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J Carrier

Publications and source records attributed to J Carrier.

At least 37 records · Page 2Linked to original sources
PubMed2000

Circadian rhythms of performance: new trends.

This brief review is concerned with how human performance efficiency changes as a function of time of day. It presents an overview of some of the research paradigms and conceptual models that have been used to investigate circadian performance rhythms. The influence of homeostatic and circadian processes on performance regulation is discussed. The review also briefly presents recent mathematical models of alertness that have been used to predict cognitive performance. Related topics such as interindividual differences and the postlunch dip are presented.

Affect↗
PubMed1999

Time course of narrow frequency bands in the waking EEG during sleep deprivation.

Electroencephalograms (EEGs) of 14 normal subjects were recorded every 2 h during 38 h constant routines. Adjacent narrow frequency bands (NFB) with similar temporal trends were grouped into frequency clusters. Clusters I (2.00-7.75 Hz) and III (11.00-14.75 Hz) exhibited similar time courses which may reflect both the duration of time awake and a circadian modulation. Cluster II (8.00-10.75 Hz) was characterized by a time course similar to the circadian modulation of core body temperature. Cluster V (18.00-24.75 Hz) was correlated with subjective sleepiness and may reflect the increasing effort made by subjects to perform the task as sleep deprivation lengthened. Various NFB in the waking EEG may reflect different physiological mechanisms underlying variations in vigilance states.

Adult↗
PubMed1999

Patient satisfaction with HIV service provision in NPMS hospitals: the development of a standard satisfaction questionnaire. NPMS Steering Group.

A self-completion satisfaction questionnaire evaluating the standard of care of HIV outpatient services was developed as part of the National Prospective Monitoring System on the Use, Cost and Outcome of HIV Service Provision in English Hospitals (NPMS). The questionnaire was designed in conjunction with service users and health care professionals, and piloted in three London and three non-London HIV clinics. In addition to testing alternative methods of administering the questionnaire, the pilot provided satisfaction scores on a variety of aspects of service provision for participating clinics. The questionnaire was completed by 548 respondents and was most effectively collected using a sealed box in the clinic waiting area. Mean satisfaction scores for the attitude and skills of staff members was 4.7 (95% CI 4.6-4.7) but satisfaction scores were significantly lower for the clinic environment with a mean of 4.1 (95% CI 4.1-4.2). Satisfaction scores did not differ significantly by gender, age, sexual orientation, ethnic group, employment status or severity of symptoms. London respondents were more satisfied with the clinic environment and seeing preferred members of staff than their non-London counterparts, however there were no other differences between clinics. The questionnaire functioned well in practice and provided meaningful and useful information for individual clinics as well as at aggregate level.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Are age differences in sleep due to phase differences in the output of the circadian timing system?

Our aim was to evaluate whether age-related changes in the phase of the output of the circadian timing system (CTS) can explain age differences in habitual bedtime/wake time and in sleep consolidation parameters. Analyses focused on a group of healthy elderly people (older than 70 years) with no sleep problems and with similar subjective sleep quality as a young control group. The 2-week sleep diary data and 24h laboratory temperature recordings were examined for 70 subjects (22 young men [YM], 19 old men [OM], 29 old women [OW]). Polysomnographic (PSG) sleep data recorded during temperature data acquisition were also available for 62 subjects. These analyses made use of our recently developed technique to demask temperature rhythm data. As expected, compared to the young subjects, older subjects showed earlier habitual bedtime and wake time, more disturbed sleep, and a tendency for an earlier minimum of the circadian temperature rhythm. Despite sleep consolidation differences, the groups showed very similar habitual phase-angle differences (interval between the time occurrence of the fitted temperature minimum and habitual wake time). Both elderly and young subjects woke up on average 3 h after the temperature minimum. After controlling for the effects of age group, habitual bedtime and wake time were related to clock time phase of the circadian temperature rhythm, with an earlier phase associated with earlier habitual bedtime and wake time. None of the sleep consolidation parameters were linked to the temperature phase angle. In conclusion, sleep consolidation changes associated with healthy aging do not appear to be related to changes in the phase-angle difference between the output signal from the CTS and sleep.

Adult↗
PubMed1998

Rocuronium is the best non-depolarizing relaxant to prevent succinylcholine fasciculations and myalgia.

PURPOSE: To determine which non-depolarizing relaxant among d-tubocurarine, vecuronium, atracurium, mivacurium and rocuronium prevented muscular fasciculations and myalgia following succinylcholine. METHODS: In this double blind randomized study, 120 female patients scheduled for laparoscopic procedures were studied. They were divided into six groups of 20 according to the non-depolarizing pretreatment used: NaCl 0.9% (control), 0.05 mg.kg-1 d-tubocurarine, 0.01 mg.kg-1 vecuronium, 0.05 mg.kg-1 atracurium, 0.02 mg.kg-1 mivacurium and 0.06 mg.kg-1 rocuronium. Four minutes after the pretreatment, 1.5 mg.kg-1 succinylcholine was injected. Side effects of the pretreatment, the presence and magnitude of fasciculations, the ease of tracheal intubation, myalgia 1, 24 and 48 hr after surgery were observed. A Puritan Bennett Datex 221 NMT Relaxograph monitor was used to evaluate the neuromuscular block. RESULTS: Muscle fasciculations were observed in 19 of the 20 patients in the control group and in 3 of the 20 patients in the rocuronium group, the best of the pretreatments in that aspect. Four patients in the mivacurium group were unable to sustain more than four seconds head-lift after pretreatment (P < 0.05). Tracheal intubation conditions were better and the onset of block was faster and longer after succinylcholine in the control group (P < 0.05). Myalgias were present in 71% of the patients 24 hr postoperatively and the frequency was not different among the groups. CONCLUSION: Among the pretreatments tested, 0.06 mg.kg-1 rocuronium was the best to prevent muscular fasciculations following succinylcholine injection. In the population studied, pretreatment did not prevent postoperative myalgia. Succinylcholine 1.5 mg.kg-1 was more effective without a non-depolarizing pretreatment.

Adult↗
PubMed1998

A parallelism between human body temperature and performance independent of the endogenous circadian pacemaker.

A battery of performance tests involving manual dexterity, serial search, and verbal reasoning was given about seven times per day to 2 healthy young male subjects (22 and 25 years of age) involved in separate forced desynchrony studies, each involving several months of temporal isolation. In these studies, the period lengths (denoted T) of the imposed day lengths (sleep/wake and light/dark cycles) were 25.8 and 26.0 h for the 2 subjects. For each subject, the endogenous circadian pacemaker (ECP) failed to entrain to a period of T and instead free ran at a period length denoted tau (24.2 and 24.5 h). By educing performance rhythms (and rectal temperature rhythms) separately at tau and at T (after three complete beating cycles for the first subject and two complete beating cycles for the second subject), the hypothesis could be tested as to whether performance and temperature were parallel, both when educed at tau (indicating ECP influence) and when educed at T (indicating sleep/wake cycle influences). The hypothesis was consistently confirmed at tau and mostly confirmed at T. For most variables, when educed at T, both performance speed and body temperature showed an inverted V-shaped function, with a peak about 9 to 12 h after waking.

Adult↗
PubMed1997

Daytime sleep propensity after moderate circadian phase shifts induced with bright light exposure.

Moderate circadian phase shifts were induced by 3 days of bright light exposure, without changing the habitual sleep schedule. Daytime sleep propensity was evaluated with multiple sleep latency tests (MSLT) conducted before and after the light treatment. Phase shifts were estimated using the core body temperature rhythm recorded during constant routines. The subjects were divided into three groups according to the timing of the bright light exposure. Morning bright light exposure (Morning group) advanced the circadian phase by about 1.2 hours, evening bright light (Evening group) delayed the circadian phase by 1.6 hours on average; whereas, bright light administered in the afternoon (Afternoon group) did not change the circadian phase. After the light treatment, daytime sleep latencies decreased in the Evening and Afternoon groups, but did not change in the Morning group. Reduced sleep latencies in the Afternoon group probably reflect an increase in the manifest sleep tendency induced by the protocol itself. It is suggested that, in the presence of a high physiological sleep tendency, a moderate circadian phase delay may increase further daytime sleep propensity, whereas a moderate circadian phase advance may help to maintain daytime sleep propensity at a lower level.

Adolescent↗
PubMed1997

Speed of mental processing in the middle of the night.

This study aimed to determine whether human mental processing actually slows down during the night hours, separately from the previously documented microsleeps, lapses in attention, and general slowing of motor responses. Eighteen healthy young adults were studied during 36 hours of constant wakeful bedrest. Every 2 hours, they performed a logical reasoning task. Items phrased in the negative voice took reliably longer to respond to than items phrased in the positive voice, indicating the need for more mental processing in those items. By subtracting "negative" from "positive" reaction times at each time of day, we were able to plot a circadian rhythm in the time taken for this extra mental processing to be done separately from microsleeps, psychomotor slowing, and inattention. The extra mental processing took longer at night and on the day following sleep loss than it did during the day before the sleep loss, suggesting that human mental processing slows down during the night under sleep deprivation.

Adult↗
PubMed1997

Sleep and morningness-eveningness in the 'middle' years of life (20-59 y).

The following four issues were assessed in a group of 110 adults between the age of 20 and 59y: (1) the effect of age (regarded as a continuous variable) on polysomnographic sleep characteristics, habitual sleep-diary patterns, and subjective sleep quality; (2) the effects of age on morningness-eveningness; (3) the effects of morningness-eveningness on sleep, after controlling for the effects of age; and (4) the role of morningness-eveningness as a mediator of the age and sleep relationship. Increasing age was related to earlier habitual waketime, earlier bedtime, less time in bed and better mood and alertness at waketime. In the laboratory, increasing age was associated with less time asleep, increased number of awakenings, decreased sleep efficiency, lower percentages of slow-wave sleep (SWS) and rapid eye movement (REM) sleep, higher percentages of Stage 1 and 2, shorter REM latency and reduced REM activity and density. Increasing age was also associated with higher morningness scores. After controlling for the effects of age, morningness was associated with earlier waketime, earlier bedtime, less time in bed, better alertness at waketime, less time spent asleep, more wake in the last 2 h of sleep, decreased REM activity, less stage REM (min and percentage), more Stage 1 (min and percentage) and fewer minutes of Stage 2. For one set of variables (night time in bed, waketime, total sleep time, wake in the last 2 h of sleep and minutes of REM and REM activity), morningness-eveningness accounted for about half of the relationship between age and sleep. For another set of variables (bedtime, alertness at waketime, percentages of REM and Stage 1), morningness-eveningness accounted for the entire relationship between age and sleep. In conclusion, age and morningness were both important predictors of the habitual sleep patterns and polysomnographic sleep characteristics of people in the middle years of life (20-59 y).

Adult↗
PubMed1997

Estimating the endogenous circadian temperature rhythm without keeping people awake.

This study was concerned with estimating endogenous temperature rhythms without imposing sleep deprivation. The aim of Experiment 1 was to quantify the masking effect on the circadian temperature rhythm in a group of 18 healthy young subjects (8 women and 10 men, ages 19-29 years). Temperature data collected under a 36-h wakeful bed rest protocol were used as a marker of the endogenous component of the rhythm ("unmasked rhythm"), and temperature data collected under 24 h of a normal nycthemeral routine (immediately before the bed rest protocol) were used as the "masked" rhythm. An algorithm to "demask" the temperature data collected under the nycthemeral condition was then developed, based on the differences observed between the temperature data collected under wakeful bed rest and nycthemeral conditions. The consistency of the demasking technique was tested in Experiment 2, using the same parameters on a group of 19 healthy elderly subjects (8 women and 11 men, ages 78-88 years) who also had experienced both nycthemeral and wakeful bed rest conditions. The demasking technique was evaluated both by comparing nycthemeral, demasked, and unmasked temperature rhythms themselves and by comparing individual estimates of circadian phase and amplitude that had been gleaned from them. In comparison to the unmasked condition, the nycthemeral condition showed lower mean nighttime temperature, earlier mean phase estimates, and higher mean amplitude estimates in both young and elderly subjects. Following application of the demasking procedure to the nycthemeral temperature data, mean demasked temperature curves were closely comparable to mean unmasked temperature curves in both young and elderly subjects. Phase and amplitude estimates derived from the demasked temperature data also were highly comparable to those in the unmasked conditions. Thus, this demasking procedure appears to be a useful tool in estimating the endogenous temperature rhythm and appears to work equally well for young and elderly subjects.

Adult↗
PubMed1997

Differences over the life span in daily life-style regularity.

A diary-based instrument-the Social Rhythm Metric (SRM)-was used to assess the level of stability of daily social and behavioral rhythms in a group of 239 healthy subjects (112 male, 127 female) ranging in age from 20 to 89 years. Each subject completed the instrument for two consecutive weeks, which were averaged to yield one measure (SRM score) of life-style regularity [range 0 (least regular) to 7 (most regular)] and another of activity level index (ALI), corresponding to the number of (diary listed) activities done per week (max. = 119). SRM score increased reliably with age group at an average rate of 0.018 units per year. ALI showed an "inverted U"-shaped function with a maximum at about 50 years. SRM changes appeared not to be related to demographic differences between the age groups, although ALI differences may have been so related. No main effects or interactions were found with gender. Life-style regularity appears to increase over the life span in response to both biological and psychosocial changes and may represent an adaptation to age-related changes in the circadian system's sensitivity to entraining agents. Regular behavioral rhythms may be conducive to continued good health and well-being.

Activities of Daily Living↗
PubMed1996

Body temperature and the return of slow wave activity in extended sleep.

The time courses of slow wave sleep (SWS) and EEG slow wave activity (SWA) were examined in relation to core body temperature (CBT) during extended sleep periods of 15 h. Ten subjects (4 male, 6 female; aged 18-29 years) slept in the laboratory for 3 consecutive nights (2 of 8 h, and the last of 15 h). Bedtime was as close as possible to subjects' habitual bedtimes, but was always between 23.00 h and 1.00 h, and was the same on all nights. Standard polysomnographic measures as well as rectal temperature were collected continuously each night. Using 3 h blocks, SWS and SWA declined with time asleep, then showed a significant increase in the final 3 h. Using a more specific measure with 15 min means, 8 of the 10 subjects showed SWA returns late in sleep, that were not related to preceding amounts of waking after sleep onset (WASO), rapid eye movement sleep (REMS), or WASO+REMS. The timing and magnitude of the SWA return was significantly associated with the phase of CBT as indexed by delay from sleep onset to CBT minimum. The findings are consistent with a 12 h rhythm of SWS and SWA that is related to the phase of the CBT rhythm, with the minor pole of SWS/SWA occurring independently of WASO and/or REMS.

Adolescent↗
PubMed1996

Inducing a 6-hour phase advance in the elderly: effects on sleep and temperature rhythms.

The aim of this experiment was to study the effects on sleep and temperature rhythms of a 6-hour (h) phase advance of the sleep/wake cycle in healthy elderly subjects. Twenty-five subjects (77-91 y.o.) lived in a time-isolation apartment on an experimenter-controlled routine for 15 days. The experiment started with five baseline days. The wake time on the 6th night was phase advanced by 6-h and the routine for the remaining nine days was held constant to the new phase position. After the phase shift, temperature circadian rhythms showed rapid phase adjustment leading to a small (1.1 h) phase angle disturbance. Sleep efficiency decreased and showed little evidence of recovery back to baseline following the phase shift. The amount of wakefulness in the first two hours of sleep increased after the phase shift while no effect was found for the amount of wakefulness in the last two hours of sleep. The 6-h phase shift did not change the percentages of REM and SWS. Early night sleep propensity appeared to be very sensitive to a small phase angle disturbance of the circadian oscillator in this healthy elderly sample. The phase angle disturbance induced in this study did not seem to be large enough to have a systematic effect on sleep propensity at the end of the night or on REM sleep parameters, suggesting that these variables are less sensitive to an altered phase relationship with the circadian oscillator than early night sleep propensity. These results indicate that there might be a variable phase tolerance for different sleep parameters in older subjects.

Aged↗
PubMed1996

Amplitude reduction of the circadian temperature and sleep rhythms in the elderly.

This study examined the relationship between circadian temperature rhythm amplitude reduction and sleep consolidation parameters in a group of healthy elders experiencing a 6-h phase advance in routine. Twenty-five healthy old people (15 women, 10 men, 77-91 years old) lived in a time-isolation apartment. Throughout the study, subjects were instructed when to go to bed, get up, and take meals. The experiment started with 5 baseline days during which subjects were kept to a daily routine corresponding to their habitual sleep-wake cycle. The wake time of the 6th night was phase-advanced by 6 h and the routine for the remainder of the experiment was held constant at the new earlier phase position. Rectal temperature was recorded continuously and all sleep episodes recorded polygraphically. Time series of temperature data for each subject were analyzed by complex demodulation (CD). Five of the subjects were excluded from analysis because the percentage of variance accounted for by the remodulate was less than 55% for the postshift days and one subject was excluded because he showed an average sleep efficiency of less than 55% during baseline. In the remaining 19 subjects, the phase shift produced a large decrease of the mean amplitude of the temperature circadian rhythm (from 0.45 degree C to 0.25 degree C). During the first 3 nights following the phase shift, sleep efficiency was decreased and amount of wakefulness in the first half of the night (WFirst) was increased. No effect was found for the amount of wake in the second half of the night (WSecond). The change in amplitude of the temperature rhythm was significantly correlated with change in sleep efficiency (r = 0.5; p = 0.03) and with change in WFirst (r = -0.7; p < 0.001). There was no correlation between change in the amplitude of the temperature rhythm and WSecond. These results suggest that in older subjects, amplitude of the output of the circadian oscillator might indeed be involved in the sleep consolidation process but, in the first, rather than the second half of the night.

Aged↗
PubMed1995

Sleep propensity and sleep architecture after bright light exposure at three different times of day.

The aim of this work was to study the effects of bright light-induced circadian phase shifts on sleep propensity and sleep architecture while the timing of the sleep/wake cycle is kept constant. Twenty-three normal subjects underwent an 11-day study including: (i) baseline sleep and vigilance evaluation; (ii) baseline evaluation of the circadian temperature rhythm with a 40-h constant routine; (iii) five hours of bright light exposure on each of three days; (iv) post-treatment sleep and vigilance evaluation; (v) post-treatment circadian rhythm evaluation with a second 40-h constant routine. Subjects were divided into three groups: eight subjects were exposed to bright light in the morning ('Morning group'), eight subjects were exposed in the evening ('Evening group'), and seven subjects were exposed in the afternoon ('Afternoon group'). After light exposure, the Morning group showed an advance of 1.23 h in the phase of the temperature rhythm, the Evening group showed a delay of 1.62 h, and the Afternoon group showed a non-significant advance of 0.5 h. In support of expectations, early-night sleep propensity was decreased by evening bright light, was increased in almost all subjects exposed to morning bright light, and was not changed by afternoon bright light exposure. The phase shift created by bright light exposure did not seem to be large enough to have a systematic effect on sleep consolidation or on REM sleep parameters in any of the three groups, suggesting that these variables are less sensitive to alterations in phase of the circadian oscillator than early-night sleep propensity.

Journal Article↗