Module 2
How does each of the following conditions influence the prevalence of a disease in a population? For each scenario, assume that no other changes occur. Your choices are increases prevalence, decreases prevalence, or has no effect on prevalence. 1. A cheap new clinical test becomes widely available that allows doctors to diagnose previously latent (i.e., hidden) disease. 2. A new treatment is developed that cures people of the disease very soon after they are diagnosed. 3. There is migration of a large number of healthy people into the population.
1. Increase prevalence 2. Decrease prevalence 3. Decrease prevalence
True or False? When calculating the incidence rate of a disease, it is necessary to follow all subjects for the same length of time.
False
True or False? The incidence rate is based upon the assumption that everyone in the candidate population have been following for a specified period of time.
False
True or False? Prevalence measures new cases whereas incidence measures existing cases.
False prevalence = existing incidence = new
True or False? If the incidence rate of a very serious disease is 75/100,000 person-years and the prevalence of this disease in the population is 25/100,000, then the average duration of this disease must be 3 years.
False (1/3 of a year)
True or False? All other things being equal, when a new prevention measure for a disease is developed, the prevalence of the disease will decrease over time.
True
True or False? All other things being equal, when a treatment is developed that prolongs the life of people suffering from a disease, the prevalence of the disease will increase over time.
True
True or False? Only the population at risk contributes to the denominator of the cumulative incidence.
True
True or False? person-time is accrued only among persons at risk while being followed
True
True or False? A unifying framework for thinking about a population is whether its membership is permanent or transient.
True
True or False? Even when clear-cut criteria are used, disease definitions often change over time as more is learned about a disease and its various manifestations.
True
True or False? Incidence rate and cumulative incidence are both similar because they both measure only new cases of a disease but they are different because time is incorporated in a different manner
True
Numerator: The number of newly diagnosed cases of tuberculosis in California from September to December 2017. Denominator: The total number of people in California on September to December, 2017. a. Cumulative incidence b. Incidence rate c. Prevalence d. None of the above
a. Cumulative incidence
Which of the following takes into account the specific amount of time that the members of a population are followed until they develop the disease? a. Incidence b. Prevalence c. Morbidity d. Mortality
a. Incidence
What measure of disease frequency is the percentage of infants weighing less than 2,500 grams at birth? a. Prevalence b. Cumulative Incidence c. Incidence Rate d. None of the above
a. Prevalence
What measure of disease frequency is the percentage of senior boys who are fathers at the time of graduation? a. Prevalence b. Cumulative Incidence c. Incidence Rate d. None of the above
a. Prevalence
Because measurement is the cornerstone of epidemiology and "health" and "sense of well-being" are nonspecific and difficult to quantify, epidemiologists have almost entirely focused their activities on which of the following, such as specific disease, injuries, disabilities, and death? a. Absence of disease b. Absence of health c. Presence of disease d. Presence of health
b. Absence of health
What measure of disease frequency is the percentage of freshman girls who become pregnant over the course of their high school years? a. Prevalence b. Cumulative Incidence c. Incidence rate d. None of the above
b. Cumulative Incidence
The "lifetime risk of breast cancer" among women is a commonly cited measure of which of the following? a. Incidence rate b. Cumulative incidence c. Point prevalence d. Period prevalence
b. Cumulative incidence
Numerator: The total number of new cases of plague in Yosemite from June to July 2015. Denominator: A total number of 500 person-months in Yosemite from June to July 2015. a. Cumulative incidence b. Incidence rate c. Prevalence d. None of the above
b. Incidence rate
Which of the following is useful for estimating the needs of medical facilities and allocating resources for treating people who already have a disease? a. Incidence b. Prevalence c. Morbidity d.Mortality
b. Prevalence
Numerator: The total number of current cases of HIV at a needle exchange program in San Francisco on June 23, 2017. Denominator: The total number of people who used that program in San Francisco on June 23, 2017. a. Ratio b. Proportion c. Rate
b. Proportion
What measure of disease frequency is the number of liveborn babies who die of sudden infant death syndrome during the first year of life per 100,000 baby-years of follow-up? a. Prevalence b. Cumulative Incidence c. Incidence Rate d. None of the above
c. Incidence Rate
Which of the following is a general word that can apply to a disease, condition, or event? a. Incidence b. Prevalence c. Morbidity d. Mortality
c. Morbidity
Numerator: The total number of current cases of HIV at a needle exchange program in San Francisco on June 23, 2017. Denominator: The total number of people who used that program in San Francisco on June 23, 2017. a. Cumulative Incidence b. Incidence rate c. Prevalence d. None of the above
c. Prevalence
What measure of disease frequency is the lifetime risk of breast cancer?
cumulative incidence
measures the occurrence of new cases of disease in a population during a specified time period (usually the first time occurrence)
cumulative incidence
A study of 100 injection drug users who tested negative for HIV infection at enrollment had their HIV status retested at 3-month intervals over a 2-year follow-up period. All of the injection drug users were followed for the entire 2-year period. None died and none were lost to follow-up. Which of the following frequency measures of HIV infection can be calculated at the end of the study? a. Prevalence b. Cumulative incidence c. Incidence rate d. All of the above
d. All of the above
Numerator: The total number of new West Nile cases in the United States from March 2014 to July 2015. Denominator: The total population in California from March 2014 to July 2015. a. Cumulative incidence b. Incidence rate c. Prevalence d. None of the above
d. None of the above
Which of the following refers to the proportion of the population that is diseased during a specified duration of time, such as the year 2017? a. Incidence rate b. Cumulative incidence c. Point prevalence d. Period prevalence
d. Period prevalence
Which of the following measures reflects both the number of individuals who died of a particular cause and the age at which the death occurred? a. Crude mortality rate b. Cause-specific mortality rate c. Age-specific mortality rate d. Year of potential life lost
d. Year of potential life lost
People who live in Winters, CA are a (fixed/dynamic) population.
dynamic
this type of population's membership is defined by being in a state or condition, so their membership is transient
dynamic
People who went to UC Davis in 2008 are a (fixed/dynamic) population.
fixed
World War II veterans are a (fixed/dynamic) population.
fixed
this type of population's membership is defined on the basis of some event, so their membership is permanent
fixed
measures the speed at which new cases of disease occur in a population (uses person-time)
incidence rate
four components of measuring disease frequency
population cases of disease size of population time
measures existing cases of disease in a population during a specified time period
prevalence
1.3 percent of the population of Los Angeles County has a diagnosis of stomach cancer is a (ratio/proportion/rate).
proportion
The odds of lung cancer are 20 to 1 in people who smoke versus non-smokers is a (ratio/proportion/rate).
ratio
