91 research outputs found
Cerebral blood flow and behavioural effects of caffeine in habitual and non-habitual consumers of caffeine: A near infrared spectroscopy study
Caffeine has been shown to modulate cerebral blood flow, with little evidence of tolerance to these effects following habitual use. However, previous studies have focused on caffeine levels much higher than those found in dietary servings and have compared high caffeine consumers with low consumers rather than 'non-consumers'. The current placebo-controlled double-blind, balanced-crossover study employed near infrared spectroscopy to monitor pre-frontal cerebral-haemodynamics at rest and during completion of tasks that activate the pre-frontal cortex. Twenty healthy young habitual and non-habitual consumers of caffeine received 75mg caffeine or placebo. Caffeine significantly decreased cerebral blood flow but this was subject to a significant interaction with consumption status, with no significant effect being shown in habitual consumers and an exaggerated effect in non-habitual consumers. These findings suggest that caffeine, at levels typically found in a single dietary serving, is able to modulate cerebral blood flow but these effects are subject to tolerance
No effect of n - 3 long-chain polyunsaturated fatty acid (EPA and DHA) supplementation on depressed mood and cognitive function : a randomised controlled trial
Low dietary intakes of the n-3 long-chain PUFA (LCPUFA) EPA and DHA are thought to be associated with increased risk for a variety of adverse outcomes, including some psychiatric disorders. Evidence from observational and intervention studies for a role of n-3 LCPUFA in depression is mixed, with some support for a benefit of EPA and/or DHA in major depressive illness. The present study was a double-blind randomised controlled trial that evaluated the effects of EPA+DHA supplementation (1.5 g/d) on mood and cognitive function in mild to moderately depressed individuals. Of 218 participants who entered the trial, 190 completed the planned 12 weeks intervention. Compliance, confirmed by plasma fatty acid concentrations, was good, but there was no evidence of a difference between supplemented and placebo groups in the primary outcome - namely, the depression subscale of the Depression Anxiety and Stress Scales at 12 weeks. Mean depression score was 8.4 for the EPA+DHA group and 9.6 for the placebo group, with an adjusted difference of - 1.0 (95 % CI - 2.8, 0.8; P = 0.27). Other measures of mood, mental health and cognitive function, including Beck Depression Inventory score and attentional bias toward threat words, were similarly little affected by the intervention. In conclusion, substantially increasing EPA+DHA intake for 3 months was found not to have beneficial or harmful effects on mood in mild to moderate depression. Adding the present result to a meta-analysis of previous relevant randomised controlled trial results confirmed an overall negligible benefit of n-3 LCPUFA supplementation for depressed mood.<br /
Effects of Reapeated Doses of Caffeine on Performance and Alertness: New Data and Secondary Analyses
Rationale The effects of caffeine on mood and performance are well established.
Some authors suggest that caffeine merely reverses effects of caffeine withdrawal
rather than having direct behavioural effects. It has also been suggested that
withdrawal may be removed by a first dose of caffeine and further doses have little
subsequent effect. These issues were examined here.
Objectives The present study aimed to determine whether caffeine withdrawal
influenced mood and performance by comparing regular consumers who had been
withdrawn from caffeine overnight with non-consumers. Following this repeated
caffeine doses were administered to test the claim that repeated dosing has no extra
effect on mood or performance. Secondary analyses of a data collected by Christopher
et al. (2003) were also carried out to examine some alternative explanations of their
results which showed effects of caffeine after a day of normal caffeine consumption.
Methods One hundred and twenty volunteers participated in the study. Regular
caffeine consumption was assessed by questionnaire and this showed that thirty six of
the sample did not regularly consume caffeinated beve rages. Volunteers were
instructed to abstain from caffeine overnight and then completed a baseline session
measuring mood and a range of cognitive functions at 08.00 the next day. Following
this volunteers were given 0, or 1mg/kg caffeine in a milkshake, glucose solution or
water (at 09:00), followed by a second 0 or 1mg/kg caffeine dose (at 09:40) and the
test battery repeated at 10:00.
Results The baseline data showed no effect of overnight caffeine withdrawal on mood
or performance. In contrast, caffeine challenge improved vigilance performance and
prevented decreases in alertness induced by completion of the task battery. The
magnitude of these effects increased as a function of the number of doses of caffeine
given. Secondary analyses of data from Christopher et al. (2003) also confirmed that
effects of caffeine did not depend on length of withdrawal.
Conclusions The present findings show no effect of overnight caffeine withdrawal on
mood and performance. Caffeine challenge did have the predicted effect on alertness
and vigilance, with the size of the effects increasing with caffeine dose. These
findings suggest that the effects of caffeine are not due to reversal of effects of
withdrawal, a view confirmed by secondary analyses of data collected after a day of
normal caffe ine consumption
SARS Surveillance during Emergency Public Health Response, United States, March–July 2003
In response to the emergence of severe acute respiratory syndrome (SARS), the United States established national surveillance using a sensitive case definition incorporating clinical, epidemiologic, and laboratory criteria. Of 1,460 unexplained respiratory illnesses reported by state and local health departments to the Centers for Disease Control and Prevention from March 17 to July 30, 2003, a total of 398 (27%) met clinical and epidemiologic SARS case criteria. Of these, 72 (18%) were probable cases with radiographic evidence of pneumonia. Eight (2%) were laboratory-confirmed SARS-coronavirus (SARS-CoV) infections, 206 (52%) were SARS-CoV negative, and 184 (46%) had undetermined SARS-CoV status because of missing convalescent-phase serum specimens. Thirty-one percent (124/398) of case-patients were hospitalized; none died. Travel was the most common epidemiologic link (329/398, 83%), and mainland China was the affected area most commonly visited. One case of possible household transmission was reported, and no laboratory-confirmed infections occurred among healthcare workers. Successes and limitations of this emergency surveillance can guide preparations for future outbreaks of SARS or respiratory diseases of unknown etiology
The effect of caffeine on working memory load-related brain activation in middle-aged males
Effects of caffeine on reaction time are mediated by attentional rather than motor processes
Background
Caffeine has a well-established effect on reaction times (RTs) but the neurocognitive mechanisms underlying this
are unclear.
Methods
In the present study, 15 female participants performed an oddball task after ingesting caffeine or a placebo, and
electroencephalographic data were obtained. Single-trial P3b latencies locked to the stimulus and to the response were extracted
and mediation models were fitted to the data to test whether caffeine’s effect on RTs was mediated by its effect on either type of
P3b latencies.
Results
Stimulus-locked latencies showed clear evidence of mediation, with approximately a third of the effect of caffeine on RTs
running through the processes measured by stimulus-locked latencies. Caffeine did not affect response-locked latencies, so could
not mediate the effect.
Discussion
These findings are consistent with caffeine’s effect on RTs being a result of its effect on perceptual-attentional
processes, rather than motor processes. The study is the first to apply mediation analysis to single-trial P3b data and this technique
holds promise for mental chronometric studies into the effects of psychopharmacological agents. The R code for performing the
single trial analysis and mediation analysis are included as supplementary materials
A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood
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