Chronobiological aspects of narcolepsy

The circadian, circasemidian and ultradian features of sleep-wake patterns in narcolepsy are reviewed with respect to the hypotheses that chronobiological disturbances might either be specific to the condition or contribute to its symptomatic profile. The position is taken that, while there are characteristic temporal features associated with the disorder, the chronobiological system is essentially intact, although quantitatively altered. It appears that the fundamental physiopathogenesis involves state boundary control mechanisms, which operate in state transitions, rather than chronobiological mechanisms affecting the timing of the manifestation of symptoms associated with the disease. We review our recent results from sleep-wake schedule studies designed to improve the maintenance of alertness in narcolepsy-cataplexy and report new analyses of subjective sleepiness data. The schedules employed were designed to take preexisting circadian, circasemidian and ultradian sleep-wake patterns of these patients into consideration.