Question

Cohort studies can be useful if you are interested in studying multiple outcomes. Why might it be challenging to study multiple outcomes in a matched cohort study?

Answer 1

Ans.

Cohort studies are a type of medical research used to investigate the causes of disease and to establish links between risk factors and health outcomes. The word cohort means a group of people. ... Prospective" studies are planned in advance and carried out over a future period of time.

An example of an epidemiological question that can be answered using a cohort study is whether exposure to X (say, smoking) associates with outcome Y (say, lung cancer). In 1951, commenced the British Doctors Study, a cohort that included both smokers (the exposed group) and non-smokers (the unexposed group).

Cohort studies are particularly advantageous for examining rare exposures because subjects are selected by their exposure status. Additionally, the investigator can examine multiple outcomes simultaneously.

One of the advantages of prospective cohort studies is they can help determine risk factors for being infected with a new disease because they are a longitudinal observation over time, and the collection of results is at regular time intervals, so recall error is minimized.

With data from cohort studies you can calculate cumulative incidences, which are the most direct measurement of the risk of developing disease. An added advantage is that you can examine a range of outcomes/diseases caused by one exposure (e.g. heart disease, lung disease, renal disease caused by smoking).

Disadvantages of Prospective Cohort Studies

They can be very expensive and time consuming. They are not good for rare diseases. They are not good for diseases with a long latency. Differential loss to follow up can introduce bias.

Examples of cohorts commonly used in sociological research include birth cohorts (a group of people born during the same period of time, like a generation) and educational cohorts (a group of people who begin schooling or an educational program at the same time, like this year's freshman class of college students).

Strengths and weaknesses of cohort studies

Multiple outcomes can be measured for any one exposure. Can look at multiple exposures. Exposure is measured before the onset of disease (in prospective cohort studies). Good for measuring rare exposures, for example among different occupations.