Epidemiology II By Dr Sabah M A Abdelkader

Epidemiology II By Dr. Sabah M. A. Abdelkader Assist. Prof. of Public Health

Objectives n By the end of this session, students should be able to: n Define health correctly. n Explain association with disease causation. n Identify health and disease spectrum. n Discuss dimensions of health. n Identify determinants of health. n Discuss iceberg phenomenon of diseases.

Introduction n Health is one of those terms which most people find it difficult to define. n Therefore, many definitions of health have been offered from time to time. n Understanding health is the basis of health care. n Health is not perceived same way by all members of a community including professionals.

Concepts of health n Biomedical concept: n Absence of disease. Minimized role of different determinants of health. n Ecological concept: n Equilibrium between man and environment. n Psychosocial concept: n Both biological and social phenomena. n Holistic concept: n All above concepts, multifactorial influence.

Definitions of health n Being sound in body, mind or spirit. n Soundness of body or mind which function duly and efficiently. n A state of relative equilibrium of body form and function resulting from dynamic adjustment to forces that disturb it. n A condition or quality of human organism expressing adequate functioning of organism in given conditions, genetic and environmental.

WHO definition of health n Health is a state of complete physical, mental and social wellbeing not merely absence of disease or infirmity. n Recently added: ability to lead a socially and economically productive life.

Some definitions related to concept of health and disease n n n Disease is physiological 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. Infection (germ theory): Entry& development and multiplication of micro-organism inside human body Epidemiological triad: Agent, Host, Environment. Multifactorial causation: New types of diseases, the so called “Modern” diseases of civilization.

Cont. n Chronic diseases: all impairments or deviations from normal, with one or more of the following characteristics: n Permanent, leave residual disability, are caused by non- reversible pathological alteration, and require a long period of supervision, observation or care. n NB: no international definition of long- term. n Many consider chronic conditions are those that having duration of at least 3 months.

Cont. n Web of causation theory: n Considers all the predisposing factors of any type and their complex interrelationship with each other. n Provides a model which shows a variety of possible intervention to reduce the disease. n

Association and disease causation n Association: n Concurrence of two variables more often than would be expected by chance. n Correlation: n Indicates degree of association between two characteristics. n Does not imply association. (temporal relation)

Cont. n n n n I- Spurious association: (not real) UK study perinatal mortality 5. 4/1000 home del. 27. 8/1000 hospital deliveries. II- Indirect association: (confounding factors) e. g endemic goitre in high altitudes. III- Direct (causal) association: A- one-to one e. g tubercle bacilli → TB Hemolytic streptococci→ scarlet fever or AFT B- Multifactorial non-communicable diseases through synergistic or commulative effects.

Health and disease Spectrum n There is no single cut-off point. n The lowest point on the health-disease spectrum is death and the highest point corresponds to the WHO definition of positive health. n There are degrees or "levels of health", as there are degrees or severity of illness.

Cont. n The spectral concept of health emphasizes that the health is not static; it is a dynamic phenomenon and a process of continuous change. n What is considered maximum health today may be minimum tomorrow. n It implies that health is a state, not to be attained once and for all, but ever to be promoted, preserved, and restored when impaired.

Health – disease spectrum + ve Positive health Better health Freedom from disease Unrecognized disease Mild disease Severe disease - Ve Death

Dimensions of health n n n n n Main dimensions: (WHO definition) 1 - Physical: perfect functioning of body (wide). At community level evaluated by: DR, IMR, life expectancy. 2 - Mental: ability to respond with flexibility to varied experiences in life. A state of balance and harmony with others. Relates to cognition. Mental health is one key to good health. 3 - Social: social skills, social functioning, ability to see oneself as a member of society. Harmoney , integration within an individual.

Other dimensions: n n n 4 - Spiritual: integrity, principles, ethics, purpose in life, commitment to our creator. 5 - Emotional: relates to feeling, psychology. Differs or related to mental dimension? ? ? 6 - Vocational: new, when work is fully adapted to human goals and capacities, work plays a role in promoting physical and mental health. Self realization in work is a source of satisfaction. (sudden loss of job? ? ? ) 7 others: philosophical, cultural, environmental, educational, nutritional, preventive and curative.

Determinants of health n Biological: n Genetics: Physical, mental traits. n Sociocultural: n Health requires promotion of healthy life style. n Environmental: n Internal: tissues, organs, systems. n External: everything to which humans are exposed to after conception.

Cont. n Socioeconomic: n Economic, education, occupation, marital status, political. n Health services: n Good care is expected from effective health service. n Aging of population: n ↑chronic diseases and disabilities. n Gender: n Consequences of violence, reproductive health services.

Other factors: n Transition from post industrial age to information technology. n Communication revolution. n Mass media. n Social welfare. Medicine is not the sole contributor To health and wellbeing of population ( Intersectoral contributions)

Iceberg phenomenon (Natural history of disease)

Cont. The vast submerged portion of the iceberg represents the hidden mass of disease (latent, inapparent, presymptomatic, and undiagnosed cases, and carriers in the community. n Hypertension, diabetes, anemia, malnutrition, mental illness are examples. n The hidden part of the iceberg thus constitutes an important, undiagnosed reservoir of infection or disease in the community, and its detection and control is a challenge to modern techniques in preventive medicine. n n

Thank you