Far less well understood are the epidemiological forces that drive NCD dynamics. From an epidemiological perspective, NCD prevalence is determined by the difference between the rate at which previously healthy people become ill (incidence) and the rate at which ill people either recover or die (from any cause).
这一“人口老化”效应已为人所熟知。不为人所熟知的是NCD动态背后的流行性因素。从流行病学的观点看，NCD的普遍性决定于先前健康的人群的发病率（事件）和病人被发现发病或死亡（不管什么原因）频率之差。