pubh chapter 2

perie: problem, etiology, recommendations, implementation, evaluation

five steps in utilizing an evidence based approach to public health practice

problem

describing the health problem by assessing its burden (frequency, distribution, and severity), course (natural history), and who/where/when it affects a population

etiology

identifying the underlying causes and risk factors (the why/how) of the disease by evaluating group associations and establishing contributory cause

recommendations

determining what works to reduce or eliminate the health problem based on evidence of effectiveness, efficacy, and safety of potential interventions

implementation

putting the recommended interventions into practice by deciding how to implement them (e.g. target populations, timing, levels of prevention)

evaluation

assessing the real world impact and effectiveness of the implemented program or policy to determine if it achieved the desired goals and whether modifications are required

mortality

the occurrence of death due to a disease or health condition within a population

morbidity

the occurrence of illness, disability, or impairment due to a health condition (non-fatal health outcomes)

burden of disease

the comprehensive impact of a health problem in a population, combining frequency, distribution, and severity through both morbidity and mortality

descriptive epidemiology

enumerate, quantify, and summarize health patterns to generate hypotheses regarding potential causes or risk factors

analytic epidemiology

test and evaluate specific hypotheses to establish cause and effect relationships (etiology) between exposures and outcomes

distribution (who/where/when)

focus of descriptive epidemiology

determinants (why/how)

focus of analytic epidemiology

case reports, case series, cross-sectional studies, ecological studies

kinds of descriptive epidemiology study designs

observational cohort, case-control studies, experimental cohort (clinical/community trials)

kinds of analytic epidemiology designs

rate

measures how rapidly a health event occurs in a defined population over a specified time unit

risk

measures the probability/likelihood that an individual will develop a disease or experience a health outcome over a specific period

incidence

measures the occurrence of NEW cases developing in a population initially free of the disease during a specified period; best for studying causes/risk factors

prevalence

measures the proportion of all EXISTING cases (both new and old) present in a population at a specific point/period of time; best for planning healthcare services

health events of interest during period / population at risk of event during period

rate formula

new cases during period / population at risk at start

cumulative incidence rate formula

new and old cases at a point / total population at that point

point prevalence rate formula

new and old cases during period / total population during period

period prevalence rate formula

exposed incidence rate - unexposed incidence rate

attributable risk formula

exposed incidence rate / unexposed incidence rate

relative risk formula

deaths / number of persons who could die x 10n

mortality rate formula

mortality rate

measure of total deaths in a population over a given time frame

infant deaths / live births x 1000

infant mortality rate formula

infant mortality rate

quantifies deaths occurring among infants (under 1 year) relative to live births

case reports, case series, cross-sectional study, ecological study, observational/experimental cohorts, case control

types of epidemiology studies

case report

detailed clinical description of single unusual cases/identifying the range of experiences

case series

detailed clinical description of small clusters of cases/identifying trends or patterns across health events

cross-sectional study

surveys that assess exposure and disease outcome simultaneously at a single point in time across individuals/associations among variables

ecological study

analyzes aggregate or group-level data rather than individual level data

ecological fallacy

mistakenly inferring that group-level associations apply to individual human beings

identify new disease, rare conditions, clinical patterns

purpose of case reports and case series

snapshot associations between variables across individual characteristics

purpose of cross-sectional studies

examine population level exposure-disease correlations quick and cheap

purpose of ecological studies

observational cohort, experimental cohort, case control

types of analytic epidemiology studies

concurrent, historical

types of observational cohort studies

clinical trials, community trials

types of experimental cohort studies

observational cohort

groups are categorized by their exposure status (exposed or not) and followed forward or through records over time to see who develops outcome (calculates relative risk)

concurrent cohort

follows participants into the future

historical cohort

uses past medical/exposure records as a cohort

case control study

groups are selected based on their disease status (with disease vs. control, without disease) and researchers look backward to compare prior exposure histories (calculates odds ratios)

experimental cohort

researchers actively assign exposure/intervention status (e.g. treatment vs. placebo) to participants, ideally blind and random

clinical trials

experimental cohort study on individuals

community trials

experimental cohort study on entire communities, schools, etc.

temporal relationship, strength of association, dose-response relationship, consistency of association, biological plausibility, reversibility/cessation of exposure

criteria to establish a contributory cause

temporal relationship

the exposure MUST come before the outcome in time

strength of association

stronger associations (e.g. RR, OR) make it more likely that the relationship is causal rather than due to confounding

dose-response relationship

increase exposure levels (e.g. higher dose, frequency, or duration) correspond to increased risk or severity of the outcome

consistency of association

similar associations are repeatedly observed across different populations, locations, study designs, and times

biological plausibility

the observed association is consistent with existing scientific, biological, and medical knowledge

reversibility/cessation of exposure

removing or reducing the exposure leads to a reduction in the risk of disease

primordial prevention

aims to avoid the emergence and establishment of social, economic, and environmental patterns of living that contribute to elevated disease risk

primary prevention

prevents disease or injury BEFORE it occurs by targeting susceptibility and eliminating exposures/risk factors (e.g. vaccines, fluoridated water, smoking ban)

secondary prevention

catches disease in its early, subclinical stages through early detection and prompt screening to halt progression (e.g. mammograms, pap smears)

tertiary prevention

manages established clinical disease to prevent further disability, severe complications, or premature death and restore function (e.g. administering tPA clot-busting drug during active stroke, stroke rehab)

exposed odds of outcome / unexposed odds of outcome

odds ratio formula