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Biomedical subjects

P Knauth

Publications and source records attributed to P Knauth.

At least 19 recordsLinked to original sources
PubMed1992

The relation of shift work tolerance to the circadian adjustment.

The amplitude and phasing of circadian rhythms are under discussion as possible predictors of tolerance to night work. In a field study, subjective sleepiness and oral temperature of 147 female nurses were measured at 2-hour intervals during a period with one morning shift and two consecutive night shifts. The nurses also filled out a questionnaire. Two types of tolerance indices were constructed: The "health index" was based on questions referring to general fatigue, gastrointestinal symptoms, and sleep disturbances, and the "sleepiness index" on the actual subjective ratings of sleepiness. According to the health index, the group with good tolerance had a larger circadian amplitude of the oral temperature rhythm on the day of the morning shift than the group with poor tolerance. However, with regard to the sleepiness index, the corresponding difference between the groups with good or poor tolerance was not significant. The data did not confirm the hypothesis that predicts a quick adjustment of the circadian rhythm when the circadian amplitude is small before the change to night work. The contradictory results found in this and in other studies do not yet permit prediction of tolerance to night work.

Adult↗
PubMed1990

The relation of age to the adjustment of the circadian rhythms of oral temperature and sleepiness to shift work.

The relation of age to the adjustment of the circadian rhythms of oral temperature (T0) and sleepiness (S) in shift work was studied. 145 healthy female nurses underwent detailed laboratory and field measurements. Self-rated sleepiness, and oral temperature measured with a special extended-scale mercury thermometer, were recorded at 2 hr intervals during a morning (M) and 2 consecutive night (N) shifts. Sleeping times were registered during the same days. The results were analyzed separately in the age-groups of 22-29, 30-39 and 40-49-year-old subjects. From the morning shift to the second night shift day, the oral temperature and sleepiness acrophases shifted significantly (p less than 0.001) forward in all age groups. The amplitude decreased in the youngest and in the 30-39-year old age groups but not in the oldest age group. During the second night shift day, the acrophases and amplitudes of oral temperature rhythms were significantly different (P less than 0.05) between the groups, but there were no significant differences by age in the change of the circadian rhythms from morning to the second night shift days. The results thus fail to corroborate that physiological adjustment to night work would be influenced by age.

Adult↗
PubMed1989

Daytime napping and its effects on alertness and short-term memory performance in shiftworkers.

Daytime napping and its effects on 145 female shiftworkers were studied by comparing the individual characteristics, alertness, and short-term memory performance of subjects who took or did not take naps. Of the subjects 56% (n = 82) took a nap before a night shift and 21% (n = 30) after a morning shift. After a morning shift, napping was more frequent among evening types and subjects living alone (not married). Before a night shift, daytime napping was not connected to individual characteristics, but the total sleep time of nappers during the preceding night was shorter than that of non-nappers. At 10.00 and at 04.00-08.00, at the end of the night shift, nappers were significantly more alert than subjects who had not taken naps. The length and timing of the daytime nap did not correlate to either alertness or performance during the following night. In a questionnaire, nappers before a night shift had less sleep disturbances than non-nappers.

Adult↗
PubMed1989

Subjective health status of day and shift-working policemen.

To assess the subjective health status of day- and shift-working police officers, a questionnaire-based study was carried out. All the day-workers had previous shift experience. To control the age factor the total population of 2659 shift-working and 1303 day-working police officers was divided into four ten-year age classes. Factor analysis revealed that all the symptoms included in the questionnaire could be grouped into six factors. The prevalence rates of complaints showed that four of these factors (autonomous symptoms, musculo-skeletal symptoms, disturbance of appetite and indigestion, respiratory infections) were influenced by the main effects of age and shift work. Across all age classes the age-related changes in prevalence rates were strengthened by shift-work. In the other two factors (nervous symptoms, gastro-intestinal symptoms) an additional interaction effect could be observed. While the prevalence rates of the day-workers increased with age, those of the shift-workers decreased in the oldest age class. This drop of prevalence rates may be attributed to the influence of selection processes.

Adult↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. III. Rhythms in physiological functions.

Oral and rectal temperature, urinary excretion of adrenaline and noradrenaline, and heart rate were measured in 28 watchkeepers working a "4-on/8-off" routine, and in 25 dayworkers, on board ships. Readings of oral temperature were taken over 4-hourly periods of up to two weeks; the rectal temperature, urine, and heart rate data were collected on selected days within these periods. Analysis of watchkeepers' temperatures and unconjugated catecholamine excretions showed slight signs of an interactive adaptation to time of day and hours of work, but it was clear that full phase adjustment of the circadian rhythms to shifted hours of work did not occur. The "split" pattern of sleep imposed by the watch system may be a major factor in preventing complete adaptation of physiological rhythms to shift work in the shipboard situation; this problem could be overcome by devising a system that allows sleep to be taken in a single uninterrupted block each day.

Body Temperature↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. V. Effects of time zone crossings.

Daily diary records of sleep and activity, and 4-h measurements of body temperature, performance and subjective alertness were collected on board ship from 15 watchkeepers on the 4-on/8-off system, and from 28 dayworkers, on both westward and eastward transatlantic voyages. The data from a balanced sample of the subjects were analysed over selected 8-d periods of the voyages where four or five time zones were crossed. During these periods the average amount of daily sleep obtained by dayworkers on the eastward voyage was more than 1 h less than that on the westward voyage, and its quality was rated lower. Watchkeepers' main sleep was also shorter when travelling eastward, but this reduction was partially compensated for by a slightly longer secondary sleep. With the exception of subjective alertness on the eastward voyage, the basic phase of the circadian rhythms in the measured variables adjusted appropriately to the clock changes associated with the time zone crossings. The normal shape of the average daily curves was, however, altered differentially in the two directions of travel; as a result, morning levels of all variables were lower on the eastward voyage than on the westward, but evening levels were higher. These distortions of rhythm waveforms, which probably arose from a combination of endogenous and exogenous factors, add another dimension to the basic problem caused by the effects of circadian rhythms on operational efficiency in the shipboard situation. This problem can only be solved by the development of alternative watchkeeping systems which take full account of these rhythms.

Attention↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. VI. A sea trial of an alternative watchkeeping system for the merchant marine.

A trial of an alternative to the traditional 4-on/8-off watchkeeping system was made on a container ship during a round trip from Europe to the Far East. The three navigating officers on the ship operated the new system, which involved "compressed" working hours with a long unbroken period of rest, during two sections of the voyage, one of which included six stops at ports. Despite unforeseen problems arising mainly from these stops, questionnaire responses concerning the new system were not altogether unfavourable to it, and daily records kept by the officers gave some support to the hypothesis that sleep would be better than under the traditional system. However, a number of difficulties were encountered; these are discussed in relation to the design of future studies of alternative watchkeeping systems.

Circadian Rhythm↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. I. Watchkeeping on board ships: a methodological approach.

The safety of a ship depends substantially on its bridge watchkeepers, whose alertness and efficiency must be maintained at all hours of the day and night. Fatigue, circadian rhythms, and sleep disruption occasioned by the unusual working hours of these personnel may all affect their performance. A methodology for assessing the magnitude of this problem is proposed. The application of this methodology in a large-scale shipboard study of merchant mariners on extended voyages is then described, and details given of the techniques used to measure sleep and activity, and temporal variations in a range of physiological und psychological parameters. A summary of the data collected in the study is provided as a reference point for the reports on the different aspects of the results that follow in subsequent articles.

Body Temperature↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. II. Sleep duration, and subjective ratings of sleep quality.

Sleep length and sleep quality scores were collected on board ships over periods of up to two weeks from 38 watchkeepers working a '4-on/8-off routine' and 29 dayworkers. All watchkeepers exhibited fragmented sleeping patterns, which indicated a lack of adaptation of the sleep/wakefulness cycle to the hours of work. There were only slight differences in total sleep length between watchkeepers and dayworkers, however, both groups did not obtain an adequate amount of sleep. Within the watchkeeping crews the 3rd Officers had by far the shortest sleep length. Concerning sleep quality, daytime sleep was generally given the lowest ratings, whereas sleep starting before midnight was on average evaluated as the best, both by watchkeepers and dayworkers. Watchkeeping personnel do not normally have any "days off" during a voyage so that missed sleep might even amount to a sleep deficit. A solution for this problem could perhaps be a new, stabilized system that allows a single uninterrupted sleep, which is required for full recuperation, to be taken each day.

Circadian Rhythm↗
PubMed1988

Physical fitness and other individual factors relating to the shiftwork tolerance of women.

Maximal oxygen consumption (VO2max), muscle strength (MS) and physical activity were compared to age, shiftwork experience, morningness, personality traits and social factors intervening in the shiftwork tolerance of 128 women. The subjects were nurses and nursing aids working irregular shifts in a hospital. Neuroticism was the most powerful negative factor connected to higher fatigue and various symptoms of the subjects. High VO2max and good MS were, on the other hand, the most important positive factors connected to lower fatigue and musculoskeletal symptoms and better sleep quality of the subjects. In different shifts, fatigue, sleep length and quality were influenced most by morningness. It is concluded that physical fitness is an important individual factor explaining the variations of shiftwork tolerance in women.

Adult↗
PubMed1984

Adjustment of the oral temperature rhythm to a fixed watchkeeping system on board ship.

Oral temperature data were collected from 12 members of the crew of an oil tanker at sea. Most of the personnel examined were engaged on watchkeeping duties on a '4 on, 8 off' fixed-hours system; the remainder included 3 "day-workers". The study commenced after the subjects had been following their particular work schedules continuously for several weeks, thus providing good opportunity for adaptation to them. Observations were made at 4-hourly intervals during waking hours, over a period ranging from 8 to 13 days in individual cases. The form of the mean curves produced by averaging the readings over all days indicated that a reasonable degree of adjustment of the temperature rhythm to the different sleep/wake routines imposed by the work system had occurred. Estimates of rhythm phase and amplitude obtained by "single cosinor" time series analyses of the sequential data supported this impression. However, further investigations are needed to substantiate these findings, and also to determine how long it takes for the rhythm adjustment process to reach completion in inexperienced workers.

Body Temperature↗
PubMed1983

Reduction of nightwork by re-designing of shift-rotas.

The reduction of nightwork is an important preventive measure to limit possible negative effects of night shifts on well-being, health and social life. An example of a gradual reduction of nightwork in a group of transport workers at an airport is presented. After having carefully analysed the real number of persons needed during nighttime for loading and unloading aircrafts the number of shiftworkers who had to work between 02.00 and 06.00 h was reduced in a first step from 104 to 66 and in a second step to 38 persons.

Aircraft↗