Distribution of dim light melatonin offset (DLMOff) and phase relationship to waketime in healthy adults and associations with chronotype

OBJECTIVES

Dim light melatonin onset, or the rise in melatonin levels representing the beginning of the biological night, is the gold standard indicator of circadian phase. Considerably less is known about dim light melatonin offset, or the decrease in melatonin to low daytime levels representing the end of the biological night. In the context of insufficient sleep, morning circadian misalignment, or energy intake after waketime but before dim light melatonin offset, is linked to impaired insulin sensitivity, suggesting the need to characterize dim light melatonin offset and identify risk for morning circadian misalignment.

METHODS

We examined the distributions of dim light melatonin offset clock hour and the phase relationship between dim light melatonin offset and waketime, and associations between dim light melatonin offset, phase relationship, and chronotype in healthy adults (N = 62) who completed baseline protocols measuring components of the circadian melatonin rhythm and chronotype.

RESULTS

74.4% demonstrated dim light melatonin offset after waketime, indicating most healthy adults wake up before the end of biological night. Later chronotype (morningness-eveningness, mid-sleep on free days corrected, and average mid-sleep) was associated with later dim light melatonin offset clock hour. Later chronotype was also associated with a larger, positive phase relationship between dim light melatonin offset and waketime, except for morningness-eveningness.

CONCLUSIONS

These findings suggest morning circadian misalignment risk among healthy adults, which would not be detected if only dim light melatonin onset were assessed. Chronotype measured by sleep timing may better predict this risk in healthy adults keeping a consistent sleep schedule than morningness-eveningness preferences. Additional research is needed to develop circadian biomarkers to predict dim light melatonin offset and evaluate appropriate dim light melatonin offset timing to promote health.

Physical sleeping environment is related to insomnia risk and measures of readiness in US army special operations soldiers

BACKGROUND

US military service members have characteristically poor sleep, even when 'in garrison' or at one's home base. The physical sleeping environment, which is often poor in military-provided housing or barracks, may contribute to poor sleep quality in soldiers. The current study aimed to assess whether the sleeping environment in garrison is related to sleep quality, insomnia risk and military readiness.

METHODS

Seventy-four US army special operations soldiers participated in a cross-sectional study. Soldiers were queried on their sleeping surface comfort and the frequency of being awakened at night by excess light, abnormal temperatures and noise. Subjective sleep quality and insomnia symptoms were also queried, via the Pittsburgh Sleep Quality Index and Insomnia Severity Index, respectively. Lastly, measures of soldier readiness, including morale, motivation, fatigue, mood and bodily pain, were assessed.

RESULTS

Soldiers reporting temperature-related and light-related awakenings had poorer sleep quality higher fatigue and higher bodily pain than soldiers without those disturbances. Lower ratings of sleeping surface comfort were associated with poorer sleep quality and lower motivation, lower morale, higher fatigue and higher bodily pain. Each 1-point increase in sleeping surface comfort decreased the risk for a positive insomnia screen by 38.3%, and the presence of temperature-related awakenings increased risk for a positive insomnia screen by 78.4%. Those living on base had a poorer sleeping environment than those living off base.

CONCLUSION

Optimising the sleep environment-particularly in on-base, military-provided housing-may improve soldier sleep quality, and readiness metrics. Providers treating insomnia in soldiers should rule out environment-related sleep disturbances prior to beginning more resource-intensive treatment.

The Association Between Sleep and Musculoskeletal Injuries in Military Personnel: A Systematic Review

INTRODUCTION

Musculoskeletal injuries (MSKIs) are a significant health problem in the military. Accordingly, identifying risk factors associated with MSKI to develop targeted strategies that attenuate injury risk remains a top priority within the military. Insufficient sleep has garnered increased attention as a potential risk factor for MSKI in both civilians and military personnel. Yet, there are no systematic evaluations of the potential association between sleep and MSKI in the military. The purpose of this review is to examine the relationship between sleep and injury in military personnel.

MATERIALS AND METHODS

Literature searches were performed in multiple electronic databases using keywords relevant to sleep quantity and quality, MSKI, and military populations. Two investigators independently assessed the methodological quality of each study using the Newcastle-Ottawa Scale for cohort studies or an adapted form of this scale for cross-sectional studies.

RESULTS

The search yielded 2402 total citations, with 8 studies (3 cohort and 5 cross-sectional) fitting the inclusion criteria. Overall, the systematic review found 5 of the 8 reviewed studies supporting an association between sleep (quality and duration) and MSKI in military personnel. Specifically, poor sleep was associated with increased injury incidence in 2 cohort and 3 cross-sectional studies.

CONCLUSION

This is the first systematic review to evaluate the published literature on the association between sleep and MSKI risk in military populations. Although there is currently limited research on this topic, findings suggest that sleep is associated with MSKI and should be considered when designing strategies aimed at reducing MSKI risk in military personnel.

Association Between Self-Reported Sleep Quality and Musculoskeletal Injury in Male Army Rangers

INTRODUCTION

Musculoskeletal injuries and insufficient sleep are common among U.S. Army Rangers. There has been limited research into whether indices of sleep differ between injured and uninjured Rangers. The purpose of this study was to investigate the association between self-reported sleep and musculoskeletal injury in Rangers.

MATERIALS AND METHODS

A total of 82 Army Rangers (male, 25.4 ± 4.0 years) were asked if they currently have any musculoskeletal injuries; completed the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), and the Stanford Sleepiness Scale; and were asked about their average sleep quality/sleep duration over the preceding week. Rangers were then dichotomized into groups, one that reported a current musculoskeletal injury and another that did not.

RESULTS

The reported musculoskeletal injury prevalence was 15.9% (n = 13). The Rangers that reported an injury, compared to those that did not, had a significantly higher Global PSQI score (6.7 ± 3.7 versus 4.5 ± 2.7, P = .012) and ISI score (10.9 ± 3.7 versus 7.2 ± 4.1, P = .003), both indicative of poorer sleep. The group reporting an injury rated their average sleep quality over the preceding week significantly lower compared to those that did not report an injury (50.8 ± 17.5 versus 68.9 ± 18.3, P = .001). There was no significant group difference in the average nightly sleep duration (6.1 ± 1.0 hours versus 6.5 ± 0.9 hours, P = .099).

CONCLUSION

In this cohort of male Army Rangers, In this cohort of male Army Rangers, those with a musculoskeletal injury reported poorer sleep quality than uninjured Rangers. Sleep duration was not associated with reported injuries; however, both the injured group and uninjured group averaged less than the recommended amounts of sleep. Further investigation into the relationship between musculoskeletal injury and sleep in military personnel is warranted.

Sleep and high-risk behavior in military service members: a mega-analysis of four diverse U.S. Army units

Experimental sleep restriction and deprivation lead to risky decision-making. Further, in naturalistic settings, short sleep duration and poor sleep quality have been linked to real-world high-risk behaviors (HRB), such as reckless driving or substance use. Military populations, in general, tend to sleep less and have poorer sleep quality than nonmilitary populations due to a number of occupational, cultural, and psychosocial factors (e.g. continuous operations, stress, and trauma). Consequently, it is possible that insufficient sleep in this population is linked to HRB. To investigate this question, we combined data from four diverse United States Army samples and conducted a mega-analysis by aggregating raw, individual-level data (n = 2,296, age 24.7 ± 5.3). A negative binomial regression and a logistic regression were used to determine whether subjective sleep quality (Pittsburgh Sleep Quality Index [PSQI], Insomnia Severity Index [ISI], and duration [h]) predicted instances of military-specific HRB and the commission of any HRB (yes/no), respectively. Poor sleep quality slightly elevated the risk for committing HRBs (PSQI Exp(B): 1.12 and ISI Exp(B): 1.07), and longer duration reduced the risk for HRBs to a greater extent (Exp(B): 0.78), even when controlling for a number of relevant demographic factors. Longer sleep duration also predicted a decreased risk for commission of any HRB behaviors (Exp(B): 0.71). These findings demonstrate that sleep quality and duration (the latter factor, in particular) could be targets for reducing excessive HRB in military populations. These findings could therefore lead to unit-wide or military-wide policy changes regarding sleep and HRB.

Sleep and occupational well-being in active duty special operations soldiers: A replication and expansion

OBJECTIVE

To assess the relationship between sleep quality and occupational well-being in active duty military Service Members.

DESIGN

Longitudinal prospective analysis.

SETTING

An annual military training event.

PARTICIPANTS

US Army special operations Soldiers (n = 60; 100% male; age 25.41 ± 3.74).

INTERVENTION

None.

MEASUREMENTS

The Pittsburgh Sleep Quality Index (PSQI) was administered prior to the training event, and the Emotional Exhaustion Scale, the Role Overload Scale, the Walter Reed Army Institute of Research Soldier-Specific Functional Impairment Scale, and the Perceived Stress Scale were administered after the event. Linear regression models were used to assess the relationship between sleep and occupational wellness measures, and the outcome measures of "good" and "poor" sleepers (per the PSQI scoring criteria) were compared with Student's t tests.

RESULTS

Higher (poorer) PSQI Global Scores predicted poorer occupational wellness of all measures (emotional exhaustion: B = 1.60, P < .001, R² = 0.25; functional impairment: B = 0.29, P = .03, R² = 0.14; role overload: B = 0.28, P = .008, R² = 0.12; and perceived stress: B = 0.34, P = .004, R² = 0.20). There were additional relationships between specific PSQI component scores and occupational wellness measures, which is a replication of This team's previous work. Furthermore, emotional exhaustion (t(58) = -4.18, P < .001), functional impairment (t(59)= -3.68, P = .001), role overload (t(58) = -3.20, P = .002), and perceived stress (t(58) = -2.43, P = .02) were all higher in poor sleepers.

CONCLUSIONS

The findings of this study suggest that US Army special operations Soldiers who have poorer sleep quality may be at increased risk for having poorer occupational well-being.

0189 Sleep Duration and Subjective Resilience to Sleep Loss Predict Functional Impairment in Elite Infantrymen During Military Training

Introduction

Insufficient sleep during military operations is detrimental to cognition, physical performance, and general health outcomes. However, there is evidence of inter-individual differences in resilience to sleep loss. Therefore, some Soldiers may be more resilient to the effects of sleep loss than others. This study examined the relationship between sleep duration, resilience, and Soldier well-being during a deployment-readiness training event.

Methods

Seventy-six male Soldiers (aged 25.7±4.0y) from the 75th Ranger Regiment participated while undergoing a two-week training exercise. Surveys were administered at the completion of training and queried subjective measures of sleep duration during training, functional impairment (Walter Reed Functional Impairment Scale), and resilience to sleep loss (Iowa Resilience to Sleepiness Test; iREST). The independent relationships between sleep duration, resilience to sleep loss, and functional impairment were assessed using linear regressions. The interaction between sleep duration and resilience to sleep loss was assessed using SPSS Process (Model 1).

Results

Shorter sleep duration during training predicted higher functional impairment at the end of training (B=-.71, p=.001). Less resilience to sleep loss also predicted higher functional impairment (B=.07,p=.004). An interaction between sleep duration and resilience predicted Soldier impairment (R2 change: .06; F(1,68)=.17,p=.03). Individuals with both shorter sleep duration during training and less resilience had the highest functional impairment. Those with more sleep, and those with high resilience and less sleep, both had lower functional impairment.

Conclusion

This study suggests the iREST can be used as a quick, subjective screening tool to indicate who may be most vulnerable to the effects of sleep loss. Identifying individual resilience to sleep loss may be useful in the military context for prescribing sleep strategies before and during missions in order to enhance Soldier readiness and performance.

Support

Support for this study came from the Military Operational Medicine Research Program (MOMRP) of the United States Army Medical Research and Development Command (USAMRDC).

0215 Sleep Duration Associated with Degraded Performance in Marksmanship and Weapon Stability During a 72-Hour Mission Training Exercise

Introduction

Military operations require vigilance and performance under stressful conditions while functioning with little to no sleep. Previous links between marksmanship performance and sleep restrictions have been shown primarily in novice Soldier populations, with significant decrements in reaction time and decision making skills rather than lethality, mobility, or weapon handling metrics. Additionally, previous research has focused on isolated static marksmanship tasks in laboratory settings. The research presented here assessed the relationship between changes in Soldier sleep duration as measured by actigraphy, and marksmanship performance when conducting a 72-hour military field training exercise.

Methods

Forty-six volunteers [42 males (age 24.5±4.2y; mean±SD)] across three platoons participated in this assessment of Soldier performance during a company-wide mission exercise. Sleep characteristics were collected via actigraphy throughout the mission. Marksmanship performance was assessed during pre-, mid-, and post-mission, utilizing an operationally relevant course that integrated a static self-paced shooting task with a dynamic, fast-paced multiple target task. Marksmanship was assessed in areas of lethality (e.g. accuracy, shot dispersion), mobility (e.g. acquisition, engagement times), and weapon handling stability (e.g. movement of barrel during aiming).

Results

Analysis utilized a multivariate analysis of covariance (MANCOVA) with platoon as the independent variable and total sleep time over the previous 24-hours as the covariant, during the mid-session assessment. The results indicated that prior sleep does significantly modulate marksmanship performance in areas of lethality and stability (ps&lt;.05), but not mobility. Although all individuals received fewer hours of sleep than typical during the mission, those who received less sleep had greater inaccuracy and dispersion in their shot groups, and more barrel movement during weapon handling.

Conclusion

Marksmanship is a key military skill required of all Soldiers. This study has linked degradations in marksmanship lethality and stability performance in the field to naturally occurring sleep restrictions due to platoon-group variances during mission activities. Additionally, it is the first study to link weapon handling stability degradations to sleep loss. Further analysis will explore performance degradations associated with aspects of sleep quality, as well as individual platoon differences, such as leadership, qualifications, and resiliency.

Support

CCDC Soldier Center and Military Operational Medicine Research Program.

0199 Sleep and Risk Taking Behavior in United States Army Soldiers: A Four Study Mega-Analysis

Introduction

In military service members, high risk-taking behavior (RTB; e.g., looking to start a fight, reckless driving) leads to injury, judicial reprimand, and removal from military service. Consequently, reducing RTB has become a priority of the United States (U.S.) Army, and identifying modifiable antecedents of RTB has become critical. In non-military populations, in-lab studies have shown sleep restriction/deprivation leads to risky decision-making. We assessed whether sleep duration/quality and RTB are related in U.S. Army soldiers in operationally-relevant settings.

Methods

Sleep and RTB questionnaire data were collected in 4 unique samples: U.S. Army soldiers from an Armored Brigade Combat Team, Reserve Officer Training Corps (ROTC) Cadets, Special Operations infantrymen, and elite mountain warfare instructors. We aggregated data to conduct a mega-analysis, which is a combined analysis of original raw data. We assessed whether RTB (assessed with an in-house measure of soldier-specific RTB) was correlated with nightly sleep hours (n=2175), Insomnia Severity Index (n=1076), and Pittsburgh Sleep Quality Index scores (n=503). Next, using a linear regression, we assessed whether sleep duration was a predictor of RTB while controlling for relevant demographic factors (age, gender, marital status, combat experience, years of education, rank, years of service; n=1198).

Results

Higher RTB was correlated with lower sleep duration (r=-.23,p&lt;.001), more insomnia symptoms (r=.29,p&lt;.001), and poorer sleep quality (r=.20,p&lt;.001). In the full model, lower age (B=-.02,p=.03) and higher combat experience (B=.05,p=.006) predicted higher RTB. Sleep duration remained a significant (and the strongest) predictor of RTB (B=-.18,p&lt;.001).

Conclusion

Military leaders should work to build in more sleep opportunities and remove environmental sleep disruptors during training and deployment operations. Leaders should also monitor soldier behavior after military operations that require sleep loss in order to reduce RTB, and, consequently, increase the readiness of the force.

Support

This work was supported by the Military Operational Medicine Research Program (MOMRP). The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the US Army or of the US Department of Defense. This abstract has been approved for public release with unlimited distribution.

Trait-like vulnerability of higher-order cognition and ability to maintain wakefulness during combined sleep restriction and circadian misalignment

STUDY OBJECTIVES

Determine stability of individual differences in executive function, cognitive processing speed, selective visual attention, and maintenance of wakefulness during simulated sustained operations with combined sleep restriction and circadian misalignment.

METHODS

Twenty healthy adults (eight female), aged 25.7 (±4.2 SD), body mass index (BMI) 22.3 (±2.1) kg/m2 completed an 18-day protocol twice. Participants maintained habitual self-selected 8-hour sleep schedules for 2 weeks at home prior to a 4-day laboratory visit that included one sleep opportunity per day: 8 hours on night 1, 3 hours on night 2, and 3 hours on mornings 3 and 4. After 3 days of unscheduled sleep at home, participants repeated the entire protocol. Stability and task dependency of individual differences in performance were quantified by intra-class correlation coefficients (ICC) and Kendall's Tau, respectively.

RESULTS

Performance on Stroop, Visual Search, and the Maintenance of Wakefulness Test were highly consistent within individuals during combined sleep restriction and circadian misalignment. Individual differences were trait-like as indicated by ICCs (0.54-0.96) classified according to standard criteria as moderate to almost perfect. Individual differences on other performance tasks commonly reported in sleep studies showed fair to almost perfect ICCs (0.22-0.94). Kendall's rank correlations showed that individual vulnerability to sleep restriction and circadian misalignment varied by task and by metric within a task.

CONCLUSIONS

Consistent vulnerability of higher-order cognition and maintenance of wakefulness to combined sleep restriction and circadian misalignment has implications for the development of precision countermeasure strategies for workers performing safety-critical tasks, e.g. military, police, health care workers and emergency responders.

Sleep problems and functioning during initial training for a high-risk occupation

OBJECTIVES

The current study sought to characterize the sleep problems of soldiers entering Basic Combat Training and to identify the link between sleep problems and subsequent performance, psychological distress, anger reactions, and attention.

DESIGN

Soldiers were surveyed at 4 time points throughout the standard 10 weeks of Basic Combat Training. Surveys were administered at weeks 1, 3, 6, and 9. Sleep problems were identified as either present or absent at each time point using a sleep problem screening questionnaire. Four sleep patterns were identified and then used to evaluate outcomes throughout training (n = 1577).

RESULTS

When compared to those who never had a sleep problem ("healthy "; 60.6%), those who recovered from their initial sleep problem ("recovered"; 12.8%) started training with higher psychological distress and anger reactions and lower attention but steadily improved throughout training. Those who developed a sleep problem during training ("new onset"; 20.0%) and those who had a sleep problem throughout training ("chronic"; 6.6%) also started off significantly worse than the healthy group. The new-onset and chronic groups saw slower psychological distress improvement and a decline in attention throughout the course compared to the healthy group. The chronic group also significantly increased their anger reactions throughout training compared to the healthy group.

CONCLUSION

Sleep problems during Basic Combat Training may be an indicator for difficulties managing entry into the military. These findings highlight the importance of improving sleep health for soldiers throughout Basic Combat Training and for others with similar training in high-risk occupations.

Objective changes in activity levels following sleep extension as measured by wrist actigraphy

OBJECTIVE/BACKGROUND

It is widely established that insufficient sleep can lead to adverse health outcomes. Paradoxically, epidemiologic research suggests that individuals who report habitual nightly sleep greater than 9 h also are at risk for adverse health outcomes. Further, studies have shown that long sleepers have decreased activity levels, which may partially explain the relationship between long sleep duration and mortality. The influence of sleep extension (longer time in bed) on levels of daily activity has not yet been established. The current study examined whether a week of sleep extension altered activity levels within the subsequent daily waking active and sleep period in order to determine whether increased time in bed indeed is related to decreased activity levels.

METHODS

A total of 26 healthy volunteers wore wrist accelerometer devices (Actiwatch 2.0, Philips) in order to objectively measure sleep and activity for six days during their normal schedules and for six days during a sleep extension (10 h time in bed) intervention.

RESULTS

There were no significant or clinically-relevant differences in 24-h activity or activity during the active or sleep period between baseline and sleep extension conditions. There were no main or interaction effects of day and condition when daily activity counts were compared between baseline and sleep extension conditions for the 24 h period (Day: F_{(5, 21)} = 1.92, p = 0.12; Condition: F_(1,25) = 2.93, p = 0.09; Day by Condition: F_(5,21) = 0.32, p = 0.83), Active Waking Period (Day: F_(5,25) = 1.53, p = 0.18; Condition: F_(1,25) = 0.26, p = 0.61; Day by Condition: F_(5,21) = 0.55, p = 0.74) or Nightly Sleep (Day: F_(5,21) = 0.86, p = 0.51; Condition: F_(1,25) = 1.78, p = 0.19; Day by Condition: F_(5,21) = 0.79, p = 0.56) periods. In contrast, there was a main effect of condition when examining sleep duration by day between conditions (Day: F_(5,21) = 1.60, p = 0.16; Condition: F_(1,25) = 167.31, p < 0.001; Day by Condition: F_(5,21) = 2.31, p = 0.07), such that sleep duration was longer during the sleep extension condition.

DISCUSSION

Sleep duration increased during six days of a sleep extension protocol but activity levels remained similar to their baseline (normal) sleep schedule. The current findings suggest that extending time in bed alone does not alter waking activity counts in young healthy adults. The link between extended sleep and adverse health outcomes may be attributable to other phenotypic factors, or other biological correlates of extended sleep and poor health.

Impact of sleep inertia on visual selective attention for rare targets and the influence of chronotype

Sleep inertia is affected by circadian phase, with worse performance upon awakening from sleep during the biological night than biological day. Visual search/selective visual attention performance is known to be sensitive to sleep inertia and circadian phase. Individual differences exist in the circadian timing of habitual wake time, which may contribute to individual differences in sleep inertia. Because later chronotypes awaken at an earlier circadian phase, we hypothesized that later chronotypes would have worse visual search performance during sleep inertia than earlier chronotypes if awakened at habitual wake time. We analysed performance from 18 healthy participants [five females (22.1 ± 3.7 years; mean ± SD)] at ~1, 10, 20, 30, 40 and 60 min following electroencephalogram-verified awakening from an 8 h in-laboratory sleep opportunity. Cognitive throughput and reaction times of correct responses were impaired by sleep inertia and took ~10-30 min to improve after awakening. Regardless whether chronotype was defined by dim light melatonin onset or mid-sleep clock hour on free days, derived from the Munich ChronoType Questionnaire, the duration of sleep inertia for cognitive throughput and reaction times was longer for later chronotypes (n = 7) compared with earlier chronotypes (n = 7). Specifically, performance for earlier chronotypes showed significant improvement within ~10-20 min after awakening, whereas performance for later chronotypes took ~30 min or longer to show significant improvement (P < 0.05). Findings have implications for decision making immediately upon awakening from sleep, and are consistent with circadian theory suggesting that sleep inertia contributes to longer-lasting impairments in morning performance in later chronotypes.

Effects of caffeine on the human circadian clock in vivo and in vitro

Caffeine's wakefulness-promoting and sleep-disrupting effects are well established, yet whether caffeine affects human circadian timing is unknown. We show that evening caffeine consumption delays the human circadian melatonin rhythm in vivo and that chronic application of caffeine lengthens the circadian period of molecular oscillations in vitro, primarily with an adenosine receptor/cyclic adenosine monophosphate (AMP)-dependent mechanism. In a double-blind, placebo-controlled, ~49-day long, within-subject study, we found that consumption of a caffeine dose equivalent to that in a double espresso 3 hours before habitual bedtime induced a ~40-min phase delay of the circadian melatonin rhythm in humans. This magnitude of delay was nearly half of the magnitude of the phase-delaying response induced by exposure to 3 hours of evening bright light (~3000 lux, ~7 W/m(2)) that began at habitual bedtime. Furthermore, using human osteosarcoma U2OS cells expressing clock gene luciferase reporters, we found a dose-dependent lengthening of the circadian period by caffeine. By pharmacological dissection and small interfering RNA knockdown, we established that perturbation of adenosine receptor signaling, but not ryanodine receptor or phosphodiesterase activity, was sufficient to account for caffeine's effects on cellular timekeeping. We also used a cyclic AMP biosensor to show that caffeine increased cyclic AMP levels, indicating that caffeine influenced a core component of the cellular circadian clock. Together, our findings demonstrate that caffeine influences human circadian timing, showing one way that the world's most widely consumed psychoactive drug affects human physiology.

Sleep inertia, sleep homeostatic and circadian influences on higher-order cognitive functions

Sleep inertia, sleep homeostatic and circadian processes modulate cognition, including reaction time, memory, mood and alertness. How these processes influence higher-order cognitive functions is not well known. Six participants completed a 73-day-long study that included two 14-day-long 28-h forced desynchrony protocols to examine separate and interacting influences of sleep inertia, sleep homeostasis and circadian phase on higher-order cognitive functions of inhibitory control and selective visual attention. Cognitive performance for most measures was impaired immediately after scheduled awakening and improved during the first ~2-4 h of wakefulness (decreasing sleep inertia); worsened thereafter until scheduled bedtime (increasing sleep homeostasis); and was worst at ~60° and best at ~240° (circadian modulation, with worst and best phases corresponding to ~09:00 and ~21:00 hours, respectively, in individuals with a habitual wake time of 07:00 hours). The relative influences of sleep inertia, sleep homeostasis and circadian phase depended on the specific higher-order cognitive function task examined. Inhibitory control appeared to be modulated most strongly by circadian phase, whereas selective visual attention for a spatial-configuration search task was modulated most strongly by sleep inertia. These findings demonstrate that some higher-order cognitive processes are differentially sensitive to different sleep-wake regulatory processes. Differential modulation of cognitive functions by different sleep-wake regulatory processes has important implications for understanding mechanisms contributing to performance impairments during adverse circadian phases, sleep deprivation and/or upon awakening from sleep.

Combination of light and melatonin time cues for phase advancing the human circadian clock

STUDY OBJECTIVES

Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure.

DESIGN

Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m(2))-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m(2))-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time.

SETTING

Sleep and chronobiology laboratory environment free of time cues.

PARTICIPANTS

Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD).

RESULTS

Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances.

CONCLUSION

Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders.

Effects of the melatonin MT-1/MT-2 agonist ramelteon on daytime body temperature and sleep

STUDY OBJECTIVES

A reduction in core temperature and an increase in the distal-proximal skin gradient (DPG) are reported to be associated with shorter sleep onset latencies (SOL) and better sleep quality. Ramelteon is a melatonin MT-1/MT-2 agonist approved for the treatment of insomnia. At night, ramelteon has been reported to shorten SOL. In the present study we tested the hypothesis that ramelteon would reduce core temperature, increase the DPG, as well as shorten SOL, reduce wakefulness after sleep onset (WASO), and increase total sleep time (TST) during a daytime sleep opportunity.

DESIGN

Randomized, double-blind, placebo-controlled, cross-over design. Eight mg ramelteon or placebo was administered 2 h prior to a 4-h daytime sleep opportunity.

SETTING

Sleep and chronobiology laboratory.

PARTICIPANTS

Fourteen healthy adults (5 females), aged (23.2 +/- 4.2 y).

MEASUREMENTS AND RESULTS

Primary outcome measures included core body temperature, the DPG and sleep physiology (minutes of total sleep time [TST], wake after sleep onset [WASO], and SOL). We also assessed as secondary outcomes, proximal and distal skin temperatures, sleep staging and subjective TST. Repeated measures ANOVA revealed ramelteon significantly reduced core temperature and increased the DPG (both P < 0.05). Furthermore, ramelteon reduced WASO and increased TST, and stages 1 and 2 sleep (all P < 0.05). The change in the DPG was negatively correlated with SOL in the ramelteon condition.

CONCLUSIONS

Ramelteon improved daytime sleep, perhaps mechanistically in part by reducing core temperature and modulating skin temperature. These findings suggest that ramelteon may have promise for the treatment of insomnia associated with circadian misalignment due to circadian sleep disorders.

Children's understanding of the risks and benefits associated with research

OBJECTIVE

The objective of the current study was to maximise the amount of information children and adolescents understand about the risks and benefits associated with participation in a biomedical research study.

DESIGN

Participants were presented with one of six hypothetical research protocols describing how to fix a fractured thigh using either a "standard" cast or "new" pins procedure. Risks and benefits associated with each of the treatment options were manipulated so that for each one of the six protocols there was either a correct or ambiguous choice.

PARTICIPANTS AND SETTING

Two hundred and fifty one children, ages 6-15 (53% boys), and 237 adults (30% men) were interviewed while waiting for a clinic appointment at the Hospital for Sick Children.

RESULTS

Using standardised procedures and questionnaires, it was determined that most participants, regardless of age group, were able to understand the basic purpose and procedures involved in the research, and most were able to choose the "correct" operation. The younger children, however, showed an overall preference for a cast operation, whereas the older participants were more likely to choose the pins.

CONCLUSIONS

By creating age appropriate modules of information, children as young as six years can understand potentially difficult and complex concepts such as the risks and benefits associated with participation in biomedical research. It appears, however, that different criteria were used for treatment preference, regardless of associated risks; older participants tended to opt for mobility (the pins procedure) whereas younger participants stayed with the more familiar cast operation.

Preliminary investigation of ultrasound scattering analysis to identify women at risk for later invasive cancer. II: Extraction of dominant scattering angle-dependent trends from excised breast tissue

Normalized estimates of the scattering angle-dependent differential scattering cross-section (DSC) at 1.0 MHz were measured from 278 samples of excised breast tissue taken from 66 women. A comparison of results for samples that contained tissue structures previously associated with an increased probability of developing breast cancer to those that did not contain high-risk structures showed that the average magnitude of DSC estimates was insufficient to identify samples with high-risk lesions. Principal component factor analysis (PCFA) was applied to extract scattering angle-dependent trends common to the entire data base. The normalized estimates of the measured DSCs (NDSC) from tissue samples are compared to estimates previously obtained from isolated breast tissue lobules as well as with results from the PCFA. Results are presented that indicate that the dominant angle-dependent trends in the NDSC results are independent of the age of the patient and are similar to trends extracted from isolated breast tissue lobules. The breast tissue structure common to all of these specimens is the terminal duct.

Preliminary investigation of ultrasound scattering analysis to identify women at risk for later invasive cancer. I: Motivation and experimental technique for characterization of isolated breast tissue lobules

A new experimental technique is described that allows the characterization of the angle-dependent ultrasonic scattering properties of isolated breast tissue lobules. A review of breast tissue micro-architecture is presented as background material. Measured estimates of the scatter angle-dependent differential scatter cross-sections (DSC) from 31 excised lobules (14 cancer in situ, 17 noncancer) were examined, and dominant trends described by statistical factors. Three factors were extracted, using principal component factor analysis, which collectively accounted for over 70% of the scatter angle-dependent variation exhibited by the measured data.

Customized implant abutments: technical notes

Custom-fabricated angulated abutments can be of value when implant angulation or position jeopardizes esthetics and/or function and makes retrievability difficult. A wax pattern is prepared over a castable pattern or gold cylinder. After the casting is completed, a secondary screw channel is created in the angulated abutment to retain the superstructure and the definitive prosthesis. The rationale for the use of customized angulated abutments is described. Technical procedures are presented that allow for modifications of individual cases.

Glucose starvation is required for insulin stimulation of glucose uptake and metabolism in cultured microvascular endothelial cells

In the present study we determined the uptake and disposition of glucose in serum-deprived rabbit coronary microvessel endothelial (RCME) cells. RCME cells exhibited stereospecific hexose uptake inhibited by cytochalasin B. Pretreatment of the RCME cells with potassium cyanide or 2,4-dinitrophenol inhibited 2-deoxyglucose uptake but not 3-O-methylglucose transport. A major proportion (30-60%) of the 2-deoxyglucose present in the RCME cells was not phosphorylated. These two observations suggested that the rate-limiting step in the uptake of 2-deoxyglucose was not transport but rather the phosphorylation of 2-deoxyglucose to 2-deoxyglucose 6-phosphate. When glucose-deprived cells were incubated 2 hr with [U-14C]glucose the disposition of the label was as follows: glycogen 60%, acid-soluble fraction 30%, and lipid less than 5%. In contrast glucose-fed cells exhibited lower overall glucose incorporation, and a slightly different disposition: glycogen 45%, acid-soluble fraction 50%, and lipid 5%. Glucose-deprived RCME cells also exhibited greater basal levels of 2-deoxyglucose uptake compared to glucose-fed cells. RCME cells incubated in the absence of glucose and serum for 16 hr exhibited dose-dependent insulin stimulation of hexose uptake and subsequent metabolism to macromolecules (i.e., glycogen and the acid-soluble fraction). Significant effects of insulin were observed with concentrations as low as 2 x 10(-10) M, well within the physiological range. In contrast, cells preincubated in serum-free culture medium containing 5.5 mM glucose did not exhibit insulin-enhanced hexose uptake or glucose metabolism (even at doses as high as 10(-7) M). These studies indicate that the effects of insulin on rabbit coronary microvascular endothelial cell glucose uptake and metabolism require both serum and glucose deprivation.

Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation

Hydrogen peroxide produces concentration-dependent relaxation of precontracted isolated bovine intrapulmonary arterial rings by a mechanism which is independent of the endothelium or prostaglandin mediators. Relaxant responses to hydrogen peroxide concentrations of up to 100 microM were markedly attenuated by the inhibitor of soluble guanylate cyclase activation, methylene blue (10 microM). Micromolar concentrations of hydrogen peroxide elicit time- and concentration-dependent increase in arterial levels of guanosine 3',5'-cyclic monophosphate that are associated with decreases in force. Soluble guanylate cyclase activity is markedly activated by enzymatically generated hydrogen peroxide in a manner that is most closely associated with the concentration of catalase present in the assay, by a mechanism that is inhibited by superoxide anion and the inactivation of catalase. Our data are most consistent with the involvement of compound I, a species of catalase formed during the metabolism of peroxide, in the mechanism of guanylate cyclase activation. The nature of this mechanism of arterial relaxation suggests that it could contribute to the regulation of pulmonary vascular tone by oxygen tension.

Hydrogen peroxide elicits activation of bovine pulmonary arterial soluble guanylate cyclase by a mechanism associated with its metabolism by catalase

Guanylate cyclase activity in the soluble extract of bovine pulmonary arteries is activated by hydrogen peroxide generated by glucose oxidase only in the presence of catalase. This mechanism of guanylate cyclase activation is not blocked by scavengers for superoxide anion or hydroxyl radical, but is selectively inhibited by methylene blue, inactivation of catalase and ethanol. The time dependency of increases in guanylate cyclase activity in the presence of peroxides that are substrates for catalase are associated with the spectral detection of compound I, a species of catalase formed during the metabolism of peroxide. Thus, activation of soluble guanylate cyclase appears to be elicited by compound I of catalase or by a mediator generated by this species.

Insulin binding and effects of insulin on glucose uptake and metabolism in cultured rabbit coronary microvessel endothelium

Microvascular endothelial cells were isolated from rabbit cardiac tissue, and cultivated by standard tissue culture techniques. The conversion of [U-14C]glucose to CO2 and lipids was significantly enhanced by insulin treatment. Insulin stimulated uptake of 2-[3H]deoxyglucose and enhanced the transport of 3-O[3H]methyl-D-glucose. Specific binding of [125I]insulin to RCME cells, displaceable by cold insulin, was also observed. These data demonstrate that insulin is capable of regulating metabolic activities in coronary microvascular endothelium.

Angular distribution of scattered ultrasound from a single steel sphere in agar gelatin: a comparison between theory and experiment

Experimental results for the angular distribution of scattered ultrasound in water from a 0.635 mm diameter steel sphere embedded in agar were obtained for interrogating frequencies of 1.0, 2.25, 3.5 and 5.0 MHz. The experimental results compared favorably with theoretical predictions based on the work of Faran. The results for both theory and experiment are presented in the form of the Differential Scattering Cross Section (DSC) for scattering angles from 170 degrees to 44 degrees. The implications of this study on calculating the expected scattering behavior of gelatin based ultrasound phantoms are briefly discussed.

Association between cyclic GMP accumulation and acetylcholine-elicited relaxation of bovine intrapulmonary artery

The objective of this study was to examine the relationship between relaxation and cyclic GMP accumulation in bovine intrapulmonary artery in response to acetylcholine. Acetylcholine relaxed or contracted isolated arterial rings possessing an intact or damaged endothelial layer, respectively. Acetylcholine-elicited relaxation of phenylephrine-precontracted rings was accompanied by a time- and concentration-dependent accumulation of arterial cyclic GMP but not of cyclic AMP. Relaxation and cyclic GMP accumulation were both antagonized by atropine and methylene blue. Quinacrine, on the other hand, antagonized relaxation without altering the accumulation of cyclic GMP. Nitroglycerin and S-nitroso-N-acetylpenicillamine also relaxed intrapulmonary rings possessing an intact endothelium and caused a concomitant rise in cyclic GMP but not cyclic AMP levels. Both effects were antagonized by methylene blue but not by atropine or quinacrine. Arterial rings prepared with damaged endothelium contracted to acetylcholine but relaxed to nitroglycerin and S-nitroso-N-acetylpenicillamine. Acetylcholine-elicited contraction was markedly inhibited by atropine, partially inhibited by quinacrine and potentiated by methylene blue. Cyclic GMP levels were increased in endothelium-damaged rings contracted by acetylcholine and this was inhibited both by atropine and methylene blue but not by quinacrine. The effects of quinacrine on acetylcholine-elicited changes in tone appear to be nonspecific. These observations indicate that relaxation of bovine intrapulmonary artery by both acetylcholine and nitrogen oxide-containing vasodilators is closely associated with the accumulation of cyclic GMP. Moreover, there appears to be a clear dissociation between contraction and cyclic GMP accumulation elicited by acetylcholine.

Fenbendazole treatment of pregnant bitches to reduce prenatal and lactogenic infections of Toxocara canis and Ancylostoma caninum in pups

A granulated formulation of fenbendazole was tested in a total of 23 treated and control, pregnant, parasite-free Beagle bitches experimentally infected with Toxocara canis and Ancylostoma caninum. The drug was administered to each treated bitch once daily in canned dog food at a dosage of 50 mg/kg body weight. Each of 2 treatment regimens tested was initiated on the 40th day of pregnancy. One regimen involved daily treatment continuing through the 14th postpartum day, and it resulted in 89% fewer ascarids and 99% fewer hookworms in pups born to medicated bitches, as compared with pups born to unmedicated controls. The other regimen of treatment, which was stopped on the day of parturition, was less effective in reducing ascarid and hookworm burdens (64% and 88% reductions, respectively). Three to 5 bitches from each of the treatment and control groups were allowed to whelp a 2nd litter without further treatment or further exposure to parasite infections. Hookworm burdens in 2nd-litter pups born of bitches that had initially received fenbendazole through the 14th postpartum day were significantly lower (P < 0.01; 85% reduction), when compared with the 2nd-litter control pups. All other parasite burdens were not significantly different. It was concluded that granulated fenbendazole is effective in reducing burdens of Ancylostoma caninum and Toxocara canis in newborn pups when the bitch is treated during the last third of pregnancy, especially when treatment (50 mg/kg/day) extends from the 40th day of pregnancy through the 14th postpartum day.

Ultrasonically tissue-mimicking liver including the frequency dependence of backscatter

Tissue-mimicking (TM) liver, previously reported by our laboratory, mimics the speed of sound, density, and attenuation coefficient (including frequency dependence) of liver; however, scatter properties are only qualitatively simulated. Two new versions of TM liver are reported here which not only mimic liver with respect to sound, density, and attenuation coefficient, but also with respect to backscatter coefficients, including the frequency dependence of the latter. Compositions, methods of production, and comparisons of ultrasonic properties with those found in the literature for human liver are presented.

X-ray linear attenuation coefficients in the mammographic range for ultrasonic breast phantom materials

X-ray linear attenuation coefficients for simulated fat and glandular parenchyma used in ultrasound breast phantoms were measured at 15.2, 20.3, 30.0, 40.0, and 60.0 keV and values compared with published figures calculated from the experimentally determined elemental composition of excised breast parenchyma. Agreement was excellent. These ultrasonic tissue-mimicking (TM) materials can be used in radiographic or ultrasound phantoms for testing imaging instruments as well as for training personnel.

Evaluation of granulated fenbendazole as a treatment for helminth infections in dogs

A granulated formulation of fenbendazole was tested in 95 dogs harbouring naturally occurring infections of Toxocara canis, Ancylostoma caninum, Trichuris vulpis, Dipylidium caninum, and Taenia spp and in 19 laboratory-reared Beagle pups experimentally infected with Toxascaris leonina. The drug was administered in moistened dry dog food or in canned dog food. In dosage titration and confirmational studies, using worm counts in naturally infected dogs, the drug was 98%-100% effective at a dosage of 50 mg/kg of body weight/day for 3 days against the commonly occurring nematodes of dogs (ascarids, hookworms, and whipworms) and against Taenia tapeworms. A dosage of 20 mg/kg for 5 days was equally effective against nematodes, but only 73% of the dogs were cleared of Taenia tapeworms. There was no activity at either dosage against Dipylidium tapeworms. Dosages of 100 or 150 mg/kg for a single treatment and 5 or 25 mg/kg daily for 3 days were unsatisfactory with respect to nematodes and tapeworms. Induced infections of T leonina were eliminated from all treated dogs at the dosage and dosing period tested (50 mg/kg/day for 3 days). Fourteen untreated controls expelled 13% of T leonina burdens. It was concluded that granulated fenbendazole is effective in dogs against natural infections of T canis, A caninum, T vulpis, Taenia spp, and experimentally induced infections of T leonina at a dosage of 50 mg/kg of body weight/day for 3 days.

Chronic respiratory disease in a horse infected with Dictyocaulus arnfieldi

A 6-year-old Thoroughbred gelding was examined because of respiratory disease that developed after it was placed on pasture occupied by a donkey. Clinical signs in the gelding included a harsh, dry paroxysmal cough and increased expiratory effort. Eosinophils were seen in smears of mucus aspirated from the trachea and the bronchi. Immature, 5th-stage Dictyocaulus arnfieldi was identified in the tracheal mucus. The cough and other clinical signs were not diminished by corticosteroid therapy or by the administration of bronchodilators. Treatment with 10-fold therapeutic dosages of thiabendazole (440 mg/kg) on each of 2 successive days resulted in permanent cessation of the clinical signs.

Estimation and minimization of fetal absorbed dose: data from common radiographic examinations

A simple method of estimating fetal absorbed dose from common abdominal and pelvic radiographic examinations is presented. The method uses experimentally determined normalized depth dose curves (rad/Roentgen exposure free-in-air) and sonographic localization of the fetus. The method is useful for estimating fetal absorbed dose when a pregnant woman inadvertently undergoes a radiographic examination. However, its primary value is in minimizing fetal dose when a woman, known to be pregnant, must undergo a radiographic examination. Selection of proper projection and deliberate adjustment of bladder volume can result in significant fetal dose reduction particularly in the critical first trimester.

Normalized organ doses for various diagnostic radiologic procedures

Organ-absorbed doses for 24 diagnostic examination projections were measured using an Alderson Rando phantom. The organs of interest were testes, ovaries, thyroid, eyes, uterus, and active bone marrow. The reported values were normalized to the unit entrance exposure of each examination. Subsequent comparison of these measured values with the experimental and calculated values of other investigators showed reasonable agreement.

Evaluation of granulated fenbendazole (22.2%) against induced and naturally occurring helminth infections in cats

A granulated formulation of 22.2% fenbendazole was tested for anthelmintic activity against helminths in cats. The drug was administered in 20 g of canned food on each of 3 days at a dosage of 50 mg/kg of body weight/day. Of 31 young adult cats harboring naturally occurring infections of Toxocara cati, 16 were treated and 15 served as controls. There was 100% clearance of ascarids from all treated cats. Among controls, 18% of the ascarid burden was expelled naturally. Thirty additional cats were acclimated for 2 months prior to infecting them experimentally with Aelurostrongylus abstrusus, Taenia taeniaeformis, and Ancylosatoma tubaeforme. Treatment caused a transitory reduction in the number of lungworm larvae. Histopathologically, cells of developing eggs and of a majority of 1st-stage larvae in lungs of treated cats had evidence of marked degeneration and necrosis, whereas the same stage of larvae in lungs of control cats were normal. Although the number of lung lesions in treated cats was approximately half the number found in controls, there was no significant (P > 0.05) indication that this was due to treatment. Fenbendazole was effective against induced infections of A tubaeforme and Taen taeniaeformis. Greater than 99.9% of hookworms were expelled from 16 treated cats as compared with a 2% natural expulsion from 15 controls. Of 24 cats that developed patent infections of Taen taeniaeformis, 12 were treated and cleared of this parasite, whereas 9 of 12 controls continued to harbor 1 to 10 tapeworms at the time of necropsy. Fenbendazole at a dosage of 50 mg/kg/day x 3 days appeared to be an effective anthelmintic against the common ascarid, hookworm, and tapeworm of cats. Its activity against lungworms was inconclusive at the dosage used, but the data suggest the need for investigating its activity against this parasite at higher dosages, for longer periods of treatment, or both.

Use of fenbendazole suspension (10%) against experimental infections of Toxocara canis and Ancylostoma caninum in beagle pups

Eleven nematode-free Beagle pups were inoculated with Ancylostoma caninum and Toxocara canis; infection became patent 13 and 35 days later, respectively. Eight pups were treated with fenbendazole oral suspension (10%) at a dosage of 50 mg/kg of body weight/day for 3 days. The remaining three animals were unmedicated controls. The drug was effective in reducing both ascarid and hookworm burdens, and there was marked improvement in the clinical condition of treated pups as compared with unmedicated control pups. Natural expulsion of worms in control animals was 53% for ascarids and 2% for hookworms. Drug-related toxicosis was not observed in any of the medicated animals. It was concluded that fenbendazole oral suspension (10%) at the 50-mg/kg dosage is easily administered and is an effective drug for reducing nematode burdens in experimentally infected pups.