Question

True or False

1. Prevalence refers to the proportion of participants with a risk factor or disease at a particular point in time

2. Censoring occurs when the event of interest (disease) is observed on every individual, usually due to time constraints.

3. Relative risk is an ideal form of measurement for a retrospective cohort study design because it allows researchers to recruit both individuals with the outcome of interest and individuals without the outcome of interest, then match individuals from each of the respective groups to individuals of the other group to determine if a specific exposure caused the outcome of interest.

4. The incidence rate is computed by taking the ratio of the number of new cases of disease to the total number of person-time units available

5. The prevalence of a disease depends on the incidence of the disease as well as the duration of the disease.

Answer 1

1. TRUE.

2. FALSE

3. TRUE ( IN COHORT STUDY RESEARCHER COMPARES AMONG TWO GROUPS WERE ONE IS EXPOSED AND OTHER IS UNEXPOSED)

4. FALSE ( INCEDENCE RATE IS JUST THE OCCURRENCE OF A EVENT FOR PARTICULAR TIME

EX: BIKE ACCIDENTS PER HOUR)

5. TRUE.

Explanation:

1. Prevalence, sometimes referred to as prevalence rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.
2. Censoring is an endemic feature of time-to-event analysis that precludes observation of the event. Censoring occurs when an event may have occurred after the last time a person was under observation, but the specific timing of the event is unknown. Censoring may occur at the end of the study period or when a person fails to return for a study visit.
3. The retrospective cohort study design involves the observation of archived data to assess the risk of disease in exposed and non-exposed individuals. This type of study is undertaken when the exposure to a particular factor and disease outcome has already happened
4. The denominator is the sum of the time each person was observed, totaled for all persons. This denominator represents the total time the population was at risk of and being watched for disease. Thus, the incidence rate is the ratio of the number of cases to the total time the population is at risk of disease.
5. Prevalence and incidence are the two fundamental measures of disease frequency. In order to interpret risk it is necessary to know the length of time that applies.

Prevalence, sometimes referred to as prevalence rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

The incidence rate is a measure of the frequency with which some event, such as a disease or accident, occurs over a specified time period. Incidence rate or “incidence” is numerically defined as the number of new cases of a disease within a time period, as a proportion of the number of people at risk for the disease.

Prevalence is the proportion of a population that has a condition at a specific time, but the prevalence will be influenced by both the rate at which new cases are occurring and the average duration of the disease. Incidence reflects the rate at which new cases of disease are being added to the population (and becoming prevalent cases). Average duration of disease is also important, because the only way you can stop being a prevalent case is to be cured or to move out of the population or die. For example, about a decade ago the average duration of lung cancer was about six months. Therapy was ineffective and almost all lung cancer cases died. From the time of diagnosis, the average survival was only about six months. So, the prevalence of lung cancer was fairly low. In contrast, diabetes has a long average duration, since it can't be cured, but it can be controlled with medications, so the average duration of diabetes is long, and the prevalence is fairly high.

Prevalence = (Incidence Rate) x (Average Duration of Disease)