用人时测量发病率存在问题分析

目前用人时测量发病率的方法考虑了动态人群的流动数量及观察时间。但是,没有考虑人群的流动速度对发病率的影响。本文分析了流行平衡的动态人群的流动速度(V)与人群平均暴露时间(t′)的关系,导出公式(t′)=1/V,即人群流动速度与平均暴露时间成反比。据此,本文认为在暴露时间长短对发病率有影响的情况下,不考虑人群的流动速度,直接用目前人时计算方法测量发病率可能造成偏差。

An analysis of the problem of measuring incidence density with Person—Time

Measure ment of incidence density with person—time can be affected by three factors: numbers of floating population, time of survey and floating speed of population. In the present method of measuring incidence density with person—time, howevet, the floating speed of population has not been considered. In this paper, the relation between floating speed of population in floating balance (v) and average exposure—time (t′)was analysed, A fomulate t′=1/v was deduced. The analysis shows that a bias can be occured by using person—time to estimiate incidence density without regard to floating speed of population.