前瞻性调查(Prospective studies)又称队列或定群研究(Cohort studies),是为研究某一因素或现象是否与某一事件或疾病的发生有关,而将一个范围明确的人口依其对该因素的暴露情况划为若干组,然后观察一定时期内各组某一事件或疾病的发生情况,比较其 Prospective studies, also known as cohort studies or cohort studies, are designed to study whether a particular factor or phenomenon is related to the occurrence of an event or disease and to assign a well-defined population to the factor Of the exposure into several groups, and then observe the occurrence of certain events or diseases in each group within a certain period, compare their