EPIDEMIOLOGY Catherine T. Horat RN MSN CS C-FNP NUR 410 Community Focused Nursing

Epidemiology Definition –“The study of the distribution and determinants of health-related states or events in specific populations, and the application of this study to control of health problems” Last, 2001, p. 62

Epidemiology Studies

Epidemiology Epidemiologic Methods used in –Health services research –Investigate associations between –To what extent Healthy People 2000 goals accomplished –Monitor progress of Healthy People 2010

Study of Distribution Distribution –Patterns of events –Influences on –Characterized as

Descriptive Epidemiology Based on distribution or patterns of health events in populations Attempts to describe a disease entry according to –Person –Place –Time

Study of Determinants Determinants of health – events or factors that determine or influence the patterns of Questions asked

Study of Determinants Include

Analytic Epidemiology Investigation of causes and association Directed toward understanding the etiology or origins and causal factors of a disease Useful for –Guiding or evaluating policies and programs that improve the health of a community

Comparison of Analytic/Descriptive Epidemiology Analytic studies rely on descriptive comparisons Descriptive comparisons shed light on determinants

Epidemiology Study of populations in order to

Key Terms Surveillance Endemic Epidemic Pandemic

Epidemiological Investigational Models Epidemiological Triangle Web of Causation Person-Place-Time

Epidemiological Triangle Agent Host Environment

Epidemiological Triangle AGENT Causative factor contributing to health problems that must be present or lacking

Epidemiological Triangle HOST A susceptible human or animal who harbors and supports a disease causing agent Intrinsic

Epidemiological Triangle ENVIRONMENT All factors internal or external to a client that constitute the context in which the client lives and that influences and are influenced by the host and agent-host interactions

Web of Causation –Complex interrelationships of numerous factors interacting to increase or decrease risk of disease The determination based on EVIDENCE or REASONING process that an event or state Resulted FROM or was CAUSED BY some other events, exposure, characteristics, or a combination of them (Causality)

Causality Criteria

Person-Place-Time Examines the characteristics of –People affected –The place or location –Time period involved Considered as variables –Person who is affected –Place where affected –Time when affected

Health Promotion and Disease Prevention Natural History of Disease the course of progression of a disease from onset to resolution –Prepathogenesis period (Environment) Disease has not developed but interactions are occurring between host, agent and environment that produce disease stimulus and increase the host’s potential for disease –Pathogenesis period (Human) Begins when disease-producing stimuli start to produce changes in the tissues of humans

Natural History and Levels of Prevention Primary Prevention –Prepathogenesis –Adaptation Adaptive processes are initiated

Natural History and Levels of Prevention Secondary Prevention –Pathogenesis –Discernable early lesions Clinical recognition Early DX and prompt treatment

Natural History and Levels of Prevention Tertiary Prevention treatment to arrest disease or rehabilitation –Clinical Disease

Mortality Rates Relative death rate Sum of deaths in a given population at a given time –Crude mortality rate –Cause-specific mortality rate –Case fatality rate –Age-specific death rate –Proportional Mortality Ratio

Mortality Rates Crude mortality rate includes based per on 100,000 population – #deaths in a year______ Average midyear population Ex – # 10,000deaths in St. Petersburg, Fl in 2002 X 100,000 # 350,000of persons in St. Petersburg Fl in July 1, 2002

Mortality Rates Cause-specific actual cause of deaths desired to be measured per 100,000 EX #75 of men who died from pneumonia in St. Petersburg Fl in 2003 X100,000 # 60,000 of men in total population of St. Petersburg, FL, 2003

Mortality Rates Case-fatality –#deaths due to a specific disease X100 cases # cases of specific disease EX 25 deaths from E-coli X 100 cases 300 cases of E-coli

Mortality Rates Age-specific –Enables comparing populations in different locations EX # 120 deaths among 45 year olds in Denver CO in 2005 X # 10,000 of 45 year old people in Denver CO July 1

Mortality Rates Proportional Compares number of deaths from a particular cause with deaths from all other causes # deaths from specific cause in a specified time period X 100 Total # deaths in same time period # 200 of Cancer deaths in 2001 X 100 # 5000 of total deaths from all causes in 2001

Morbidity Rates Relative incidence of disease –Incidence –Prevalence

Morbidity Rates Incidence –Rates that measure ALL NEW CASES arising in a population during a defined period of time, usually 1 year # of new cases in place during time of observation X K Population in place at midpoint of time 60 new mump cases from 1/07 to 1/08 X 100,000 50,000 population K = unit of population

Morbidity Rates Prevalence measures total number of persons with a characteristic with the total number in the population 50 people with chicken pox X K 1000 people in population