Epidemiology Flashcards
Epidemiology Definition
The study of the occurrence and distribution of health-related states or events in specific populations, including the study of the determinants influencing such states and the application of the knowledge to control the health problem
- the science used in community health practice
- infectious disease/public health epidemiology
- To describe, explain, predict & control challenges to population health
- How & why: examine causality & modes of transmission
- The who, what, where, when of disease causation and distribution patterns. Contact tracing
Public Health Nursing Role: Communicable Disease control is considered the number one priority of the public health system
- Are frontline in identification of outbreaks
- Do case management and support for quarantined individuals
-Provide information to the public - Are responsible for case finding0identification of the contacts
Outbreak
sudden occurrence of a disease in a community which has never experienced the disease before OR cases occur in > numbers than expected
Epidemic
Occurrence of illness/disease is excess of what would normally be expected in community or region (example: SARS)
Endemic
a disease occurring regularly within a geographic region (ie. Lice)
Pandemic
a disease affecting large portions of the population throughout the world (globally)
Screening
secondary prevention - tool for early diagnosis and test to detect presence of disease (mammogram, pap smear)
Case Finding (contact tracing)
determining individuals whose health status is at risk
Surviellance
constant monitoring of disease to assess patterns & identify events that do not fit the pattern
- surveillance of Reportable diseases: diseases that are required (by Drs./nurses) to be reported by law (TB, STIs, AIDS)
Premordial Prevention
starts at the very beginning. looking at how society structures, the changes, can cause changes in SDOH and could be possibly causing disease. Climate change, inadequate housing. Bigger pieces that could lend themselves to disease
Primary Prevention
education. Health promotion. How we might be able to alter the exposure. Promotion of healthy behaviours. Harm reduction, safe spaces. Children vaccinations
Secondary Prevention
early detection of disease and the treatment. Looking at pathology that might be leading to other treatment. Mammogram/papsmear/testicular screening. Something is already going on and we are looking for it
Tertiary prevention
managing the effects of disease and trying to manage the hospitalization. Referrals, case management.
Quaternary Prevention
Identifying people at risk due to overmedicalization. Seen with antibiotics
Descriptive epidemiology
uses person, place and time variables to describe disease patterns
- what people/where/when did this disease take place
- Ex. heart disease occurred in X% of men and X% of women over 40 yrs. In BC in the year 2000
Analytic epidemiology
examines complex relationships among determinants of disease
- why? (causation)
- focus on disease etiology
- cardiac disease is related to smoking and lack of exercise and diet which is related to culture and Socioeconomic determinants of health
Epidemiologic model
host, agent & environment
Epidemiologic variables
descriptive factors to describe events
Susceptibility
vulnerability, determines individual response
Modes of transmission
direct/indirect (can be > 1 mode)
Natural Hx/Progression
- Enhanced susceptibility (pre-pathogenesis period)
- Stage 1 in disease process (pathogenesis period - host begins to react to agent to recovery, disability, or death)
- Primary Prevention - measures alter exposure promote optimal health
- Secondary Prevention - detect pathol process/early diagnosis - screening
- Tertiary prevention - increased vulnerability/susceptibility, prevent relapsed/deterioration - education, rehab, palliation
Association & Causation
connection between stressor & disease/confirmed (definite cause and effect relationship)
Web of Causation
relationship among influences of health challenge
Web of Causation
relationship among influences of health challenge
Epidemiologic Model: Host
human being in which disease occurs
- age, sex, ethnicity, genetic, previous disease/immune system, birth place, marital status, immigration, education, family hx, occupation
Epidemiologic Model: Agent
contangious/non-contagious force that begins or prolongs a health problem (virus, bacteria or stimuli such as smoking or absence of Vit C) Stressor
- biological/infectious (bacteria, virus, fungi), chemical (smoke, poison, alcohol), physical (heat, cold)
Epidemiologic Model: Environment (context that promotes the exposure)
context that promotes the exposure of the host to the agent
- physical (weather, geography, polution)
- Biological (plants, animals, Micro-organisms)
- Social (neighborhood, housing, work, education, resources, econ. status, poverty)
Horizontal transmission
from host to host. STIs
Vertical transmission
parent to child. Placenta, breast milk
Pathological triangle
used to analyze diseases dependent on exposure and the agent (infectious disease)
Web of Causation
Multiple direct & indirect causal factors
- complexity of interaction of risk factors that can lead to development of an illness
- ie. diarrheal illness in an infant. Start with diarrhea and work up
Identification of Risk factors
- Assoc. with chronic disease reduction
- Variables shown to increase rate of disease in people who have or have been exposed to them
- Critical to development of prevention interventions
Risk
are some individuals more at risk/vulnerable to a disease than others?
- what is the likelihood healthy people exposed to a factor will acquire a specific disease?
- what is the risk I will get lung cancer if I smoke? (specific exposure factor is smoking)
Risk Factor
the specific exposure factor. Rates of disease are used to determine risk
Attributable risk
- burden of disease in a population based on risk factors
- how much of disease is caused by this risk factor?
- Rate of disease in people who smoke compared to rate in people who don’t smoke
Relative Risk
the excess risk caused by a risk factor
- how much more likely am I to get lung cancer if I smoke?
- Incidence rate of disease (20/1000 pop) incidence rate of unexposed pop (2/1000) = 10 times more likely
Disease Prevention: Establishing Causality
- Disease causality cannot be proven but it can be established in terms of association of identified causal factors
Criteria to determine a cause-and-effect relationship
- particular stressor must be present (necessary)
- temporal relationship (time relation)
- strength of association (sufficient stressor)
- dose-response relationship
- specificity
- consistency
- biological plausibility
- experimental replication
Rates
- Rates are population proportions or fractions that are used to interpret raw data and to make comparisons (of rates for other times) and assess trends
- The numerator is the number of events that occurred in a specified period of time
- The denominator consists of the population at a specified time period
Basic Formula for Rates
Rate = number of events over a period of time / population at risk at that time x 1000d
- events represented in the numerator arise from the population at risk in the denominator
- resulting rate is multiplied by a constant value (usually 10,000) so rates for populations of different sizes can be compared
Incidence Rate
of new cases of the disease in a given time period
- identification of new cases of disease in a population over time (usually 1 year)/ relative to the population at risk
Prevalence Rate
total # of people who have a disease at any one given time period
- the number of all cases of a specific disease in a population at a given point in time/relative to the population at risk (H1N1)
Morbidity (Illness) Rate
Provides information of population an disease/health challenge over time
- offers info on susceptibility of the population & effectiveness of health promotion/treatment strategies
Mortality Rates
- The ratio of the number of deaths in various categories to the number of people in a given population
Crude Rates
Compare # of deaths/health event from a specific cause within the entire population
- birth rate
- death rate
- Note: can be misleading or biased due to whole population focus
- Age or gender specific rate
Crude Rates Notes
- Death rate in whole population is not predictive of death rate in children
- birth rate in whole population is different than for the child-bearing years
- infant mortality: birth to one year
- Neonatal mortality: birth to 28 days
- Maternal death rate: maternal deaths/live births x 100,000
Screening: purpose
to identify risk factors and diseases in earliest stages
Screening: Sensitivity
Screening tests need high sensitivity
- ability to test those with the disease (positives)
Screening: Specificity
Screening tests need high specificity
- extent to which a test can identify those without the disease (false positives)
Surveillance
- ongoing collection of information regarding a health issue
- monitoring diseases/ people with the disease & contacts to assess patterns
- nurses evaluate trends in morbidity by identifying new cases and calculating incidence rates
- reportable diseases-required to be reported by law
- Stats can be found at Public Health Agency of Canada website
Surveillance
- ongoing collection of information regarding a health issue
- monitoring diseases/ people with the disease & contacts to assess patterns
- nurses evaluate trends in morbidity by identifying new cases and calculating incidence rates
- reportable diseases-required to be reported by law
- Stats can be found at Public Health Agency of Canada website
Descriptive Epidemiological Research Method
the Person-Place-Time Model (who, when, where)
Analytical Epidemiological Research model
how and why (examine associations & test hypothesis)
Observational Studies
- Cross-Sectional/Correlational Studies
- Retrospective Studies (begin in present - search in past for info)
- Prospective (begin to present to future)
Experimental Studies
Manipulates/controls selected variables
- clinical trials
