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1.
Adolescent habitual caffeine consumption and hemodynamic reactivity during rest, psychosocial stress, and recovery.
James, JE, Baldursdottir, B, Johannsdottir, KR, Valdimarsdottir, HB, Sigfusdottir, ID
Journal of psychosomatic research. 2018;:16-23
Abstract
OBJECTIVE Most adolescents regularly consume caffeine. Whereas observational studies have suggested that coffee may be cardio-protective, pharmacological experimentation with adults shows that caffeine at dietary doses increases blood pressure, thereby implicating regular caffeine consumption as a potential source of harm for cardiovascular health. The present study was in response to the dearth of caffeine research among younger consumers. It was hypothesised that compared to the consumption of little or no caffeine, adolescents who habitually consume caffeine have overall higher blood pressure and increased vascular resistance. METHOD Using a quasi-experimental design, continuous measurements of blood pressure, cardiac output, and total peripheral resistance were taken non-invasively from adolescents (n = 333) aged 14-15 years and 18-19 years who reported "low", "moderate", or "high" levels of caffeine intake. Measurements were conducted when participants generally had negligible or low systematic caffeine levels while at rest, during stress, and during recovery from stress. RESULTS Whereas habitual caffeine consumption did not predict blood pressure level, higher caffeine intake was associated with modestly increased vascular resistance during all phases of the experiment (i.e., at rest, during stress, and during recovery from stress). CONCLUSIONS Present findings are important because they suggest that early exposure to caffeine may lead to persistent increases in vascular resistance, which in turn is an acknowledged risk factor for the development of hypertension. These results highlight the need for further studies of adolescents to determine the robustness of any persistent caffeine-related hemodynamic effects, and the implications such effects could have for long-term cardiovascular health.
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2.
Acute Ingestion of Caffeinated Chewing Gum Improves Repeated Sprint Performance of Team Sport Athletes With Low Habitual Caffeine Consumption.
Evans, M, Tierney, P, Gray, N, Hawe, G, Macken, M, Egan, B
International journal of sport nutrition and exercise metabolism. 2018;(3):221-227
Abstract
The effects of acute ingestion of caffeine on short-duration high-intensity performance are equivocal, while studies of novel modes of delivery and the efficacy of low doses of caffeine are warranted. The aims of the present study were to investigate the effect of acute ingestion of caffeinated chewing gum on repeated sprint performance (RSP) in team sport athletes, and whether habitual caffeine consumption alters the ergogenic effect, if any, on RSP. A total of 18 male team sport athletes undertook four RSP trials using a 40-m maximum shuttle run test, which incorporates 10 × 40-m sprints with 30 s between the start of each sprint. Each participant completed two familiarization sessions, followed by caffeine (CAF; caffeinated chewing gum; 200 mg caffeine) and placebo (PLA; noncaffeinated chewing gum) trials in a randomized, double-blind manner. RSP, assessed by sprint performance decrement (%), did not differ (p = .209; effect size = 0.16; N = 18) between CAF (5.00 ± 2.84%) and PLA (5.43 ± 2.68%). Secondary analysis revealed that low habitual caffeine consumers (<40 mg/day, n = 10) experienced an attenuation of sprint performance decrement during CAF relative to PLA (5.53 ± 3.12% vs. 6.53 ± 2.91%, respectively; p = .049; effect size =0.33); an effect not observed in moderate/high habitual caffeine consumers (>130 mg/day, n = 6; 3.98 ± 2.57% vs. 3.80 ± 1.79%, respectively; p = .684; effect size = 0.08). The data suggest that a low dose of caffeine in the form of caffeinated chewing gum attenuates the sprint performance decrement during RSP by team sport athletes with low, but not moderate-to-high, habitual consumption of caffeine.
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3.
l-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging study.
Kahathuduwa, CN, Dhanasekara, CS, Chin, SH, Davis, T, Weerasinghe, VS, Dassanayake, TL, Binks, M
Nutrition research (New York, N.Y.). 2018;:67-78
Abstract
Oral intake of l-theanine and caffeine supplements is known to be associated with faster stimulus discrimination, possibly via improving attention to stimuli. We hypothesized that l-theanine and caffeine may be bringing about this beneficial effect by increasing attention-related neural resource allocation to target stimuli and decreasing deviation of neural resources to distractors. We used functional magnetic resonance imaging (fMRI) to test this hypothesis. Solutions of 200mg of l-theanine, 160mg of caffeine, their combination, or the vehicle (distilled water; placebo) were administered in a randomized 4-way crossover design to 9 healthy adult men. Sixty minutes after administration, a 20-minute fMRI scan was performed while the subjects performed a visual color stimulus discrimination task. l-Theanine and l-theanine-caffeine combination resulted in faster responses to targets compared with placebo (∆=27.8milliseconds, P=.018 and ∆=26.7milliseconds, P=.037, respectively). l-Theanine was associated with decreased fMRI responses to distractor stimuli in brain regions that regulate visual attention, suggesting that l-theanine may be decreasing neural resource allocation to process distractors, thus allowing to attend to targets more efficiently. l-Theanine-caffeine combination was associated with decreased fMRI responses to target stimuli as compared with distractors in several brain regions that typically show increased activation during mind wandering. Factorial analysis suggested that l-theanine and caffeine seem to have a synergistic action in decreasing mind wandering. Therefore, our hypothesis is that l-theanine and caffeine may be decreasing deviation of attention to distractors (including mind wandering); thus, enhancing attention to target stimuli was confirmed.
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4.
Neurobehavioral Outcomes 11 Years After Neonatal Caffeine Therapy for Apnea of Prematurity.
Mürner-Lavanchy, IM, Doyle, LW, Schmidt, B, Roberts, RS, Asztalos, EV, Costantini, L, Davis, PG, Dewey, D, D'Ilario, J, Grunau, RE, et al
Pediatrics. 2018;(5)
Abstract
BACKGROUND AND OBJECTIVES Caffeine is effective in the treatment of apnea of prematurity. Although caffeine therapy has a benefit on gross motor skills in school-aged children, effects on neurobehavioral outcomes are not fully understood. We aimed to investigate effects of neonatal caffeine therapy in very low birth weight (500-1250 g) infants on neurobehavioral outcomes in 11-year-old participants of the Caffeine for Apnea of Prematurity trial. METHODS Thirteen academic hospitals in Canada, Australia, Great Britain, and Sweden participated in this part of the 11-year follow-up of the double-blind, randomized, placebo-controlled trial. Measures of general intelligence, attention, executive function, visuomotor integration and perception, and behavior were obtained in up to 870 children. The effects of caffeine therapy were assessed by using regression models. RESULTS Neurobehavioral outcomes were generally similar for both the caffeine and placebo group. The caffeine group performed better than the placebo group in fine motor coordination (mean difference [MD] = 2.9; 95% confidence interval [CI]: 0.7 to 5.1; P = .01), visuomotor integration (MD = 1.8; 95% CI: 0.0 to 3.7; P < .05), visual perception (MD = 2.0; 95% CI: 0.3 to 3.8; P = .02), and visuospatial organization (MD = 1.2; 95% CI: 0.4 to 2.0; P = .003). CONCLUSIONS Neonatal caffeine therapy for apnea of prematurity improved visuomotor, visuoperceptual, and visuospatial abilities at age 11 years. General intelligence, attention, and behavior were not adversely affected by caffeine, which highlights the long-term safety of caffeine therapy for apnea of prematurity in very low birth weight neonates.
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5.
Association between obstructive sleep apnea and alcohol, caffeine and tobacco: A meta-analysis.
Taveira, KVM, Kuntze, MM, Berretta, F, de Souza, BDM, Godolfim, LR, Demathe, T, De Luca Canto, G, Porporatti, AL
Journal of oral rehabilitation. 2018;(11):890-902
Abstract
The aim of this systematic review was to answer the focused question, "Is there an association between obstructive sleep apnea (OSA) and alcohol, caffeine or tobacco use?" Five electronic databases (Cinahl, Literatura Latth American and Caribbean, PubMed, Scopus, Web of Science) and 3 grey literature (Google Acadêmico, ProQuest, OpenGrey) were searched, as well as search on reference list of included papers and contacts with study authors. Observational studies were included. The Meta-Analysis of Statistics Assessment and Review Instrument (MAStARI) tool assessed the potential risk of bias (RoB) among the studies, while the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach determined the level of evidence. Meta-Analysis was performed with RevMan 5.3 software. Among 3,442 identified studies, 14 were included. Eleven studies were classified as moderate RoB and 3 as high RoB. Meta-analysis showed OSA has no association with tobacco and presented a positive association with alcohol. The odds ratio for OSA increased almost 1.33 times (95% confidence interval [CI]; 1.10-1.62) for alcohol users. There was insufficient published data to evaluate whether OSA is associated with caffeine. The overall quality of evidence ranged from low to very low. OSA was associated with the use of alcohol, however there is not enough evidence to confirm the association with tobacco or caffeine. Due to the very low GRADE level of evidence, caution should be applied when considering these findings.
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6.
Caffeine: A Potential Protective Agent Against Cognitive Decline in Alzheimer's Disease.
Hussain, A, Tabrez, ES, Mavrych, V, Bolgova, O, Peela, JR
Critical reviews in eukaryotic gene expression. 2018;(1):67-72
Abstract
Over the past few decades, caffeine has been well recognized as a stimulant whose effects can be detected particularly in the central nervous system. A stimulating effect of caffeine has been found useful in treating patients with many neurological disorders, including Alzheimer's disease (AD). AD is reported to be a rapidly increasing public health problem with lack of a remedial treatment. However, the assumed protective effects of caffeine against AD are of huge interest. This study substantiates caffeine's role as a potential prevention agent against AD through several epidemiological studies. More than 75% of available study reports support the opinion that caffeine has a favorable effect against cognitive decline and AD. Moreover, other studies have discussed the effect of caffeine drinking and concluded several positive effects on cognitive functioning. The present study, however, focuses more on the potential mechanisms by which caffeine diminishes effects as well as delays the onset of AD.
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7.
Caffeine Improves Triathlon Performance: A Field Study in Males and Females.
Potgieter, S, Wright, HH, Smith, C
International journal of sport nutrition and exercise metabolism. 2018;(3):228-237
Abstract
The ergogenic effect of caffeine on endurance exercise is commonly accepted. We aimed to elucidate realistically the effect of caffeine on triathlon event performance using a field study design, while allowing investigation into potential mechanisms at play. A double-blind, randomized, crossover field trial was conducted. Twenty-six triathletes (14 males and 12 females; mean ± SD: age = 37.8 ± 10.6 years, habitual caffeine intake = 413 ± 505 mg/day, percentage body fat = 14.5 ± 7.2%, and training/week = 12.8 ± 4.5 hr) participated in this study. Microencapsulated caffeine (6 mg/kg body weight) was supplemented 60 min pretrial. Performance data included time to completion, rating of perceived exertion, and profile of mood states. Blood samples taken before, during, and postrace were analyzed for cortisol, testosterone, and full blood count. Capillary blood lactate concentrations were assessed prerace, during transitions, and 3, 6, 9, 12, and 15 min after triathlons. Caffeine supplementation resulted in a 3.7% reduction in swim time (33.5 ± 7.0 vs. 34.8 ± 8.1 min, p < .05) and a 1.3% reduction in time to completion (149.6 ± 19.8 vs. 151.5 ± 18.6 min, p < .05) for the whole group. Gender differences and individual responses are also presented. Caffeine did not alter the rating of perceived exertion significantly, but better performance after caffeine supplementation suggests a central effect resulting in greater overall exercise intensity at the same rating of perceived exertion. Caffeine supplementation was associated with higher postexercise cortisol levels (665 ± 200 vs. 543 ± 169 nmol/L, p < .0001) and facilitated greater peak blood lactate accumulation (analysis of variance main effect, p < .05). We recommend that triathlon athletes with relatively low habitual caffeine intake may ingest 6 mg/kg body weight caffeine, 45-60 min before the start of Olympic-distance triathlon to improve their performance.
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8.
The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis.
Southward, K, Rutherfurd-Markwick, KJ, Ali, A
Sports medicine (Auckland, N.Z.). 2018;(8):1913-1928
Abstract
BACKGROUND Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise. OBJECTIVES To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance. METHODS A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance. RESULTS Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial. CONCLUSION Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.
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9.
The effects of acute carbohydrate and caffeine feeding strategies on cycling efficiency.
Cole, M, Hopker, JG, Wiles, JD, Coleman, DA
Journal of sports sciences. 2018;(7):817-823
Abstract
To assess the effect of carbohydrate and caffeine on gross efficiency (GE), 14 cyclists (V̇O2max 57.6 ± 6.3 ml.kg-1.min-1) completed 4 × 2-hour tests at a submaximal exercise intensity (60% Maximal Minute Power). Using a randomized, counter-balanced crossover design, participants consumed a standardised diet in the 3-days preceding each test and subsequently ingested either caffeine (CAF), carbohydrate (CHO), caffeine+carbohydrate (CAF+CHO) or water (W) during exercise whilst GE and plasma glucose were assessed at regular intervals (~30 mins). GE progressively decreased in the W condition but, whilst caffeine had no effect, this was significantly attenuated in both trials that involved carbohydrate feedings (W = -1.78 ± 0.31%; CHO = -0.70 ± 0.25%, p = 0.008; CAF+CHO = -0.63 ± 0.27%, p = 0.023; CAF = -1.12 ± 0.24%, p = 0.077). Blood glucose levels were significantly higher in carbohydrate ingestion conditions (CHO = 4.79 ± 0.67 mmol·L-1, p < 0.001; CAF+CHO = 5.05 ± 0.81 mmol·L-1, p < 0.001; CAF = 4.46 ± 0.75 mmol·L-1; W = 4.20 ± 0.53 mmol·L-1). Carbohydrate ingestion has a small but significant effect on exercise-induced reductions in GE, indicating that cyclists' feeding strategy should be carefully monitored prior to and during assessment.
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10.
The impact of genetic polymorphisms on CYP1A2 activity in humans: a systematic review and meta-analysis.
Koonrungsesomboon, N, Khatsri, R, Wongchompoo, P, Teekachunhatean, S
The pharmacogenomics journal. 2018;(6):760-768
Abstract
A large interindividual variation in the activity of cytochrome P450 1A2 (CYP1A2) raises concern about therapeutic failure or toxicity when medical professionals prescribe drugs extensively metabolized by CYP1A2. To date, a number of studies have assessed the association between genetic polymorphisms and CYP1A2 activity; however, there are controversies as to the functional importance of CYP1A2 polymorphisms on the metabolism of CYP1A2 substrates. This systematic review and meta-analysis assessed the effects of genetic polymorphisms on CYP1A2 activity, as measured by caffeine metabolism, in a total of 3570 individual subjects. Higher enzyme activity was observed among those who were homozygous or heterozygous for the -163C>A polymorphism (rs762551), when compared to the wild-type individuals (SMD = 0.40, 95%CI = 0.12-0.68, p = 0.005; SMD = 0.32, 95%CI = 0.11-0.54, p = 0.003, respectively) and this was more pronounced among smokers (SMD = 0.92, 95%CI = 0.27-1.57, p = 0.005; SMD = 0.56, 95%CI = 0.22-0.90, p = 0.001, respectively). For other CYP1A2 polymorphisms, altered caffeine metabolic ratios were not seen. Our results indicate the functional importance of -163C>A polymorphism on CYP1A2 inducibility in humans.