Introduction To Epidemiology Lecture Notes PDF

Lecture (1) Introduction to Epidemiology By Dr. Reham Elhofy lecturer of public health and community medicine  Definition of epidemiology The study of the distribution and determinants of diseases and health-related states or events in specified populations,...

Lecture (1) Introduction to Epidemiology By Dr. Reham Elhofy lecturer of public health and community medicine  Definition of epidemiology The study of the distribution and determinants of diseases and health-related states or events in specified populations, and the application of this study to the prevention and control of health problems ”. 2  Key words in the definition Distribution (frequency & pattern of disease) - Frequency: number of cases and deaths / size of population - Pattern: includes analysis of data according to: ▪ Person: who is experiencing the disease ▪ Place: where the occurrence is highest or lowest ▪ Time: when the disease occurs most or least (Descriptive epidemiology) 3  Key words in the definition Determinants are all the biological, physical, chemical, behavioural, social, cultural, economic, genetic and behavioural factors that influence health. (Analytic epidemiology) 4  Key words in the definition Health-related states or events include diseases, causes of death, health-related events and behaviours such as injury, drug abuse, smoking, physical activity, nutrition, reactions to preventive regimens, and provision and use of health services. 5  Aims of epidemiology Promote, protect, and restore health The major purpose of epidemiology is to obtain, interpret and use health information to: Promote the health and well-being of the society as a whole, and to Eliminate or reduce the health problems or their consequences. 6  Uses of Epidemiology Natural history of disease Classification of disease Identify determinants (risk factors) Planning and evaluation of prevention and control measures Data related to availability, accessibility and utilization of services 7  Epidemiology and the information generated by epidemiologic methods have many uses. 1. In Health Care Management Uses of Epidemiology 2. In Understanding the disease process 3. In Public Health Practice 4. In Clinical and preventive practice Uses of Epidemiology 1. In Health Care Management (a) Assessment of community health needs (Community Diagnosis): To set policy and plan health programs, public health officials must assess the health of the population or community they serve, and must determine whether health services are available, accessible, effective, and efficient.  Uses of Epidemiology 2. In Understanding the disease process (a) Searching for the causes and risk factors of diseases. (b) Study of the natural history (and prognosis) of diseases. It signifies the way in which a disease evolves over time from the earliest stage of its pre-clinical phase to its termination as recovery, disability or death, in the absence of treatment or prevention. Uses of Epidemiology 3. In Public Health practice (a) Investigations of Epidemics. (b) Surveillance for Diseases. Surveillance essentially monitors trends in the occurrence of selected diseases, thereby giving early warning about increase in their occurrence so that early control measures can be instituted.  Uses of Epidemiology 3. In Public Health practice (d) Assessing the planning and evaluation of Screening Programs for Diseases in large population groups. (e) Assisting in designing medical curricula: The principles of epidemiology can be utilized to quantify the priority health problems in a given community, as well as the available resources to tackle these problems. This could help in planning a very effective community-oriented medical curriculum. Uses of Epidemiology 4. In Clinical and preventive Practice (a) Assessing effectiveness of preventive and treatment modalities. (b) Helps in defining (establishing a case definition), and classifying diseases, (e.g. classification of viral hepatitis into A, B, C, D and E). (c) Studying prognostic factors.  Introduction to epidemiology Sources of Epidemiological Data 14  1. Population statistics For planning of social and health services, current demographic information related to the general health of population is needed. Population census A census is the enumeration at specific point of time of individuals comprising the population within the area as regards age, sex and economic data. A census is carried every 10 years. Data from census are used as the denominator for mortality, morbidity and fertility rates. 15 1. Population statistics The ten-year census data may be outdated and of little value so current data are needed. Population estimates So a population estimate is needed. This is done by using statistical methods.  2. Vital records: These include data on births and deaths. They are required for legal, demographic and epidemiological purposes. A. Birth registration. All live births should be registered by law. The document characterizes both parents as well as births (birth date, sex, place of residence, birth weight and duration of gestation). 17  2. Vital records: B. Importance of birth data: They provide the denominator for: - Infant mortality and morbidity rates. - Maternal mortality and morbidity rates. the numerator for: - Fertility rates. 18  2. Vital records (cont.) B. Death registration ✓All deaths should be registered and a burial permission is only issued after registration is done. ✓Death register provides information about date and place of death, residence, sex, marital status, occupation as well as causes of death. ✓Death registration is the basic document for: Determining the number of deaths. Calculating mortality rates and ratios. Determining the causes of deaths. 19  3. Notification of infectious diseases: Certain diseases are of sufficient importance to public health to require their notification to the health authorities. Notification is done internationally and nationally. A. International reporting is required for diseases that: - require international measures (e.g. cholera, plague, yellow fever). OR - those under international surveillance (e.g. louse-borne typhus, relapsing fever, poliomyelitis). 20  3. Notification of infectious diseases: B. National reporting: Each country establishes what health events must be reported by health care providers. In the majority of countries, reportable conditions are primarily infectious diseases (e.g. measles, meningitis and typhoid). 21  3. Notification of infectious diseases: Limitations ✓The number of cases notified is usually much lower than what really exists. ✓Not all health problems are notifiable. 22  4. Disease registers These are registers for diseases of major public health concern and may be national or local. Ex: tuberculosis, cancer and mental disorders. 23  5. Hospital records All hospitals have their own records. These records include demographic data, diagnosis, operative procedures, length of stay, etc. They are the most accurate source. Hospital records include inpatient and outpatient records. Utilities ✓The diagnosis is correct. ✓A good source for studying serious and severe conditions. ✓A source for studying hospital acquired infections. 24  5. Hospital records Limitations ✓Information recorded may not be complete. ✓Users are not representative of the population. ✓Hospitals usually deal with severe conditions. 25