Introduction To Epidemiology PDF

INTRODUCTION TO EPIDEMIOLOGY DENA MOHAMED CPHQ, MPH, MFDRCSI, BDS Define epidemiology 01 Objectives of epidemiology 02 Measure of health 03 Terminology in epidemiology 04 OBJECIVES Types of epidemiologic...

INTRODUCTION TO EPIDEMIOLOGY DENA MOHAMED CPHQ, MPH, MFDRCSI, BDS Define epidemiology 01 Objectives of epidemiology 02 Measure of health 03 Terminology in epidemiology 04 OBJECIVES Types of epidemiological studies 05 Epidemiology definition 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 control health problems These terms reflect the important principles of epidemiology 1. Distribution Concerned with frequency pattern Frequency includes: numbers of events rate of disease risk of population  pattern refers to occurrence of health-related events Time: Person: Annual, seasonal, Place: Demographic factors, occurrence, or in Geographic variation, genetic factors, relation to an event urban- rural behaviors and such as consumption differences and environmental of food location of worksites exposure or school The characterization of distribution of health-related events is one broad term aspect of epidemiology called descriptive epidemiology provide what, who, when, and where of health-related event 2. Determinants Determine Causes and other factors that influence the occurrence of health-related events. Analytic epidemiology provides why and how of such event by comparing rates of disease occurrence among groups that differ with regard to potential risk factors.  3. Health-related events Epidemiology concerned with communicable disease Concerned with chronic diseases, injuries, birth defect, maternal-child health, occupational health, environmental health, use of Concerned with the endemic medical and surgical services, and of communicable and non- behavior-related disease. communicable diseases. 4. Specified population Epidemiologist Physician Both are concerned with the disease and disease control Concerned with the collective health of Concerned with the health of individual population Epidemiologist Physician Both are interested in establishing correct diagnosis Focus on exposure, NO. of person who may Focus on treating individual have similar exposure, potential of further spread in the community, and intervention to prevent additional cases or recurrence 5. Application to control Application to control It is the goal of epidemiology, Concerned with: Identify population at risk Identify causes of disease Evaluate prevention and control of diseases 5. Application to control Epidemiology uses all methods to study: Distribution Outcomes of Determinants health-related events The information needed for epidemiology Who are affected Where it did happen When did it happen What is the diseases How did occur Why did occur Objectives of epidemiology 1. Study the natural course of disease from onset to resolution 2. Determine the extent of disease in a population 3. Identify pattern and trends in disease occurrence 4. Identify the cause of the disease 5. Evaluate the effectiveness of measures that prevent and treat disease Measuring health The epidemiological measure has at least two components; a numerator and a denominator Numerator The number of times the event has occurred. Denominator The population at risk or the population in which cases exist or have occurred The mathematical quantity used to measure health status and the occurrence of health events on populations No relationship between numerator and Ratio denominator obtained by dividing one quantity by another and Example express a relation in size 𝑁𝑜. 𝑜𝑓 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 𝑤𝑖𝑡ℎ 𝑀𝑎𝑙𝑎𝑟𝑖𝑎 𝑎𝑡 𝑎 𝑐𝑒𝑟𝑡𝑎𝑖𝑛 𝑡𝑖𝑚𝑒 between two random 𝑁𝑜. 𝑜𝑓 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 𝑤𝑖𝑡ℎ 𝑚𝑎𝑙𝑛𝑢𝑡𝑟𝑖𝑡𝑖𝑜𝑛 𝑎𝑡 𝑎 𝑐𝑒𝑟𝑡𝑎𝑖𝑛 𝑡𝑖𝑚𝑒 quantities The mathematical quantity used to measure health status and the occurrence of health events on populations Proportion ▪ There is a relationship between numerator and ▪ A comparison of a part to denominator. Numerator must be included in the whole denominator ▪ Example: 𝑁𝑜.𝑜𝑓 𝑐ℎ𝑖𝑙𝑑𝑟𝑒𝑛 𝑤𝑖𝑡ℎ 𝑀𝑎𝑙𝑎𝑟𝑖𝑎 𝑎𝑡 𝑎 𝑐𝑒𝑟𝑡𝑎𝑖𝑛 𝑡𝑖𝑚𝑒 ▪ 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐ℎ𝑖𝑙𝑑𝑒𝑟𝑛 𝑖𝑛 𝑡ℎ𝑒 𝑣𝑖𝑙𝑙𝑎𝑔𝑒 𝑎𝑡 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑡𝑖𝑚𝑒 The mathematical quantity used to measure health status and the occurrence of health events on populations ▪ Rate ▪ There is a distinct relationship between the ▪ Measures the occurrence numerator and denominator of a particular event during a given time ▪ A specified time period is an essential period in a population at component of the denominator risk ▪ Example: ▪ it allows valid ▪ 𝑑𝑒𝑎𝑡ℎ 𝑟𝑎𝑡𝑒 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑎𝑡ℎ𝑠 𝑖𝑛 𝑜𝑛𝑒 𝑦𝑒𝑎𝑟 comparison across 𝑝𝑜𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑟𝑖𝑠𝑘 different population  Measurement of morbidity Incidence: The number of new cases of disease in Prevalence: defined population The number of during specified existing (new and period of time, old) cases of diseases incident can be in defined population obtained from and defined time, longitudinal studies prevalence can be obtained from cross sectional studies Measurement of mortality Use of mortality data: Explaining trends Indicating priorities for health action 𝑑𝑒𝑎𝑡ℎ 𝑜𝑐𝑐𝑢𝑟𝑖𝑛𝑔 𝑑𝑢𝑟𝑖𝑛𝑔 𝑎 𝑔𝑖𝑣𝑒𝑛 𝑡𝑖𝑚𝑒 𝑝𝑒𝑟𝑖𝑜𝑑 Designing priority programs 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑎𝑚𝑜𝑛𝑔 𝑤ℎ𝑖𝑐ℎ 𝑡ℎ𝑒 𝑑𝑒𝑎𝑡ℎ𝑠 𝑜𝑐𝑐𝑢𝑟𝑒𝑑 Measurement of mortality The mortality rate from all causes of death for a population Crude mortality rate 𝑡𝑜𝑡𝑎𝑙 𝑑𝑒𝑎𝑙𝑡ℎ 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟 𝑎𝑣𝑎𝑟𝑔𝑒 𝑡𝑜𝑡𝑎𝑙 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡ℎ𝑎𝑡 𝑦𝑒𝑎𝑟 Related to the cause or disease specified, or related to specific group Cause-specific death rate 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑎𝑙𝑡ℎ𝑠 𝑓𝑟𝑜𝑚 𝑎 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑎 𝑦𝑒𝑎𝑟 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑟𝑖𝑠𝑘 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑡𝑖𝑚𝑒 Measurement of mortality A mortality rate among either male or female Sex-specific mortality 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑎𝑙𝑡ℎ𝑠 𝑎𝑚𝑜𝑛𝑔 𝑚𝑎𝑙𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑎 𝑦𝑒𝑎𝑟 rate 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑟𝑖𝑠𝑘 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑡𝑖𝑚𝑒 The Tendancy of a disease to cause the death of affected patient Case fatality rate 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑎𝑡ℎ𝑠 𝑑𝑢𝑒 𝑡𝑜 𝑝𝑎𝑟𝑡𝑖𝑐𝑢𝑙𝑎𝑟 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑡𝑜𝑡𝑎𝑙 𝑚𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑎𝑠𝑒𝑠 𝑑𝑢𝑒 𝑡𝑜 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 Measurement of mortality Describes the proportion of deaths in a specified population Proportional mortality over a period of time attributable to different causes rate 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑎𝑙𝑡ℎ𝑠 𝑓𝑟𝑜𝑚 𝑎 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑖𝑛 𝑎 𝑦𝑒𝑎𝑟 𝑡𝑜𝑡𝑎𝑙 𝑑𝑒𝑎𝑙𝑡ℎ 𝑓𝑟𝑜𝑚 𝑎𝑙𝑙 𝑐𝑎𝑢𝑠𝑠𝑒𝑠 𝑖𝑛 𝑡ℎ𝑎𝑡 𝑦𝑒𝑎𝑟 Often stated as a five-year survival rate, which is the percentage of people in a study or treatment group who are Survival rate alive five years after their diagnosis or the start of treatment 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑡𝑖𝑒𝑛𝑡𝑠 𝑎𝑙𝑖𝑣𝑒 𝑎𝑓𝑡𝑒𝑟 𝑎 𝑓𝑖𝑣𝑒 𝑦𝑒𝑎𝑟𝑠. 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑡𝑖𝑒𝑛𝑡𝑠 𝑑𝑖𝑎𝑔𝑛𝑜𝑠𝑒𝑑 𝑜𝑟 𝑡𝑟𝑒𝑎𝑡𝑒𝑑 Terminologies in epidemiology Communicable disease: An illness due to specific infectious agent or its toxic products, capable of being directly or indirectly transmitted from human to human, animal to animal, or from environmental to human or animal Terminologies in epidemiology ▪ Epidemic: the rapid spread of disease to a Endemic: large number of patients among a given population within an area in Constant presence of a a short period of time. disease or infectious agent within a given geographical area or population Pandemic is a disease outbreak that spreads across countries or continents. Terminologies in epidemiology Infection: The entry and development or multiplication of an infectious agent in human or animal Contamination: The presence of an infectious agent on a body, clothes, surfaces, substances (water, milk and food) Terminologies in epidemiology Infectious disease: A clinically manifest disease of human or animal resulting of an infection Nosocomial Infection: ▪ Infection originated in a patient while in a hospital or other health facility Terminologies in epidemiology Opportunistic Infection: Infection by an organism that takes the opportunity provided by a defect in host defense to infect the host Iatrogenic Disease: and hence cause disease Any adverse consequence of a preventive, diagnostic or therapeutic regimen or procedure resulting from physician professional activity or other health professionals. EPIDEMIOLOGICAL STUDIES Types of epidemiological studies Non experimental studies Experimental studies (observational) Randomized control trail Descriptive studies Analytical studies Non-randomized trial Case-report Cohort studies Case-control Ecological studies studies Cross sectional studies Descriptive studies Describe the experience of a single patient or group of Case report, case series patients with similar diagnosis or clinical presentation A study characterized by trying to relate exposure and disease at the region and population level, rather than at Ecological studies the individual level. It is used to measure prevalence and incidence of disease A study that includes as subjects all persons in the population at the time of study or a representative Cross sectional study sample of all such persons selected regardless to exposure or disease status Analytical studies A study in which a population is defined according to the presence or absence of a factor that might influence the probability of occurrence of a given Cohort study disease or other outcome. The population is then followed to compare the outcome rates associated with different exposures or risk factor level A study that compares two groups of people: those with the disease or condition under study (cases) and a very Case-control study similar group of people who do not have the disease or condition (controls).  THANK YOU ! QUESTIONS