Daniel P. Redmond

Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study

Daytime performance changes were examined during chronic sleep restriction or augmentation and following subsequent recovery sleep. Sixty‐six normal volunteers spent either 3 (n = 18), 5 (n= 16), 7 (n = 16), or 9 h (n = 16) daily time in bed (TIB) for 7 days (restriction/augmentation) followed by 3 days with 8 h daily TIB (recovery). In the 3‐h group, speed (mean and fastest 10% of responses) on the psychomotor vigilance task (PVT) declined, and PVT lapses (reaction times greater than 500 ms) increased steadily across the 7 days of sleep restriction. In the 7‐ and 5‐h groups speed initially declined, then appeared to stabilize at a reduced level; lapses were increased only in the 5‐h group. In the 9‐h group, speed and lapses remained at baseline levels. During recovery, PVT speed in the 7‐ and 5‐h groups (and lapses in the 5‐h group) remained at the stable, but reduced levels seen during the last days of the experimental phase, with no evidence of recovery. Speed and lapses in the 3‐h group recovered rapidly following the first night of recovery sleep; however, recovery was incomplete with speed and lapses stabilizing at a level comparable with the 7‐ and 5‐h groups. Performance in the 9‐h group remained at baseline levels during the recovery phase. These results suggest that the brain adapts to chronic sleep restriction. In mild to moderate sleep restriction this adaptation is sufficient to stabilize performance, although at a reduced level. These adaptive changes are hypothesized to restrict brain operational capacity and to persist for several days after normal sleep duration is restored, delaying recovery.

Neural basis of alertness and cognitive performance impairments during sleepiness. I. Effects of 24 h of sleep deprivation on waking human regional brain activity.

The negative effects of sleep deprivation on alertness and cognitive performance suggest decreases in brain activity and function, primarily in the thalamus, a subcortical structure involved in alertness and attention, and in the prefrontal cortex, a region subserving alertness, attention, and higher‐order cognitive processes. To test this hypothesis, 17 normal subjects were scanned for quantifiable brain activity changes during 85 h of sleep deprivation using positron emission tomography (PET) and 18Fluorine‐2‐deoxyglucose (18FDG), a marker for regional cerebral metabolic rate for glucose (CMRglu) and neuronal synaptic activity. Subjects were scanned prior to and at 24‐h intervals during the sleep deprivation period, for a total of four scans per subject. During each 30 min 18FDG uptake, subjects performed a sleep deprivation‐sensitive Serial Addition/Subtraction task. Polysomnographic monitoring confirmed that subjects were awake. Twenty‐four hours of sleep deprivation, reported here, resulted in a significant decrease in global CMRglu, and significant decreases in absolute regional CMRglu in several cortical and subcortical structures. No areas of the brain evidenced a significant increase in absolute regional CMRglu. Significant decreases in relative regional CMRglu, reflecting regional brain reductions greater than the global decrease, occurred predominantly in the thalamus and prefrontal and posterior parietal cortices. Alertness and cognitive performance declined in association with these brain deactivations. This study provides evidence that short‐term sleep deprivation produces global decreases in brain activity, with larger reductions in activity in the distributed cortico‐thalamic network mediating attention and higher‐order cognitive processes, and is complementary to studies demonstrating deactivation of these cortical regions during NREM and REM sleep.

Comparative utility of instruments for monitoring sleepiness- related performance decrements in the operational environment

As both military and commercial operations increasingly become continuous, 24‐h‐per‐day enterprises, the likelihood of operator errors or inefficiencies caused by sleep loss and/or circadian desynchrony also increases. Avoidance of such incidents requires the timely application of appropriate interventions – which, in turn, depend on the ability to measure and monitor the performance capacity of individuals in the operational environment. Several factors determine the potential suitability of candidate measures, including their relative sensitivity, reliability, content validity, intrusiveness and cumbersomeness/fieldability. In the present study, the relative sensitivity (defined as the ratio of effect size to 95% confidence interval) of several measures to the effects of sleep loss was compared in a sleep restriction experiment, in which groups were allowed 3, 5, 7, or 9 h time in bed (TIB) across seven consecutive nights. Of the measures compared, the Psychomotor Vigilance Test was among the most sensitive to sleep restriction, was among the most reliable with no evidence of learning over repeated administrations, and possesses characteristics that make it among the most practical for use in the operational environment.

The Walter Reed palm-held psychomotor vigilance test.

This field-portable reaction time test and analysis software run on devices using the Palm operating system. It is designed to emulate a test and commercial device widely used in sleep deprivation, shift work, fatigue, and stimulant drug research but provides additional capabilities. Experimental comparisons with the standard commercial device in a 40-hour total sleep deprivation study show it to be comparably sensitive to selected experimental variables. A Pocket PC-compatible version is under developement.

Observations on the design and specification of a wrist-worn human activity monitoring system

Monitoring motor activity provides an important index of sleep, rest, and activity in field studies of sustained operations, shift-work schedules, and sleep deprivation. Poor results with previous methods led to development of a program to design a technologically improved monitoring system. In this 3-year program, specific issues were examined, ranging from the empirical characteristics of the wrist-movement signal and transduction methods to conversion of that signal to a useful index of motility. In this report, we discuss the several design issues encountered as well as observations, conclusions, and resulting specifications. The product of this program is a microprocessor-controlled, self-contained activity recording system, with 16K of digital storage and an operating life of over 30 days. The Walter Reed Activity Monitoring System is designed to examine further the behavioral and physiological correlates of activity.

Behavioral Methods in the Treatment of Hypertension: A Review of Their Clinical Status

Behavioral methods to lower blood pressure include biofeedback, relaxation, psychotherapy, suggestion and placebo, and environmental modification. Reported data for each method have been examined applying the clinical pharmacologic format used to study other therapeutic agents. Most studies have been Phase I type, small numbers of subjects in acute (short-term) treatment situations. Phase II studies, controlled trials with comparison with known effective agents, are sparse, and Phase III studies are not yet appropriate. These Phase I studies indicate blood pressure effects that are small, with minimal data about their duration and their relation to the use of pharmacologic agents. The methods are adjunctive and not alternative, while the compliance problem is similar to that with pharmacologic agents. The major differences between the methods are the ease with which they can be used. Widespread application of the nonpharmacologic methods cannot currently be recommended, but further basic and clinical research into mechanisms and outcomes is encouraged.

Oculomotor impairment during chronic partial sleep deprivation

OBJECTIVE The effects of chronic partial sleep (sleep deprivation) and extended sleep (sleep augmentation) followed by recovery sleep on oculomotor function were evaluated in normal subjects to explore the usefulness of oculomotor assessment for alertness monitoring in fitness-for-duty testing. METHODS Sixty-six commercial drivers (24-62 years, 50m/16f) participated in a 15 day study composed of 3 training days with 8h time in bed per night, 7 experimental days with subjects randomly assigned to either 3, 5, 7, or 9h time in bed, and 3 recovery nights with 8h time in bed. Data from 57 subjects were used. Saccadic velocity (SV), initial pupil diameter (IPD), latency to pupil constriction (CL), and amplitude of pupil constriction (CA) were assessed and correlated with the sleep latency test (SLT), the Stanford sleepiness scale (SSS), and simulated driving performance. RESULTS Regression analyses showed that SV slowed significantly in the 3 and 5h groups, IPD decreased significantly in the 9h group, and CL increased significantly in the 3h group. SLT and SSS significantly correlated with SV, IPD, CL, and driving accidents for the 3h group, and with CL for the 5h group. Analyses also showed a significant negative correlation between decreasing SV and increasing driving accidents in the 3h group and a significant negative correlation between IPD and driving accidents for the 7h group. CONCLUSIONS The results demonstrate a sensitivity primarily of SV to sleepiness, and a correlation of SV and IPD to impaired simulated driving performance, providing evidence for the potential utility of oculomotor indicators in the detection of excessive sleepiness and deterioration of complex motor performance with chronic partial sleep restriction. SIGNIFICANCE This paper shows a relationship between sleep deprivation and oculomotor measures, and suggests a potential utility for oculometrics in assessing operational performance readiness under sleep restricted conditions.

Core body temperature is normal in chronic fatigue syndrome

BACKGROUND Subjects with chronic fatigue syndrome (CFS) frequently report symptoms of subnormal body temperature and low-grade fever. We conducted a study to determine whether CFS subjects manifest any abnormality of core body temperature (CBT) that might help explain their fatigue. METHODS Continuous 24-hour recordings of CBT measured every 5 min were performed in 7 subjects meeting the Centers for Disease Control definition of CFS. Three additional groups were studied: normal controls, subjects with seasonal allergy, and subjects with major depression. Subjects (n = 7) in each group were age-, sex-, and weight-matched to the CFS group and had normal basal metabolic rates, thyroid function, and 24-hour urinary free cortisol excretions. CBT was measured with an ingestible radio frequency transmitter pill and a belt-worn receiver-logger. Each pill was factory-calibrated to +/- 0.1 degree C and field-calibrated with a water bath calibration prior to use. RESULTS The 24-hour mean calibration-adjusted CBTs of each group were not significantly different (control: 37.00 +/- 0.17 degrees C; CFS: 37.04 +/- 0.31 degrees C; allergy: 37.15 +/- 0.18 degrees C; depression: 37.16 +/- 0.18 degrees C). Similarly, the mean peak and trough circadian temperatures were not statistically different. The mean 24-hour profile of CBT for each group showed a similar circadian rhythm. In simultaneously collected blood samples, each group showed a similar circadian profile of serum cortisol with a peak occurring at 08:00. CONCLUSIONS Subjects with CFS have normal CBT despite frequent self-reports of subnormal body temperature and low-grade fever.

Blood pressure and heart-rate response to verbal instruction and relaxation in hypertension.

&NA; Recent data have suggested that instructional set and task awareness may play a substantial role in the achievement of directional changes in blood pressure associated with “operant conditioning” techniques. Six hypertensive patients were instructed alternately to raise (UP) and lower (DOWN) their blood pressure by concentrating on changing “heart rate, force of contraction, and blood vessel resistance to flow.” Paired 10 min periods were separated by the experimenters entry and exit. Five of the subjects were taught progressive muscular relaxation (PMR), and the protocol repeated, with PMR induced throughout this session. The immediate cardiovascular response to PMR, induced in both the presence and absence of the experimenter, was studied. Systolic (SBP) and diastolic (DBP) blood pressure and heart rate (HR) were measured every 30 sec in all sessions. Direction of changes in BP and HR for UP and DOWN periods was appropriate and significant in both instruction sessions, and these differences for BP frequently reached significant levels of magnitude. In general, interactions for HR did not reach significant levels. Comparison of the two sessions yielded little difference between them. PMR uniformly lowered BP and HR, but was of significant magnitude only when induction of PMR involved the active participation of the experimenter. Interview data revealed considerable dramatic mental imagery associated with directional shifts in BP. The results indicate that directional instruction may result in appropriate changes in BP and HR of a magnitude comparable to those reported in studies using “external biofeedback.” PMR did not alter the response. This study adds to other data which point to the potential for nonspecific or “placebo” effects to be operative in conditioning studies.

Alpha and beta adrenergic‐induced renin release in man

Changes in hemodynamic variables and renin release, induced with both alpha and beta adrenergic agonists, were studied in 5 normal men. Saline (0.9% NaCl), methoxamine (1.6 and 5.9 µg/kg/min), and isoproterenol (0.015 and 0.026 µg/kg/min) were infused individually in a random order for 30 min. Methoxamine and isoproterenol caused the predicted directionally opposite cardiovascular changes but caused nearly equal and dose‐related increases in plasma renin activity, as measured by radioimmunoassay. Saline irifusion had no effect. Propranolol (0.125 mg/kg) caused decreases in systolic pressure and heart rate, and a significant decrease in plasma renin activity. Propranolol prevented the renin‐releasing effects of isoproterenol and methoxamine, but only the cardiovascular effects of isoproterenol. It appears that alpha or beta agonists stimulate renin release equally in man and that at least one step in renin release is propranolol‐sensitive. Such sensitivity may be independent of its beta receptor blocking activity.