Dynamics of recovery sleep from chronic sleep restriction.

Sleep loss is common in our 24/7 society with many people routinely sleeping less than they need. Sleep debt is a term describing the difference between the amount of sleep needed, and the amount of sleep obtained. Sleep debt can accumulate over time, resulting in poor cognitive performance, increased sleepiness, poor mood, and a higher risk for accidents. Over the last 30 years, the sleep field has increasingly focused attention on recovery sleep and the ways we can recover from a sleep debt faster and more effectively. While there are still many unanswered questions and debates about the nature of recovery sleep, such as the exact components of sleep important for recovery of function, the amount of sleep needed to recover and the impacts of prior sleep history on recovery, recent research has revealed several important attributes about recovery sleep: (1) the dynamics of the recovery process is impacted by the type of sleep loss (acute versus chronic), (2) mood, sleepiness, and other aspects of cognitive performance recover at different rates, and (3) the recovery process is complex and dependent on the length of recovery sleep and the number of recovery opportunities available. This review will summarize the current state of the literature on recovery sleep, from specific studies of recovery sleep dynamics to napping, "banking" sleep and shiftwork, and will suggest the next steps for research in this field. This paper is part of the David F. Dinges Festschrift Collection. This collection is sponsored by Pulsar Informatics and the Department of Psychiatry in the Perelman School of Medicine at the University of Pennsylvania.

Correlation of Electrodiagnostic Findings in C8 Radiculopathies With Radiographic Data: A Retrospective Chart Review.

ABSTRACT: Signs and symptoms of a C8 radiculopathy could mimic common comorbidities such as entrapment and peripheral neuropathies. These conditions and a C8 radiculopathy both can result in abnormal findings on needle examination of intrinsic hand muscles. It was hypothesized that needle examination of C8-innervated muscles in the forearm might improve concordance with magnetic resonance imaging (MRI) in the presence of underlying comorbidities. A retrospective analysis of electromyogram and C-spine MRI data in 80 patients with negative MRI of C-spine for C8-T1 neuroforaminal stenosis was performed. The percentage of false-positive results in the MRI-negative group undergoing electromyogram testing for hand and forearm muscles (MRI-NH + F) was 3% compared with 18% (P = 0.06) in the group with electromyogram of the hand intrinsic muscles only (MRI-NH). The false-positive result tends to be lower in the MRI-NH + F group in comparison with the MRI-NH group especially in the presence of underlying peripheral and entrapment neuropathies.

Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend.

Reduced exposure to daytime sunlight and increased exposure to electrical lighting at night leads to late circadian and sleep timing [1-3]. We have previously shown that exposure to a natural summer 14 hr 40 min:9 hr 20 min light-dark cycle entrains the human circadian clock to solar time, such that the internal biological night begins near sunset and ends near sunrise [1]. Here we show that the beginning of the biological night and sleep occur earlier after a week's exposure to a natural winter 9 hr 20 min:14 hr 40 min light-dark cycle as compared to the modern electrical lighting environment. Further, we find that the human circadian clock is sensitive to seasonal changes in the natural light-dark cycle, showing an expansion of the biological night in winter compared to summer, akin to that seen in non-humans [4-8]. We also show that circadian and sleep timing occur earlier after spending a weekend camping in a summer 14 hr 39 min:9 hr 21 min natural light-dark cycle compared to a typical weekend in the modern environment. Weekend exposure to natural light was sufficient to achieve ∼69% of the shift in circadian timing we previously reported after a week's exposure to natural light [1]. These findings provide evidence that the human circadian clock adapts to seasonal changes in the natural light-dark cycle and is timed later in the modern environment in both winter and summer. Further, we demonstrate that earlier circadian timing can be rapidly achieved through natural light exposure during a weekend spent camping.