Nineteen-hour variation of postural sway, alertness and rectal temperature during sleep deprivation

Effects of short-term exposure to whole-body vibration on wakefulness level

To investigate the relationships between whole-body vibration and changes in wakefulness, We measured the change of a subjective wakefulness level and electroencephalogram (EEG). Subjects are ten healthy male university students. The subjects were exposed to whole-body vibration with frequency (10 Hz) and acceleration level (0.6 ms(-2) r.m.s.) for 12 min in the seated position. Subjective wakefulness level was evaluated using the questionnaire of VASS (Visual Analog Sleepiness Scale) and KSS (The Kwansei Gakuin Sleepiness Scale). For the electroencephalogram (EEG) measurement, AAT (Alpha Attenuation Test) which repeats three times each opened and closed eye for 1 min was conducted. Wakefulness levels were defined as the ratio of mean alpha-wave power during eyes closed versus eyes opened. VASS and KSS increased and subjective level of wakefulness decreased from pre- to post exposure in all subjects, regardless of vibration exposure. The objective wakefulness levels of AAT were reduced at the post-exposure test in all subjects. In the case with exposure to whole-body vibration was a significant difference from the case without exposure to whole-body vibration. It is suggested that a short-term exposure to whole-body vibration may cause a reduction of wakefulness level.

Brief posturographic test as an indicator of fatigue

The purpose of the present paper was to analyze the efficiency of an abbreviated, albeit objective posturographic test as an indicator of fatigue. Posturography was measured in 10 healthy adults (age 18-33 years, male/female 7/3). Baseline posturographic measurements were taken for each subject. Later, a shorter (3-min) posturographic test was administered 12 times during 25 h of sleep deprivation. This was correlated with subjective assessment of fatigue using a questionnaire and cognitive performance assessed with a reaction time test (Psychomotor Vigilance Test). Although showing significant individual differences, the score of the abbreviated posturographic examination, normalized to each subject's baseline performance ('fatigue index') had a pronounced circadian pattern with a peak of instability in the early morning hours. Fatigue index was highly correlated with the cognitive test (r=0.80-0.90). A substantial, albeit weaker correlation was found between the fatigue index and the subjective fatigue scores (r=0.59-0.75). Fourier spectral analysis showed that low median sway (0.10-0.50 Hz), considered to be an expression of vestibular control, was most affected by fatigue. The study demonstrates that cognitive deterioration caused by fatigue can be objectively predicted by an abbreviated postural test of <or=3 min. This test is promising to be valid, reliable, and practicable, while being significantly correlated with physiological markers and validated cognitive measures of fatigue obtained by substantially more time-consuming and less convenient methods.

Postural balance changes in on-duty firefighters: effect of gear and long work shifts

OBJECTIVE

The objective of this study was to investigate the impact of long work shifts and turnout gear, including the self-contained breathing apparatus (SCBA) on firefighters' postural stability.

METHODS

Sixteen firefighters were assessed using a portable forceplate system at the fire station. Postural sway parameters were recorded at the beginning of the work shift and repeated until the work shift ended.

RESULTS

Task had the greatest impact on postural stability for all sway parameters. Turnout gear, with and without SCBA, improved postural stability. Postural stability decreased as firefighters spent more time on duty.

CONCLUSIONS

Prolonged work shifts may be an important contributor to the high prevalence of slips and falls among firefighters. In all, the results indicate that many aspects of the firefighters' job may adversely impact their postural stability and potentially increase the risk of falling.

Postural control after a night without sleep

The present study analysed the efficiency of postural control after 12 h of nocturnal forced wakefulness using Romberg's test comprising 1 min of recording with eyes-open and 1 min of recording with eyes-closed, with a 1 min break between the two sessions. Our aim was to see if the decreased postural control efficiency after a sleepless night was unspecific (in both eyes-closed and eyes-open conditions) or selective (in only one of the conditions). A total of 55 students spent a whole night awake at our laboratory and were tested at 22:00 and 08:00 h. In general, the results showed that postural sway increased, performing the recording from eyes-open to eyes-closed condition. The statokinesigram length (SL or efficiency of the postural system) increased after the sleepless night, while in eyes-open condition, the length in function of surface (LFS or accuracy of postural control) and Romberg's index (or contribution of vision to maintain posture) significantly decreased. This could indicate that after a night without sleep, there is a slower elaboration of visual inputs in the postural control process. On the basis of these results, the effects of sleep deprivation on cognitive performance were considered from a neuropsychological point of view.

Effects of Mixed Organic Solvents on Neuromotor Functions among Workers in Buddhist Altar Manufacturing Factories

To clarify the neuromotor effects of long-term exposure to mixed organic solvents, postural sway and tremor were measured in 62 solvent workers of four Buddhist altar manufacturing factories who had worked for 1-46 (mean 12) yr. By using the passive gas sampler, 8-h time-weighted average concentrations in the workers were estimated to be 0.02-8.7 ppm for toluene, 0.02-7.7 ppm for xylene, 0.02-5.5 ppm for styrene and 0.02-40.5 ppm for n-hexane. Sagittal sway and sway area of the posturography with eyes closed were significantly larger in the solvent workers than in 35 age-matched controls (p<0.05), and there was a significant difference in Romberg quotient of sagittal sway between the two groups (p<0.05). Also, tremor intensities at 1.0-5.9 Hz, 6.0-9.9 Hz and 10.0-13.9 Hz with the right hand, and at 6.0-9.9 Hz with the left hand were significantly stronger in the solvent workers than in the controls. Among the solvent workers, transversal and sagittal sways with eyes open and tremor intensity at 10.0-13.9 Hz were significantly related to toluene exposure (p<0.05), which may have been due to the acute effects of such solvents. These findings suggest that long-term exposure to mixed organic solvents may impair neuromotor functions as measured by postural sway and tremor.