Research subjects are immediately included in the cohort at the beginning of the study and are grouped according to their exposure status. The study outcome has not yet occurred and needs to be observed for a certain period of time to obtain it. It is also called an immediate cohort study.

Advantages: The results are correct and reliable.

Disadvantages: large sample size required, long observation time, high cost

Study subjects were identified and grouped based on the history obtained at the beginning of the study Depending on the exposure status of the subjects in the data, disease outcomes were determined at the start of the study. It has also been obtained from historical data, also known as historical cohort study

Advantages: saving time, effort, quick results

Disadvantages: The completeness and accuracy of historical data affects the results

is a combination of prospective and retrospective cohort studies, after completing a historical After the cohort study, proceed with the prospective cohort study

Offers the best of both worlds, but takes longer and is more expensive

For a relatively stable observational cohort, cumulative incidence or mortality can be calculated

When the dynamic changes of objects in the queue are large

observing time human time

Also known as rate ratio or hazard ratio

It is the ratio of the incidence rate of the exposed group to the incidence rate of the non-exposed group, indicating how many times the risk of disease in the exposed group is that of the non-exposed group, that is, the risk of disease increased due to exposure

The meaning of RR value

How to estimate the 95% confidence interval for RR:

Also known as specific risk or rate difference

It is the difference between the incidence rate of the exposed group and the incidence rate of the unexposed group, indicating the excess incidence of diseases increased due to exposure.

The relationship between RR and AR

The proportion of morbidity or mortality in an exposed population that is attributable to a factor as a percentage of all morbidity or mortality

Subtopic 1

1. The morbidity or mortality rate can be directly obtained, and the relative risk can be directly estimated; 2. Exposure history data is more accurate, and exposure levels can be divided into grades, making it easier to calculate the dose-response relationship; 3. Strong ability to identify antecedents and consequences, and test etiological hypotheses; 4. Helps understand the natural history of disease; 5. Can be used to understand the relationship between an exposure and multiple disease outcomes.