Basic Epidemiology-1 ( 15th Sept 2011) edited

Basic Epidemiology for Dental students-1: 

Basic Epidemiology for Dental students-1 Dr Tin Myo Han Department of Community Dentistry Kulliyyah of Dentistry International Islamic University, Malaysia 9/18/2011 1

Outline of lecture: 

Outline of lecture What is epidemiology Triad of causation Triad of distribution Chain of disease transmission Why we need to learn epidemiology ( uses of epidemiology Take home message Assignments for students Bonus ( History of Epidemiology) 9/18/2011 2

Community Medicine/Community Dentistry : 

Community Medicine/Community Dentistry 9/18/2011 3 Link of these subjects will be discussed in Tutorial-1

What is Epidemiology? : 

What is Epidemiology? Oral Health

Slide 5: 

What is epidemiology ? epi “on” or “upon” demos “people” or “mass” logos “study of” “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 control of health problems. ” Last JM: A Dictionary of Epidemiology

Definitions of Epidemiology : 

Definitions of Epidemiology Oxford English Dictionary THE BRANCH OF MEDICAL SCIENCE WHICH TREATS OF EPIDEMICS Kuller LH: Am J Epid 1991;134:1051 EPIDEMIOLOGY IS THE STUDY OF "EPIDEMICS" AND THEIR PREVENTION Anderson G,quoted in Rothman KJ: Modern Epidemiology THE STUDY OF THE OCCURRENCE OF ILLNESS

Terminology : 

Terminology Endemic Hyperendemic Holoendemic Epidemic Pandemic Epizootic Incidence Prevalence Must know basic epidemiological Terminology as a profession

Slide 8: 

Endemic: a disease or pathogen present or usually prevalent in a given population or geographic region at all times Epidemic: a disease occurring suddenly in numbers far exceeding those attributable to endemic disease; occurring suddenly in numbers clearly in access of normal expectancy Pandemic: a widespread epidemic distributed or occurring widely throughout a region, country, continent, or globally

Endemic - Epidemic - Pandemic: 

Endemic - Epidemic - Pandemic Endemic -Transmission occur, but the number of cases remains constant Epidemic The number of cases increases Pandemic -When epidemics occur at several continents – global epidemic Time Cases Endemic Epidemic ( www )

SCOPE AND JURISDICTION: 

SCOPE AND JURISDICTION STRICTLY SPEAKING, THERE IS NO LIFE SCIENCE, WHERE EPIDEMIOLOGICAL APPROACH AND PRINCIPLES CANNOT BE APPLIED FROM WOMB TO TOMB EPIDEMIOLOGY IS APPLICABLE PREVENTIVE PAEDIATRICS GERIATRICS DENTISTRY CARDIOLOGY CLINICAL EPIDEMIOLOGY

Recent applications of epidemiology: 

Recent applications of epidemiology Study of communicable diseases. E.g. TB, leprosy. Study of NCDs. E.g. Cancer, IHD, Dental Caries Health related states. E.g. Accidents. Public health. E.g. Utilization rates, vaccination coverage, health needs and demands. Psychological epidemiology social epidemiology Molecular and genetic epidemiology Nutritional epidemiology

Main Components of epidemiology: 

Main Components of epidemiology Disease frequency: rates, ratios & proportions.( will discuss Basic Epidemology-2) Distribution of disease: with relation to time, place and person) Determinant of disease: agent, host and environment.

Slide 13: 

Communicable Diseases (CDs) communicable diseases can be passed on from one person to another e.g tuberculosis, chickenpox, HIV/AIDS Non-Communicable Diseases(NCDs) Non-communicable diseases can not be passes on from one person to another e.g hypertension, DM, Metabolic Syndrome Dental caries? Gingivitis ?

Epidemiological triad of distribution ( Descriptive Epidemiology): 

Epidemiological triad of distribution ( Descriptive Epidemiology) 9/18/2011 14

The Basic Triad of Descriptive Epidemiology : 

The Basic Triad of Descriptive Epidemiology THE THREE ESSENTIAL CHARACTERISTICS OF DISEASE WE LOOK FOR IN DESCRIPTIVE EPIDEMIOLOGY: TIME PLACE PERSON

Slide 16: 

Short term fluctuations (hrs, days, weeks) Periodic fluctuations ( June, December) Long term or Secular trends Time Distribution

(A) Short-term fluctuations: 

(A) Short-term fluctuations The best known short-term fluctuation is an epidemic/ outbreak. - Epidemic is defined as "the occurrence in a community or region of cases of an illness or other health-related events clearly in excess of normal expectancy”. - Out break is defined “ Occurrence of more cases of disease than expected in a given area among a specific group of people over a particular period of time”

Slide 18: 

(B) Periodic fluctuations (months and years) 1) Seasonal: Rainy- malaria, filariasis. Winter- RS infections. Summer- Diarrhea. NCD – sum stroke , Hay fever, Snakebite 2) Cyclical trend: diseases occur in cycles , for a short periods(days, wks, months or yrs). e.g.. measles every 2-3 yrs, mumps every 5-7 yrs, influenza 7-10yrs This occurs due to naturally occurring variations in “ Herd Immunity” Non infectious – accidents at week-ends

Herd Immunity : 

Herd Immunity “ Community immunity” by giving mass immunization - Immunised individuals provide indirect protection to susceptible (unvaccinated, partially vaccinated) individuals: fewer people infected,lower shedding by vaccinees 9/18/2011 19           

c. Secular trends or long term trends: 

c. Secular trends or long term trends Changes occur over long period of time (usually > 10yrs). It could be increasing or decreasing, real or apparent, communicable diseases or non-communicable disease. e.g.. 1) Real downward trend: Plague & cholera. 2) Real upward trend: DM, CHD. TB? 3) Dental Caries in Asia-Pacific Region ? Malaysia???

Why we should know time trends? : 

Why we should know time trends? Can know diseases which are increasing or decreasing Can frame effective measures to control diseases Formulate etiological hypothesis Provide guidelines to health administrator in matters of prevention or control of disease

The Basic Triad of Descriptive Epidemiology : 

The Basic Triad of Descriptive Epidemiology TIME PLACE PERSON

Place : 

Place Place distributions Geographical comparisons To study the geographical variations of disease ( dental caries in Kuantan & KL) Factors influencing geographical variations are culture, standards of living, external environment and genetic factors. 9/18/2011 23

Slide 24: 

1) International: a) Malaria, Leprosy in hot and humid climate. E.g.. Africa and South America. b) Dental Caries in USA, Japan, UK, Malaysia, South Africa 2) National: 1) DM , IHD in KL, Pahang, Sabah, Sarawak, Place

Slide 25: 

3) Local: Studied with the help of spot maps in a given area. E.g.. a) John Snow study on cholera in London. b) Endemic flurosis in Nalgonda, Kolar c) Periodontal diseases in Kuantan ??? 4) Urban- Rural: e.g.. - Tetanus, OP poisoning common in rural area. - Road traffic accidents, drug abuse in urban areas. - More denture wearing in Urban ??? Place Do these variations and help to frame guidelines for prevention and control of diseases?

The Basic Triad of Descriptive Epidemiology : 

The Basic Triad of Descriptive Epidemiology TIME PERSON Place

Slide 27: 

PERSON 1) Age 2) Gender ( Male, Female, ??) 3) Occupation ( agricultural/ Industry ) . 4) Marriage ( Single, married, divorce, separated) 5) Residence. 6) Socio-Cultural environment. 7) Socio-Economic background. 8) Stress ??? 9) Migration ????

Epidemiological Triad of Causation ( Analytic epidemiology): 

Epidemiological Triad of Causation ( Analytic epidemiology) 9/18/2011 28

Traditional Model of Infectious Disease Causation ( CDs): 

Traditional Model of Infectious Disease Causation ( CDs) The epidemiologic triangle recognized three factors in the pathogenesis of diseases: Agent Environment Host

Agents : 

Agents Non- Living thing Nutrients Poisons Allergens Radiation Physical trauma Psychological experiences Living thing Microbes: Bacteria, virus, protozoa, parasites, fungus Helminthes

Host: 

Host Genetic endowment Immunologic state Age Gender Personal behavior Underlying Health Status Nutritional status

Environment: 

Environment Macro–environment W eather Housing/ crowding G eography Occupational setting A ir quality (CO, SO2) F ood/water (fluoride , chlorine ) Micro-environment Acid-base balance, Fluid& Electrolyte of Intra-cellular (ICF), extra-cellular (ECF), interstitial fluid (ISF) of body

Slide 33: 

Agent Host Environment Age gender G enotype Behaviour N utritional status Health status Non Living things Physical ( light, cold, heat, noise); Chemicals (acid, alkali, toxic materials) - Duration of exposure, intensity Macro-Environment (External) W eather Housing G eography Occupational setting A ir quality F ood EPIDEMIOLOGICAL TRIAD OF CAUSATION Living things( bacteria, virus, parasites,fungi) Infectivity Pathogenicit y Virulence Immunogenicit y Antigenic stabi lity Survival Micro-Environment(Internal) Acid-base balance, Fluid& Electrolyte of Intra-cellular and extra-cellular and interstitial fluid of body

Disease transmission: 

Disease transmission 9/18/2011 34

Chain of disease transmission for Communicable Diseases: 

9/18/2011 35 Chain of disease transmission for Communicable Diseases

Slide 36: 

Horton & Parker: Informed Infection Control Practice ( www ) Chain of Disease transmission for CDs

Means of of transmission: 

Means of of transmission Direct Skin-skin ( Herpes type 1) Mucous-mucous ( STI) Across placenta (toxoplasmosis) Through breast milk (HIV) Sneeze-cough(Influenza) Indirect Food-borne (Salmonella) Water-borne ( Hepatitis A) Vector-borne ( Malaria) Air-borne ( Chickenpox) Exposure A relevant contact – depends on the agent Skin, sexual intercourse, water contact, etc

Epidemiology of NCDs: 

Epidemiology of NCDs 9/18/2011 38

Epidemiology of NCDs: 

Epidemiology of NCDs Absence of known agent: in most of NCDs the causes is not known Multi-factorial causation -web of causation , risk factors - individual (smoking, sweet consumption) - community risk factors ( fluoride ) Long latent period Indefinite onset ( slow in onset) 9/18/2011 39

Web of Causation: 

Web of Causation RS Bhopal Disease behavior Unknown factors genes phenotype workplace social organization microbes environment

Web of Causation – CHD: 

Web of Causation – CHD CHD smoking Unknown factors gender genetic susceptibility inflammation medications lipids physical activity blood pressure stress

Prevention of NCDs: 

Prevention of NCDs Level of prevention - Primordial prevention - Primary prevention -Secondary prevention - Tertiary prevention 9/18/2011 42 Healthy people Unhealthy people

Primordial prevention: 

Primordial prevention Prevention of the emergence or development of risk factors in countries or population groups in which they have not yet appeared. Efforts are directed towards discouraging children from adopting harmful life styles 9/18/2011 43 Primary prevention Action taken priori to the onset of disease which removes the possibility that disease will ever occur. Can be divided into population & high risk streategy

Primary prevention interventions : 

Primary prevention interventions Health promotion e.g -proper tooth brushing/Smoking cessation - reduction of sweet consumption Specific protection e.g Regular dental check up/plaque removal Adequate nutrition e.g healthy diet / nutrition Safe water and sanitation -fluoride water and oral hygiene 9/18/2011 44

Secondary prevention: 

Secondary prevention Action which halts the progress of disease at its incipient stage & events complications. Mostly curative.( Early Diagnosis & treatment ) 9/18/2011 45 Tertiary prevention Defined as all measures available to reduce impairments & disabilities, minimize suffering due to departure from good health & promote patients’ adjustment to irremediable conditions ( Disability limitation & Rehabilitation e.g Stoke)

NATURAL HISTORY OF DISEASE: 

NATURAL HISTORY OF DISEASE

Uses of Epidemiology: 

Uses of Epidemiology 47

Morris’ seven uses of epidemiology: 

Morris’ seven uses of epidemiology Trend study Community diagnosis Health services evaluation To know the individual risks and chances Syndrome identification Completing the clinical picture Searching for causes / risk factors for establishing causal relationship

1. TREND STUDY: 

1. TREND STUDY -STUDYING THE PAST HISTORY FOR RISE AND FALL -STUDYING ITS CHANGING BEHAVIOUR -MAKING FUTURE PREDICTIONS -GIVING EARLY WARNINGS OR FEED-BACK

Slide 50: 

SOCIAL ANATOMY COMMUNITY DIAGNOSIS SOCIAL PATHOLOGY SOCIAL PHYSIOLOGY QUANTIFICATION QUALITATIVE ESTIMATION 2. COMMUNITY DIAGNOSIS

2. COMMUNITY DIAGNOSIS: 

2. COMMUNITY DIAGNOSIS Social anatomy : race, age and sex composition, socio economic status, population at risk, resources available. Social physiology : positive &negative lifestyles, occupation, health services awareness and utilization, nutritional polices, labor. Social pathology : morbidity, mortality, disability, alcoholism, smoking, crime & violence, risk prone behavior.

3. HEALTH SERVICES EVALUATION: 

3. HEALTH SERVICES EVALUATION Health planning for Appropriate Cost effective Community need based Judicial mix of preventive, promotive, curative , rehabilitative and public health services

4. SYNDROME IDENTIFICATION: 

4. SYNDROME IDENTIFICATION LUMPERS & SPLITTERS -Grouping and dividing the symptom complex and naming them as syndromes is the starting point for the study of natural history of any diseases

5.SEARCH FOR CAUSES: 

5.SEARCH FOR CAUSES Several causes  Single diseases Single causes  Several diseases Search for causes in interrelated diseases may yield clues for new causes / risk factors

6. COMPLETING THE CLINICAL PICTURE OF DISEASE: 

6. COMPLETING THE CLINICAL PICTURE OF DISEASE IN BREADTH Hospital studies has to be broadened with simultaneous community studies as they poorly representative the health event in general population. Mere dependence on studies conducted in hospital or any health facility setting is biased because they do not included the pre-pathogenic and follow-up phages of the diseases studied IN DEPTH Going to the bottom, the deeper part of the iceberg to study the earlier part of diseases which is either stoppable or at least preventable by searching for: Precursors of the disease Dispositions due to disease Asymptomatic disease Subclinical cases Latent cases Carrier state

Ultimate aim of Epidemiology: 

Ultimate aim of Epidemiology To eliminate or reduce the health problems or its consequences. To promote the health and well being of society as a whole.

Take home Message: 

Take home Message Every student should understand at least basic epidemiology on: - definition - Causal triad, distribution triad and chain of disease transmission and - use of epidemiology This basic knowledge can be applied in the daily professional practices. 9/18/2011 57

Assignments for students : 

Assignments for students 9/18/2011 58

Web of Causation – Dental Caries: 

Web of Causation – Dental Caries Dental Caries smoking Unknown factors gender genetic susceptibility ? medications ?? ??? ??? age Assignment 1

Web of Causation – Periodontal diseases: 

Web of Causation – Periodontal diseases Dental Caries smoking Unknown factors gender genetic susceptibility ? medications ?? ??? ??? age Assignment 2

Bonus : 

Bonus 9/18/2011 61 History of Epidemiology

Slide 62: 

Hippocrates (460-377 B.C.) On Airs, Waters, and Places Idea that disease might be associated with physical environment

Slide 63: 

John Snow (1813-1858) Father of epidemiology Careful mapping of cholera cases in East London during cholera epidemic of 1854 Traced source to a single well on Broad Street that had been contaminated by sewage

Slide 64: 

Ignas Semmelweis (1840’s) Pioneered hand washing to help prevent the spread of septic infections in mothers following birth

Slide 65: 

Edward Jenner (1749-1823) Pioneered clinical trials for vaccination to control spread of smallpox Jenner's work influenced many others, including Louis Pasteur who developed vaccines against rabies and other infectious diseases

Slide 66: 

Typhoid Mary Role of carrier in disease transmission

Slide 67: 

Typhoid Mary & George Soper Mary Mallon, a cook responsible for most famous outbreaks of carrier-borne disease in medical history Recognized as carrier during 1904 N.Y. typhoid fever epidemic When source of disease was traced, Mary had disappeared only to resurface in 1907 when more cases occurred Again Mary fled, but authorities led by George Soper, caught her and had her quarantined on an island In 1910 the health department released her on condition that she never accept employment involving the handling of food Four years later, Soper began looking for Mary again when two new epidemics broke out; Mary had worked as a cook at both places She was found and returned to North Brother Island, where she remained the rest of her life until a paralytic stroke in 1932 led to her slow death, six years later