Chapter 9: Principles of Epidemiology
What are crude rates?
The number of events in a population over a given period of time, usually a calendar year
Describe the epidemiological triad/triangle.
● Epidemiologist understand that disease results from complex relationships among causal agents, susceptible persons, and environment factors. ● Epidemiologic triangle has 3 elements: Agent, Host, and Environment ● Changes in one of the element os the triangle can influence the occurrence of disease by increase or decrease a person's risk for disease. -- Agent: an animate or inanimate factor that must be present or lacking for a disease or condition to develop. --- Infectious agents, chemical agent, and physical agent. -- Host: A living species (human or animal) capable of being infected or affected by an agent. -- Environment: All that is internal or external to a given host or agent, and that is influenced and influences the host and/or agent.
Discuss how epidemiological data is used for development of preventive health care guidelines.
● To make the proper diagnosis and prescribe appropriate treatment for a patient, the clinician combines medical (scientific) knowledge with experience, clinical judgment, and understanding of the patient. ● Similarly, the epidemiologist uses the scientific methods of descriptive and analytic epidemiology as well as experience, epidemiologic judgment, and understanding of local conditions in "diagnosing" the health of a community and proposing appropriate, practical, and acceptable public health interventions to control and prevent disease in the community. ● Epidemiology is the study (scientific, systematic, data-driven) of the distribution (frequency, pattern) and determinants (causes, risk factors) of health-related states and events (not just diseases) in specified populations (patient is community, individuals viewed collectively), and the application of (since epidemiology is a discipline within public health) this study to the control of health problems.
What are determinants?
● any factor, whether event, characteristic (age), or other definable entity, that brings about a change in a health condition or other defined characteristic. -- eg: event, age ● causes and other factors that influence the occurrence of disease and other health-related events.
What are the uses of epidemiology?
● assessing health of community ● making individual decisions ● completing clinical picture ● searching for causes
What are the core functions of epidemiology?
● public health surveillance, -- systematic collection of data concerning disease occurrence. -- disseminate health data to help us guide public health decision making and action. -- Accomplished through collection of morbidity and mortality data ● field investigation, -- surveillance provides info for action; -- investigation may be limited as a phone call to the HCP to confirm or clarify the circumstances of the reported case, or it may involve a field investigation requiring the coordinated efforts of dozens of people to characterize the extent of an epidemic and to identify its cause. ● analytic studies, -- hallmark of an analytic epidemiologic study is use of valid comparison group --- Looking at difference between comparision group and effective group --- can look at clusters or outbreaks of disease --- Looking at "who, what, when, where" and distribution and determinants ● evaluation, -- process of determining, as systematically and objectively as possible; -- looks at relevance, effectiveness, efficiency, impact of activities with respect to established goals ● linkages, -- During an investigational epidemiologist usually participates as either a member or the leader of a multidisciplinary team. -- other team members may be: Laboratorian, sanitarians, infection control personnel, nurses or other clinical staff, and computer information specialists. ● policy development -- Epidemiologists working in public health regularly provide input, testimony, and recommendations regarding disease control strategies, reportable disease regulations, and health care policy.
What is epidemiology?
● 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.
What are specific rates?
Used to construct rates for specific segments of the population so we can compare among strata or between groups (used especially for age, race, ethnicity, gender)
What does effectiveness refer to?
ability of program to produce the intended or expected results in the field
What is efficacy?
ability to produce results under ideal conditions
What are examples of specific rate?
age, gender, race, and cause specific rates
What are health-related states or events of epidemiology?
communicable disease, non-communicable infectious disease, health behaviors/events
What do rates allow?
comparison
What is the role of an epidemiologist?
counts cases or health events; divides # of cases; compares rates over time
Epidemiology is ____________ and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of data.
data-driven
What is the focus of epidemiology?
epidemiologist is concerned about the collective health of the people in a community or population. ("science of population health")
What may a high prevalence reflect?
high risk, prolonged survival without cure
What do rates tell us?
how fast disease is occurring
What may a low prevalence reflect?
low risk, rapid fatal disease progression, rapid cure
What is rate?
number of cases divided by size of population per unit of time
What is frequency?
number of health events that occur and relationships of that number to the size of pupulation
What is the goal of epidemiology?
prevention
What is efficiency?
refers to ability of program to produce the intended results with minimum expenditure of time/resources
What do crude rates reflect?
the probability of an event
What is the purpose of policy development in epidemiology?
to provide input, testimony, and recommendations regarding disease control strategies
What do proportions tell us?
what fraction of population is affected
Discuss/contrast methods of epidemiological investigations.
● Descriptive epidemiology -- health outcomes are considered in terms of what, who, where, and when. That is: --- What is terms of the outcome? --- Who is affected? --- Where are they? --- When do events occur? -- Descriptive epidemiology discusses a disease in terms of person, place, and time. --- How and Why are the determinants of health events. ● Epidemiologists assume that illness DOES NOT occur randomly in a population, but happens only when the right accumulation of risk factors or determinants exists in an individual.
***Define and discuss: Epidemic, pandemic, outbreak, cluster
Epidemic ● refers to an increase (often sudden) in number of cases of a disease above what is normally expected in that population in that area. Pandemic ● epidemic that has spread over several countries or continents, usually affecting a large number of people. Outbreak ● carries same definition of epidemic but is often used for more limited geographic area Cluster ● refers to aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known.
***Define and describe calculation of: incidence rate, prevalence rate, morbidity rate, mortality rate, infant mortality rate, neonatal mortality rate.
Incidence rate ● # of new events during time / population at risk x 1000 ● Incidence is always calculation for a given period of time ● an attack rate incidence rate calculated for a specific disease for a limited period of time during an epidemic Prevalence ● # of existing events (old & new) / population at risk x 1000 ● Prevalence is not a rate ● Point prevalence = measures the frequency of all current events (old and new) at a given instant in time ● Period prevalence = measures the frequency of all current events (old and new) for a prescribed period of time Morbidity rate ● illness rate Mortality rate ● death rate ● death/live births x 1000 Infant mortality rate ● # of deaths in infant under 1 year of age in a year/# of live births in the same year x 1000 -- eg: If there were 28,035 infant deaths and 4,098,814 live birth---> 28,035/4,098,814 x 1000 = 6.9 infant died in 1000 infants Neonatal mortality rate ● # of deaths of infants under 28 days of age in a year/# of live births in the same year x 1000
Father of Epidemiology
John Snow
