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# Epi Block 1

### Epi

When we measure rates of disease, typically start characterizing in terms of ____, ______, and ____ – these are basic features necessary for descriptive studies of a disease, and all of these may be helpful in defining a population person, place, and time (who, where, and when)
Sampling Populations (Three Groups) [1]Total Population of (everyone), [2] Defined [3] Study Population
_______Population in which we want to measure some feature Defined (Target)
Our defined population could be either _____ or ______ Open (dynamic), Closed (fixed)
______populations are defined by a changeable characteristic, and so individuals can enter and leave. E.g. living on Saba, being a student at SUSOM, being married Open (dynamic
______ populations are defined by a unchangeable event, and individuals cannot enter or leave the population Being born in the U.S.A., having fought in WWII, having had an organ transplant Closed (fixed)
_____:the division of two numbers where time is a unit in the denominator Rate
______: the division of two numbers where the numerator is a subset of the denominator Proportion
_____:the division of two unrelated numbers Ratio
______measures the number of new cases of a disease in a population. = (# of new cases of disease in time period)/(Total # of population at risk for getting disease) Incidence
_______measures the number of existing cases of disease in a population. (# of existing cases of disease at time)/(Total # of population) Prevalence
If a new treatment lengthens survival of patients with a chronic disease, prevalence of that disease will _____ increase
The 3 Standard rules apply for only counting individuals at risk of developing the disease calculating Person Time [1]A person must have the relevant body part [2]A person must not have the disease [3]A person must be alive
To calculate _____ _____ Add up the units of time (typically years) for at-risk persons followed by the study. End with loss to follow up, the end of the study, death, or diagnosis with the outcome disease Person Time
You want to determine the risk that a student at SUSOM starts using drugs for ADHD. What figure should you calculate?A.Incidence B. Incidence Rate C.Morbidity D. Prevalence Incidence Rate
______ = A disease is habitually present in a geographic area Endemic
______ = The incidence of a disease is increasing (above the normal expected incidence) Epidemic
______ = There is a global (or at least very widespread) epidemic of a particular disease Pandemic
In exposure Curves: Three features are relevant: ______, _______, _______ (all of these are likely to be ranges) If we know two of these, we can calculate the third date of exposure, incubation period, date of disease onset
_____ _____exposures are typically defined as _____ if they continue for longer than one incubation period. continuous source [common vehicle], continuous
____ -__- ____spread epidemic curve.incubation periods differ from human to human, and so we will see a range. Because each cycle is the exposure for the next, we can always estimate the average incubation period by counting the time from peak to peak. Person-to-person spread epidemic curve
Ideally, we have the date of the exposure, and then can measure from the date of the exposure to the median of distribution of onset dates to establish an “average” incubation period. point source or single exposure
______ = Incidence of symptoms in people with exposure status. (# of people developing symptoms)/(Total # of people with exposure) Attack rate
______-_______ can be used to determine which of the many exposures of people with symptoms is most likely to be responsible for those symptoms. Cross-tabulation
______ ______ is a measure of how much a particular cause of death contributes to deaths overall. ______ ______ = (number of deaths from cause X)/(total number of deaths) Proportionate mortality
Success in reducing deaths from one cause will reduce the proportionate mortality from that cause, but ____ the proportionate mortality from other causes increase [because the total number of deaths will drop making the number in the denominator smaller, ultimately making the proportionate higher]
The number of people who die from a condition divided by the total number of people in the population at risk of dying from that condition Mortality rate
The number of people who die from a condition who have that condition Case-fatality rate
The age at which it is more likely that you will be dead than that you will be alive, given the underlying chance of death per year of life in the time and place you are living Life expectancy
The oldest age you could live to, given what species of you are and that species’ underlying biology Life span
life expectancy = the _____age at death in a population median
The key factor determining life expectancy in a given time and place is _____ and _____ _____ mortality. infant and early childhood
________ _______ are the major cause of early childhood deaths Preventable Infections
A ______ ______ is a graphical representation of what percentage of a population falls in different age groups population pyramid
Total fertility rate and E0 are _____ related inversely
Global fertility and infant mortality rates both _______ over time decline
Kaplan-Meier plots are commonly used to show differences in _______ rates for patients in different groups survival
________ studies are the first step in the search for risk factors Descriptive
__________studies include no comparison group, whereas ______ studies include a comparison group Descriptive, analytic
study based on just a single patient & that patient’s outcome. very rare diseases about which little is known, or for the first time a particular disease has been seen, or for a very unique presentation of something we though was well characterized. Case Report
a study based on a small set of patients and reporting on their outcomes. It is similar to a case report, but includes more patients. Case Series
________studies are studies in which a group is the unit of analysis E.g. do seatbelt laws reduce mortality in car accidents Ecological
The ______ _____ is when we try to draw a conclusion about individuals from an ecologic study Ecologic Fallacy
studies that Measures an instant in time “snapshot” .sometimes called prevalence studies. Cheap, may use existing data, but very limited Cross-Sectional Studies
Any study that goes over time is ________ rather than cross-sectional longitudinal
______ ______ [r] , measures the strength of bivariate association . Quantifies the degree to which two variables are related; it does not find a best-fit line Correlation Coefficient
The ____ ____ ______ is a prediction equation that estimates the values of y for any given x Linear regression line
X is called an _______ variable independent
Y is called the______ variable dependent
_______study: A group of study participants is followed over time. Incidence of disease in participants exposed to a risk factor and those not exposed to a risk factor is compared. It may be prospective or retrospective. Cohort
_______ study: A group of study participants is divided between those with a disease (cases) and those without a disease (controls). Then, participants’ exposure status is compared. Case-Control
Cohort and case-control studies are observational, not experimental studies. Participants are ____ _______ to exposure status groups. not randomized
Relative Risk (RR) or Attributable Risk (AR), which both compare ______ in exposed and not-exposed groups. incidence
We cannot measure incidence or prevalence of a disease based on a ________ study. case-control
We can’t intentionally expose people to suspected risks, so RCTs are typically trials of _______ treatments
A study is _______ valid if the measures of the two groups accurately reflect the study population internally
A study is externally valid if two things: 1) it is internally valid, and 2) the conclusions about the study population can be generalized to the defined population or beyond
______ :a systematic defect in the design or conduct of a study that distorts the results. If there is significant _____ in a study, it will likely not have internal validity bias
________= [I.exposed/I.unexposed] Relative risk
RR = X, when _____ 1 = Convert to 1/X=Y -> This makes you Y times _____ likely to get the disease below, less
RR = X, when ______ 1 = This makes you X times ______likely to get the disease above, more (as)
_______ _____ = (Incidence in exposed population) – (Incidence in non-exposed population) Attributable risk
_________ (also called etiologic fraction) = (Iexposed-Iunexposed)/Iexposed Proportionate Attributable Risk
_________ (also called attributable fraction) = (Itotal- Iunexposed)/Itotal Proportional Population Attributable Risk
_____ _____ means that our conclusions are limited by what data we have access to. The data we have might not always be accurate. This can lead to misclassification of exposure and disease state. Information bias
_____ _____ is a kind of information bias. _____ _____ means that people in a study might not accurately report exposure status. Example: Alcohol consumption in Canada. Recall bias
______ _____ means that the information about disease status and patient exposures communicated by physicians and other health care record keepers may not be accurate or complete. person recording the exposure did not record it right Reporting bias
_____ means that our study results can also be skewed by who participates in our study—study participants may not be representative of the underlying population. Selection bias
is a kind of selection bias. A cohort study relies on following study participants over time. People who develop disease may be more likely to _____ _____ of the study than healthy people, or vice-versa. Drop-out bias
Members of a special cohort selected by occupation, or a general cohort selected by occupation, have jobs. People with jobs tend, on average, to be healthier than the general population So the exposed group may be healthier than the unexposed group Healthy Worker Bias
A variable is a_______ if it is 1) associated with the exposure, 2) associated with the outcome, and 3) not associated with exposure and outcome as a step on the causal pathway between the exposure and outcome confounder
Study begins with list of participants, none of whom have disease. Exposures are assessed, participants followed for period of time to allow disease to develop, researchers calculate differences in incidence in exposed and non-exposed group. Prospective study:
Study participant list is derived from past records allowing us to survey a population in which disease may have arisen in the past. Participants are assessed for disease status, and for exposure status at the same time, in the present Retrospective study
The _____of an event happening are the chance that the event happens divided by the chance that the event does not happen. odds
this is the most common source of information in case control studies. Flexible but expensive. Must be carefully designed and administered Questionnaires
In general, it is MUCH better to use _______cases than ______cases, but as diseases become more rare, this becomes harder to do. incident, prevalent
Controls should satisfy the “_______” criterion. If a control had gotten the disease, they ______be a case in the study. would
________are people who do not have the disease we’re studying and so who have to be recruited into our study. controls
_______ _____, we examine the characteristics of our population of cases, and then choose controls who collectively are similar to the cases., if 25% of cases are married, we want our control group also to be comprised of 25% married people. group matching
_____ _____ we are attempting to match every individual in our group of cases with a similar control individual. if a newly-admitted case is a married, 35-year-old, female farmer, we want to find a married, 35-year-old, female farmer as a control. “matched pairs,”
A______ uses cases who have an acute disease where we suspect a brief, transient, exposure Those individuals are used as their own controls case crossover trial
So a Randomized Clinical Trials[RCT] primarily has to worry about _______ biases information
__________are thus never used to establish whether there is an association between an exposure and a disease outcome, but rather to determine whether treatments improve prognosis, cure disease, or prevent disease Randomized clinical trials
___ ____ are where we compare the outcomes of patients provided with a treatment in the present with the outcomes of patients with the same diagnosis in the past. Historical controls
Use of hospital controls can lead to _____ ______ bias. systematic selection
_____ ______ is the most effective at preventing errors Forcing function
Created by: SabaMDJuan