is the denominator?
25 people at risk (5 people already developed the
disease in Year 1 and are thus not at risk)
Incidence = 11/25 = 0.44
The incidence (risk) of disease in Years 2 and 3 is
44%
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62. Summary: Incidence
For incidence, we need a numerator (number
of new cases), and denominator (total sample
size at risk), and a time period of interest
The time period should again be specified as
much as possible
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63. The relation between
incidence and prevalence
For incidence, we need a numerator (number
of new cases), and denominator (total sample
size at risk), and a time period of interest
The time period should again be specified as
much as possible
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65. Examples of the relation between
incidence and prevalence
High incidence, steady prevalence
Example: highly contagious infectious disease
with very short duration or a high case-fatality
Low incidence, high prevalence
Examples: diseases with long duration such as
arthritis, diabetes, Crohn’s disease, and other
chronic illnesses
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66. Examples of the relation between
incidence and prevalence
Impact of a new treatment that prolongs life with the disease but does not cure it
New HIV Infections
People Living with HIV
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67. Summary, incidence, prevalence
Prevalence is affected by incidence and duration
If a disease has short duration,
Prevalence ~= incidence*
If a disease has long duration, in general,
Prevalence > incidence
* Assumes that incidence is constant over time
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