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EPID 403
Epidemiology
83
Environmental Studies
Graduate
02/06/2014

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Term

Epi -

Demos -

Logos -

Definition

Upon, on top of

people or population

study of

Term
Epidemiology
Definition
The study of distribution and determinants of health-related states and events in specified populations, and the application of this study to control health problems
Term
Assumptions in epidemiology
Definition

-disease and ill health are not randomly distributed

-factors that determine this distribution are knowable and mostly modifiable

-modification = prevention and control of disease

Term
Descriptive vs Analytic
Definition

D - concerned with distribution of disease by persons, places, and times.  Without a hypothesis - hypothesis generating

 

A - Concerned with identifying disease determinants.  Hypothesis testing.  Casual inference is ultimate goal.  

Term
Epi study design
Definition

Hypothesis (the link)

Description

Analysis

Term
Surveillance
Definition

Describes changing patterns of community health problems

 

Provides clues

 

Health services planning

 

Public health policy

Term
Epi - Demos - Logos
Definition
Upon, on top of
people or population
study of
Term
Primary prevention
Definition
prevent initial development of disease (risk factor reduction, immunization)
Term
Secondary prevention
Definition
Early detection of existing disease to reduce morbidity (screening for cancer, high blood pressure, etc.)
Term
Tertiary prevention
Definition
Reduce the impact of acute worsening of disease
Term
Epi Triad of infectious disease
Definition
Host - Susceptible
Agent - infectious or non-infectious
Environment - promotes exposure
Middle - vehicle

*or vector organism for indirect transmission
Term
Triad of Non-infectious disease
Definition
Host - genetics, stress, psychological factors
Agent - behavior, diet, tobacco
Environment - neighborhood, parks, food outlets
Term
Modes of disease transmission
Definition
1. escape of the agent from a source or reservoir
2. Conveyance
3. entry into host
Term
Direct transmission
Definition
person-to-person
Term
Indirect transmission
Definition
1. common vehicle
a. single exposure (potato salad)
b. multiple exposures
c. continuous exposure (telephone receiver)
2. vector (organism)
Term
Definition of "carrier" status
Definition
A host "harbors" the infectious agent but appears not infected and there are no detectable signs or symptoms
Term
effect of non-apparent infection on disease control and disease statistics
Definition
when the proportion with non-apparent infection is high, statistics will underestimate rates of infection and overstate overall disease severity
Term
endemic
Definition
habitual presence of a disease in a geographical area or population
Term
epidemic
Definition
occurrence of a disease in a geographical area that is unusually frequent
Term
pandemic
Definition
worldwide epidemic
Term
primary case
Definition
the first disease case that appears in the population
Term
index case
Definition
the disease case that brings the group or population to the attention of public health personnel
Term
incubation
Definition
time between infection and appearance of signs or symptoms
Term
herd immunity
Definition
resistance of group or population to invasion and spread of infectious agent based on the immunity of a high proportion of the group
Term
point source
Definition
from a single brief and essentially simultaneous source of exposure

- all of the cases usually result in a single incubation period
Term
propagated ("progressive")
Definition
transmission from one individual to another

- epidemic extends over many incubation periods
Term
general approach to outbreak investigation
Definition
- verify the diagnosis - perform clinical studies
- verify existence of epidemic - compare with past levels
- person, place and time - calc. attack rates
Term
attack rate
Definition
new cases rapidly occuring in a well-defined population over a short period of time
------------------------------------------
total number of people at risk during that same period of time
Term
secondary attack rate
Definition
*All times 100

new cases among contacts of initial cases occurring during a short period of time
---------------------------------------
(total number of people at risk during same period of time) - (initial cases)
Term
morbidity
Definition
1. a diseased state or symptom
2. the incidence of disease: the rate of sickness
Term
Rate
Definition
a ratio where time is included in the denominator
Term
incidence rate
Definition
-special type of proportion that includes time
- represents the probability of disease in a defined population
- the basic measure of disease occurence
Term
incidence rate formula
Definition
number of new cases of disease occurring during a defined period of time
-------------------------------------
number of people at risk for disease during defined period of time
Term
cumulative incidence
Definition
all observed throughout a defined period of time
- closed cohort
- denominator = sum of all people at risk
Term
incidence density
Definition
all NOT observed for the full defined period of time
- person-time units
- denominator = sum of person observation time for each person at risk
Term
cumulative incidence formula
Definition
number of new cases of disease occurring during a defined period of time
--------------------------------------
initial population at risk of the disease
Term
incidence density formula
Definition
number of new cases of disease occurring during a defined period of time
--------------------------------------
person-time at risk for the disease
Term
Incidence rate based on group level data
Definition
number of new cases of disease occurring during a defined period of time
-----------------------------------------
number of people in population at risk at the mid-point of the period
Term
ICD
Definition
International Statistical Classification of Diseases and related health problems
- used for coding and classifying mortality data from death certificates
Term
ICD-CM
Definition
International Statistical Classification of Diseases - Clinical Modification
- Used to code and classify disease morbidity data from inpatient and outpatient records
Term
problems determining who goes into the numerator
Definition
1. what is the best case definition
2. detection (under or over diagnosis)
3. prevalent or incident (existing cases or new cases)
Term
problems determining who goes into the denominator
Definition
1. under-counting of certain population subgroups
2. not everyone in the denominator is at risk for disease
3. population studied may have limited external applicability
Term
Limitations of hospital data
Definition
1. admissions are selective
2. Hospital records are not designed for research
3. Populations at risk are not generally well defined
Term
point prevalence
Definition
number of existing cases AT a point in time
-----------------------------------
number of people in the popualtion AT that point in time
Term
Period prevalence
Definition
Number of existing cases DURING a defined period of time
------------------------------------------------
number of people in the population DURING that defined period of time
Term
Relationship between incidence and prevalence
Definition
P = I*D
Term
Crude Rate
Definition
number of all new events during a period of time
----------------------------------------
number of people at risk for these events during same period
Term
Problems with crude rates
Definition
Crude rates can obscure the fact that subgroups in the population at risk exhibit significant differences in risk. Thus, rates may not be comparable across populations unless there is adjustment for population-specific subgroup composition.
Term
Why look at mortality quantitatively?
Definition
- can indicate disease severity and determine if treatment has become more effective over time
-serve as a surrogate for incidence when the disease is severe
- pinpoint difference in the risk of dying from a disease between population subgroups
Term
Mortality rate formula
Definition
number of people who die during a period of time
----------------------------------------
size of population during midpoint of the period
Term
all-cause annual mortality formula
Definition
total number of people who die from any cause during 1 year
--------------------------------------------------
population at midpoint of that year
Term
disease specific annual mortaity
Definition
number of people who die of a specific disease during 1 year
------------------------------------------------
population at risk at midpoint of that year
Term
Case fatality rate
Definition
* proportion, so a %

number of people who die of a disease
--------------------------------
number of people with the disease
Term
proportionate mortality
Definition
*proportion, so a %

number of people who die of a disease
-----------------------------
total deaths
Term
Age-adjusted rates
Definition
1. age is associated with the disease or health state of interest
2. age distribution structure of the populations being compared are different
Term
Direct method for age-adjustment
Definition
compute the overall mortality rate that would be expected if each population had the same age structure as the standard population
Term
Age-adjustment pros
Definition
- holds age constant
- gives a more accurate picture of differences in rates across populations
Term
Age-adjustment cons
Definition
- fictional rates are calculated
- suppresses details of how subgroups differ across the variable used for adjustment
Term
Indirect age-adjustment
Definition
- used when age group-specific rates are not available
Term
prognosis
Definition
probability of death vs probability of survival
Term
Case fatality rate formula
Definition
*rate, so a %

number of people who die of a disease
-------------------------------
number of people with the disease
Term
case fatality rate
Definition
- good index of severity of a short-term, acute disease
- can measure benefit of a new therapy
Term
survival rate
Definition
percentage of people with a disease who are alive at the end of a specified time interval
Term
5-year survival rate formula
Definition
*rate, so a %

number of cases of the disease who are alive 5 years later
--------------------------------------------
number of cases of the disease
Term
limitations of 5-year survival rate
Definition
- assumes the probability of surviving is equal throughout
- does not use actual observed survival
- cannot account for survival affect
Term
creator of the first life table
Definition
edmond halley
Term
limitations of classic life tables
Definition
- assumes the probability of surviving is equal throughout the year or fixed interval
Term
Numerators in Kaplan-Meier life tables
Definition
- an event is instantaneous
- numerator = the number of people who died at that instant
- denominator = the number of people alive up to that instant, including those who died
- minus withdrawals that occurred before that instant
Term
Kaplan-Meier life table assumptions
Definition
- no secular(temporal) changes in effectiveness of treatment or tendency toward survival over time
- censoring must be independent of the probability of survival
Term
median survival
Definition
the length of time that half of the study population survives
Term
mean survival
Definition
the sum of the individual survival times divided by the total number of people in the study population
Term
relative survival
Definition
observed survival in people with the disease
-------------------------------------
expected survival without the disease
Term
cumulative incidence in an open cohort or closed cohort with incomplete follow-up
Definition
number of cases of disease occurring during a defined period of time
-------------------------------------------------
initial population at risk of the disease
Term
risk
Definition
the probability of an event occurring
- difficult to measure over time
- applies to a population, not individuals
- values range from 0-1, unit-less
- also expressed as a %
- defined for a certain time period
Term
Rate
Definition
- special form of proportion that includes a specification of time
- probability of disease in a defined population over time
- the basic measure of disease occurrence
- a risk in disguise
- the risk of acquiring a disease, and death from a disease is the best approx. by a measure of its incidence
Term
Which measures of disease occurrence below gives you the most accurate information about risk?
Definition
incidence density
Term
approximate formula
Definition
Risk = (incidence rate * time)
Term
exact formula
Definition
Risk = 1 - [exp ^-(rate * time)]
Term
Canons of Inductive Reasoning
- Method of Difference
Definition
examines differences among groups for clues as to why disease rates or other health problems vary across groups
Term
Canons of Inductive Reasoning
- Method of Agreement
Definition
looks for commonality in groups that manifest the same health problem
Term
Canons of Inductive Reasoning
- Method of Concomitant Variation
Definition
traces how exposure to a hazard varies in relation to disease or other health problem
Term
Relative Risk
Definition
A/(A+B)
--------
C/(C+D)
Term
Odds Ratio
Definition
A*D
-----
B*C
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