Relevance of chronobiology to the research and clinical practice of neurorehabilitation

The major goals of this article relative to neurorehabilitation are to stimulate new research into (1) the chronobiology of neurologic conditions and their therapy as a means of improving patient management and outcomes, and (2) work schedules to enhance well-being and productivity of involved health care workers. Chronobiology has been little investigated for its relevance to neurorehabilitation; nonetheless, findings of patient investigations involving a broad spectrum of other medical conditions suggest the field is likely to play a strong role in improving the management and therapy for patients with neurologic deficits. The mood, motivation, tolerance for, and therapeutic benefit of cognitive and physical retraining all can vary in a predictable manner during the 24 hour as a result of the staging of the multitude of rhythms that comprise the CTS. Primary and secondary neurologic deficits may disrupt the CTS, manifesting as altered sleep-wake cycling, melancholy/depression, and extreme fatigue/poor stamina, which may be unknowingly worsened by unnatural, inappropriate, and illogical LAN coupled with poorly lit daytime ambient conditions of patient housing. The CTS also has been shown to influence the PK and PD of most classes of medications. Thus, poorly chosen times to administer medications, both for neurologic and coexisting acute and chronic medical conditions, can compromise the extent of desired outcomes, magnify adverse effects, and perhaps interfere with neurorehabilitation. Brain trauma itself may result in disruption of the CTS, which may interfere with the success of physical and cognitive retraining programs. In certain circumstances, patients can benefit from resynchronization of their CTS, either by use of properly timed bright-light therapy or physiologic melatonin dosing at optimal circadian times, resulting in better tolerance to and effects of interventions. The work schedule of health care personnel may also be disruptive to their CTS. Day-work schedules that commence too early in the morning or rotating and night shift work arrangements can result in undue fatigue with risk of less than optimal work performance and patient management. Relevant investigations of circadian rhythm are warranted to improve both patient outcomes and the working-time arrangements and welfare of neurorehabilitation employees.