Modules 1 and 2 Flashcards
Lectures 1 & 2, book chapters 1-3, Rothman Module 2
What are the characteristics of an effective surveillance system?
Simplicity, flexibility, data quality, acceptability, sensitivity, positive predictive value, representativeness, timeliness, stability
What are the differences between public health and clinical medicine?
Public health focuses on the population at large
It is interested in prevention and aligns with epidemiology, environmental science, biostatistics, social science, etc. and uses a systematic approach
Medicine focuses on the individual and curing individual conditions
It aligns with biological sciences & pathology and uses nonsystematic approaches
What is epidemiology?
Epi (on or upon) Demos (the common people) Logy (study)
The study of that which falls upon the common people
The study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems (Aschengrau)
What is an epidemiologist?
A professional who strives to study and control the factors that influence the occurrence of disease or health-related conditions and events in specified populations and societies, has an experience in population thinking and epidemiologic methods, and is knowledgeable about public health and causal inference in health
What areas should epidemiologists have knowledge of?
Public health, clinical medicine (numerators), pathophysiology, biostatistics (denominators, testing hypotheses), social sciences
What are the objectives of epidemiology?
Identify etiology or cause of a disease
Determine extent of disease in a community
Study natural history and prognosis of disease
Evaluate preventative and therapeutic measures and modes of healthcare delivery
Provide foundation for policy development
What is a population?
Group of people with a common characteristic
What is disease frequency?
Quantifying how often disease arises in a population
Involves: developing disease definition, instituting mechanism for counting cases of disease within a specific population, and determining the size of a population
What are disease determinants?
factors that bring about change in a person’s health (demographics, environmental, social)
What is disease distribution?
analysis of disease patterns according to characteristics of person, place, and time
How is disease control achieved?
Through research and surveillance
What is the principal goal of epidemiology?
to produce information that will prove useful in improving health on a population level
What are the 3 major components of applying epidemiology?
Design (analytic, descriptive, exploratory), methods (sampling, data collection, data analysis), and methodology (quantitative versus qualitative).
How have the goals of epidemiology changed over the years?
19th century: focus on infectious disease
20th century: high income countries shifted towards non-communicable diseases
Mid 20th Century (1970s): methods formalized
Late 20th Century: formalized central disciplinary principles (180s)
What graphic format is typically used to measure time?
Y axis for frequency
X axis for time
What is public health?
A multidisciplinary field whose goal is to promote the health of the population through organized community efforts
Key activities: assessing health status of the population and diagnosing its problems, searching for causes of problems and designing solutions for them
What is secular change (Temporal variation)?
Changes which occur slowly over long periods of time (over a year)
What are point epidemics?
short term changes over limited time frames; used for short term exposures or diseases with short incubations and/or illness durations
What is seasonal variation?
a method that can be used to suggest possible etiology
What is time clustering?
Data that can be used to trace the “beginning” / intro of a specific causal agent
E.g. thalidomide causing birth defects (linked back to sleeping pill used for morning sickness)
What are epidemiological variations relating to place?
International
Variation within countries (urban-rural, local)
Building maps
What is prognosis?
Predicting the progress or outcome of the disease (expressed in terms of deaths or survivors from the disease)
What measures are used to quantify prognosis?
Cased based numbers; the denominator is the number of people with the specific disease
What are common measures of expressing prognosis?
Case Fatality Rate (CFR)
Five year survival rate
Observed survival rate
Median survival time
Relative survival rate
What is the Case Fatality Rate (CFR) specifically?
Numbers of individuals dying during a specific period of time after disease onset or diagnosis / number of individuals with specified disease
It does not include any explicit statement of time, and so is best used for short term / acute conditions
How does CFR differ from mortality?
Mortality rates include anyone at risk of dying from a disease in the denominator - both those with a disease and those who do not (yet) have a disease
What is a study design?
the program that directs the researcher along the path of systematically collecting, analyzing, and interpreting data
What is the function of descriptive epidemiology?
describe the extent of a public health problem according to key variables (person, place, time)
communicate a public health problem using tables and graphs
identify who is at greatest risk for selected health related states or events
Use surveillance methods to monitor whether unusual health related states or events exist and evaluate public health intervention programs
Provide clues as to the causes of disease
What is a variable?
any measured characteristic of individuals that differs across individuals
What are binary variables?
Variable that takes on two values
(Health outcome: present or absent)
What are ordinal variables?
Variable that takes on multiple (>2) graded values
What are continuous variables?
Variables with continuous (unlimited) response options
What is surveillance?
ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice closely integrated with the timely dissemination of these data to those who need to know
What are the two types of surveillance?
Passive (looking up available data)
Active (periodic facility visits to identify diseases or deaths due to disease) - more accurate and more expensive / time consuming
What are types of trends seen in data?
Secular (long term)
Short term
Cyclical
How is descriptive epidemiology useful?
provides information about a disease or condition
identifies the extent of a public health problem & the population at highest risk
Obtains a description of the problem that can be easily communicated
Assists in planning and resource allocation
Identifies avenues for further research
What are analytic observational studies versus analytic experimental studies?
Observational - researchers observe relationships between variables
Experimental - exposure is manipulated by the researcher
What was the Streptomycin Tuberculosis Trial?
1940s trial conducted by the British Medical Research Council (Sir Austin Bradford Hill) using Streptomycin to treat TB
One of the first uses of randomization in medical trials
Restrictions on types of patients (only those who couldn’t use other treatments, none who might have spontaneous regression)
Data collection methods were free from bias
Ethics taken into concern
What was the significance of Doll and (Sir Austin Bradford) Hill’s 1950 Smoking Study?
Large sample size
Significant longitude
Ability to examine smoking cessation effects
What did John Graunt do?
summarized the patterns of mortality in 17th century London
What did James Lind do?
discovered the cause and prevention of scurvy using experimental study design in the 18th century
What did William Farr do?
originated many modern epidemiological methods in the 19th century, including combination of numerator and denominator data
What is a catchment population?
population served by a medical facility
What is a fixed population?
membership is based on an event and is permanent (e.g. Japanese atomic bomb survivors)
What is a dynamic / open population?
membership is based on a condition and is transitory (e.g. residents of a city)
What is a steady state in terms of population?
a state in which number of people entering the population is equal to the number leaving
What are ratios, proportions, and rates?
Ratio: division of two unrelated number
Proportion: division of 2 related numbers (numerator is subset of denominator)
Rate: division of two numbers; time is always in the denominator
What is incidence?
the occurrence of new cases of disease that develop in a candidate population over a specified time period
What is candidate population?
a population of people who are “at risk” for getting a disease
What is cumulative incidence?
the proportion of a candidate population that becomes diseased over a specific period of time
Describe the differences between proportion, incidence, and cumulative incidence.
What is incidence rate?
the occurrence of new cases of disease that arise during person-time of observation
accrual (denominator of person-time) is only calculated up until person is diagnosed with the disease
e.g. women studied in effects of racism on obesity; 1,043 incident cases occurred in 23,403 person-years (44.6/1000 person-years) compared to 33.2/1000 person-years in those who did not experience racism
what is the commonality between cumulative incidence and incidence rate?
both focus on measuring the transition from health to disease
What is point prevalence?
the proportion of the population that is diseased at a single point in time (like a snapshot of the population)
What is period prevalence?
the proportion of the population that is diseased during a specified duration of time (garnered from a collection of snapshots)
What is a disease?
a disorder of structure or function in a human, animal, or plant, especially one that has a known cause and a distinctive group of symptoms, signs, or anatomical changes.
What are commonly used measures of disease frequency in public health?
crude mortality rate
cause specific mortality rate
age specific mortality rate
years of potential life lost
livebirth rate
infant mortality rate
birth defect rate
morbidity rate
attack rate
case fatality rate
survival rate
What is a major difference between incidence and prevalence?
Incidence measures the occurrence of new disease
Prevalence measures existing disease
What are mathematical differences between incidence rate and cumulative incidence?
Cumulative Incidence is a dimensionless proportion (time is not integral, just words placed after the calculations)
Incidence rate is a true rate (uses person-time, does not just tack on words for time)
What are other names for exposed and unexposed groups?
Index group
Referent or comparison group
What does Rate / Risk Difference show?
the number of of diseases cases that would be eliminated if the exposure were eliminated (or contained to the level of the reference group)
What does the Attributable Proportion among the Exposed (APe) show?
the proportion of disease among the exposed that would be eliminated if exposure were eliminated.
What does the Attributable Proportion among the Total Population show?
the proportion of disease among the total population that would be eliminated if exposure were eliminated.
Describe the RR (Relative Risk, Risk Ratio) formula:
Re is the incidence rate, cumulative incidence, or prevalence in the exposed group
Ru is the incidence rate, cumulative incidence, or prevalence in the unexposed group
What are crude rates?
measures of disease frequency that are based on raw data
These are often standardized for comparison due to differences between populations / units
What is the function of age standardized or age adjusted rates?
to equal out uneven number in age populations between two compared groups (e.g. if Florida has 40,000 people ages 8-12 and Alaska only has 8,000 ages 8-12)
These are calculated as weighted averages of age specific rates with weights equal to the proportion of the standard population in each age category
What are absolute measures of comparison of disease frequency?
these are based on the difference between two measures of disease frequency (describe public health impact of an exposure)
they include: risk difference, population risk difference, and attributable proportion among exposed / total populations
What are relative measures of comparison of disease frequency?
based on the ratio of two measures of disease frequency
(describe the strength of the relationship between exposure and disease)
Include Risk Ratio / Relative Risk
How are all measures of disease frequency compared (whether relative or absolute)?
via two by two tables
