11 Midterm
The denominator of a measure of incidence should include only those who
are considered "at risk" of developing a certain disease-that is the total population from which the new cases should arise.
What are the main differences between clinical focus and epidemiologic focus?
clinical focus treats the patient as an individual, epi focus deals with health problems among populations
Attack Rate is also called
cumulative incidence or incidence proportion
Characterizing health events by person, place and time are activities of
descriptive epidemiology
Name the five components of epidemiology
distribution, determinants, diseases or other health related conditions, populations, and control of health problems
A summary measure is calculated by
dividing the total number of cases of the outcome in the population by the total number of individuals in that population in a given time period
While Incidence Rates directly measures risk, high prevalence
do not necessarily signify high risk; it may reflect an increase in survival (maybe due to a change in virulence or in host factors)
Mortality Rate
expresses the incidence of death in a particular population during a period of time by the total population.
If the incidence of a disease is low, but those affected have the condition for a long period of time, the proportion of the population that has the disease at a particular point in time will be
high relative to the incidence rate.
There is a direct interrelationship between
incidence, prevalence and the mean duration of time of the disease (if any two are known, the third one can be calculated)
Total Mortality Rate
includes in the numerator deaths from all causes
Earlier, in the 1930's, mortality rates declined because of improvements in
living conditions AND largely because of control of infectious diseases and improved nutrition.
If the rate of development of a disease in a population is high, if the duration is short, either through prompt recovery or death, the prevalence will be
low relative to the incidence.
Case-fatality rate
number of deaths from a disease divided by all cases of that illness; is a function of the severity of disease; and represents the proportion of fatal cases among affected individuals and is often expressed as a percentage.
Cause-specific death rate
number of deaths from a stated cause in 1 year / average (midyear) population
Cause-specific mortality
numerator includes the number of deaths from a particular disease or event.
A high infant mortality rate has been taken to indicate unmet health needs and unfavorable environmental factors such as
nutrition, economic conditions, sanitation and medical care and education.
When incidence data is not available, what may be used to estimate the importance of a disease in a population, but with the realization that the it may not be a good estimator of incidence?
prevalence
number of women in state A who died from lung cancer in 2004 / estimated revenue (in dollars) in state A from cigarette sales in 2004
ratio (comparison of 2 quantities with the same units- state A in 2004)
Adjusted Rates
summary rates that have undergone statistical information to permit fair comparison between groups differing in some characteristic that may affect risk of disease.
Morbidity rate
the incidence rate of nonfatal cases in the total population at risk during a specified time period.
If persons who are not at risk for a certain disease are included in the denominator, the resultant measure will
underestimate the true incidence of disease.
Infant Mortality Rate
# deaths in a yr of children less than 1 year / # live births in 1 yr.
Neonatal mortality rate
# of deaths in a year of children less than 28 days old / # live births in that one year (per 1000 births)
Crude death rate
(number of deaths to residents in an area in a calendar year / Ave. pop in the area in that year) per 1000 population
Crude birth rate
(number of live births to residents in an area in a calendar year / Ave. pop in the area in that year) per 1000 population
Proportionate Mortality Ratio equation
(the deaths assigned to the disease in a certain year / the total deaths in the population in the same year) (x's 100)
Proportionate Mortality Ratio
used to demonstrate the proportion of the overall mortality that can be ascribed to a specific cause.
The distinguishing feature of the attack rate is that it is
useful in situations where the development of the outcome of interest rapidly follows the exposure during a time period that is fixed because of the nature of the disease process
By comparing Incidence Rates among populations
we can determine analytically a proposed hypothesis
Birth Rate is expressed per
1,000
Fertility Rate is expressed per
1,000
Infant Mortality Rate is expressed per
1,000
Attack Rate is expressed per
100
Point Prevalence Proportion is expressed per
100
Proportionate Mortality is expressed per
100
Cause-Specific death rate is expressed per
100,000
Incidence Rate is expressed per
100,000
Mortality Rate is expressed per
100,000
Probability of dying for the individuals and Age distribution of the population (the higher the elderly population in a community, the higher the crude death rate in the population).
2 factors that contribute to the magnitude of the crude rates
Neonatal mortality rate is a subset of children who die less than
28 days in a year
Examples of Specific Rates
Age-specific death rate Race- and sex-specific death rate Cause-specific death rate
Crude Rate
Any rate can be expressed for a total population (crude or adjusted) or for a population subgroup (specific rate).
What are 3 core functions of Public Health?
Assurance, Assessment, Policy Development
Dr. John Snow removed the pump handle off the broad street pump to examine if deaths from cholera would decline. Which component of the definition of epidemiology would most directly apply? This is an example of: A. Distribution in person, place, time, B. Intervention to control a health problem C. Identify determinants of cholera
B.
The infant mortality rate in North Carolina was higher than the U.S. infant mortality rate in 2016 (7.2 deaths per 1,000 live births vs 5.9 deaths per 1,000 live births). The populations under study are: A. North Carolina live births B. U.S. live births C. Both A and B D. Infant Mortality Rate
C.
CFR of deaths related to drunk drivers = # deaths due to drunk driving / # cases of drunk driving
Case-fatality rate example
Prevalence Proportion Equation
New and existing cases of the disease or event at a point in time / Total study population at a point in time 𝑥's 10𝑛
Secondary Attack Rate Equation
New cases among contacts of primary cases during a short time period / Population at beginning of time period−primary cases 𝑥's 10𝑛
General Incidence Rate Equation
New cases occuring during a given period of time / Population at risk during the same time period 𝑥's 10𝑛
Cumulative Incidence (attack rate) Equation
New cases occuring during a short time period / Population at risk at beginning of the time period 𝑥's 10𝑛
Incidence Density or Person-Time Rate Equation
Number of cases during observation period / Time each person observed; totaled for all persons 𝑥's 10𝑛
Point Prevalence Proportion Numerator
Number of current cases new and old, of a specified disease at a given point in time. (a measure that reflects burden)
Cause-Specific death rate Numerator
Number of deaths assigned to a specific cause during a given time interval
Proportionate Mortality Numerator
Number of deaths assigned to a specific cause during a given time interval
Infant Mortality Rate Numerator
Number of deaths under 1 year of age during a given time interval
Birth Rate Numerator
Number of live births reported during a given time interval
Fertility Rate Numerator
Number of live births reported during a given time interval
Infant Mortality Rate Denominator
Number of live births reported during the same time interval
Incidence Rate Numerator
Number of new cases of a specified disease reported during a given time interval
Attack Rate Numerator
Number of new cases of a specified disease reported during an epidemic period
Attack Rate
Number of people at risk in whom a certain illness develops divided by total number of people at risk (it's often due to a very specific exposure & It is good for investigating acute epidemics)
number of women in state A who died from heart disease in 2004 / number of women in state A who died from cancer in 2004
Ratio (comparison of 2 quantities with the same units- women in state A in 2004)
What is the definition of Health?
The state of complete physical, mental, and social well-being, not just the absence of disease of infirmity
What is the definition of epidemiology?
The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control health problems.
may obscure the fact that subgroups of the pop exhibit significant differences in risk
Crude rates
The infant mortality rate in North Carolina was higher than the U.S. infant mortality rate, 7.2 deaths per 1,000 live births vs 5.9 deaths per 1,000 live births, in 2016. The health-related event under study is: A. North Carolina live births B. U.S. deaths at age less than 395 days C. Both A and B D. Deaths among Infants
D.
Mortality Rate Equation
Deaths occuring during a given time period / Population from which death occurred X's 10𝑛
Specific Rates
Detailed rates specific for age and other demographic components (sex or race)
What are the causes of the problem? What works to fix the problem? Is the solution having the intended effect? Does it work in general population? Is there a problem? We think so....
Determinants Intervention Implementation Surveillance
Which of these is not a component of the definition of epidemiology: A. Determinants B. Etiology C. Population D. Intervene to control health problem E. individual patient clinical management
E
Cause-Specific death rate Denominator
Estimated mid-interval population
Mortality Rate Denominator
Estimated mid-interval population
Fertility Rate Denominator
Estimated number of women ages 15-44 years at mid-interval
Incidence Rate Denominator
Estimated population at mid-interval
Point Prevalence Proportion Denominator
Estimated population at the same point in time
Birth Rate Denominator
Estimated total population at mid-interval
Morbidity rate of TB in 1985 can be calculated by dividing the number of nonfatal cases newly reported during that year by the total US midyear population.
Example of Morbidity Rate
It is a fundamental tool for etiologic studies of acute and chronic disease, since they are direct indicators of risk of disease.
Incidence Rates
Provides a direct measure of the rate at which individuals in a given population develop disease and thus provide a basis for statements about probability or risk of disease.
Incidence Rates
A change in prevalence from one time period to another may be the result of changes in
Incidence rates, Changes in the duration of disease or Both
Is good for tracking changes of disease over time; can be determined by cross-sectional studies (less expensive, less time consuming); and will give an idea of the burden of the disease in a population at a given point in time.
POINT PREVALENCE
Health has been defined as consisting of six interactive dimensions- what are they?
Physical, social, mental, emotional, spiritual, and environmental
Attack Rate Denominator
Population at start of the epidemic period
An adequate sample size can be achieved more quickly if existing cases are used rather than waiting for new or incident cases to accumulate.
Prevalence
Can be used to express the burden of some attribute or condition in a population
Prevalence
Most useful for health care providers to assess the public health impact of a specific disease within a community and to project medical care needs for affected individuals, such as number of health care personnel or hospital beds that will be needed.
Prevalence
Useful for monitoring programs for chronic conditions.
Prevalence
Factors (lifestyle, exposures, etc) can affect the occurrence of disease and result in influencing the duration or severity of the illness.
Prevalence disadvantage
Creates a bias
Prevalence disadvantage (it favors the inclusion of chronic over acute disease)
number of women in State A who died from heart disease in 2004 / number of women in State A who died in 2004
Proportion (a type of ratio in which the numerator is included in the denominator)
number of women in state A who died from lung cancer in 2004 / number of women in state A who died from cancer (all types) in 2004
Proportion (type of ratio in which the numerator is included in the denominator)
Displays the percentage of deaths due to the cause under study, usually in a certain age and sex group compared with a different age group in the same sexed population
Proportionate Mortality Ratio
used to emphasize the importance of the contribution of one cause-specific mortality to overall mortality
Proportionate Mortality Ratio
Describe how public health relates to the six interactive dimensions of health?
Public health is "What we as a society do collectively to assure the conditions in which people can be healthy"
number of women in state A who died from heart disease in 2004 / estimated number of women living in state A on July 1st, 2004
Rate (compares disease frequency in different locations, different times, or among different groups of people with different size populations; a measure of risk)
When calculating measures of incidence what things should, in principle, be excluded from the denominator.
Those who currently have or have already had the disease under study or persons who cannot develop the disease for reasons such as age, immunization, or prior removal of organ.
Mortality Rate Numerator
Total number of deaths reported during a given time interval
Proportionate Mortality Denominator
Totally number of deaths from all causes during the same time interval
Low prevalence may reflect
a rapidly fatal process or rapid cure of disease as well as low incidence.
