T. Leigh Signal

Sleep duration and quality in healthy nulliparous and multiparous women across pregnancy and post-partum.

Background:  Longitudinal studies of sleep during normal pregnancy and post‐partum are rare, and interpretation of the findings is often hampered by methodological issues. Consequentially, there is still limited information on what constitutes normal sleep quality and quantity across pregnancy and early post‐partum, for both nulliparous and multiparous women.

Flight Crew Fatigue Management in a More Flexible Regulatory Environment: An Overview of the New Zealand Aviation Industry

Since 1995, air transport operators in New Zealand have been able to meet the flight and duty time (FDT) regulations by operating according to prescriptive FDT limits or by seeking approval to operate under a potentially more flexible company‐specific FDT scheme. There has been no formal assessment of the impact of this increased flexibility on fatigue management processes. The aim of the present study was to determine the strategies and processes that commercial aircraft operators in New Zealand have in place for managing fatigue and whether these differed according to the type of FDT system under which organizations were operating. All air transport operators in New Zealand were sent questionnaires that were to be completed by an individual in a management role, a line pilot, and an individual in a rostering role. Questions were asked about the FDT system under which the organization operated, the strategies and processes in place for managing fatigue, and the consequences of the organizations approach to managing fatigue. One hundred and fifty‐three responses were received from 88 organizations (55% of all air operators) and were representative of the structure of the New Zealand industry. Air operators were most likely to report that they monitored flight and duty times and pilot workload to manage fatigue (used by 90–99% and 70–90%, respectively), while educating rostering staff and reviewing the processes for managing fatigue were the least utilized strategies (used by 36–50% and 39–60%, respectively). Within the same organization, managers were more likely than line pilots to report the use of specific fatigue management strategies. There were no differences found between organizations operating under prescriptive regulations and those using a company‐specific scheme on ratings of how well fatigue was managed, the number of fatigue management strategies employed, or the frequency of use of selected strategies. Across the industry as a whole, the provision of more flexible regulatory options has not greatly changed fatigue management practices, although some operators have implemented innovative strategies. The findings suggest a need to raise the level of knowledge within the industry regarding the causes and consequences of fatigue and of processes for its management. This is further supported by the discrepancies between the responses of line pilots and managers, which raise doubts about the effectiveness of some strategies nominally being employed. The regulator and other relevant industry groups should consider how to move the industry toward a mature safety culture and solid knowledge base because these are fundamental to more flexible fatigue management regimes, as is adequate regulatory knowledge, support, and oversight.

Effects of sleep/wake history and circadian phase on proposed pilot fatigue safety performance indicators

The Karolinska Sleepiness Scale and Samn–Perelli fatigue ratings, and psychomotor vigilance task performance are proposed as measures for monitoring commercial pilot fatigue. In laboratory studies, they are sensitive to sleep/wake history and circadian phase. The present analyses examined whether they reliably reflect sleep/wake history and circadian phase during transmeridian flight operations. Data were combined from four studies (237 pilots, 730 out‐and‐back flights between 13 city pairs, 1–3‐day layovers). Sleep was monitored (wrist actigraphy, logbooks) before, during and after trips. On duty days, sleepiness, fatigue and mean response speed were measured pre‐flight and at the top of the descent. Mixed‐model analysis of variance examined associations between these measures and sleep/wake history, after controlling for operational factors. Circadian phase was approximated by local (domicile) time in the city where each trip began and ended. More sleep in the 24 h prior to duty was associated with lower pre‐flight sleepiness and fatigue and faster response speed. Sleepiness and fatigue were greater before flights departing during the domicile night and early morning. At the top of the descent, pilots felt less sleepy and fatigued after more in‐flight sleep and less time awake. Flights arriving in the early–mid‐morning (domicile time) had greater sleepiness and fatigue and slower response speeds than flights arriving later. Subjective ratings showed expected associations with sleep/wake history and circadian phase. The response speed showed expected circadian variation but was not associated with sleep/wake history at the top of the descent. This may reflect moderate levels of fatigue at this time and/or atypically fast responses among pilots.

In‐flight sleep, pilot fatigue and Psychomotor Vigilance Task performance on ultra‐long range versus long range flights

This study evaluated whether pilot fatigue was greater on ultra‐long range (ULR) trips (flights >16 h on 10% of trips in a 90‐day period) than on long range (LR) trips. The within‐subjects design controlled for crew complement, pattern of in‐flight breaks, flight direction and departure time. Thirty male Captains (mean age = 54.5 years) and 40 male First officers (mean age = 48.0 years) were monitored on commercial passenger flights (Boeing 777 aircraft). Sleep was monitored (actigraphy, duty/sleep diaries) from 3 days before the first study trip to 3 days after the second study trip. Karolinska Sleepiness Scale, Samn–Perelli fatigue ratings and a 5‐min Psychomotor Vigilance Task were completed before, during and after every flight. Total sleep in the 24 h before outbound flights and before inbound flights after 2‐day layovers was comparable for ULR and LR flights. All pilots slept on all flights. For each additional hour of flight time, they obtained an estimated additional 12.3 min of sleep. Estimated mean total sleep was longer on ULR flights (3 h 53 min) than LR flights (3 h 15 min; P(F) = 0.0004). Sleepiness ratings were lower and mean reaction speed was faster at the end of ULR flights. Findings suggest that additional in‐flight sleep mitigated fatigue effectively on longer flights. Further research is needed to clarify the contributions to fatigue of in‐flight sleep versus time awake at top of descent. The study design was limited to eastward outbound flights with two Captains and two First Officers. Caution must be exercised when extrapolating to different operations.

Prevalence of abnormal sleep duration and excessive daytime sleepiness in pregnancy and the role of socio-demographic factors: comparing pregnant women with women in the general population.

OBJECTIVES To compare the prevalence of self-reported abnormal sleep duration and excessive daytime sleepiness in pregnancy among Māori (indigenous New Zealanders) and non-Māori women versus the general population, and to examine the influence of socio-demographic factors. METHODS Self-reported total sleep time (TST) in 24-hrs, Epworth Sleepiness Scale scores and socio-demographic information were obtained from nullipara and multipara women aged 20-46 yrs at 35-37 weeks pregnant (358 Māori and 717 non-Māori), and women in the general population (381 Māori and 577 non-Māori). RESULTS After controlling for ethnicity, age, socio-economic status, and employment status, pregnant women average 30 min less TST than women in the general population. The distribution of TST was also greater in pregnant women, who were 3 times more likely to be short sleepers (≤6 h) and 1.9 times more likely to be long sleepers (>9 h). In addition, pregnant women were 1.8 times more likely to report excessive daytime sleepiness (EDS). Pregnant women >30 years of age experienced greater age-related declines in TST. Identifying as Māori, being unemployed, and working at night increased the likelihood of reporting abnormal sleep duration across all women population in this study. EDS also more likely occurred among Māori women and women who worked at night. CONCLUSIONS Pregnancy increases the prevalence of abnormal sleep duration and EDS, which are also higher among Māori than non-Māori women and those who do night work. Health professionals responsible for the care of pregnant women need to be well-educated about the importance of sleep and discuss sleep issues with the women they care for.

Post-Sleep Inertia Performance Benefits of Longer Naps in Simulated Nightwork and Extended Operations

Operational settings involving shiftwork or extended operations require periods of prolonged wakefulness, which in conjunction with sleep loss and circadian factors, can have a negative impact on performance, alertness, and workplace safety. Napping has been shown to improve performance and alertness after periods of prolonged wakefulness and sleep loss. Longer naps may not only result in longer-lasting benefits but also increase the risk of sleep inertia immediately upon waking. The time course of performance after naps of differing durations is thus an important consideration in weighing the benefits and risks of napping in workplace settings. The objective of this study was to evaluate the effectiveness of nap opportunities of 20, 40, or 60 min for maintaining alertness and performance 1.5–6 h post-nap in simulated nightwork (P1) or extended operations (P2). Each protocol included 12 participants in a within-subjects design in a controlled laboratory environment. After a baseline 8 h time-in-bed, healthy young males (P1 mean age 25.1 yr; P2 mean age 23.2 yr) underwent either ≈20 h (P1) or ≈30 h (P2) of sleep deprivation on four separate occasions, followed by nap opportunities of 0, 20, 40, and 60 min. Sleep on the baseline night and during the naps was recorded polysomnographically. During the nap opportunities, sleep onset latency was short and sleep efficiency was high. A greater proportion of slow-wave sleep (SWS) was obtained in nap opportunities of 40 and 60 min compared with 20 min. Rapid eye movement (REM) sleep occurred infrequently. A subjective sleepiness rating (Karolinska Sleepiness Scale, KSS), 2-Back Working Memory Task (WMT), and Psychomotor Vigilance Task (PVT) were completed 1.5, 2, 2.5, 3, 4, 5, and 6 h post-nap. The slowest 10% of PVT responses were significantly faster after 40 and 60 min naps compared with a 20 min (P1) or no (P2) nap. There were significantly fewer PVT lapses after 40 and 60 min naps compared with no nap (P2), and after 60 min naps compared with 20 min naps (P1). Participants felt significantly less sleepy and made more correct responses and fewer omissions on the WMT after 60 min naps compared with no nap (P2). Subjective sleepiness and WMT performance were not related to the amount of nap-time spent in SWS. However, PVT response speed was significantly slower when time in SWS was <10 min compared with 20–29.9 min. In conclusion, in operationally relevant scenarios, nap opportunities of 40 and 60 min show more prolonged benefits 1.5–6 h post-nap, than a 20 min or no nap opportunity. Benefits were more apparent when the homeostatic pressure for sleep was high and post-nap performance testing occurred across the afternoon (P2). For sustained improvement in cognitive performance, naps of 40–60 min are recommended. (Author correspondence: t.l.signal@massey.ac.nz)

fMRI correlates of behavioural microsleeps during a continuous visuomotor task

Behavioural microsleeps (BMs) are brief episodes of absent responsiveness accompanied by slow-eye-closure. They frequently occur as a consequence of sleep-deprivation, an extended monotonous task, and are modulated by the circadian rhythm and sleep homeostatic pressure. In this paper, a multimodal method to investigate the neural correlates of BMs using simultaneous recording of fMRI, eye-video, VEOG, and continuous visuomotor response is presented. The data were collected from 20 healthy volunteers while they performed a continuous visuomotor tracking task inside an MRI scanner for 50 min. The BMs were identified post-hoc by expert visual rating of eye-video and visuomotor response using a set of pre-defined criteria. fMRI analysis of BMs revealed changes in haemodynamic activity in several cortical and sub-cortical regions associated with visuomotor control and arousal.

Sleep at Simulated 2438 m: Effects on Oxygenation, Sleep Quality, and Postsleep Performance

INTRODUCTION Crewmembers on ultra long-range commercial flights have the opportunity for rest and sleep in onboard areas in which the barometric pressure is 75.3 kPa (565 mmHg) or higher, equivalent to a terrestrial altitude of 2438 m (8000 ft) or lower. Sleep at higher altitudes is known to be disturbed, resulting in postsleep neurobehavioral performance decrements. We investigated the effects of sleep at 2438 m on oxygen saturation, heart rate, sleep quantity, sleep quality, postsleep neurobehavioral performance, and mood. METHODS Twenty men, 30-56 yr of age, participated in a blinded cross-over investigation conducted in a hypobaric chamber to compare the effects of sleep at altitude (ALT, 2438 m) and ground level (GND, 305 m). RESULTS SpO2 measured before sleep was significantly lower at ALT than at GND, 90.7 +/- 2.0% (average +/- SD) and 96.2 +/- 2.0%, respectively. During sleep, SpO2 decreased further to 86.1 +/- 2.0% at ALT, and 92.3% +/- 2.0% at GND. The percent of time during which SpO2 was below 90% was 44.4% (3.6-86.9%) at ALT and 0.1% (0.0-22.9%) at GND. Objective and subjective measurements of sleep quantity and quality did not differ significantly with altitude, nor did postsleep neurobehavioral performance or mood. DISCUSSION The absence of significant changes in sleep and post-sleep neurobehavioral performance associated with pronounced oxygen desaturation during sleep was unexpected. Further study is needed to determine if the same effects occur in women and to characterize the changes in respiratory physiology that occur during sleep at 2438 m in both sexes.

Lapses of responsiveness: Characteristics, detection, and underlying mechanisms

Lapses in responsiveness (‘lapses’), particularly microsleeps and attention lapses, are complete disruptions in performance from ∼0.5–15 s. They are of particular importance in the transport sector in which there is a need to maintain sustained attention for extended periods and in which lapses can lead to multiple-fatality accidents.

Self-reported sleep in late pregnancy in relation to birth size and fetal distress: the E Moe, Māmā prospective cohort study.

Objectives To explore associations between features of sleep during pregnancy and adverse outcomes for the infant. Setting E Moe, Māmā is a cohort study in Aotearoa/New Zealand that investigates self-reported sleep and maternal health in late pregnancy and the postpartum period. Participants Women (N=633; 194 Māori) reported detailed information on their sleep duration, quality, disturbances, disorders (snoring, breathing pauses, twitching legs, restless legs) and daytime sleepiness between 35 and 37 weeks gestation. Outcome measures Birthweight and fetal distress during labour were extracted from medical records. Associations between each sleep variable and small or large for gestational age (SGA/LGA) using customised birthweight centile or fetal distress were estimated using multinomial/logistic regression, controlling for potential confounders. Secondary analyses considered differences in associations between Māori and non-Māori women. Results There was some indication that breathing pauses (a measure of sleep apnoea) were associated with both SGA (OR 2.8, 95% CI 0.9 to 9.0, p=0.08) and LGA (OR 2.0, 95% CI 0.7 to 5.7, p=0.20), with the association for LGA being stronger when only pregnancy-onset breathing pauses were considered (OR 3.5, 95% CI 1.3 to 9.6, p=0.01). There was also some evidence that pregnancy-onset leg twitching (OR 3.3, 95% CI 1.1 to 10.0, p=0.03) and frequent sleep disturbance due to feeling too hot or too cold (OR 1.7, 95% CI 0.9 to 3.6, p=0.13) were associated with higher risk of fetal distress. Other sleep measures, including snoring, were not associated with SGA, LGA or fetal distress. Many of the associations we observed were considerably stronger in Māori compared with non-Māori women. Conclusions We did not find evidence of previously reported associations between snoring and SGA. Our findings tentatively suggest that self-reported breathing pauses and leg twitching in late pregnancy are associated with infant outcomes, and highlight ethnic inequalities.