Concepts of Disease.pdf
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This document discusses concepts of disease. It begins with definitions of disease from various perspectives, such as a condition that impairs body function or a deviation from normal health. Disease is distinguished from illness, which is a subjective feeling, and sickness, which refers to social roles when ill. Key concepts discussed include the germ theory of disease, epidemiological triad and tetrad, multifactorial causation, natural history of disease, and levels of prevention including primary, secondary and tertiary prevention. The document also covers disease classification systems, changing patterns of disease, and concludes that understanding disease pathology is important for formulating preventive measures.
Concepts of Disease.pdf
- 1. 1 CONCEPTS OF DISEASE BY. Kailash Nagar
- 2. CONTENTS 2 • INTRODUCTION • CONCEPTS OF DISEASE • CONCEPTS OF CAUSATION • NATURAL HISTORY OF DISEASE • CONCEPTS OF CONTROL • CONCEPTS OF PREVENTION • CHANGING PATTERN OF DISEASE • DISEASE CLASSIFICATION • CONCLUSION
- 3. INTRODUCTION • The concept of disease has been the subject of a vast, vivid and versatile debate. • Disease is a central notion to modern health care, it effects society and is important to the process of discovering and identifying disease entities. 3
- 4. CONCEPTS OF DISEASE 4 DEFINITIONS “Acondition in which body function is impaired, departure from a state of health, an alteration of the human body interrupting the performance of the vital functions.” “The condition of body or some part of organ of body in which its functions are disrupted or deranged.” “Disease is considered a social phenomenon, occuring in all societies and defined and fought in terms of the particular cultural forces prevalent in the society.” ‘a maladjustment of human organism to the environment’
- 5. TO KEEP IT SIMPLE Simplest definition – OPPOSITE TO HEALTH . 5 Any deviation from normal functioning or state of complete physical or mental well-being.
- 6. DISEASE ILLNESS SICKNESS 6 DISEASE is a physiological/ psychological dysfunction. ILLNESS is a subjective state of the person who feels aware of not being well. SICKNESS is a state of social dysfunction i.e. a role that the individual assumes when ill (sickness role).
- 7. Discovery of microbiology - turningpoint • GERM THEORY OF DISEASE • Microbes as sole cause of disease 7 CONCEPT OF CAUSATION EARLIER THEORIES • Supernatural theory • Theory of Humors • Concept of contagion • Miasmatic theory • Theory of spontaneous generation
- 8. EPIDEMIOLOGICAL TRIAD • Factors relating host and environment • Mission of epidemiology – break one of the legs of triangle and disrupt the connection between these and thereby stopping outbreak. 8
- 9. THE TETRAD OF EPIDEMIOLOGY 9
- 10. MULTIFACTORIAL CAUSATION • CONCEPT- disease is due to multiple factors and not a single one. • PETTENKOFER OF MUNICH(1819-1901)-early proponent of this concept. “Germ theory of disease "or “single cause idea "in late 19 century overshadowed the multiple cause theory. 10
- 11. 11 Causative Factors Groups or populations and their characteristics Environment behaviour, culture physiological factors ecological elements TIME ADVANCED MODEL OF THE TRIANGLE OF EPIDEMIOLOGY
- 12. WEB OF CAUSATION • Suggested by- Mac Mahon and Pugh • Considers all the predisposing factors of any type and their complex interaction with each other. 12
- 13. 41 Changes in life style Stress Obesity HTN Smoking Emotional stress Aging Changes in the walls of arteries Coronary Occlusion Myocardial ischemia Hyperlipidemia Coronary Atherosclerosis Myocardial Ischemia Fig: Web of causation of MI 13
- 14. NATURAL HISTORY OF DISEASE It refers to the progress of a disease process in an individual over time, in the absence of intervention. • History of disease is a key concept in epidemiology. 14
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- 16. PRE PATHOGENESIS PHASE • Disease agent has not entered man, but factors favouring disease exist in the environment. • What required is an interaction of these factors to initiate the disease process. Agent Host Environment 16
- 17. PATHOGENESIS PHASE • Entry of disease agent in susceptible human host. • Disease agent multiplies and induces tissue and physiological changes. • final outcome- recovery, disability or death. • This phase may be modified by intervention measures such as immunization, chemotherapy 17
- 18. AGENT FACTORS 18 Substance living or non living , or a force, tangible or intangible, the excessive presence or relative lack of which may initiate or perpetuate a disease process. Pathogenicity Virulence 1. Biological Agents – Infectivity 2. Nutrient 3. Physical 4. Chemical 5. Mechanical 6. Absence or insufficiency of a factor 7. Social
- 19. HOST FACTORS • Host - SOIL Disease agent – SEED Classified as • Demographic characteristics • Biologic • Social & Economic • Lifestyle factors 19
- 20. ENVIRONMENTAL FACTORS • All that which is external to the individual human host, living and non-living, and with which he is in constant interaction. -Macro-environment (external) • Physical • Biological • Psycho social 20
- 21. RISK FACTORS • Where the disease agent is not established, the is generally in terms of risk firmly aetiology discussed factors. • The term risk factor by different authors is used with at least two meanings- An attribute or significantly exposure that is associated with development of disease. A determinant that can be modified by intervention, thereby reducing the possibility of occurrence of disease or other specified outcomes. 21
- 22. RISK GROUPS • Something for all but more for those in need- in proportion to the need. • Another approach developed and promoted by WHO is to identify precisely the risk groups or target groups in population by certain defined criteria and direct appropriate action to them first- risk approach. 22
- 23. SPECTRUM OF DISEASE • Graphic representation of variations in the manifestations of disease. • Infectious disease – gradient of infection 23
- 24. ICEBERG OF DISEASE • Disease in a community is compared to an iceberg. 24
- 25. CONCEPTS OF CONTROL 25 The term disease control refers ongoing operation aimed at reducing: o The incidence of disease. o The duration of disease and the consequently the risk of transmission. o The effect of infection including physical and psychological complication. o The financial burden to the community.
- 26. •DISEASE ELIMINATION: Reduction of case transmission to a predetermined very low level or interruption in transmission. E.g. measles, polio, leprosy from the large geographic region or area. • DISEASE ERADICATION: Termination of all transmission of infection by extermination of the infectious agent through surveillance and containment. “All or none phenomenon”. E.g. Small pox. 26
- 27. • DISEASE MONITORING: 27 • Defined as “the performance and analysis of routine measurement aimed at detecting changes in the environment or health status of population.” e.g. growth monitoring of child, Monitoring of air pollution, monitoring of water quality etc. • DISEASE SURVEILLANCE: • Defined as “the continuous scrutiny of the factors that determine the occurrence and distribution of disease and other conditions of ill health.” E.g. Poliomyelitis surveillance programme of WHO.
- 28. CONCEPTS OF PREVENTION The goals of medicine are to • Promote health, • To preserve health, • T o restore health when it is impaired • And to minimize suffering and distress. These goals are embodied in the word "prevention" 28
- 29. • Actions aimed at eradicating, eliminating or minimizing the impact of disease and disability, or if none of these are feasible, retarding the progress of the disease and disability. • The concept of prevention is best defined in the context of levels, traditionally called primary , secondary and tertiary level, called primordial prevention. A fourth prevention, was later added. 29
- 30. Leavell’s Levels of Prevention Stage of disease Level of prevention Type of response Pre-disease Primary Prevention Health promotion and Specific protection Latent Disease Secondary prevention Pre-symptomatic Diagnosis and treatment Symptomatic Disease Tertiary prevention •Disability limitation for early symptomatic disease •Rehabilitation for late Symptomatic disease 30
- 31. PRIMORDIAL PREVENTION • DEFINITION “It is development of the prevention risk factors in of the emergence or countries or population groups in which they have not yet appeared.” • INTERVENTION The main intervention in primordial prevention is through individual and mass health education. 31
- 32. PRIMARY PREVENTION • • Goal: • Reduce number of new cases Rationale: • By reducing exposure rates and increasing resistance, can reduce number of new cases • Target population: • Those who are most likely to be exposed and/or could increase their resistance • Typical activities: • Remove or reduce source of the risk • Educate and make aware of disease risk o Include behavioral changes to reduce exposure • Improve general health • Outcome measure: incidence of exposure; incidence of disease Primary prevention can be defined as the action taken prior to the onset of disease, which removes the possibility that the disease will ever occur. 32
- 33. SECONDARY PREVENTION 33 • • Goal: • Reduce number of new cases; reduce number of severe cases Rationale: • By reducing number of exposures and early disease that progress to more severe disease, mortality and morbidity can be reduced • Target population: • Those who have been exposed to the disease-causing agent or have early symptoms of the disease • Typical activities: • Screening for exposure and/or disease • Post-exposure prophylaxis • Early treatment to reduce impact of disease/reverse course • Outcome measure: incidence of disease Secondary prevention can be defined as the action which halts the progress of a disease at its incipient stage and prevents complications.
- 34. TERTIARY PREVENTION 34 • • r of Goal: • Reduce number of complications, deaths Rationale: • By reducing disease severity and increasing recovery, can reduce numbe premature deaths or complications • Target population: • Those who have disease and need treatment • Typical activities: • Treatment tailored to the patient • Rehabilitation to promote recovery • Outcome measure: incidence of death and long- term disability Tertiary prevention can be defined as all measures available to reduce or limit impairments and disabilities, minimize suffering caused by existing departures from good health and to promote the patients adjustment to irremediable conditions.
- 35. MODES OF INTERVENTION 35 • Intervention is any attempt to intervene or interrupt the usual sequence in the development of disease. • Five modes of intervention corresponding to the natural history of any disease are: o Health Promotion o Specific Protection o Early Diagnosis and Adequate Treatment o Disability Limitation o Rehabilitation
- 36. HEALTH PROMOTION 36 • It is the process of enabling people to increase control over diseases, and to improve their health. It is not directed against any particular disease but is intended to strengthen the host through a variety of approaches(interventions): o Health Education o Environmental Modifications o Nutritional Interventions o Lifestyle and Behavioral Change
- 37. SPECIFIC PROTECTION 37 • Some of the currently available interventions aimed at specific protection are: immunization, use of specific nutrients, chemoprophylaxis, protection against accidents, protection from carcinogens, avoidance of allergens, control of specific hazards in general environment .eg air pollution , noise control Control of consumer product quality and safety of foods,drugs etc
- 38. EARLY DIAGNOSIS AND TREATMENT 38 •A WHO defined early detection of health impairment as “the detection of disturbances of homeostatic and compensatory mechanism while biochemical, morphological, and functional changes are still reversible.” •Early detection and treatment are the main interventions of disease control. •Earlier a disease is diagnosed and treated the better it is from the point of view of prognosis and preventing the occurrence of further cases or any long-term disability. •Ex – essential hypertension, cancer of cervix and Breast cancer
- 39. DISABILITY LIMITATION 39 • Objective- is to prevent or halt the transition of the disease process from impairment to handicap. Sequence of events leading to disability & handicap: • Disease → Impairment → Disability→ Handicap. WHO defined these terms- • Impairment: Loss or abnormality of psychological, physiological/anatomical structure or function. • Disability: Any restriction or lack of ability to perform an activity in a manner considered normal for one’s age, sex, etc. • Handicap: Any disadvantage that prevents one from fulfilling his role considered normal.
- 40. REHABILITATION “combined educational and coordinated use of medical, social, and vocational measures for training and retraining the individual to the highest possible level of functional ability”. • Areas of concern in rehabilitation: Medical rehabilitation (restoration of function), Vocational rehabilitation (restoration of the capacity to earn a livelihood), Social rehabilitation ( restoration of family and social relationships), Psychological rehabilitation (restoration of personal dignity and confidence). 40
- 41. CHANGING PATTERN OF DISEASE • Although diseases have not changed significantly through human history, their patterns have. • Every decade produces its own patterns of disease. 41
- 42. 42 Spanish flu
- 43. EPIDEMIOLOGICAL TRANSITION. 43 • A characteristic shift in the disease pattern of a population as mortality falls during the demographic transition: acute, infectious diseases are reduced, while chronic, degenerative diseases increase in prominence, causing a gradual shift in the age pattern of mortality from younger to older ages. (Omran 1970)
- 44. DEVELOPED COUNTRIES 44 • Causes of diseases have shifted from and deaths infectious to chronic diseases. Common disease- HEART DISEASE - 23.81% CANCER-22.95% CVS- 5.16% . These 3 together- constitutes about 51.92% of deaths in US. OTHERS- Alzheimer's disease, lung cancer, environmental health problems, and microbial diseases
- 45. • DEVELOPING COUNTRIES • Nation with a low level of material well-being. • In a typical developing country about 40%of death are from infectious ,parasite, and respiratory diseases compared with about 8%in developed countries. • In India ,as in other developing countries ,most death result from infectious and parasite disease, abetted by malnutrition. 45
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- 48. DISEASE CLASSIFICATION • A system of classification was needed whereby diseases could be grouped according to certain common characteristics , that would facilitate the statistical study of disease phenomena. • JOHN GRAUNT in 17th century- in his study of Bills ofmortality – arranged diseases in an alphabetic order. 48
- 49. ICD CLASSIFICATION 49 • International classification of disease (ICD)by WHO - accepted for national and international use. • Revised once in 10 years. • The ICD is a classification system developed collaboratively between the World Health Organization WHO) and 10 international centers so that the medical terms reported by physicians, medical examiners, and coroners on death certificates can be grouped together for statistical purposes
- 50. ICD-10 ARRANGED IN 21 DIFFERENT CHAPTERS 50
- 51. Why we need disease??? • HAEMOCHROMATOSIS - BUBONIC PLAGUE • DIABETES - YOUNGER DRYAS • FAVISM - MALARIA 51 Natural selection is maintaining this genetic defect because it had conferred some benefit in the past.
- 52. CONCLUSION 52 • Understanding disease pathology is the first step towards formulating preventive measures. • As a dentist or public health worker it is our primary responsibility for the prevention of diseases in community as well as individual.
- 53. REFERENCES 53 • Park, Park’s Textbook of Preventive &Social Medicine, 22nd Edition, Jabalpur: Banarsidas Bhanot,2013. • Soben Peter. Essentials of Public Health Dentistry. 4th ed. New Delhi: Arya Publising House; 2013. • Epidemiology, L. Gordis, Fourth ed, 2009, Saunders • Moalem, S., & Prince, J. (2007). Survival of the sickest: A medical maverick discovers why we need disease. NewYork: William Morrow.
- 54. Thank You !