Biomedical subjects

N Lamond

Publications and source records attributed to N Lamond.

8 recordsLinked to original sources

PubMed2003

The impact of a week of simulated night work on sleep, circadian phase, and performance.

AIMS: To investigate factors that may contribute to performance adaptation during permanent night work. METHODS: Fifteen healthy subjects participated in an adaptation and baseline night sleep, directly followed by seven simulated eight-hour night shifts (2300 to 0700 hours). At the end of each shift they were taken outside and exposed to natural light for 20 minutes. They then slept from approximately 0800 hours until they naturally awoke. RESULTS: There was a significant increase in mean performance on a visual psychomotor vigilance task across the week. Daytime sleep quality and quantity were not negatively affected. Total sleep time (TST) for each of the daytime sleeps was reduced, resulting in an average cumulative sleep debt of 3.53 hours prior to the final night shift. TST for each of the daytime sleep periods did not significantly differ from the baseline night, nor did TST significantly vary across the week. There was a significant decrease in wake time after sleep onset and sleep onset latency across the week; sleep efficiency showed a trend towards greater efficiency across the consecutive daytime sleeps. Hours of wakefulness prior to each simulated night shift significantly varied across the week. The melatonin profile significantly shifted across the week. CONCLUSIONS: Results suggest that under optimal conditions, the sleep debt that accumulates during consecutive night shifts is relatively small and does not exacerbate decrements in night-time performance resulting from other factors. When sleep loss is minimised, adaptation of performance during consecutive night shifts can occur in conjunction with circadian adaptation.

Adaptation, Physiological↗

PubMed2001

Performance, sleep and circadian phase during a week of simulated night work.

The current study investigated changes in night-time performance, daytime sleep, and circadian phase during a week of simulated shift work. Fifteen young subjects participated in an adaptation and baseline night sleep, directly followed by seven night shifts. Subjects slept from approximately 0800 hr until they naturally awoke. Polysomnographic data was collected for each sleep period. Saliva samples were collected at half hourly intervals, from 2000 hr to bedtime. Each night, performance was tested at hourly intervals. Analysis indicated that there was a significant increase in mean performance across the week. In general, sleep was not negatively affected. Rather, sleep quality appeared to improve across the week. However, total sleep time (TST) for each day sleep was slightly reduced from baseline, resulting in a small cumulative sleep debt of 3.53 (SD = 5.62) hours. Finally, the melatonin profile shifted across the week, resulting in a mean phase delay of 5.5 hours. These findings indicate that when sleep loss is minimized and a circadian phase shift occurs, adaptation of performance can occur during several consecutive night shifts.

Adolescent↗

PubMed2001

Daytime cardiac autonomic activity during one week of continuous night shift.

Shift workers encounter an increased risk of cardiovascular disease compared to their day working counterparts. To explore this phenomenon, the effects of one week of simulated night shift on cardiac sympathetic (SNS) and parasympathetic (PNS) activity were assessed. Ten (5m; 5f) healthy subjects aged 18-29 years attended an adaptation and baseline night before commencing one week of night shift (2300-0700 h). Sleep was recorded using a standard polysomnogram and circadian phase was tracked using salivary melatonin data. During sleep, heart rate (HR), cardiac PNS activity (RMSSD) and cardiac SNS activity (pre-ejection period) were recorded. Night shift did not influence seep quality, but reduced sleep duration by a mean of 52 +/- 29 min. One week of night shift evoked a small chronic sleep debt of 5 h 14 +/- 56 min and a cumulative circadian phase delay of 5 h +/- 14 min. Night shift had no significant effect on mean HR, but mean cardiac SNS activity during sleep was consistently higher and mean cardiac PNS activity during sleep declined gradually across the week. These results suggest that shiftwork has direct and unfavourable effects on cardiac autonomic activity and that this might be one mechanism via which shiftwork increases the risk of cardiovascular disease. It is postulated that sleep loss could be one mediator of the association between shiftwork and cardiovascular health.

Adolescent↗

PubMed2001

A week of simulated night work delays salivary melatonin onset.

In most studies, the magnitude and rate of adaptation to various night work schedules is assessed using core body temperature as the marker of circadian phase. The aim of the current study was to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as an alternative circadian phase marker. It was hypothesised that the night work schedule would result in a phase delay, manifest in relatively later DLMO, but that this delay would be somewhat inhibited by exposure to natural light. Participants worked seven consecutive simulated 8-hour night shifts (23:00-07:00 h). By night 7, there was a mean cumulative phase delay of 5.5 hours, equivalent to an average delay of 0.8 hours per day. This indicates that partial circadian adaptation occurred in response to the simulated night work schedule. The radioimmunoassay used in the current study provides a sensitive assessment of melatonin concentration in saliva that can be used to determine DLMO, and thus provides an alternative phase marker to core body temperature, at least in laboratory studies.

Adaptation, Physiological↗

PubMed2000

Factors predicting sleep disruption in Type II diabetes.

This study investigated four correlates of diabetes as potential predictors of sleep disruption in people with Type II diabetes. A tentative causal model proposed obesity would lead to more severe diabetes, which would result in increased physical complications, which might in turn affect emotional adjustment, and all of these might combine to cause sleep disruption. It was found that within a diabetic sample, severity of diabetes was related to sleep disruption. Path analysis indicated that the relationship between Type II diabetes and sleep disruption was mediated by physical complications of the disease (pain and nocturia), and not by either obesity or emotional adjustment.

Adaptation, Psychological↗

PubMed2000

The ability to self-monitor performance when fatigued.

The present study aimed to systematically investigate the effects of elevated fatigue levels on the ability to self-monitor performance. Eighteen participants, aged 19-26 y, remained awake for a period of 28 h. Neurobehavioural performance was measured at hourly intervals using four tests from a standardized computer test battery. From these four tests, six measures of performance were obtained: grammatical reasoning (accuracy and response latency); vigilance (accuracy and response latency); simple sensory comparison and tracking. In addition, before and after each test, participants completed visual analogue scales which required them to rate their alertness level and the speed and accuracy of their performance. Individual test results for both self-ratings and neurobehavioural performance were converted to z-scores. Planned comparison analysis indicated that scores on four of the six performance measures decreased significantly as hours of wakefulness increased. Similarly, predicted performance scores for all six measures of performance decreased significantly. Analysis revealed moderate correlations between predicted and actual performance for the four parameters affected by fatigue. Furthermore, moderate to high correlations were found between all six performance parameters and their respective post-test self-ratings. In addition, moderate to high correlations were found between predicted performance and alertness. Taken together, these findings suggest that as fatigue levels increase, subjects globally assess performance decrements. Results suggest that subjective alertness may in part mediate an individual's global assessment of performance.

Adult↗

PubMed1999

Quantifying the performance impairment associated with fatigue.

The present study systematically compared the effects of fatigue and alcohol intoxication on a range of neurobehavioural tasks. By doing so, it was possible to quantify the performance impairment associated with fatigue and express it as a blood alcohol impairment equivalent. Twenty-two healthy subjects aged 19-26 years participated in three counterbalanced conditions. In the sustained wakefulness condition, subjects were kept awake for 28 h. In the alcohol and placebo conditions, subjects consumed either an alcoholic or non-alcoholic beverage at 30 min intervals, until their blood alcohol concentration reached 0.10%. In each session, performance was measured at hourly intervals using four tasks from a standardised computer-based test battery. Analysis indicated that the placebo beverage did not significantly effect mean relative performance. In contrast, as blood alcohol concentration increased performance on all the tasks, except for one, significantly decreased. Similarly, as hours of wakefulness increased performance levels for four of the six parameters significantly decreased. More importantly, equating the performance impairment in the two conditions indicated that, depending on the task measured, approximately 20-25 h of wakefulness produced performance decrements equivalent to those observed at a blood alcohol concentration (BAC) of 0.10%. Overall, these results suggest that moderate levels of fatigue produce performance equivalent to or greater than those observed at levels of alcohol intoxication deemed unacceptable when driving, working and/or operating dangerous equipment.

Adult↗

PubMed1976

Becoming a nurse.

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Career Choice↗