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1.
Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis.
Lorenzo Calvo, J, Fei, X, Domínguez, R, Pareja-Galeano, H
Nutrients. 2021;(3)
Abstract
Cognitive functions are essential in any form of exercise. Recently, interest has mounted in addressing the relationship between caffeine intake and cognitive performance during sports practice. This review examines this relationship through a structured search of the databases Medline/PubMed and Web of Science for relevant articles published in English from August 1999 to March 2020. The study followed PRISMA guidelines. Inclusion criteria were defined according to the PICOS model. The identified records reported on randomized cross-over studies in which caffeine intake (as drinks, capsules, energy bars, or gum) was compared to an identical placebo situation. There were no filters on participants' training level, gender, or age. For the systematic review, 13 studies examining the impacts of caffeine on objective measures of cognitive performance or self-reported cognitive performance were selected. Five of these studies were also subjected to meta-analysis. After pooling data in the meta-analysis, the significant impacts of caffeine only emerged on attention, accuracy, and speed. The results of the 13 studies, nevertheless, suggest that the intake of a low/moderate dose of caffeine before and/or during exercise can improve self-reported energy, mood, and cognitive functions, such as attention; it may also improve simple reaction time, choice reaction time, memory, or fatigue, however, this may depend on the research protocols.
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2.
Does Acute Caffeine Supplementation Improve Physical Performance in Female Team-Sport Athletes? Evidence from a Systematic Review and Meta-Analysis.
Gomez-Bruton, A, Marin-Puyalto, J, Muñiz-Pardos, B, Matute-Llorente, A, Del Coso, J, Gomez-Cabello, A, Vicente-Rodriguez, G, Casajus, JA, Lozano-Berges, G
Nutrients. 2021;(10)
Abstract
INTRODUCTION Recent original research and meta-analyses suggest that acute caffeine supplementation improves exercise performance in team-sport athletes (TSA). Nonetheless, most of the studies testing the effects of caffeine on TSA included samples of male athletes, and there is no meta-analysis of the performance-enhancing effects of caffeine on female TSA. The aim of the present study was to synthesize the existing literature regarding the effect of caffeine supplementation on physical performance in adult female TSA. METHODS A search was performed in Pubmed/Medline, SPORTDiscus and Scopus. The search was performed from the inception of indexing until 1 September 2021. Crossover randomized controlled trials (RCT) assessing the effects of oral caffeine intake on several aspects of performance in female TSA were selected. The methodological quality and risk of bias were assessed for individual studies using the Physiotherapy Evidence Database scale (PEDro) and the RoB 2 tool. A random-effects meta-analysis of standardized mean differences (SMD) was performed for several performance variables. RESULTS The search retrieved 18 articles that fulfilled the inclusion/exclusion criteria. Overall, most of the studies were of excellent quality with a low risk of bias. The meta-analysis results showed that caffeine increased performance in specific team-sport skills (SMD: 0.384, 95% confidence interval (CI): 0.077-0.691), countermovement jump (SMD: 0.208, CI: 0.079-0.337), total body impacts (SMD: 0.488; 95% CI: 0.050, 0.927) and handgrip strength (SMD: 0.395, CI: 0.126-0.665). No effects were found on the ratings of perceived exertion, squat jumps, agility, repeated sprint ability or agility tests performed after fatigue. CONCLUSIONS The results of the meta-analysis revealed that acute caffeine intake was effective in increasing some aspects of team-sports performance in women athletes. Hence, caffeine could be considered as a supplementation strategy for female athletes competing in team sports.
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3.
Isolated effects of caffeine and sodium bicarbonate ingestion on performance in the Yo-Yo test: A systematic review and meta-analysis.
Grgic, J, Garofolini, A, Pickering, C, Duncan, MJ, Tinsley, GM, Del Coso, J
Journal of science and medicine in sport. 2020;(1):41-47
Abstract
OBJECTIVES To conduct a systematic review and a meta-analysis of studies exploring the effects of caffeine and/or sodium bicarbonate on performance in the Yo-Yo test. DESIGN Systematic review and meta-analysis. METHODS A total of six databases were searched, and random-effects meta-analyses were performed examining the isolated effects of caffeine and sodium bicarbonate on performance in the Yo-Yo test. RESULTS After reviewing 988 search records, 15 studies were included. For the effects of caffeine on performance in the Yo-Yo test, the meta-analysis indicated a significant favoring of caffeine as compared with the placebo conditions (p=0.022; standardized mean difference [SMD]=0.17; 95% CI: 0.08, 0.32; +7.5%). Subgroup analyses indicated that the effects of caffeine were significant for the level 2 version of the Yo-Yo test, but not level 1. Four out of the five studies that explored the effects of sodium bicarbonate used the level 2 version of the Yo-Yo test. The pooled SMD favored the sodium bicarbonate condition as compared with the placebo/control conditions (p=0.007; SMD: 0.36; 95% CI: 0.10, 0.63; +16.0%). CONCLUSIONS This review demonstrates that isolated ingestion of caffeine and sodium bicarbonate enhances performance in the Yo-Yo test. Given these ergogenic effects, the intake of caffeine and sodium bicarbonate before the Yo-Yo test needs to be standardized (i.e., either restricted or used in the same way before each testing session). Furthermore, the results suggest that individuals competing in sports involving intermittent exercise may consider supplementing with caffeine or sodium bicarbonate for acute improvements in performance.
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4.
The Effect of Caffeine on the Risk and Progression of Parkinson's Disease: A Meta-Analysis.
Hong, CT, Chan, L, Bai, CH
Nutrients. 2020;(6)
Abstract
Coffee and caffeine are speculated to be associated with the reduced risk of Parkinson's disease (PD). The present study aimed to investigate the disease-modifying potential of caffeine on PD, either for healthy people or patients, through a meta-analysis. The electronic databases were searched using terms related to PD and coffee and caffeinated food products. Articles were included only upon fulfillment of clear diagnostic criteria for PD and details regarding their caffeine content. Reference lists of relevant articles were reviewed to identify eligible studies not shortlisted using these terms. In total, the present study enrolled 13 studies, nine were categorized into a healthy cohort and the rest into a PD cohort. The individuals in the healthy cohort with regular caffeine consumption had a significantly lower risk of PD during follow-up evaluation (hazard ratio (HR) = 0.797, 95% CI = 0.748-0.849, p < 0.001). The outcomes of disease progression in PD cohorts included dyskinesia, motor fluctuation, symptom onset, and levodopa initiation. Individuals consuming caffeine presented a significantly lower rate of PD progression (HR = 0.834, 95% CI = 0.707-0.984, p = 0.03). In conclusion, caffeine modified disease risk and progression in PD, among both healthy individuals or those with PD. Potential biological benefits, such as those obtained from adenosine 2A receptor antagonism, may require further investigation for designing new drugs.
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5.
Coffee consumption and risk of bladder cancer: a pooled analysis of 501,604 participants from 12 cohort studies in the BLadder Cancer Epidemiology and Nutritional Determinants (BLEND) international study.
Yu, EYW, Dai, Y, Wesselius, A, van Osch, F, Brinkman, M, van den Brandt, P, Grant, EJ, White, E, Weiderpass, E, Gunter, M, et al
European journal of epidemiology. 2020;(6):523-535
Abstract
Recent epidemiological studies have shown varying associations between coffee consumption and bladder cancer (BC). This research aims to elucidate the association between coffee consumption and BC risk by bringing together worldwide cohort studies on this topic. Coffee consumption in relation to BC risk was examined by pooling individual data from 12 cohort studies, comprising of 2601 cases out of 501,604 participants. Pooled multivariate hazard ratios (HRs), with corresponding 95% confidence intervals (CIs), were obtained using multilevel Weibull regression models. Furthermore, dose-response relationships were examined using generalized least squares regression models. The association between coffee consumption and BC risk showed interaction with sex (P-interaction < 0.001) and smoking (P-interaction = 0.001). Therefore, analyses were stratified by sex and smoking. After adjustment for potential confounders, an increased BC risk was shown for high (> 500 ml/day, equivalent to > 4 cups/day) coffee consumption compared to never consumers among male smokers (current smokers: HR = 1.75, 95% CI 1.27-2.42, P-trend = 0.002; former smokers: HR = 1.44, 95% CI 1.12-1.85, P-trend = 0.001). In addition, dose-response analyses, in male smokers also showed an increased BC risk for coffee consumption of more than 500 ml/day (4 cups/day), with the risk of one cup (125 ml) increment as 1.07 (95% CI 1.06-1.08). This research suggests that positive associations between coffee consumption and BC among male smokers but not never smokers and females. The inconsistent results between sexes and the absence of an association in never smokers indicate that the associations found among male smokers is unlikely to be causal and is possibly caused by residual confounding of smoking.
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6.
Drugs to Prevent Bronchopulmonary Dysplasia: Effect of Baseline Risk on the Number Needed to Treat.
Jensen, EA, Roberts, RS, Schmidt, B
The Journal of pediatrics. 2020;:244-247
Abstract
Infants born very preterm have a variable baseline risk of bronchopulmonary dysplasia (BPD). Using the example of evidence-based drug therapies to prevent BPD, we designed a visual aid that displays the "number needed to treat" with CIs for caffeine, vitamin A, and hydrocortisone over a range of baseline risks.
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7.
Wake up and smell the coffee: caffeine supplementation and exercise performance-an umbrella review of 21 published meta-analyses.
Grgic, J, Grgic, I, Pickering, C, Schoenfeld, BJ, Bishop, DJ, Pedisic, Z
British journal of sports medicine. 2020;(11):681-688
Abstract
OBJECTIVE To systematically review, summarise and appraise findings of published meta-analyses that examined the effects of caffeine on exercise performance. DESIGN Umbrella review. DATA SOURCES Twelve databases. ELIGIBILITY CRITERIA FOR SELECTING STUDIES Meta-analyses that examined the effects of caffeine ingestion on exercise performance. RESULTS Eleven reviews (with a total of 21 meta-analyses) were included, all being of moderate or high methodological quality (assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist). In the meta-analyses, caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping performance and exercise speed. However, not all analyses provided a definite direction for the effect of caffeine when considering the 95% prediction interval. Using the Grading of Recommendations Assessment, Development and Evaluation criteria the quality of evidence was generally categorised as moderate (with some low to very low quality of evidence). Most individual studies included in the published meta-analyses were conducted among young men. SUMMARY/CONCLUSION Synthesis of the currently available meta-analyses suggest that caffeine ingestion improves exercise performance in a broad range of exercise tasks. Ergogenic effects of caffeine on muscle endurance, muscle strength, anaerobic power and aerobic endurance were substantiated by moderate quality of evidence coming from moderate-to-high quality systematic reviews. For other outcomes, we found moderate quality reviews that presented evidence of very low or low quality. It seems that the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise. More primary studies should be conducted among women, middle-aged and older adults to improve the generalisability of these findings.
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8.
Effects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis.
Salinero, JJ, Lara, B, Del Coso, J
Research in sports medicine (Print). 2019;(2):238-256
Abstract
The aim of this investigation was to perform a systematic review and meta-analysis to determine the efficacy of the acute ingestion of caffeine (from 3 to 6 mg/kg) to increase performance on variables related to team sports. A systematic review was performed in scientific databases from January to April 2018. All studies included had cross-over experimental designs comparing caffeine to an identical placebo condition. A meta-analysis was performed using the random effects model and pooled standardized mean differences (Glass's Δ). Thirty-four studies published between 2001 and 2018 were included in the analysis. The meta-analysis revealed that caffeine increased single (Δ;95% confidence intervals = 0.19;0.14-0.25; p < 0.01) and repeated jump height (0.29;0.16-0.42; p < 0.01), single (0.16;0.02-0.30; p = 0.03) and repeated sprint velocity (0.14;0.03-0.25; p = 0.02), and reduced the time to complete agility tests (0.41;0.04-0.77; p = 0.03). During team sport matches, caffeine increased total running distance (0.41;0.20-0.62; p < 0.01), distance covered at sprint velocity (0.36;0.12-0.59; p < 0.01) and the number of sprints (0.44;0.18-0.69; p < 0.01). The acute ingestion of a moderate dose of caffeine had a small but significant positive effect on several aspects related to physical performance in team sports.
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9.
Caffeine, Type of Coffee, and Risk of Ovarian Cancer: A Dose-Response Meta-Analysis of Prospective Studies.
Salari-Moghaddam, A, Milajerdi, A, Surkan, PJ, Larijani, B, Esmaillzadeh, A
The Journal of clinical endocrinology and metabolism. 2019;(11):5349-5359
Abstract
CONTEXT Prospective studies on caffeine and different types of coffee intake in relation to the risk of ovarian cancer have shown conflicting results. OBJECTIVE The aim of the present study was to perform a dose-response meta-analysis of cohort studies on the association between dietary caffeine intake, different types of coffee consumption, and the risk of ovarian cancer. DATA SOURCES PubMed/Medline, ISI Web of Science, Scopus, and EMBASE were searched to identify relevant studies reported until October 2018. STUDY SELECTION Prospective cohort studies that had considered caffeine or different types of coffee as the exposure variable and ovarian cancer as the main outcome variable or as one of the outcome variables were included in our systematic review and meta-analysis. Two of us independently screened 9344 publications. A total of 14 cohort studies were included in the meta-analysis. DATA EXTRACTION Two of us independently extracted the data. Any disagreements were resolved in consultation with the principal investigator. RESULTS Combining 13 effect sizes, we found no substantial association between coffee consumption and risk of ovarian cancer [risk ratio (RR), 1.08; 95% CI, 0.89 to 1.33]. Also, one additional cup daily of coffee consumption was marginally associated with an increased risk of ovarian cancer (RR, 1.02; 95% CI, 0.99 to 1.05; P = 0.21; I2 = 0.0%; Pheterogeneity = 0.68). No statistically significant association was observed between caffeine intake or caffeinated or decaffeinated coffee consumption and the risk of ovarian cancer. CONCLUSIONS We found no statistically significant association between caffeine intake or different types of coffee and the risk of ovarian cancer.
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10.
The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis.
Grgic, J, Pickering, C
Journal of science and medicine in sport. 2019;(3):353-360
Abstract
OBJECTIVES The aims of this paper are threefold: (1) to summarize the research examining the effects of caffeine on isokinetic strength, (2) pool the effects using a meta-analysis, and (3) to explore if there is a muscle group or a velocity specific response to caffeine ingestion. DESIGN Meta-analysis. METHODS PubMed/MEDLINE, Scopus, and SPORTDiscus were searched using relevant terms. The PEDro checklist was used for the assessment of study quality. A random-effects meta-analysis of standardized mean differences (SMDs) was done. RESULTS Ten studies of good and excellent methodological quality were included. The SMD for the effects of caffeine on strength was 0.16 (95% CI=0.06, 0.26; p=0.003; +5.3%). The subgroup analysis for knee extensor isokinetic strength showed a significant difference (p=0.004) between the caffeine and placebo conditions with SMD value of 0.19 (95% CI=0.06, 0.32; +6.1%). The subgroup analysis for the effects of caffeine on isokinetic strength of other, smaller muscle groups indicated no significant difference (p=0.092) between the caffeine and placebo conditions. The subgroup analysis for knee extensor isokinetic strength at angular velocities of 60°s-1 and 180°s-1 showed a significant difference between the caffeine and placebo conditions; however, no significant effect (p=0.193) was found at an angular velocity of 30°s-1. CONCLUSIONS This meta-analysis demonstrates that acute caffeine ingestion caffeine may significantly increase isokinetic strength. Additionally, this meta-analysis reports that the effects of caffeine on isokinetic muscular strength are predominantly manifested in knee extensor muscles and at greater angular velocities.