Chronobiology international
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Review Comparative Study
Euchronism, allochronism, and dyschronism: is internal desynchronization of human circadian rhythms a sign of illness?
The authors define a subject as euchronic when the circadian parameters--tau (tau=period), Ø (acrophse or peak time), A (amplitude), and M (MESOR=24 h rhythm-adjusted mean)--of a set of circadian variables are within the confidence limits of appropriate reference values of healthy subjects (HS). We define internal desynchronization as a state in which the circadian tau of a set of rhythms differs from 24 h and when the tau of a given variable differs from that of other variables. Such a state was first observed in singly isolated HS without access to time cues and clues. ⋯ Taking into account the high incidence of internal desynchronization found in past investigations and the clinical observation that sleep deprivation is a consequence of many acute and chronic medical conditions (nocturnal pain, nocturnal asthma, etc.), it is suggested that dyschronism may be responsible for the asthenia of unknown origin, at least for some persons. The interindividual (including sex-related) variability in the propensity to exhibit an altered temporal organization, whether it be transient or persistent (i.e., reversible or non-reversible) suggests the involvement of genetic factors. The Dian-Circadian genetic model previously proposed by the authors seems pertinent to conceptualize and explain the various levels and output of internal desynchronization.