Person years意思

"Person years" is a term used in various contexts, particularly in medicine, public health, and epidemiology, to measure the total amount of time individuals contribute to a study or to calculate disease rates or mortality rates. It is used to express the number of years that all the individuals in a study or a population have lived.

For example, if a study follows 100 people for 5 years, then the total person-years of follow-up would be 500 person-years (100 people x 5 years). If the study follows 200 people for 2 years, then the total person-years would be 400 person-years (200 people x 2 years).

Person-years can be used to calculate incidence rates, prevalence rates, or mortality rates. For example, if a certain disease occurs in 10 people out of 1,000 person-years, then the incidence rate would be 10 per 1,000 person-years.

Person-years can also be used to adjust for differences in the size of populations or the length of time that people have been followed. For example, if one study has a higher incidence of a disease but has followed people for a shorter period of time, calculating person-years can help to compare the true amount of time that people in different studies have been at risk for the disease.