Select the cohort to which you belong. Review the column titles “Dominant Work Values”. Discuss whether you hold those values yourself and how they are demonstrated in your work. Why are they important?
Dominant Work Values
In a well-developed academic essay of 3 – 4 pages, use Exhibit 5.4 p. 137 and select the cohort to which you belong. Review the column titles “Dominant Work Values”. Discuss whether you hold those values yourself and how they are demonstrated in your work. Why are they important?
If you do not hold those same values, explain why and describe the values you do hold and why they are useful. Please use supportive material from your reading of chapters 3-5. If you are not employed outside the home, you can adapt this assignment to any environment such as home, church, or community organization.
This assignment requires you to reference material from your text readings with your citations presented in accurate APA style. Please review the Written Assignment Evaluation Rubric to determine how you will be evaluated.
The characteristic feature of a cohort study is that the investigator identifies subjects at a point in time when they do not have the outcome of interest and compares the incidence of the outcome of interest among groups of exposed and unexposed (or less exposed) subjects. (We can refer to the groups being compared as exposure cohorts.) Cohorts may be identified retrospectively or prospectively, but in either case the outcome status needs to be established at least twice. It must be established that a cohort did not have the outcome of interest at the beginning of the observation period, and the cohort needs to be examined again to determine whether or not the outcome subsequently developed, i.e., the incidence in each of the exposure groups.
Upon successful completion of this section of the course, the student will be able to:
– Prospective cohort study
– Retrospective cohort study
– Ambidirectional study
– An internal comparison group
– An external comparison group
– A general population comparison group
There are two fundamental types of cohort studies based on when and how the subjects are enrolled into the study:
In prospective cohort studies the investigators conceive and design the study, recruit subjects, and collect baseline exposure data on all subjects, before any of the subjects have developed any of the outcomes of interest. The subjects are then followed into the future in order to record the development of any of the outcomes of interest. The follow up can be conducted by mail questionnaires, by phone interviews, via the Internet, or in person with interviews, physical examinations, and laboratory or imaging tests. Combinations of these methods can also be used.
Typically, the investigators have a primary focus, for example, to learn more about cardiovascular disease or cancer, but the data collected from the cohort over time can be used to answer many questions and test many possible determinants, even factors that they hadn’t considered when the study was originally conceived.
The Framingham Heart Study, the Nurses Health Study, and the Black Women’s Health Study are good examples of large, productive prospective cohort studies. In each of these studies, the investigators wanted to study risk factors for common chronic diseases. The investigators identified a cohort (group) of possible subjects who would be feasible to follow for a prolonged period. Eligible subjects had to meet certain criteria (inclusion criteria) to be included in the study as subjects. The investigators then determine the initial or “baseline” characteristics, behaviors, and other “exposures” of all subjects at the beginning of the study. Information is collected from all subjects in the same way using exactly the same questions and data collection methods for all subjects. They design the questions and data collection procedures very carefully in order to have accurate information about exposures before disease develops in any of the subjects.
For more information:
Link to Framingham Heart Study
Link to The Nurses Health Study
Link to The Black Women’s Health Study
Of course, data analysis cannot take place until enough ‘events’ or ‘outcomes’ have occurred, so time must elapse, and the analyses will look at events that have occurred during the period of time from the beginning of the study until the time of the analysis or the end of the study. It goes without saying that analysis is always done retrospectively, because a span of time has to have elapsed before you can compare incidence. The thing that makes prospective cohort studies prospective is that they were designed prospectively, and subjects were enrolled and had baseline data collected before any of them developed any of the outcomes of interest. Determining baseline exposure status before disease events occur gives prospective studies an important advantage in reducing certain types of bias that can occur in retrospective cohort studies and case-control studies, though at the cost of efficiency.
After baseline information is collected, subjects in a prospective cohort study are then followed “longitudinally,” i.e. over a period of time, usually for years. This enables the investigators to know when follow up began, if and when subjects become diseased, if and when they become lost to follow up, and whether their exposure status changed during the follow up period. By having individual data on these details for each subject, the investigators can compute and compare the incidence rates for each of the exposure groups.
The illustration below shows a hypothetical group of 12 subjects followed over a number of years. They were enrolled into the study at different times, and some of them became lost to follow up, i.e., they stopped responding to letters, emails and phone calls, so we don’t know what happened to them; these are show by the horizontal follow up line stopping.