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Item Sleeping in a bubble: factors affecting sleep during New Zealand’s COVID-19 lockdown(Oxford University Press on behalf of Sleep Research Society, 2022-05-16) Gibson R; Shetty H; Carter M; Münch MNew Zealand (NZ) enforced a rigorous lockdown in response to the outbreak of COVID-19 in 2020. Infection rates remained remarkably low, yet social and personal routines were affected. Factors associated with reporting worsening sleep were explored using an anonymous online survey launched during New Zealand’s 2020 lockdown. Participants were 723 adults aged 20–85 years (median: 45 years, 82% women). Bed and wake times occurred significantly later compared to pre-lockdown estimates and resulted in shorter social jetlag (15 min). During lockdown, 54.5% were identified as “poor sleepers” [i.e. score > 5 on the Pittsburgh Sleep Quality Index (PSQI)]. Overall, 45% rated their sleep quality to worsen compared to pre-lockdown, 22% reported an improvement. Reports of worsening sleep were significantly related to increased sleep latency, reduced sleep efficiency, and heightened PSQI scores compared to those with better sleep or no change. Subjectively worse sleep was significantly associated with less time engaging in physical activity, less exposure to daylight, and social interactions compared to pre-lockdown estimates (p < .05). Logistic regression models identified significant relationships between having more vivid dreams and worsening sleep. Worse sleepers also had increased likelihoods of reporting poorer mood and they also scored higher for anxiety compared to those with no change or improved sleep during lockdown (p < .05). Pandemic-related restrictions contributed to poorer self-reported sleep which was linked to deterioration of mood. Negative affect was comparatively lower than reported elsewhere. These findings provide unique insights to the psychosocial impact of the initial COVID-19 lockdown in New Zealand, where the disease outbreak remained low.Item The effect of a 2 week ketogenic diet, versus a carbohydrate-based diet, on cognitive performance, mood and subjective sleepiness during 36 h of extended wakefulness in military personnel: An exploratory study(John Wiley & Sons Ltd on behalf of European Sleep Research Society, 2023-08) Henderson LR; van den Berg M; Shaw DExtended wakefulness, or sleep deprivation, impairs cognitive performance and brain glucose metabolism. A ketogenic diet (KD) provides an alternative fuel source, ketone bodies, that could elicit a metabolic benefit during sleep deprivation. A randomised, cross-over trial was conducted with seven male military personnel. Participants ingested an iso-energetic ketogenic diet or carbohydrate-based diet for 14 days, immediately followed by 36 h of extended wakefulness and separated by a 12 day washout. Cognitive performance, mood, subjective sleepiness, capillary blood glucose, and D-β-hydroxybutyrate concentrations were measured every 2 h during extended wakefulness. Linear mixed models were used to analyse data. D-β-hydroxybutyrate was higher (p < 0.001) and glucose was lower (p < 0.01) on the KD compared with the carbohydrate-based diet. The KD improved psychomotor vigilance task performance (number of lapses, mean reciprocal response time, mean fastest 10% response time (RT), and mean slowest 10% RT; all p < 0.05), running memory continuous performance test performance (RT and number of correct responses per minute; both p < 0.01), and vigour, fatigue, and sleepiness (all, p ≤ 0.001) compared with the carbohydrate-based diet. In conclusion, a KD demonstrated beneficial effects on cognitive performance, mood, and sleepiness during 36 h of extended wakefulness compared with a carbohydrate-based diet.Item Will night shift workers ratings of well-being and fatigue and performance on prospective memory and sustained vigilance tasks recover after three nights rest? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Psychology at Massey University, Manawatu, New Zealand(Massey University, 2022) Hudson, LucyAs the demand for a 24-hour world increases so does the need for more shift workers. To maintain the standard expected of them, shift workers often work long hours, including night work where their main opportunity for sleep is during the day. Research has found that shift workers experience fatigue, difficulties in cognition and impaired wellbeing after working shifts like these. Despite this, minimal research has been conducted to explore how many days of recovery should be rostered after one night shift. This study aimed to find evidence to guide workplaces on how many days of rest employees should be rostered to recuperate from one night of sleep loss. A sample of 39 night shift (n=22) and day shift workers (n=17) completed a five day experiment from pre-night shift to rest day three (or five consecutive days for controls) and were assessed in tasks of prospective memory, sustained vigilance, self-reported fatigue levels and self-reported affect to measure well-being. The results indicated that while there was no significant change in vigilant attention or prospective remembering across the five days that self-reported fatigue and positive affect experienced significant changes. These findings indicate that night shift workers may need two to three days of rest to recover from some of the effects from a night of sleep deprivation. However this study repeated with a larger sample size and stricter conditions could yield different results.Item The effect of a two-week ketogenic diet, versus a carbohydrate-based diet, on cognitive performance, mood and subjective sleepiness during 36 hours of extended wakefulness in military personnel : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics, Massey University, Albany, New Zealand(Massey University, 2022) Henderson, Lydia RoseBackground: Sleep deprivation (SD) compromises cognitive performance of military personnel, jeopardising operational performance and safety. Since SD-related performance deficits coincide with decreased glucose metabolism in associated brain regions, the ketogenic diet (KD) may mitigate cognitive impairments by providing an alternative fuel source (i.e. ketone bodies [KB]). Aim: To investigate the effect of a 2-week KD compared with a carbohydrate (CHO)-based diet on cognitive function, mood and sleepiness during 36 hours of extended wakefulness. Methods: A randomised, cross-over trial was conducted with 7 military personnel (range, 26- 45 years). Participants ingested a KD (~25 g·day⁻¹ CHO) or CHO-based diet (~285 g·day⁻¹ CHO) for 14 days, immediately followed by 36 hours of wakefulness and separated by a 12-day washout period. Cognitive performance (5-minute Psychomotor Vigilance Task; PVT), mood (fatigue and vigour), subjective sleepiness, and capillary blood glucose and D-β-hydroxybutyrate (D-βHB) concentrations were measured every 2 hours (1, 3 and 5 hours after each meal). Linear mixed models tested the effect of diet, period (6 x 6-hourly bins), test time (1-3) within periods, and their interactions. Results: D-βHB was higher (+0.75 to +1.45 mM; p < 0.001) and glucose was lower (-0.26 to -1.16 mM; p < 0.01) in the KD compared with the CHO-based diet. The KD improved performance for all PVT variables (number of lapses, mean reciprocal reaction time [RRT], slowest 10% RT and fastest 10% RT) (p < 0.05), mood (p = 0.001), and sleepiness (p < 0.001) compared with the CHO-based diet; however, there were no interactions with period or test. Number of lapses and subjective sleepiness increased, and mood, mean RRT and slowest 10% RT deteriorated during the 36 hours of extended wakefulness independent of diet (all p < 0.01). Circadian effects were also observed for fastest 10% RT, mood and sleepiness independent of diet (all p < 0.01). Conclusion: The KD appeared to improve cognitive performance, mood and sleepiness during 36 hours of extended wakefulness compared with the CHO-based diet. This suggests the KD could be considered for military operations when sleep deprivation is anticipated.