Implementation of 12-hour shifts in a Brazilian petrochemical plant: impact on sleep and alertness

A recent worldwide trend in chemical and petrochemical industries is to extend the duration of shifts. Optimization of the labor force to reduce costs is one reason to increase the length of working time in a shift. Implementation of 12h shifts is a controversial decision for managers and scientists. Literature reviews show alertness is lower during the nighttime hours, and sleep duration is reduced and worse during the daytime. The main objective of this study was to evaluate the impacts of 12h shifts on alertness and sleep. To evaluate the duration and quality of sleep and alertness during work, 22 male shift workers on a continuous rotating schedule at a petrochemical plant completed activity logs and estimated alertness using analog 10-cm scales for 30 consecutive days, three times (at 2h, 6h, and 10h of the shift) every work shift. Statistical tests (analysis of variance [ANOVA] and Tukey) were performed to detect differences between workdays and off days. The shift schedule was 2 days/3 nights/4 off days, followed by 3 days/2 nights/5 off days, followed by 2 days/2 nights/5 off days. Sleep duration varied significantly (p < .001) among the work shifts and off days. Comparing work nights, the shortest mean sleep occurred after the second night (mean = 311.4 minutes, SD = 101.7 minutes), followed by the third night (mean = 335.3 minutes, SD = 151.2 minutes). All but one shift (sleep after the first work night) were significantly different from sleep after the first 2 workdays (p < .002). Tukey tests showed no significant differences in sleep quality between workdays and nights, with the exception of sleep after the third day compared to sleep after night shifts. However, significant differences were detected between off days and work nights (p < .01). ANOVA analysis showed borderline differences among perceived alertness during day shifts (p = .073) and significant differences among the hours of the shifts (p = .0005), especially when comparing the 2nd hour of the first day with the 10th hour of all the day shifts. There were no significant differences in perceived alertness during night work among the first, second, and third nights (p = .573), but there were significant differences comparing the times (2nd, 6th, 10th hour) of the night shifts (p < .001). The evaluation of sleep (duration and quality) and level of alertness have been extensively used in the literature as indicators of possible performance decrements at work. The results of this study show poorer sleep after and significantly decreased alertness during night work. Shifts of 12h are usually implemented for technical and economic reasons. These results point out the necessity of a careful trade-off between the financial and technical gains longer shifts might bring and the possible losses due to incidents or accidents from performance decrements during work.     

Protein-energy malnutrition during pregnancy alters caffeine's effect on brain tissue of neonate rats

We studied whether protein-energy malnutrition changed brain susceptibility to a small dose of caffeine in newborn rats. Since we had demonstrated previously that caffeine intake during lactation increased the brain neuropeptide on newborns, we investigated further the effects of the prenatal administration of caffeine on TRH and cyclo (His-Pro). From day 13 of gestation to delivery day, pregnant rats in one group were fed either a 20% or a 6% protein diet ad libitum, and those in the other group were pair-fed with each protein diet supplemented with caffeine at an effective dose of 2 mg/100 g body weight. Upon delivery, brain weight, brain protein, RNA, DNA and the neuropeptides thyrotropin-releasing hormone (TRH) and cyclo (His-Pro) were measured in the newborn rats. A 6% protein without caffeine diet caused reductions in brain weights and brain protein, RNA and DNA contents, but did not alter brain TRH and cyclo (His-Pro) concentrations in the newborn animals. In the offspring from dams fed a 6% protein diet, caffeine administration significantly elevated brain weights and brain contents of protein, RNA and DNA. In contrast, these values were similar between noncaffeine and caffeine-supplemented animals in a 20% protein diet group. Brain TRH and cyclo (His-Pro) concentrations were not changed by caffeine administration. These data suggest that caffeine augments protein synthesis in the newborn rat brain when malnourished, but that the same dose of caffeine did not affect protein synthesis in brains of newborn rats from normally nourished dams. Therefore, the present findings indicate that the nutritional status of mothers during pregnancy has important implication in the impact of caffeine on their offspring's brains.     

Cognitive Performance during Sustained Wakefulness: A Low Dose of Caffeine Is Equally Effective as Modafinil in Alleviating the Nocturnal Decline

Cognitive performance at night exhibits a substantial drop, typically before dawn. One of the means of dealing with this phenomenon, as well as with the accompanying sleepiness during sustained wakefulness, is the administration of stimulants. The most widely used and well‐documented stimulants are caffeine, amphetamines, and modafinil. Of these, amphetamines are the least recommended, as they may severely affect behavior. Caffeine and modafinil seem to produce relatively milder side effects and usually only at high doses. Previous comparison studies have revealed equal efficacy of both the stimulants in maintaining alertness and performance during sustained wakefulness. However, these studies used relatively high, and thus not completely safe, doses of these drugs (600 mg caffeine and 400 mg modafinil). Therefore, the aim of the present study was to assess the efficacy of a low and medically safe dose of caffeine (200 mg) and modafinil (200 mg) in maintaining cognitive performance during sustained wakefulness. A flight simulation task was chosen for the assessment of the stimulants in a counter‐balanced, within‐subject design under four different conditions: baseline (no drugs), placebo, caffeine (200 mg), and modafinil (200 mg). The equal effectiveness of both drugs in abolishing the nocturnal drop in cognitive performance, as well as of oral temperature and blood pressure, supported the use of low doses of caffeine and modafinil for the maintenance of alertness in healthy subjects during sustained wakefulness.     

Cognitive performance during sustained wakefulness: A low dose of caffeine is equally effective as modafinil in alleviating the nocturnal decline

Cognitive performance at night exhibits a substantial drop, typically before dawn. One of the means of dealing with this phenomenon, as well as with the accompanying sleepiness during sustained wakefulness, is the administration of stimulants. The most widely used and well-documented stimulants are caffeine, amphetamines, and modafinil. Of these, amphetamines are the least recommended, as they may severely affect behavior. Caffeine and modafinil seem to produce relatively milder side effects and usually only at high doses. Previous comparison studies have revealed equal efficacy of both the stimulants in maintaining alertness and performance during sustained wakefulness. However, these studies used relatively high, and thus not completely safe, doses of these drugs (600 mg caffeine and 400 mg modafinil). Therefore, the aim of the present study was to assess the efficacy of a low and medically safe dose of caffeine (200 mg) and modafinil (200 mg) in maintaining cognitive performance during sustained wakefulness. A flight simulation task was chosen for the assessment of the stimulants in a counter-balanced, within-subject design under four different conditions: baseline (no drugs), placebo, caffeine (200 mg), and modafinil (200 mg). The equal effectiveness of both drugs in abolishing the nocturnal drop in cognitive performance, as well as of oral temperature and blood pressure, supported the use of low doses of caffeine and modafinil for the maintenance of alertness in healthy subjects during sustained wakefulness.     

IMPLEMENTATION OF 12-HOUR SHIFTS IN A BRAZILIAN PETROCHEMICAL PLANT: IMPACT ON SLEEP AND ALERTNESS

A recent worldwide trend in chemical and petrochemical industries is to extend the duration of shifts. Optimization of the labor force to reduce costs is one reason to increase the length of working time in a shift. Implementation of 12h shifts is a controversial decision for managers and scientists. Literature reviews show alertness is lower during the nighttime hours, and sleep duration is reduced and worse during the daytime. The main objective of this study was to evaluate the impacts of 12h shifts on alertness and sleep. To evaluate the duration and quality of sleep and alertness during work, 22 male shift workers on a continuous rotating schedule at a petrochemical plant completed activity logs and estimated alertness using analog 10-cm scales for 30 consecutive days, three times (at 2h, 6h, and 10h of the shift) every work shift. Statistical tests (analysis of variance [ANOVA] and Tukey) were performed to detect differences between workdays and off days. The shift schedule was 2 days/3 nights/4 off days, followed by 3 days/2 nights/5 off days, followed by 2 days/2 nights/5 off days. Sleep duration varied significantly (p <. 001) among the work shifts and off days. Comparing work nights, the shortest mean sleep occurred after the second night (mean = 311.4 minutes, SD = 101.7 minutes), followed by the third night (mean = 335.3 minutes, SD = 151.2 minutes). All but one shift (sleep after the first work night) were significantly different from sleep after the first 2 workdays (p <. 002). Tukey tests showed no significant differences in sleep quality between workdays and nights, with the exception of sleep after the third day compared to sleep after night shifts. However, significant differences were detected between off days and work nights (p <. 01). ANOVA analysis showed borderline differences among perceived alertness during day shifts (p =. 073) and significant differences among the hours of theshifts(p =. 0005), especially when comparing the 2nd hour of the first day with the 10th hour of all the day shifts. There were no significant differences in perceived alertness during night work among the first, second, and third nights (p =. 573), but there were significant differences comparing the times (2nd, 6th, 10th hour) of the night shifts (p ≤. 001). The evaluation of sleep (duration and quality) and level of alertness have been extensively used in the literature as indicators of possible performance decrements at work. The results of this study show poorer sleep after and significantly decreased alertness during night work. Shifts of 12h are usually implemented for technical and economic reasons. These results point out the necessity of a careful trade-off between the financial and technical gains longer shifts might bring and the possible losses due to incidents or accidents from performance decrements during work. (Chronobiology International, 17(4), 521–537, 2000)     

Influence of Magnetic Field on Brain Activity During Administration of Caffeine

The aim of the present work is to evaluate the effect of caffeine, the world’s most popular psychoactive drug, on the electric activity of the rat’s brain that exposed to extremely low-frequency magnetic field (ELF-MF), during 15 days. The obtained results showed that administration of caffeine in a group of rats by dose of 10 mg/kg (equivalent to human daily consumption) caused a reduction in the mean power amplitude of electroencephalogram (EEG) trace for almost all frequency bands especially α (8–12 Hz). It was observed that the influence of caffeine was more evident in motor cortex than in visual cortex. While the exposure of another group to ELF-MF of intensity 0.2 mT during the same period caused an enhancement in the mean power amplitude of most EEG frequency bands; this was more observed in the right hemisphere of the brain than that of the left hemisphere. The administration of caffeine while rats were exposed to ELF-MF, led, after 5 days of exposure, to a great increase in the mean power amplitude of α band at all places of recording electrodes. It may be concluded that caffeine administration was more effective in reducing the hazardous of ELF-MF in motor cortex than in visual cortex.     

Effect of psychotropic substances on orienting-exploratory behavior after startling caused by acoustic stimulation

Frightening sound stimulation induced alarm and alertness which resulted in weakening of attention to novel environment and increasing of orienting response to the source of the frightening sound. Defense motivation occurring under these conditions failed to alter with the increase of sound loudness. Tranquilizers (diazepam, chlordiazepoxide, benatyzine), antidepressants (amytriptiline, imipramine) and some neuroleptics (trifluoperazine, haloperidol) in a low doze prevented these disturbances. High doses of pentobarbital, chlorpromazine, as well as trifluoperazine and haloperidol did not prevent the mentioned consequences of emotional excitation.     

Differential effects of acute and chronic treatment with typical and atypical neuroleptics on c-fos mRNA expression in rat forebrain regions using non-radioactive in situ hybridization.

The regional difference in the expression of c-fos mRNA in rat forebrain after either acute or chronic administration of typical (haloperidol and fluphenazine) and atypical neuroleptics (clozapine and (+/-)-sulpiride) was investigated. Rats were injected intraperitoneally with vehicle or neuroleptics daily for 14 days. Twenty-four hours after the last injection, the rats were challenged with vehicle or neuroleptics. C-fos mRNA expression was determined by non-radioactive in situ hybridization. Acute treatment with typical neuroleptics induced a remarkable induction of c-fos mRNA in the dorsolateral striatum, whereas this induction was greatly attenuated by chronic administration. All neuroleptics examined induced c-fos mRNA in the shell region of N. accumbens by acute administration and this expression was still elevated after chronic treatment. Since chronic neuroleptics do not induce tolerance to their antipsychotic activities, our study suggests that the shell region of N. accumbens is an important target site for antipsychotic effects of neuroleptics.     

Gambling when sleep deprived: don't bet on stimulants

Recent evidence suggests that sleep deprivation leads to suboptimal decision-making on the Iowa Gambling Task (IGT), a pattern that appears to be unaffected by moderate doses of caffeine. It is not known whether impaired decision-making could be reversed by higher doses of caffeine or by other stimulant countermeasures, such as dextroamphetamine or modafinil. Fifty-four diurnally active healthy subjects completed alternate versions of the IGT at rested baseline, at 23 and 46?h awake, and following a night of recovery sleep. After 44?h awake, participants received a double-blind dose of caffeine (600?mg), dextroamphetamine (20?mg), modafinil (400?mg), or placebo. At baseline, participants showed a normal pattern of advantageous performance, whereas both sleep-deprived sessions were associated with suboptimal decision-making on the IGT. Following stimulant administration on the second night of sleep deprivation, groups receiving caffeine, dextroamphetamine, or modafinil showed significant reduction in subjective sleepiness and improvement in psychomotor vigilance, but decision-making on the IGT remained impaired for all stimulants and did not differ from placebo. Decision-making returned to normal following recovery sleep. These findings are consistent with prior research showing that sleep deprivation leads to suboptimal decision-making on some types of tasks, particularly those that rely heavily on emotion processing regions of the brain, such as the ventromedial prefrontal cortex. Moreover, the deficits in decision-making were not reversed by commonly used stimulant countermeasures, despite restoration of psychomotor vigilance and alertness. These three stimulants may restore some, but not all, aspects of cognitive functioning during sleep deprivation.     

A Comparison of Blue Light and Caffeine Effects on Cognitive Function and Alertness in Humans

The alerting effects of both caffeine and short wavelength (blue) light have been consistently reported. The ability of blue light to enhance alertness and cognitive function via non-image forming neuropathways have been suggested as a non-pharmacological countermeasure for drowsiness across a range of occupational settings. Here we compare and contrast the alerting and psychomotor effects of 240 mg of caffeine and a 1-h dose of ~40 lx blue light in a non-athletic population. Twenty-one healthy subjects performed a computer-based psychomotor vigilance test before and after each of four randomly assigned trial conditions performed on different days: white light/placebo; white light/240 mg caffeine; blue light/placebo; blue light/240 mg caffeine. The Karolinska Sleepiness Scale was used to assess subjective measures of alertness. Both the caffeine only and blue light only conditions enhanced accuracy in a visual reaction test requiring a decision and an additive effect was observed with respect to the fastest reaction times. However, in a test of executive function, where a distraction was included, caffeine exerted a negative effect on accuracy. Furthermore, the blue light only condition consistently outperformed caffeine when both congruent and incongruent distractions were presented. The visual reactions in the absence of a decision or distraction were also enhanced in the blue light only condition and this effect was most prominent in the blue-eyed participants. Overall, blue light and caffeine demonstrated distinct effects on aspects of psychomotor function and have the potential to positively influence a range of settings where cognitive function and alertness are important. Specifically, despite the widespread use of caffeine in competitive sporting environments, the possible impact of blue light has received no research attention.     

Audiogenic seizure in the mouse according to strain and sex: the effect of the magnesium ration and neuromediators

Mice of the DBA/2/M strain are audio-sensitive only for a short period (5 to 10 days). When this period is over, 100 p. 100 audiogenic seizures can be obtained with experimental magnesium deficiency. When AKR/R, OF1 and C57BL/R mice were deprived of magnesium for 15 or 21 days, they manifested an audiogenic attack only when given amphetamine sulfate, caffeine or isonicotinylhydrazine. If they had been deprived for 43 days, it was no longer necessary to administer these substances. The audiogenic attack could be prevented by correcting the deficiency with magnesium chloride or by preliminary administration of a single dose of various barbiturics, anti-convulsives, tranquillizers or parachlorophenylalanine, but not neuroleptics.     

Promotion of forskolin-induced long-term potentiation of synaptic transmission by caffeine in area CA1 of the rat hippocampus

Caffeine which is present in soft drinks has been shown to increase alertness and allays drowsiness and fatigue. The aim of this study is to investigate whether caffeine could produce a long-term effect on the synaptic transmission using extracellular recording technique in the hippocampal slices. Bath application of caffeine (100 microM) reversibly increased the slope of field excitatory postsynaptic potential (fEPSP). Forskolin (25 microM) by its own did not affect the fEPSP significantly. However, in the presence of caffeine, forskolin induced a long-term potentiation (LTP) of fEPSP. Enprofylline which has been shown to exhibit some actions like caffeine but with a low adenosine antagonistic potency did not affect the normal synaptic transmission or the effect of forskolin at a lower concentration (10 microM). However, when the concentrations were increased to 20 and 50 microM, enprofylline significantly enhanced the fEPSP slope and promoted forskolin-induced LTP. The parallel increase of fEPSP and promotion of LTP observed with enprofylline suggests that adenosine A1 antagonism is the primary mechanism behind caffeine's effect. This hypothesis was further strengthened by the finding that promotion of forskolin-induced LTP was mimicked by the non-xanthine adenosine antagonist 9-chloro-2-(furyl)[1,2,4]triazolo [1,5-c]quinazolin-5-amine (CGS 15943). The promotion of forskolin-induced LTP provides a cellular basis behind caffeine's increase in capacity for sustained intellectual performance.     

The Effects of Caffeine on <Emphasis Type="SmallCaps">l</Emphasis>-Arginine Metabolism in the Brain of Rats

In our study, the short-term effects of caffeine on L- arginine metabolism in the brains of rats were investigated. Caffeine was given orally at two different doses: 30 mg/kg and 100 mg/kg (a high non-toxic dose). Brain tissue arginase activity in rats from the caffeine-treated groups decreased significantly compared with the control group. Malondialdehyde (MDA) levels in the brain tissue and serum of animals in the caffeine groups also decreased significantly. Brain tissue and serum nitric oxide (NO) levels increased significantly after caffeine administration. Tumor necrosis factor-α (TNF-α) levels were also investigated in rat serum, but there was no statistically significant difference between the TNF-α levels of the caffeine-treated rats groups and the control rats. Our study indicates that brain arginase activity decreases after caffeine administration at doses of 30 mg/kg and 100 mg/kg. As a result, we can say that arginine induces production of NO in the organism.     

Effect of acute or chronic administration of caffeine on performance and on catecholamines during maximal cycle ergometer exercise

Seven men were studied during maximal cycle ergometer exercise, to assess the effects of a single or continuous caffeine ingestion on performance and catecholamine secretion. A single blind and randomised procedure was followed with three trials at 100 +/- 5% VO2 max until exhaustion. The first trial was performed after a single administration of 250 mg of caffeine (a). The second and third trials were performed after a treatment of 5 days with 250 mg caffeine per day (continuous = c) and after placebo (p). a and c caffeine administration, 60 min prior to exercise, did not significantly change the time to exhaustion, but increased the plasma levels of both epinephrine (E) and norepinephrine (NE) at exhaustion (p less than 0.05). Single ingestion of caffeine accelerated the elimination of E and NE and increased the maximal blood lactic acid. These data suggest that both single and continuous administration of caffeine do not enhance performance during maximal cycle ergometer exercise, but do increase the exercise response of catecholamine. Only a single administration modifies the blood lactate accumulation.     

The activity of hippocampal neurons during several types of behavior]

The activity of 87 hippocampal units and the EEG (field CAI) were studied in unrestrained rabbits during calm and active alertness and at different stages of sleep. Correlation has been established between the characteristics (mean frequency and the pattern) of unit firing, EEG and the animal's activity. For most of the neurones, fixed values of mean frequency and the discharge pattern corresponded to a definite functional state. With transition from sleep to alertness, 63.6% of the units became active, 29.1% were inhibited, and the rest of the units changed the firing pattern only. The cells which became activated during awakening, showed a reduced firing frequency during a more profound sleep and higher discharge frequency during the paradoxal phase of sleep, while the inhibitory cells revealed reverse dynamics of discharge frequency. In a state of alertness, the most pronounced shifts in firing activity were observed in 33.3% of the nerve cells at orienting investigating behaviour, in 27.1%, during attention reaction, in 22.9% at some kinds of movement, and in 16.7%, in the course of feeding and drinking. A conclusion has been drawn that the role of the hippocampus in achieving different behavioral reactions is probably to a great extent determined by its participation in setting up a level of the brain central tone, specific for each state.     

The effect of phenamine and caffeine on the ability to extrapolate in rats]

Solution of an extrapolation problem was studied on 28 albino rats (Way strain and laboratory population) and 68 hybrids (the first generation) of wild and laboratory rats in experiments with a screen--the search of food after the disappearance of the food stimulus from the animal's sight. Administration of caffeine (20 mg/kg) and d,l-amphetamine (0.1 mg/kg), though not changing the share of correct solutions, diminishes the number of "refusals" to solve it. Increased motor activity and diminished emotionality of the rats due to administration of the drugs, recorded in an open field test, are likely to cause a decrease in the number of refusals. Administration of d,l-amphetamine facilitates the process of conditioning which contributes to the greater number of positive solutions of the repeatedly presented task.     

Comparative study of sulpiride and haloperidol on dopamine turnover in the rat brain

The effects of the neuroleptics, sulpiride and haloperidol, on dopamine (DA) turnover were compared following the acute and chronic administration of these drugs alone or in combination with levodopa or apomorphine. In the acute treatment, the increase in DA metabolites in the striatum and nucleus accumbens was more marked in the haloperidol-treated rats than in the sulpiridetreated rats. Following the additional administration of levodopa, however, the potency of the neuroleptics in elevating DA metabolites was reversed. A low dose of apomorphine induced a marked reduction in the striatal DA metabolite levels by approximately 50%. When rats were pretreated with the neuroleptics, haloperidol was more effective in preventing an apomorphine-induced reduction in DA metabolites. On repeated administration of the neuroleptics, a tolerance occurred in the striatum and nucleus accumbens, but not in the prefrontal cortex. This differential development of tolerance was observed in the different brain regions and with the different drugs administered. These results suggests that the pharmacological mechanism of sulpiride on DA turnover differs from that of haloperidol.     

Seasonal changes in the behavioral effects of neuroleptics on white rats

Summarized results of the experiments (conducted in 1981-1984) demonstrate seasonal rhythms of some behavioural effects (catalepsy and depression of locomotor activity) of haloperidol (0.5 mg/kg) and levomepromazine (5 mg/kg) in white rats. In intact rats neuroleptics were more effective in depressing high than low motor activity. Catalepsy induced by single administration of neuroleptics was more pronounced in spring and autumn months. A certain negative correlation exists between seasonal variations of neuroleptic catalepsy and the speed of monoamine (dopamine and serotonin) metabolism in the brain of intact rats.     

Long-Term Caffeine Inhibits Ehrlich Ascites Carcinoma Cell-Induced Induction of Central GABAergic Activity

Long-term administration (for 22–27 consecutive days) of caffeine (20 mg/kg/day p.o) developed tolerance to this drug by upregulating the central GABAergic activity. Development of Ehrlich ascites carcinoma (EAC) cell induced the whole brain GABAergic activity. But pre-treatment of caffeine and continuation of its treatment in the course of development of EAC cells restored the EAC cell-induced change of GABAergic activity to control values. Thus, it may be concluded that caffeine (adenosine receptor antagonist) suppresses the EAC cell-induced induction of whole brain GABAergic activity in mice.