From a static to a dynamic concept of risk: The circadian epidemiology of cardiovascular events

A growing body of evidence substantiates that the occurrence of cardiovascu lar events is unevenly distributed in time, especially during the 24h. Thes e temporal patterns are indicative of temporal variation in the (1) pathoph ysiological mechanisms that trigger cardiovascular events and (2) physiolog ical status of the cardiovascular system, which combine to give rise to 24h and other periodicities in the susceptibility to disease. The classic assu mption of epidemiologic studies is constancy (or homeostasis) in one's risk to disease during the 24h, as well as other, time domains. However, we pro pose a new concept, that of chronorisk since it takes into account the temp oral variability in the pathophysiological mechanisms and their reciprocal temporal interactions that lead to day-night and other time-dependent patte rns in cardiovascular events. This chronobiological approach, which is expe cted to contribute new insight into the prognostic and therapeutic assessme nt of cardiovascular events, is worthy of broader application in cardiovasc ular and other fields of medicine and warrants further investigation.