1. Biostatistics Methods and Epidemiology
Mansoor Nasser Mohammed AL Yarubi
MSc in Medical Statistics
Oxford Brookes University
Head of Research and Studies Section
Ministry of Health

2. Epidemiology – An Introduction
University of Nizwa
Epidemiology – An Introduction
College of Arts and Science

3. College of Arts and Science
University of Nizwa
Outlines
Introduction to Epidemiology
Concepts
Evolution and historical context
Uses
College of Arts and Science

4. University of Nizwa
What is Epidemiology?

5. College of Arts and Science
University of Nizwa
Epidemiology
The word ‘from the Greek words epi, meaning "on or upon," demos, meaning "people," and logos, meaning "the study of."
(R Bonita)
College of Arts and Science

6. Definition of Epidemiology
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Definition of Epidemiology
"Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the prevention and control of health problems.“
(Last, 2001).
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7. Key terms in the definition of Epidemiology
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Key terms in the definition of Epidemiology
STUDY: It is a scientific discipline based on sound methods of scientific inquiry include observation, hypothesis testing and analytic research.
DISTRIBUTION: studies the frequency and pattern of health events in the population including time, persons and place(descriptive analysis)
DETERMINANTS: searches for the causes including factors that may influence occurrence (analytical epidemiology)
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8. Key terms in the definition of Epidemiology
University of Nizwa
Key terms in the definition of Epidemiology
HEALTH-RELATED EVENTS: refer to disease, ,cause of death, behaviours such as tobacco , reactions to preventive regimes and use of health
SPECIFIED POPULATIONS: concerned with identifiable characteristics such as people in a community or other geographical area.
APPLICATION: provides data needed for public health action. It help to promote, protect and restore health.
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9. Objectives of epidemiology
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Objectives of epidemiology
Study the natural course of disease
Determine the extent of disease in a population
Identify patterns and trends in disease occurrence
Identify the causes of disease
Evaluate the effectiveness of measures that prevent and treat disease
These provide scientific knowledge for making sound policy decisions that protect public health.
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10. Cont...
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Epidemiologists are required to have some knowledge of the disciplines of these sciences:
Public health, because of the emphasis on disease prevention.
Clinical medicine, because of the emphasis on disease classification and diagnosis. 
Pathophysiology, because of the need to understand basic biological mechanisms in disease.
Statistics, because of the need to quantify disease frequency and its relationships to antecedents.
Social sciences, because of the need to understand the social context in which disease occurs and presents.

11. Environmental factors
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Causation of disease
Genetic factors
Good health
Ill health (disease)
Environmental factors
Psychological Stress ,unemployment
Biological Bacteria , virus ,parasites
Accidental speed, influence of alcohol, drugs
Chemical Tobacoo , chemicals , dust ,pollution

12. The natural history of disease
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The natural history of disease
The nature of disease commences with interaction between the three factors leading into three main outcomes :
The host overcomes the agent No disease
The host mainly overcomes the agent Subclinical disease
The agent overcomes the host Full development of disease
exposure
Pathologic changes
Onset of Symptoms
Usual time of diagnosis
Death
Good health
Subclinical changes
Clinical disease
Recovery
The Natural history of disease figure

13. Determine the extent of a disease or condition in a population
University of Nizwa
Determine the extent of a disease or condition in a population
Identify the frequency of health events in the population (number, rate or risk of the event in the population are also included)
Example :
What is the prevalence rate of migraine headaches in adolescents in Oman?
What are the incidence rate of anaemia in pregnancies in Nizwa Hospital?
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14. Identify patterns and trends in disease occurrence
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Identify patterns and trends in disease occurrence
Study the direction of trends and patterns of disease.
Do the trends vary according to the age, sex, geographic location of the subjects?
Are people drinking more alcohol now than they did 10 years ago?
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15. Identify the causes of disease
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Identify the causes of disease
What are the causes of disease ?
Environmental factors including personal behaviours.
Genetic factors
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16. Evaluate the effectiveness of measures that prevent and treat disease
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Evaluate the effectiveness of measures that prevent and treat disease
Epidemiologists evaluate the effectiveness and efficiency of health services by evaluating the interventions:
Does adding fluoride to drinking water prevent dental caries?
Does increasing car insurance reduce road traffic accidents?
Treatment
Medical care
Good health
Ill health (disease)
Health promotion
Preventive measures
Public health services
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17. Evolution and historical context
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Early thinkers in Epidemiology included:
400 B.C. – Hippocrates tried to explain disease occurrence from a rational rather than supernatural angle by suggesting that environment and host factor might have contributed to disease occurrence.
1662 – John Graunt published an analysis of mortality data in London to become the landmark in the understanding of patterns of births, deaths, and disease occurrence.
College of Arts and Science

18. College of Arts and Science
University of Nizwa
William Farr ( )
A leading British epidemiologist and medical statistician
Set up a system for recording causes of death. This provided the raw data for detailed analysis of death within the general population. For example, the mortality rates of different professions or of those living in different locations could be compared.
College of Arts and Science

19. College of Arts and Science
University of Nizwa
John Snow ( )
In 1854 – John Snow, a physician, carried out series of investigations during a cholera outbreak that earned him the title ‘the father of field epidemiology’.
His investigations developed from descriptive epidemiology to analytic epidemiology.
He used the detailed statistics produced by Farr to develop his own alternative theory
The results were used to control the cholera outbreak
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20. Summary of John Snow’s data
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Summary of John Snow’s data
Water supply company
Cholera deaths
Populationin 1851
Mortality rate
Southwark & Vauxhall
844
167654
5 /10,000
Lambeth 18
19133
1 /10,000
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21. College of Arts and Science
University of Nizwa
Modern epidemiology
Examples of use of epidemiologic technique in chronic diseases
Fluoride supplementation to prevent dental caries (1940s)
1948 Framingham (USA) heart study began - aim was to identify common factors contributing to cardiovascular disease by following its development over a long period of time in a large group of participants
1954 – Richard Doll demonstrated the association between cigarette smoking and lung cancer
1960’s- early 1970’s health workers from all over the world used epidemiologic methods to eradicate smallpox worldwide
2010 – BIOBANK seeks to look at genetic determinants of health and disease
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22. Science of Epidemiology: Population focus
University of Nizwa
Science of Epidemiology: Population focus
“Traditional” epidemiology starts at the population level and the first step is to ascertain variations in the occurrence of disease within and between populations
“Populations” include not only countries, but geographical regions, demographic groups, communities, extended families, etc.
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23. College of Arts and Science
Uses of Epidemiology
University of Nizwa
Study the history of the health of populations for future projection
Population or community health assessment – for diagnosis – measuring the true dimensions and distribution of ill health
Evaluate health services
Estimate the average individual risks of diseases or health-related states
Identify syndromes
Making decisions
Completing the clinical picture
Investigate causal factors
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24. Main branches of Epidemiology
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Main branches of Epidemiology
Descriptive epidemiology (observational)
Analytical Epidemiology
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25. Descriptive epidemiology
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Descriptive epidemiology
– The most basic
Answers the questions of “Who?”, “What?” “Where?” and “When?”
Information only available about occurrence of disease or associations among exposures, demographic characteristics and disease rates in population groups
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26. The Basic Triad Of Descriptive Epidemiology
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The Basic Triad Of Descriptive Epidemiology
The three essential characteristics of disease we look for in descriptive epidemiology are:
TIME
PLACE
PERSON

27. Time Changing or stable? Seasonal variation. Endemic or epidemic
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Time
Changing or stable?
Seasonal variation.
Endemic or epidemic

28. Place Geographically restricted or widespread (Pandemic)?
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Place
Geographically restricted or widespread (Pandemic)?  
Relation to water or food supply.  

29. Person Age Socio-economic status Gender Ethnicity/Race Behavior
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Person
Age
Socio-economic status
Gender
Ethnicity/Race
Behavior

30. Analytical Epidemiology
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Analytical – Design, execution and analysis of studies in groups to evaluate potential associations between risk factors and health outcomes – tests hypotheses
Answers the question “Why?”
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31. The Basic Triad Of Analytic Epidemiology
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The Basic Triad Of Analytic Epidemiology
HOST
Human or animal characteristics , age ,sex, genetic factors, marital status, demographic factors, socio economic factors, personal behavior
Define host, agent?
ENVIRONMENT
Biological:(bacteria, virus, fungi and parasites (protaoza living in water)
Chemical:(poison, alcohol, smoke)
Physical : (trauma, radiation, fire)
Nutritional :(lack , excess)
AGENT
Temperature, humidity, crowding, housing, soil, water, radiation, pollution, noise

32. Importance of epidemiology in disease prevention
University of Nizwa
Importance of epidemiology in disease prevention
Levels of prevention:
Primary prevention aims to prevent the occurrence of the disease and health disorder.
Secondary Prevention aims to prevent complication by early diagnosis and prompt treatment.
Tertiary Prevention aims to limit disabilities to minimum possible extent by arresting the progression of complications.

33. Cont… Primary prevention
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Primary prevention
Health promotion (Non specific protection which attempts to improve the resistance of the host to enable person to resist any disease.
Nutrition (The body produce proteins and these proteins produce more cells in the body (white and red blood cells) and these cell produce antibiotics against the antigens.
Exercises (the exercises reduce the risk factors like diabetes, heart disease ,hypertension and other diseases and reduce the cholesterol level in the blood and prevent hypertension by reducing glucose in the blood. And helps in build up of the body muscle.

34. Cont…
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Secondary Prevention Example : Tuberculosis destroy the lung and make cavity in the lung . It is a killing disease if it is not treated . Early diagnosis and using the treatment properly prevent the complications. Tertiary Prevention : To limit the disabilities to minimize possible extent of disease by arresting the progression of complications. In this example , rehabilitation is used to enable person become as useful as possible and prevent the person becoming burden to family and community.

35. Cont… The aspects of Rehabilitations:
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The aspects of Rehabilitations:
Physical (prevent deformities of rheumatoid arthritis by physiotherapy.
Mental ( example : if somebody lost his leg or arm will feel depression ) .
Social ( handicapped people should work and don't feel that are not unemployed.

36. Routine data Definition of Routine data Uses of routine data
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Routine data
Definition of Routine data
Uses of routine data
Sources of routine health and health related data
The strengths and weaknesses of routinely collected data

37. Definition of Routine data
University of Nizwa
Definition of Routine data
“data that are routinely collected and recorded in an ongoing systematic way, often for administrative purpose and without any specific research question in mind at the time of collection”
Hansell, A. & Aylin, P (2001)

38. College of Arts and Science
Types of routine data
University of Nizwa
Type of Data
Possible Sources
Demographic and lifestyle data
Census; Mid Year population estimates
Morbidity data
Morbidity statistics from General Practice;
Communicable disease surveillance
Outpatient morbidity
Hospital admissions;
Cancer registration
Mortality data
Deaths certificates
RTAs Mortality from ROP
Specific datasets
Abortion data
Congenital abnormalities
Fetal deaths notifications
Health services data
Immunisation levels achieved; Uptake of screening
Other
Social statistics
Private sector
National Statistical Center
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39. Non- routine sources of data
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Non- routine sources of data
Scientific studies
Surveys
Questionnaires
Interviews

40. Census Every 10 years Population estimates Health questions
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Census
Every 10 years
Population estimates
Health questions
Other health indicators
Unemployment
Age
Sex
Nationality

41. Advantages and disadvantages of Census
University of Nizwa
Advantages and disadvantages of Census
Disadvantages
Advantages
Extremely expensive
Most accurate count of country population
It can be done after long time (10 years)
It include wide range of population data and characteristics
Time consuming
Covers most of variables like housing , income , etc.
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42. Sources of data on disease
University of Nizwa
Routine mortality data
Routine morbidity data
Notifications of infectious diseases e.g. cholera and typhoid, chickenpox
School health reports
Private health institutions reports
Accident statistics e.g RTA, Falls, burns
Record of immunizations and vaccinations
Studies and surveys.

43. Disease prevention data
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Disease prevention data
Breast screening
Cervical screening
Immunisation uptake

44. Geographic data Population Census Mid year population estimates
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Population Census
Mid year population estimates

45. Uses of routine health statistics
University of Nizwa
Uses of routine health statistics
Routine health data may be utilized for a variety of epidemiological investigations such as:
Descriptive studies (cross sectional surveys or mortality or morbidity studies) and disease surveillance.
For example, cancer routine registration data may be used to examine trends in cancer incidence over time or differences in the incidence of particular cancers by age, sex, socio-economic status or in different regions.
To evaluate the effectiveness of any screening programmes .
May also be used in analytical studies.
How useful they are will depend on the issues relating to their completeness, accuracy, coverage and comparability between different regions or countries.

46. Strengths of Routine data
University of Nizwa
Value of routine data
Readily available
Limited costs
Up-to date
Useful for identifying hypothesis
Provide baseline on expected level of health /disease
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47. weakness of Routine data
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limitations of routine data
lack of completeness
Potential for bias
Often poorly presented and analysed
occasionally subject to political influence
limited details of determinants
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48. References / further reading
University of Nizwa
References / further reading
R Bonita , R Beaglehole, T Kjellstrom (2009). Basic epidemiology. WHO
Adetunji, HA (2009). Principles of Epidemiology in Key concepts in Public Health (Wilson and Mabhala eds). Sage, Los Angeles.
Friis, R.H, & Sellers, T.A. (2004). Epidemiology for Public Health Practice. Jones and Bartlett Publishers, Boston.
Webb, P, Bain, C & Pirozzo, S. (2005). Essential Epidemiology. An Introduction for Students and Health Professionals. Cambridge University Press
Course handout on Routine Data
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