Biomedical subjects

Ulf Landström

Publications and source records attributed to Ulf Landström.

9 recordsLinked to original sources

PubMed2005

Electroencephalography and subjective ratings of sleep deprivation.

BACKGROUND AND PURPOSE: Sleep-related vehicle accidents account for many injuries and fatalities each year on monotonous motorways and roads. To effectively prevent such incidents requires greater knowledge of the mechanisms and development of the effects of sleep deprivation. Ten volunteers participated in a laboratory study aimed to analyze the way changes in wakefulness were described in terms of EEG changes and subjective ratings. PATIENTS AND METHODS: For each subject, the study consisted of four testing sessions that varied in length on different days: one session each of 60, 90, and 120 min when sleep-deprived, and one session of 120 min when rested. Changes in wakefulness were analyzed using electroencephalographic recordings and ratings on two different scales, the Karolinska Sleepiness Scale (KSS) and the Category-Ratio Scale (CR-10). RESULTS: The results indicate quite conclusively that significant changes in the perception of sleepiness occur during the first 60-90 min of sedentary, monotonous work. Beyond this time period, subjective and physiological changes remained constant throughout the rest of the 120-min period. CONCLUSION: In general, the subjective rating scales highly and significantly correlated with theta activity in both tired and rested states and with alpha activity in the rested state. Similar results were seen using both subjective rating scales.

Adult↗

PubMed2005

Heart rate variability during sedentary work and sleep in normal and sleep-deprived states.

The possibility of using heart rate variability (HRV) as an indicator of sleepiness was investigated by analysing heart rate (HR) activity and electroencephalography (EEG) recordings from 10 individuals who performed a monotonous attention task for 120 min in both sleep-deprived and rested states. In both conditions, measurements were collected during 60 min of sleep immediately following a 120 min of non-sleep (awake phase). Although HR decreased significantly in both the rested and the sleep-deprived states during the awake phase, HR significantly changed sooner when subjects were sleep-deprived than when they were rested. No significant changes in HRV were found during the awake phase; however, HRV correlated significantly with alpha and theta power densities when rested but not when sleep-deprived. During the sleep phase, the total HRV and very low and low frequency HRV components significantly decreased approximately 40 min after sleeping in the sleep-deprived condition. These HRV components were also significantly and negatively correlated with delta power densities. HRV does not seem to be a viable indicator of sleepiness; however, HRV may be useful for determining sleep stages.

Adult↗

PubMed2004

Missing a meal: effects on alertness during sedentary work.

The purpose of this investigation was to evaluate the acute effects of missing a meal on alertness. The participants were ten university students between 20-29 years old, five females and five males. Participants were chosen on the basis of their good sleep and eating practices. Measurements were collected during an eight hour period starting at 8.00 AM on four separate days. During the test period, participants carried out their normal study activities while on separate days receiving either just breakfast, just lunch, both lunch and breakfast, or no meal at all. During the test period, EEG was monitored continuously while subjective ratings of performance and tiredness were collected every half-hour. The results showed that while there were neither physiological nor subjective indications of tiredness which could be attributed to meal consumption, subjective feelings of lack of energy and motivation was significantly more pronounced at the end of the workday when missing a meal or two.

Adult↗

PubMed2004

Effect on truck drivers' alertness of a 30-min. exposure to bright light: a field study.

Reduced alertness is common during night driving. Light treatment may constitute one countermeasure to reduce sleepiness. To test this idea six professional drivers participated in this study in which they self-administered a 30-min. light treatment during a break in the middle of a night drive of about 9 hours. Two experimental conditions were used, including light exposures with a light box and a light visor. There was a control condition. Alertness was measured on a 100-mm visual analogue scale. No significant effect of light was found, but ratings of sleepiness increased significantly through the night drive. The experimental light treatment was not correlated with any increased wakefulness compared to the drivings where no extra light exposures were carried out.

Adult↗

PubMed2003

Sound levels in classrooms and effects on self-reported mood among school children.

The principle of this field study is an investigation of recorded sound levels in 24 classrooms and relations between sound level measures and aspects of children's rated annoyance, task orientation, and inattentiveness. The background sound-exposure levels were distributed within the interval of 33-42 dB(A)eq and the activity sound level exposure ranged between 47-68 dB(A)eq. The recorded levels must be considered as high for work environments where steady concentration and undisturbed communication is essential. Results do not support the hypothesis that lower background-sound level and fewer students per class would improve the sound environment by generating a lower activity noise or the hypothesis that higher sound levels should increase annoyance and inattentiveness as well as deteriorate task orientation ratings.

Acoustics↗

PubMed2003

Bright light as a sleepiness prophylactic: a laboratory study of subjective ratings and EEG.

Sleepiness is a major problem when driving a vehicle and contributes to 15 to 30% of all road accidents. One possible countermeasure may be exposure to light. This study was designed to test whether 30 min. of exposure to a bright light would reduce subjective sleepiness and EEG indicators of sleepiness, such as alpha and theta power density. 10 female and 10 male university students (recruited through advertisements) participated in a laboratory study, consisting of 30 min. of dim light followed by 30 min. of bright light (or red light in the control condition) exposures and then by 30 min. of dim light exposure. In the dim light exposure, the luminance was 20 cd/m2, and the illuminance was about 5 Lux. In the bright exposure, the luminance was 500 cd/m2 and the illuminance about 2000 Lux. In the red light exposure, the luminance was 10 cd/m2 and the illuminance about 30 Lux. The subject sat in a chair with a seating comfort corresponding to that of a driver's seat. Analysis showed that the subjects became subjectively sleepier during the pre-exposure condition, and alpha and theta power density increased in their EEGs. The intervention significantly reduced subjective sleepiness but did not have significant effects on alpha or theta power density. The results suggest that a short (30 min.) exposure to bright light may not be a useful prophylactic against sleepiness for the period following the exposure.

Adult↗

PubMed2002

Postprandial responses of glucose, insulin and triglycerides: influence of the timing of meal intake during night work.

The objective was to study the postprandial responses of glucose, insulin and triglycerides to meal intake at different clock times during night work. Eleven night shift working nurses participated. Identical test meals were ingested at 19:30, 23:30 and 03:30, and contained 440 kcal/1,860 kJ of energy (33 E% fat, 51 E% carbohydrate, 16 E% protein). The food intake was standardized three days before the first test meal. Blood samples were drawn just before the test meals were ingested and thereafter at 30, 60, 90, 120, 180 and 240 minutes. The postprandial responses were estimated as the total area under the curve (AUC) and significance testing was done using repeated measures ANOVA. The highest insulin level was found after meal intake at 23:30, and the lowest after meal intake 03:30. The glucose response showed the same pattern. The insulin response to food intake in night working nurses is more pronounced in the night compared with morning and evening. The results would have implications for metabolic and cardiovascular disorders in night workers.

Adult↗

PubMed2002

Use of temperature variations to combat drivers' drowsiness.

The purpose of the present study was to evaluate the efficiency of temperature variations as a measure against drivers' drowsiness. A system for regulation of the air temperature in the cab was installed in two trucks. Irregular temperature reductions of about 8 degrees C were introduced. The periods between the temperature reductions varied among 5, 6, 7, and 8 min. The periods for the temperature reductions varied between 2, 4, 6, and 8 min. The system was tested with 6 drivers on 54 trips. The system was applied for periods varying between 30 to 300 min. Changes in wakefulness were analysed using subjective ratings by the lorry drivers. The application of the system significantly improved subjectively rated wakefulness. The wakefulness was rated with a questionnaire completed after 10 min. use of a cooling system and at the end of its use. Analysis showed individual differences in the usefulness of the system: 3 of the 6 truck drivers reported positive reactions to the use of the temperature cooling system.

Accidents, Traffic↗

PubMed2000

Annoyance and effects on work from environmental noise at school.

The aim of this study is to investigate how students rate the annoyance and effects of noise in their working environment. 216 students, between the ages 13-15 years, and 12 teachers took part in this study. Sound level measurements were made for 20 minutes in the middle of a lesson for each class. On the measurement occasion the students were seated in a class room working on mathematics. Immediately after the sound level measurement, the students and the teachers filled in a questionnaire. The correlation between sound level and perceived annoyance and rated effect of noise on the students' schoolwork was poor. The correlation between the annoyance and rated effect of noise on the students' schoolwork was significant. Equivalent sound levels during mathematics lessons were 58-69 dB(A). Even though the sound levels were relatively high the students claimed that they were just moderately annoyed. More than 1/3 of the students claimed that the existing sound environment obstructed their work. No difference was found between boys and girls in rated annoyance and rated effect on their work. The younger students were more annoyed than the older ones. The participants claimed that chatter in the class room and scraping sounds from tables and chairs were the most annoying sound sources. The teachers shared this opinion. The concurrency between the students' rating of their annoyance and the teachers' rating of the students annoyance was remarkably low.

Journal Article↗