title: Living by the clock: the circadian pacemaker in older people.
abstract: The suprachiasmatic nucleus (SCN) of the hypothalamus is considered to be a critical component of a neural oscillator system implicated in the timing of a wide variety of biological processes. The circadian cycles established by this biological clock occur throughout nature and have a period of approximately 24 h. With advancing age, however, these daily fluctuations deteriorate, leading to disrupted cycles with a reduced amplitude. In humans, age-related changes have been described for hormonal rhythms, body core temperature, sleep-wakefulness and several other behavioral cycles. It appears that the disruption of circadian rhythms and the increased incidence of disturbed sleep during aging are paralleled by age-related alterations in the neural and temporal organization of the SCN and a decreased photic input to the clock. The many lines of evidence of age-related decrements in circadian time-keeping and the observed neuronal degeneration of the SCN in senescence strongly suggest that the circadian pacemaker in the human brain becomes progressively disturbed during aging.
authors.affiliation: Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, The Netherlands. M.Hofman@nih.knaw.nl
authors.forename: Michel A
authors.initials: MA
authors.lastname: Hofman
authors.forename: Dick F
authors.initials: DF
authors.lastname: Swaab
mesh_terms: D000375:Aging / Q000235:genetics / Q000473:pathology / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D006801:Humans; D013493:Suprachiasmatic Nucleus / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology*