In terms of data analysis, commonly used effect estimation parameters in cohort studies include

The basic principle of a cohort study is to divide the population into an exposed group and a non-exposed group according to whether they were exposed to a certain factor at the beginning of the study, and then follow up the two groups for a certain period of time to observe and collect information from the two groups. To study the occurrence of diseases, calculate and compare the morbidity or mortality rates between exposed and unexposed groups.

The knowledge points we can extract from the concept are: grouping form: divided into exposed and non-exposed groups, study population: non-diseased people, time sequence: prospective, result analysis: incidence ( or mortality), etc. Its characteristics are: it is prospective in time, it is an observational study, the research subjects are grouped according to exposure or not, and it is a study from "cause" to "effect".

Calculation of rates:

When calculating incidence and mortality rates, cohort studies often take a long time to study and have a large study population. Demographic instability occurs when calculating morbidity and mortality. Therefore, when we are doing the questions, we must pay attention to the different calculation methods selected in different situations.

1. Cumulative incidence rate (CI): If the study population is large and relatively stable, the population at the beginning of the observation can be used as the denominator, and the number of incidence (or deaths) during the entire observation period is Numerator, which calculates the cumulative incidence of a disease.

2. Incidence density (ID): It is suitable for cohort studies where the observation time is relatively long and it is difficult to stabilize the study population. Incidence density (ID) = number of cases during the observation period/total number of observation hours.

Estimation of effect:

1. Relative risk (RR): refers to the ratio of incidence or mortality in the exposed group (Ie) to the incidence or mortality in the non-exposed group (Io) , indicating how many times the risk of illness or death in the exposed group is that of the control group, RR=Ie/Io.

2. Specific risk (AR) is also called attributable risk: it refers to the absolute value of the difference between the incidence or mortality rate of the exposed group (Ie) minus the incidence rate or mortality rate of the non-exposed group (Io). , indicating the degree of risk caused entirely by exposure factors. AR=Ie-IoRR has etiology significance, and AR has more significance in disease prevention and public hygiene.