Epidemiology Exam 2

Epidemiologic studies that are concerned with characterizing the amount and distribution of health and disease within a population.

• Time
• Place
• Person

• Age
• Sex
• Race
• Socioeconomic Status

• Cyclic fluctuation
• Point epidemic
• Secular trends
• Temporal Clustering

• International
• Within Country
• Localized/spatial clustering
• Urban-rural

Perhaps the most important factor to consider when describing occurrence of a disease or illness.

• 2.5 per 100,000 cases ages 5-14
• 1637 per 100,000 cases over age 85

Highest ages 15-24 and over age 75

Risk of death from all causes is higher in the first year of life than any othe rage until age 55

Peak 25-29 sharp decline after 50

Epidemiologic studies have shown sex differences in a wide scope of health phenomena including morbidity and mortality.

• More males are born each year and more males die every year.
• Females outlive males 5-7 years.
• Risk of cancer in males is greater.

• Somewhat amibiguous classifications
• Tends to overlap with nativity and religion
• Some scientists propose that it is a social construct rather than a biological construct
• Used to track various health outcomes.

• White
• Black or African American
• American Indian and Alaska Native
• Asian
• Native Hawaiian and other Pacific Islander

Place of origin of the individual or his or her relatives.

Descriptive term for a person's position in society

• A person's income level
• Education level
• Type of occupation

Climate, cultural factors, national dietary habits, and access to health care.

Regional differences may affect the prevalence and incidence of disease.

Urban and rural sections of the US show variations in morbidity and mortality related to environmental and lifestyle isues.

Associated with specific environmental conditions that may exist in a particular geographic area.

An increase or decrease in the frequence of a disease or health condition in a population over a period of years or within each year

Response of a group of people circumscribed in place to a common source of infection, contamination, or other etiologic factor to which they were exposed almost simultaneously.

Gradual changes in disease frequency over long time periods

Association between common exposure to an etiologic agent at the same time and the development of mrobidity or mortality in a group or population.

Accounts of a single occurrence of a note-worthy health related incident or of a small collection of such events.

A larger collection of cases of a disease, often grouped consecutively and listing common features.

A type of prevalence study that examines the relationship between diseases and other variables of interest as they exist in a defined population at one particular time.

• 1. prevention of disease
• 2. Design of interventions
• 3. conduct of additional research

X does not cause y

X causes Y

If the value of one variable increases, the value of the other variable increases as well.

If the value of one variable increases, the value of the other variable decreases.

• Measure of assocation used with continuous variables
• Varies from -1 to +1
• As r approaches either -1 or +1 the association is stronger

One that can have an infinite number of values within a specified range (ht and wt)

• No association
• Causally Associated
• Noncausally associated

The plot of a dose-response relationship, which is a type of correlative association between an exposure and an effect.

The lowest dose at which a particular response occurs

One that has several peaks in the frequency of a condition

• A graphic plotting of the distribution of cases by time of onset.
• Aids in identifying the cause of a disease outbreak.

• Another method for demonstrating associations
• A type of table that tabulates data according to two dimensions

• Method of difference
• Method of concomitant variation

All of the factors in two or more domains are the same except for a single factor, which is hypothesized to be the "cause" of a disease.

A type of association in which the frequency o fan outcome increases with the frequency of exposure to a factor, the hypothesized cause of the outcome

Refers to the process of defining measurement procedures for the variables used in a study

• One of the central concerns of epidemiology is to be able to assert that a causal association exists between an exposure factor and disease.
• Complex issue
• Several criteria must be satisfied in order to asser that a causal association exists.

• 1. Strength
• 2. Consistency
• 3. Specificity
• 4. Temporality
• 5. Biological gradient
• 6. Plausibility
• 7. Coherence
• 8. Analogy

Strong associations give support to a causal relationsihp between factor and disease

An association has been observed repeatedly

Association is constrained to a particular disease-exposure relationship

The cause must be observed before the effect

Also known as dose-response curve, shows a linear trend in the association between exposure and disease

The association must be biologically plausible from the standpoint of ceontemporary biological knowledge

The cause-and-effect interpretation of our data should not seriously conflict with the generally known facts of the natural history and biology of the disease

Relates to the correspondence between known associations and one tha tis being evaluated for causality

• Subjects are defined on the basis of the presence of absence of an outcome of interest.
• Cases are those individuals who have the outcome or disease of interest, whereas controls do not.

Is one in which the cases and controls have been matched according to one o rmore criteria such as sex, age, race, or other variables.

Defined as a population group, or subset thereof, tha tis followed over a period of time

• Prospective
• Retrospective
• Historical Prospective

A study in which the units of analysis are populations or groups rathe rthan individuals

Involves an assessment of th eassociation between expousre rates and disease rates during the same time period

An association betwen two variables measure at the group level.

An investiagion involving intentional change in some aspect of the status of the subject

• Does not have control over the exposure factor
• Usually is unable to assign subjects randomly to study conditions

• Controls who is exposed to a factor of interest
• Assigns subjects randomly to study groups

Subjects ar eclassified according to their exposure to a factor of interest and then are observed over time to document the occurrence of new cases of disease or other health events

• Makes use of historical data to determine exposure level at some baseline in the past
• Follow-up for a subsequent occurrences of disease between baseline and present is performed

Combines retrospective and prospective approaches

An erroneous inference that may occur because an association observed between variables on an aggregate level doe snot necessarily represent or reflect the assocation that exists at an individual level

• May provide information about the context of health
• Can be performed when individual level measurements are not available
• Can be conducted rapidly and with minimal resources

• Ecologic fallacy
• Imprecise measurement of exposure

• A measure of the association between frequency of exposure and frequency of outcome used in case-control study.
• AD/BC

• Can be used to study low-prevalence conditions
• relatively quick and easy to complete
• Usually inexpensive
• Involve smaller number of subjects

• Measurement of exposure may be inaccurate
• representativeness of cases and controls may be unknown
• Provide indirect estiamates of risk
• The temporal relationship between expousre factor and outcome cannot always be ascertained

The ratio of the incidence rate of a disease or health outcome in an exposed group to the incidence rate of the disease or condition in a non-exposed group

Inidence in the total population- incidence in the nonexposed segment

• Permit direct observation of risk
• Exposure factor is well defined
• Can study expousres that are uncommon in the population
• The temporal relationship between factor and outcome is known

• Expensive and time consuming
• Complicated and difficult to carry out
• Subjects may be lost to follow-up during the course of the study
• Exposures can be mis classified

Subjects in a population are randomly allocated into groups, usualy called study and control groups, to receive or not to receive an experimental preventative or therapeutic procedure, maneuver, or intervention

Systematic devation of results or inferences from truth

• Hawthorne effect
• Recall bias
• Selection bias
• Healthy worker effect
• Confounding

Participant's behavioral changes as a result of their knowledge of being in a study

Cases may remember an exposure more clearly than controls

Distortions that result from procedures used to select subjects and from factors that influence participation in the study

the observation that employed populations tend to have a lower mortality experience than the general population

the distortion of a measure of the effect of an exposure on an outcome due to the association of the exposure with other factors that influence the occurrence of the outcome

Specificity

• X causes Y
• Example: Delta F508 causes Cystic Fibrosis

• X causes Y causes Z
• High cholesterol causes artery thickening which caueses hemostatic factors which can lead to MI

• Factor can produce disease, but is not necessary
• Radiation exposure and leukemia

• Multiple factors, including main factor, required
• Example: Development of TB and immunosuppression to cause disase
• Bacteria still necessary, but not sufficient to cause disease.

• Without factor, disease doesn't develop
• HIV

• Complex models of disease etiology
• High fat diet and heart disease

• Necessary and Sufficient
• Necessary but not sufficient
• Sufficient but not necessary
• Neither sufficient nor necessary

Model of multifactorial causality