Chapter 8 Flashcards
A branch of science that investigates the frequency and distribution of diseases in a defined population in an attempt to determine their causes, to discover ways to alleviate them, and to prevent their reoccurrences
Epidemiology
What is the main feature of epidemiology?
Observe people in their natural setting over a specific period of time, at one point in time, or retrospectively. The objective is to describe specific traits that may be present among members of a population
One group was exposed and the other was not exposed to a variable. Question asks if the exposed group develop a higher incidence of the disease
Risk factors or predictor variables.
-Valuble type of study because it is unethical for researchers to ask patients to do or take something known to be harmful.
T/F Epidemologic studies are considerd observational
True
-Data are collected via surverys, revie, or medical records, etc. and analyzed using statistical tests designed to identify patterns and correlations.
Father of epidemiology. Why?
Dr. John Snow.
-Discovered the cholera epidemic was caused by a contaminated pump. His methods to track and discover this information lead to the foundation of epidemiology
The probability of a person being diagnosed with a disease during a specific period of time (one year usually). The number of newly diagnosed cases of a disease during a specific period of time.
Incidence
I = new cases/population x 100,000
An estimate of the population of an unaffected persons in a population who will develop the disease of interest over a specific period of time.
Risk
-Estimated by observing a population over a defined period of time to determine the number of new cases as compared with the total number of persons.
The proportion of persons in a given population that have a disease at a certain point in time.
Prevalence
-Total number of cases of the disease in a population regardless of when they were diagnosed
P = number of existing cases/population x 100,000
The proportion of a population with a disease at a given point in time
Point prevalence
-May underestimate the frequency of certain conditions
The proportion of a population that has a disease within a defined period of time
Period Prevalence
-Involves repeated monitoring or a population (thus, is better depiction of the overall frequency of a disease)
T/F Incidence and prevalence are sometimes reported as %
True
T/F Prevalence is usually much lower than incidence in short duration diseases like the common cold
True
-Many people contract colds each year, but relatively few people have a cold at one time because the duration is so short
T/F Prevalence in chronic condition is lower than its incidence (type 2 diabetes)
FALSE
Prevalence in chronic conditions is higher than its incidence
-There are 1.2 million new cases of diabetes each year, but once diagnosed, the condition remains and each years incidence is added to the overall prevalence, minus those who die having the condition = 18.2 million.
What key critieria must be met to determine if an exposure to a specific risk factor actually caused a particular disease within a population?
- Temporality
- Consistency
- Dose-response
The exposure must occur prior to the onset of a disease. However, just becuse a given exposure precedes a given disease does not necessarily mean there is a cause-and-effect relationship.
Temporality
-a.k.a. temporal precedence
What are the 4 possible interpretations of temporal relationships?
1) Event A caused Event B
2) Event B caused Event A
3) Both Events A and B were caused by a third related event
4) Neither A or B are related to each other or a third event, but the temporal relationship was merely by chance.
Studies on the relationship carried out by other researchers using different populations get similar results.Need a large number of good quality these to conclude that A caused B
Consistency
Occurs when a greater exposure to a risk factor results in a greater effect on health
Dose-response
-Ex: more cigarettes smoked per day = more likely to get lung cancer
Six additional criteria used to identify cause and effect relationships.
Bradford Hill’s Criteria for Causation
-Keep in mind, none of there can bring indusputable evidence for or against a cause and effect relationship
Bradford Hills Criteria of Causation
1) Strength of Association (stronger the relation, the less likely it was caused by othe factors)
2) Consistency (replication of results by different researchers in different settings)
3) Specificity in the cause (exposure should be associated with a single specific disease)
4) Temporality (exposure must precede the disease)
5) Dose-response relationship
6) Plausibility (Rational scientific basis for the association risk of disease)
7) Coherence (assosication must be consistent with other knowledge on the subject)
8) Experiemental evidence (research that is based on experiments reinforces a causal inference)
9) Analogy (The association is analogous to a known causal relationship)
Which of the following is not true of the epidemologic approach
a) Focus is on prevention rather then treatment
b) Deals with individual populations rather than individual patients
c) Approach is to identify subgroups that are at high-risk of developing a disease and then find out what factors caused it.
d) All of the above are true
d) All of the above are true
T/F
RCTs are always preferred over epidemiologic studies
FALSE
Epidemiologic studies are preferred to RCTs when questions are about diagnosis, prognosis, or causation (related to ethical concerns and feasbility)
Why is there more potential for bias in epidemiologic studies?
- Subjects are not randomly assigned to be en exposure vs. non-exposure groups.
- Differences may exist in the baseline risk of disease between the groups
KEY: Lack of randomization causes increased bias
T/F
The validity of epidemiologic studies depends to a large extent on the reliability of the data that is collected. (usally directly from people or by relying on others; all are potentually unreliable sources)
True
