[Aging of the circadian system]

Ageing affects all organic structures and processes, including the circadian system and its principal sign, the biological rhythms. The circadian system temporarily organizes the living organisms. It is made up of structures receiving information from the external environment (that synchronize the circadian clock), the central circadian pacemaker and the peripheral clocks that depends on it, and several outputs that are the overt rhythms. Ageing produces losses in function of all these three components: receptors (the eye in its capacity to transmit the more active light information to the circadian system), the central pacemaker (due to alterations in neuronal function) and the outputs. This leads to the alteration of overt rhythms, with losses in the phase relationship between them, a reduction in amplitude, an increase in fragmentation and an advancement of its phase.