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Biomedical subjects

J A Horne

Publications and source records attributed to J A Horne.

At least 19 recordsLinked to original sources
PubMed2006

A high sugar content, low caffeine drink does not alleviate sleepiness but may worsen it.

Although the ingestion of high levels of glucose might have a short acting alerting effect, there is evidence of an ensuing enhancement of sleepiness in people already sleepy. Some 'energy drinks' contain large quantity of sugars. We compared 250 ml of a well known 'energy drink' (42 g sugars, containing a low [30 mg] level of caffeine for 'flavouring') with a nil sugar nil caffeine, similar tasting control. These were given a week apart, in a repeated measures, double blind, balanced design, to 10 participants sleep restricted to 5 h the prior night. They had a light lunch, consumed a drink at 13:50 h, and 10 min later underwent 3 x 30 min consecutive periods at a reaction time (RT) task (the Psychomotor Vigilance Test), separated by 3 min breaks when self-ratings of sleepiness were made. The energy drink did not counteract sleepiness, and led to slower RTs and more lapses during the final 30 min session, around 80 min after consumption.

Adolescent↗
PubMed2004

Alcohol continues to affect sleepiness related driving impairment, when breath alcohol levels have fallen to near-zero.

Epidemiological findings point to very low blood alcohol levels heightening the risk of sleep-related fatal road crashes. This was further assessed using a full sized interactive car simulator. Twenty, sleep restricted, healthy young men underwent a 2 h simulated afternoon monotonous drive, having previously consumed nil alcohol or 3 units >90 min previously, and having near-zero breath alcohol (BrACs) at the start of the drive. In a repeated measures, double-blind, balanced design, driving performance, subjective sleepiness and EEG were monitored throughout. Compared with nil alcohol, the alcohol condition initially increased sleepiness-related driving impairment. However, this was not mirrored by subjective sleepiness or EEG. An unexpected reversal (i.e. improvement) in driving impairment occurred with the alcohol group, in the second hour of the drive. This was supported by a trend for improved subjective alertness. Alcohol continued to interact with sleepiness-related driving impairment after BrACs had reached zero. However, a lack of subjective perception of increased sleepiness, at this time, further points to the dangerous combination of even modest alcohol intake and sleepiness, and confirms the road crash findings. BrACs are a poor guide to driver impairment.

Adult↗
PubMed2004

Screening for hepatitis C virus in the Dartmoor prison population: an observational study.

BACKGROUND: Prisons are a potential setting for hepatitis C screening. This study describes prisoner flows through such screening for all prisoners entering Dartmoor prison between 1 January 1998 and 30 June 2001. METHODS: We identified numbers at each step of the screening pathway, from screening to result, referral, biopsy and outcome. We describe the proportions of those screened who were seropositive; seropositives who were confirmed virus-positive; virus-positive cases attending for biopsy; and virus-positive cases eligible for treatment. RESULTS: Of 3034 entries into Dartmoor, 12 per cent were screened, with 16 per cent of these seropositive. Seventynine per cent of seropositive prisoners with a polymerase chain reaction result were confirmed virus-positive, and 27 per cent of these prisoners had a biopsy. Two prisoners were eligible for treatment. CONCLUSIONS: Screening uptake is low. Attrition rates are high, especially at the referral interface between the prison and specialist care. Finally, the yield of individuals eligible for treatment is low, at 7/1000 tested.

Cohort Studies↗
PubMed2003

Driving impairment due to sleepiness is exacerbated by low alcohol intake.

AIMS: To assess whether low blood alcohol concentrations (BACs), at around half the UK legal driving limit, and undetectable by police roadside breathalysers, further impair driving already affected by sleepiness, particularly in young men, who are the most "at risk" group of drivers for having sleep related crashes. METHODS: Twelve healthy young men drove for two hours in the afternoon, in an instrumented car on a simulated motorway. In a repeated measures, counterbalanced design, they were given alcohol or placebo under conditions of normal sleep or prior sleep restriction. Measurements were: driving impairment (lane drifting), subjective sleepiness, and EEG measures of sleepiness. RESULTS: Whereas sleep restriction and alcohol each caused a significant deterioration in all indices, the combined alcohol and sleep restriction further and significantly worsened lane drifting (which typifies sleep related crashes). This combined effect was also reflected to a significant extent in the EEG, but not with subjective sleepiness. That is, alcohol did not significantly increase subjective sleepiness in combination with sleep loss when compared with sleep loss alone. CONCLUSIONS: Modest, and apparently "safe" levels of alcohol intake exacerbate driving impairment due to sleepiness. The sleepy drivers seemed not to have realised that alcohol had increased their sleepiness to an extent that was clearly reflected by a greater driving impairment and in the EEG.

Accidents, Traffic↗
PubMed2002

Efficacy of a 'functional energy drink' in counteracting driver sleepiness.

Driver sleepiness is a major cause of serious road crashes. Coffee is often used as an effective countermeasure to driver sleepiness. However, the caffeine levels in coffee are variable, whereas certain proprietary "functional energy drinks" (FEDs) contain known levels of caffeine (and other ingredients). We investigated the effectiveness of a well-known FED in reducing sleepiness in drivers. Twelve healthy young adults drove an instrumented car simulator between 14:00 and 17:00 h. Their sleepiness was enhanced by sleep restriction to 5 h the night before. Following a pretreatment 30-min drive and at the beginning of a 30-min break, participants were given double-blind 250-ml FED (containing sucrose, glucose, 80-mg caffeine, taurine, glucuronolactone and vitamins) vs. a control drink with the same volume and same taste but without caffeine, taurine and glucuronolactone. Two hours of continuous driving ensued. Lane drifting, subjective sleepiness and the electroencephalogram (EEG) were monitored throughout. Compared with the control, the FED significantly reduced sleep-related driving incidents and subjective sleepiness for the first 90 min of the drive. There was a trend for the EEG to reflect less sleepiness during this period. It was concluded that the FED is beneficial in reducing sleepiness and sleep-related driving incidents under conditions of afternoon monotonous driving following sleep restriction the night before.

Adult↗
PubMed2001

Driver sleepiness--evaluation of reaction time measurement as a secondary task.

The application of reaction time (RT) as a secondary task to determine sleepiness in drivers is of increasing interest, but is a problematic area. We assessed the extent to which RT reflected this sleepiness, and/or otherwise affected driving behaviour in sleep restricted, moderately sleepy people. They drove a real-car interactive simulator for two, two hour afternoon monotonous drives, with and without RT (counterbalanced). Simple auditory RT was used, with a semi-random inter-stimulus interval averaging 21/2 minutes. Lane wandering (driving "incidents"), subjective and EEG measures of sleepiness were obtained. For both conditions all three indices changed significantly during the course of the afternoon circadian "dip". However, this was not reflected in RT, which remained relatively stable. Nevertheless, RT provided more "stimulation" for the sleepy driver, and significantly reduced subjective sleepiness, with a trend for fewer incidents and a more alert EEG. Possible reasons for the disparity in sensitivity between RT and the other measures are discussed. Under this experimental protocol, RT did not provide a useful guide to driver sleepiness; it was merely a mechanism for increasing task load and reducing monotony. The drivers' own insight into their sleepiness had more validity as a tool for assessing sleepiness.

Acoustic Stimulation↗
PubMed2001

Beneficial effects of an "energy drink" given to sleepy drivers.

500 ml of a glucose based "energy" drink versus a control without the active ingredients (caffeine, taurine, glucuronolactone) were given double blind to 11 sleepy participants driving an interactive real-car driving simulator. Lane drifting and a secondary task (reaction time) were measured for two hours post-treatment. The energy drink significantly improved both indices, particularly for the first hour.

Adult↗
PubMed2000

Prefrontal neuropsychological effects of sleep deprivation in young adults--a model for healthy aging?

Neuropsychological testing and brain imaging show that healthy aging leads to a preferential impairment of the prefrontal cortex (PFC). Interestingly, in young adults sleep deprivation (SD) has similar effects. Psychological tasks not so oriented to the PFC are less sensitive both to SD and aging. The PFC is a cortical region working particularly hard during wakefulness, which may make it more vulnerable to "deterioration," whether this is through aging or SD. In these respects SD in young adults may offer a model for aging. No study has directly compared aging with SD. We compared groups comprising (equal sexes): YOUNG (av. 23y), MIDDLE AGED (av. 60y) and OLD (av. 73y). Young were subdivided into SD and non-sleep deprived groups. All participants were carefully screened, were healthy, good sleepers and with a similar educational background. A battery of PFC-oriented, short and straightforward neuropsychological tests was used to compare the effects of 36h of SD in the young group, with findings from the healthy, alert, non-sleep deprived groups. Tests relied on accuracy rather than speed (which took into account the problem of "global slowing" in the older participants), and were administered once (i.e., were novel). Test outcomes were significantly affected by: (1) SD in the young groups, and (2) by age. A non-PFC component of one test was not affected by SD or by age. It was concluded that 36h SD in young adults produces effects on the PFC similar to those found in normal, alert people aged about 60 years. However, it can not be concluded that an aged brain is a sleep-deprived brain.

Adult↗
PubMed2000

REM sleep - by default?

Elements of three old, overlapping theories of REM sleep (REM) function, the Ontogenetic, Homeostatic and Phylogenetic hypotheses, together still provide a plausible framework - that REM (i) is directed towards early cortical development, (ii) "tones up" the sleeping cortex, (iii) can substitute for wakefulness, (iv) has a calming effect. This framework is developed in the light of recent findings. It is argued that the "primitiveness" of REM and its similarity to wakefulness liken it to a default state of "non-wakefulness" or a waking antagonist, anteceding "true" (non-REM) sleep. The "toning up" is reflected by inhibition of motor, sensory and (importantly) emotional systems, together pointing to integrated "flight or fight" activity, that preoccupies/distracts the organism when non-REM is absent and wakefulness unnecessary. Dreaming facilitates this distraction. In rodents, REM can provide stress coping and calming, but REM deprivation procedures incorporating immobility may further enhance stress and confound outcomes. REM "pressure" (e.g. REM rebounds) may be a default from a loss of inhibition of REM by non-REM. REM can be reduced and/or replaced by wakefulness, without adverse effects. REM has little advantage over wakefulness in providing positive cerebral recovery or memory consolidation.

Animals↗
PubMed2000

The impact of sleep deprivation on decision making: a review.

Few sleep deprivation (SD) studies involve realism or high-level decision making, factors relevant to managers, military commanders, and so forth, who are undergoing prolonged work during crises. Instead, research has favored simple tasks sensitive to SD mostly because of their dull monotony. In contrast, complex rule-based, convergent, and logical tasks are unaffected by short-term SD, seemingly because of heightened participant interest and compensatory effort. However, recent findings show that despite this effort, SD still impairs decision making involving the unexpected, innovation, revising plans, competing distraction, and effective communication. Decision-making models developed outside SD provide useful perspectives on these latter effects, as does a neuropsychological explanation of sleep function. SD presents particular difficulties for sleep-deprived decision makers who require these latter skills during emergency situations.

Decision Making↗
PubMed2000

Sleep loss and temporal memory.

Historical evidence suggests that sleep deprivation affects temporal memory, but this has not been studied systematically. We explored the effects of 36 hr of sleep deprivation on a neuropsychological test of temporal memory. To promote optimal performance, the test was short, novel, and interesting, and caffeine was used to reduce "sleepiness". A total of 40 young adults were randomized into four groups: control + caffeine (Cc), control + placebo (Cp), sleep deprived + caffeine (SDc), and sleep deprived + placebo (SDp). Controls slept normally. Caffeine (350 mg) or placebo were given just prior to testing. The task comprised colour photographs of unknown faces and had two components: recognition memory (distinction between previously presented and novel faces), and recency discrimination (temporal memory), when a previously shown face was presented. An interpolated task, self-ordered pointing, acted as a distraction. Caffeine had no effects within control conditions, but significantly reduced subjective sleepiness in SDc. Recognition was unaffected by sleep deprivation, whereas for recency, sleep deprivation groups scored significantly lower than controls. There was no significant improvement of recency with caffeine in the SDc group. Both sleep deprivation groups had poorer insight into their performance with recency. Self-ordered pointing remained unchanged. In conclusion, sleep deprivation impairs temporal memory (i.e. recency) despite other conditions promoting optimal performance.

Adolescent↗
PubMed2000

Early morning driver sleepiness: effectiveness of 200 mg caffeine.

Sleep-related vehicle accidents are prevalent early morning, especially in younger drivers. In two independent studies following a night of either restricted or nil sleep, young experienced drivers drove for 2 hr (0600-0800 h) continuously in an immobile car on an interactive, computer-generated, dull, and monotonous roadway. This exercise followed ingestion (at 0530 h) of 200 mg caffeine (= 2-3 cups coffee) versus placebo, counterbalanced, double blind. Driving incidents (lane drifting), subjective sleepiness, and 4-11 Hz electroencephalogram (EEG) activity were logged. In Study 1 (sleeping 0000-0500 h), caffeine significantly reduced incidents and subjective sleepiness throughout the 2-hr drive, and EEG power for the second 30-min period. In Study 2 (no sleep), sleepiness affected all measures profoundly, and driving was terminated after 1 hr. Nevertheless, caffeine reduced incidents significantly for the first 30 min and subjective sleepiness for the hour. This caffeine dose, feasibly taken via coffee, effectively reduces early morning driver sleepiness for about 30 min following nil sleep, and for around 2 hr after sleep restriction.

Adult↗
PubMed1999

One night of sleep loss impairs innovative thinking and flexible decision making.

Recent findings with clinically oriented neuropsychological tests suggest that one night without sleep causes particular impairment to tasks requiring flexible thinking and the updating of plans in the light of new information. This relatively little investigated field of sleep deprivation research has real-world implications for decision makers having lost a night's sleep. To explore this latter perspective further, we adapted a dynamic and realistic marketing decision making "game" embodying the need for these skills, and whereby such performance could be measured. As the task relied on the comprehension of a large amount of written information, a critical reasoning test was also administered to ascertain whether any failure at the marketing game might lie with information acquisition rather than with failures in decision making. Ten healthy highly motivated and trained participants underwent two counterbalanced 36 h trials, sleep vs no sleep. The critical reasoning task was unaffected by sleep loss, whereas performance at the game significantly deteri orated after 32-36 h of sleep loss, when sleep deprivation led to more rigid thinking, increased perseverative errors, and marked difficulty in appreciating an updated situation. At this point, and despite the sleep-deprived participants' best efforts to do well, their play collapsed, unlike that of the nonsleep-deprived participants. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Falling asleep whilst driving: are drivers aware of prior sleepiness?

Falling asleep at the wheel is a common cause of road accidents, but little is known about the extent to which drivers are aware of their sleepiness prior to such accidents. It is an area with medico-legal implications. To simulate this situation 28 healthy young adult experienced drivers, sleep restricted the night before drove for 2 h in the afternoon in an interactive real-car simulator incorporating a dull and monotonous roadway. Lane drifting, typifying sleepy driving, was subdivided into minor and major incidents, where the latter was indicative of actually falling asleep. A distinction was made between the subjective perceptions of sleepiness and the likelihood of falling asleep which drivers reported separately. Increasing sleepiness was closely associated with an increase in the number of incidents. Major incidents were preceded by self-awareness of sleepiness well beforehand and typically, subjects reached the stage of fighting sleep when these incidents happened. Whilst the perceived likelihood of falling asleep was highly correlated with increasing sleepiness, some subjects failed to appreciate that extreme sleepiness is accompanied by a high likelihood of falling asleep. It was not possible for our subjects to fall asleep at the wheel and have an "accident" without experiencing a sustained period of increasing sleepiness, of which they were quite aware. There is a need to educate at least some drivers that extreme sleepiness is very likely to lead to falling asleep and a high accident risk.

Accidents, Traffic↗
PubMed1998

Sleep loss impairs short and novel language tasks having a prefrontal focus.

Most cognitive tests administered during sleep loss are well rehearsed to remove practice effects. This can introduce tedium and a loss of novelty, which may be the key to the test's subsequent sensitivity to sleep loss, and why it may need only a few minutes administration before sleep loss effects are apparent. There is little evidence to show that any of these tests are actually affected by sleep loss is given de novo, without practice, but using a non-sleep deprived control group. Although the sleep deprivation literature advocates that short, novel and stimulating tests would not be expected to be sensitive to sleep loss, recent sleep loss findings using neuropsychological tests focussing on the prefrontal cortex, indicate that such tests may challenge this maxim. Twenty healthy young adults were randomly assigned to two groups: nil sleep deprivation (control). and 36h continuous sleep deprivation (SD). Two, novel, interesting and short (6 min) language tests, known (by brain imaging) to have predominantly a PFC focus, were given, once, towards the end of SD: (i) the Haylings test--which measures the capacity to inhibit strong associations in favour of novel responses, and (ii) a variant of the word fluency test--innovation in a verb-to-noun association. Subjects were exhorted to do their best. Compared with control subjects both tasks were significantly impaired by SD. As a check on the effects on the Haylings test, a repeat study was undertaken with 30 more subjects randomly divided as before. The outcome was similar. Linguistically, sleep loss appears to interfere with novel responses and the ability to suppress routine answers.

Adolescent↗
PubMed1998

Evaluation "in-car" countermeasures to sleepiness: cold air and radio.

The efficacy of putative "in-car" countermeasures to driver sleepiness is unknown. Sixteen young adult drivers within the normal range for the Epworth Sleepiness Scale (ESS), had their sleep restricted to 5 hours the night before, and drove an interactive car simulator in the afternoon for 2.5 hours, under monotonous conditions. After 30 minutes of driving they were exposed to: (1) cold air to the face (AIR) from the vehicle's air conditioning vents, (2) listening to the vehicle's radio/tape (RADIO) according to subjects' choice, or (3) NIL treatment. The active treatments typified those experienced under real driving conditions. Drifting over lane markings were "incidents." EEGs were recorded and spectrally analyzed in the alpha and theta range. Subjects responded to the Karolinska Sleepiness Scale (KSS) every 200 seconds. Overall, RADIO and AIR had no significant effects on incidents, although there was a trend for RADIO to reduce incidents, particularly during the first 30 minutes, when AIR also had some effect. KSS scores were significantly lower for RADIO for most of the drive, whereas AIR had only transient and non-significant effects. The EEG showed no significant effects of the active treatments. Compared with other countermeasures such as caffeine and a brief nap, which we have previously shown to be more effective (using the same equipment and protocols), AIR and RADIO are at best only temporary expedients to reduce driver sleepiness, perhaps enabling drivers to find a suitable place to stop, take a break and avail themselves of caffeine and a nap.

Accidents, Traffic↗
PubMed1997

Sleep deprivation affects speech.

Historical accounts of sleep loss studies have described changes in the content and patterns of speech, although to date these claims have not been systematically studied. We examined the effects of sleep loss on the spontaneous generation of words during a verbal word fluency task and the articulation of speech during a vocalized reading task. Nine subjects underwent two counterbalanced 36-hour trials involving sleep deprivation (SD) and no sleep deprivation (NSD). After SD, there was a significant deterioration in word generation and a tendency for subjects to become fixated within a semantic category. There was a significant reduction in the subjects' use of appropriate intonation in the voice after SD, with subjects displaying more monotonic or flattened voices. These findings are discussed in light of neuropsychological evidence concerning the functions of sleep in relation to the frontal cortex and in light of the implications for interpersonal communication in the event of sleep loss.

Adult↗