Gender Differences in Subjective and Physiological Responses to Caffeine and the Role of Steroid Hormones

Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?

Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords "caffeine" and "exercise" yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist regarding the effectiveness and safety of caffeine. These include but are not limited to: 1. Does caffeine dehydrate you at rest? 2. Does caffeine dehydrate you during exercise? 3. Does caffeine promote the loss of body fat? 4. Does habitual caffeine consumption influence the performance response to acute caffeine supplementation? 5. Does caffeine affect upper vs. lower body performance/strength differently? 6. Is there a relationship between caffeine and depression? 7. Can too much caffeine kill you? 8. Are there sex differences regarding caffeine's effects? 9. Does caffeine work for everyone? 10. Does caffeine cause heart problems? 11. Does caffeine promote the loss of bone mineral? 12. Should pregnant women avoid caffeine? 13. Is caffeine addictive? 14. Does waiting 1.5-2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?" To answer these questions, we performed an evidence-based scientific evaluation of the literature regarding caffeine supplementation.

Warm-up music and low-dose caffeine enhance the activity profile and psychophysiological responses during simulated combat in female taekwondo athletes

To assess the effects of warm-up music and low dose (3 mg·kg-1) of caffeine (CAF) on female taekwondo athlete's activity profile and psychophysiological responses during simulated combat. In a double-blinded, randomized, crossover study, 16 female athletes participated in simulated combats under one control and 5 experimental conditions [i.e., CAF alone (CAF), placebo alone (PL), CAF with music (CAF + M), PL with music (PL + M), and no supplement with music (M)]. After warming-up, athletes rated their felt arousal (FAS). Mean (HRmean) and peak (HRpeak) heart rate values were determined for each combat. After fighting, athletes rated their perceived exertion (RPE), feeling scale (FS), FAS, and physical enjoyment (PACES). Time-motion and technical-tactical variables were analyzed. CAF + M induced shorter skip and pause time, while attack time increased compared to other conditions (p < 0.05). Moreover, CAF + M increased single attacks, combined attacks, counter-attacks (p < 0.001), and defensive actions (p < 0.05) than other conditions. HRmean and HRpeak were lower under CAF + M than other conditions (p < 0.05). Additionally, higher FAS post-combat, FS, and PACES were observed under CAF + M, while RPE was lower (except CAF condition) compared to the other conditions (p < 0.05.Using CAF with warm-up music may increase combat cadence and improve the psychological state in female athletes more effectively than either strategy alone.

Multi-Ingredient Preworkout Supplementation Compared With Caffeine and a Placebo Does Not Improve Repetitions to Failure in Resistance-Trained Women

There has been an increase in the use of commercially available multi-ingredient preworkout supplements (MIPS); however, there are inconsistencies regarding the efficacy of MIPS in resistance-trained women.

PURPOSE

To determine the effect of varying doses of MIPS compared with caffeine only (C) and a placebo (PL) on resistance-training performance in trained women.

METHODS

Ten women (21.5 [2.3] y) completed 1-repetition-maximum tests at baseline for leg press and bench press. A within-group, double-blind, and randomized design was used to assign supplement drinks (ie, PL, C, MIPS half scoop [MIPS-H], and MIPS full scoop [MIPS-F]). Repetitions to failure were assessed at 75% and 80% to 85% of 1-repetition maximum for bench and leg press, respectively. Total performance volume was calculated as load × sets × repetitions for each session. Data were analyzed using a 1-way repeated-measures analysis of variance and reported as means and SDs.

RESULTS

There were no differences in repetitions to failure for bench press (PL: 14.4 [3.2] repetitions, C: 14.4 [2.9] repetitions, MIPS-H: 14.2 [2.6] repetitions, MIPS-F: 15.1 [3.1] repetitions; P = .54) or leg press (PL: 13.9 [7.8] repetitions, C: 10.8 [5.9] repetitions, MIPS-H: 13.1 [7.1] repetitions, MIPS-F: 12.4 [10.7] repetitions; P = .44). Furthermore, there were no differences in total performance volume across supplements for bench press (PL: 911.2 [212.8] kg, C: 910.7 [205.5] kg, MIPS-H: 913.6 [249.3] kg, MIPS-F: 951.6 [289.6] kg; P = .39) or leg press (PL: 4318.4 [1633.6] kg, C: 3730.0 [1032.5] kg, MIPS-H: 4223.0 [1630.0] kg, MIPS-F: 4085.5 [2098.3] kg; P = .34).

CONCLUSIONS

Overall, our findings suggest that caffeine and MIPS do not provide ergogenic benefits for resistance-trained women in delaying muscular failure.

Autonomic brain functioning and age-related health concerns

The autonomic nervous system (ANS) regulates involuntary bodily functions such as blood pressure, heart rate, breathing, and digestion, in addition to controlling motivation and behavior. In older adults, the ANS is dysregulated, which changes the ability of the ANS to respond to physiological signals, regulate cardiovascular autonomic functionality, diminish gastric motility, and exacerbate sleep problems. For example, a decrease in heart rate variability, or the variation in the interval between heartbeats, is one of the most well-known alterations in the ANS associated with health issues, including cardiovascular diseases and cognitive decline. The inability to perform fundamental activities of daily living and compromising the physiological reactivity or motivational responses of older adults to moving toward or away from specific environmental stimuli are significant negative consequences of chronic and geriatric conditions that pose grave threats to autonomy, health, and well-being. The most updated research has investigated the associations between the action responsiveness of older adults and the maintenance of their physiological and physical health or the development of mental and physical health problems. Once autonomic dysfunction may significantly influence the development of different age-related diseases, including ischemic stroke, cardiovascular disease, and autoimmune diseases, this review aimed to assess the relationship between aging and autonomic functions. The review explored how motivational responses, physiological reactivity, cognitive processes, and lifelong developmental changes associated with aging impact the ANS and contribute to the emergence of health problems.

Optimizing Short-Term Maximal Exercise Performance: The Superior Efficacy of a 6 mg/kg Caffeine Dose over 3 or 9 mg/kg in Young Female Team-Sports Athletes

Caffeine (CAF) is among the most extensively researched dietary supplements worldwide. However, little is known about the relationship between dosage and performance enhancement, particularly in female athletes. This study aimed to explore the effects of three different CAF dosages (3 mg·kg-1, 6 mg·kg-1, and 9 mg·kg-1) on high-intensity exercise and the prevalence of undesirable side effects related to these doses among female team-sports athletes. All participants (n = 16; age: 16.9 ± 0.6 y; height: 1.64 ± 0.1 m; BMI: 21.6 ± 1.5 kg·m-2) were mild CAF consumers. This study had a randomized, crossover, double-blind design in which each athlete performed four experimental sessions after ingesting either a placebo (PLAC), 3 mg·kg-1 CAF (CAF-3), 6 mg·kg-1 CAF (CAF-6), or 9 mg·kg-1 of CAF (CAF-9), with an in-between washout period of at least 72 h. In each experimental session, 60 min after ingesting the capsules, participants underwent a countermovement jumps test (CMJ), modified agility t-test (MATT), repeated sprint ability (RSA) test, and a rating of perceived exertion (RPE) and completed the CAF side effects questionnaire. Our findings revealed that in comparison to the PLAC condition, the MATT, RSAmean, and RSAbest performances were significantly greater only under the CAF-6 and CAF-9 conditions. Although the RPE scores remained unchanged, CMJ performance improved under all CAF conditions. All the performance outcomes were better for the CAF-6 and CAF-9 conditions than for the CAF-3 condition. Notably, no significant difference between the CAF-6 and CAF-9 conditions was observed for any of these parameters despite the highest incidence of side effects being noted for the CAF-9 condition. In summary, our findings highlight the recommendation for a moderate CAF dosage of 6 mg·kg-1 rather than 3 or 9 mg·kg-1 to enhance various aspects of short-term maximal performance in mild-CAF-consumer female team-sports athletes while mitigating the occurrence of adverse CAF side effects.

Estimating Physical Activity and Sleep using the Combination of Movement and Heart Rate: A Systematic Review and Meta-Analysis

The purpose of this meta-analysis was to quantify the difference in physical activity and sleep estimates assessed via 1) movement, 2) heart rate (HR), or 3) the combination of movement and HR (MOVE+HR) compared to criterion indicators of the outcomes. Searches in four electronic databases were executed September 21-24 of 2021. Weighted mean was calculated from standardized group-level estimates of mean percent error (MPE) and mean absolute percent error (MAPE) of the proxy signal compared to the criterion measurement method for physical activity, HR, or sleep. Standardized mean difference (SMD) effect sizes between the proxy and criterion estimates were calculated for each study across all outcomes, and meta-regression analyses were conducted. Two-One-Sided-Tests method were conducted to metaanalytically evaluate the equivalence of the proxy and criterion. Thirty-nine studies (physical activity k = 29 and sleep k = 10) were identified for data extraction. Sample size weighted means for MPE were -38.0%, 7.8%, -1.4%, and -0.6% for physical activity movement only, HR only, MOVE+HR, and sleep MOVE+HR, respectively. Sample size weighted means for MAPE were 41.4%, 32.6%, 13.3%, and 10.8% for physical activity movement only, HR only, MOVE+HR, and sleep MOVE+HR, respectively. Few estimates were statistically equivalent at a SMD of 0.8. Estimates of physical activity from MOVE+HR were not statistically significantly different from estimates based on movement or HR only. For sleep, included studies based their estimates solely on the combination of MOVE+HR, so it was impossible to determine if the combination produced significantly different estimates than either method alone.

Higher caffeine consumption is associated with insufficient sleep time in Brazilian adults (CUME study)

We aimed to evaluate the association between caffeine intake and sleep time in Brazilian adults. This cross-sectional study was conducted with 6,356 participants from the Cohort of Universities of Minas Gerais (CUME Study). Data was collected through an online self-report questionnaire. Of the total, 31.9% of the participants had insufficient sleep. Women were found to sleep less than men (64.1 vs. 35.9%; p < 0.001), as well as being more likely to consume higher doses of caffeine (55.2%, p < 0.001). Coffee (35.7%), dark chocolate (25.2%), milk chocolate (15.2%), and diet soda (11.0%) were the foods that more contributed to caffeine intake. Individuals in the highest quartile of caffeine intake (87.0 - 572.0 mg/day) had a 19% higher prevalence of insufficient sleep compared with the lowest quartile (PR: 1.19; 95%CI: 1.08 - 1.31). Future studies are needed to investigate the genetic and hormonal factors involved in the interindividual response in this population.

Acute effects of caffeine supplementation on taekwondo performance: the influence of competition level and sex

The purpose of this study was to assess the effects of acute caffeine supplementation on physical performance and perceived exertion during taekwondo-specific tasks in male and female athletes with varying expertise. In a double-blinded, randomized, placebo-controlled crossover study design, 52 young athletes from elite (n = 32; 16 males and 16 females) and sub-elite competitive level (n = 20; 10 males and 10 females) participated. Athletes performed taekwondo-specific tasks including the taekwondo-specific agility test (TSAT), 10 s frequency speed of kick test (FSKT-10 s) and multi-bout FSKT (FSKT-multi) under the following conditions: (1) Caffeine (CAF; 3 mg kg-1), placebo (PLA), and no supplement control (CON). Session rating of perceived exertion (s-RPE) was determined after the tests. Findings show that regardless of condition, males performed better than females (p < 0.05) and elite athletes had superior performance compared to their sub-elite counterparts (p < 0.05). For the TSAT (p < 0.001), FSKT-10s (p < 0.001), and FSKT-multi (p < 0.001), CAF enhanced performance in elite female athletes compared to sub-elite females. Likewise, CAF ingestion resulted in superior performance in elite males compared to sub-elite males for FSKT-10s (p = 0.003) and FSKT-multi (p < 0.01). The ergogenic potential of CAF during taekwondo-specific tasks appears to be related to a competitive level, with greater benefits in elite than sub-elite athletes.

ENVIRONMENTAL STRESSORS DIFFERENTIALLY MODULATE ANXIETY-LIKE BEHAVIOUR IN MALE AND FEMALE ZEBRAFISH

How differently male and female responds in a stressful situation is a matter of curiosity. Apart from curiosity, this opens a new arena to the synthesis of personalized/individualized medications. Here, we used zebrafish, a suitable experimental animal model to study stress and anxiety. We evaluated the differential responses in adult male and female zebrafish on the acute exposure of three different stressors: Caffeine (100mg/L), Conspecific alarm substance (3.5ml/L), and sight of sympatric predators (Leaf fish and Snakehead) with the help of two different behavioural paradigms (Novel tank test & Predator exposure). Behavioural responses were captured over 6minutes and quantified using Smart 3.0. Male zebrafish were found to be more responsive to caffeine treatment. Conspecific alarm substance-challenged males and females showed robust alarm reactions whereas females were found to be more prone to it. Female zebrafish showed statistically significant aversion to the visual representation of sympatric predators. Taken together, each stressor induced differential responses in male and female zebrafish.

Gender Differences in the Frequency of Positive and Negative Effects after Acute Caffeine Consumption

Gender-specific caffeine-related adverse effects should be thoroughly investigated. Sixty-five adult participants were included in the study, 30 men and 35 women (age, 22.5 ± 2.8; body weight, 71.7 ± 16.2 kg; BMI, 23.6 ± 4.4). The participants who were classified as low and moderate caffeine users received 3 mg/kg, and high caffeine users received 6 mg/kg of caffeine in one dose. One hour after ingestion of caffeine and within twenty-four hours, the participants completed a side effect questionnaire. Effects after the ingestion of CAF were divided into two subgroups: negative (muscle soreness, increased urine output, tachycardia and palpitations, anxiety or nervousness, headache, gastrointestinal problems, and insomnia) and positive (perception improvement; increased vigor/activeness). Caffeine ingestion resulted in a statistically significant association between gender and negative effects one hour after ingestion (p = 0.049). Gender and positive effects one hour after ingestion (p = 0.005), and between gender and positive effects within 24 h after ingestion (p = 0.047). There were significant associations between gender and perception improvement (p = 0.032) and gender and increased vigor/activeness (p = 0.009) one hour after ingestion. Nearly 30% of men and 54% of women reported negative effects. At the same time, 20% of women and more than 50% of men reported positive effects. Gender is an important factor in the negative and positive effects of caffeine consumption.

Use of Caffeine-Containing Energy Drinks by Japanese Middle School Students: A Cross-Sectional Study of Related Factors

Excessive consumption of caffeine negatively affects individuals' health. Therefore, we studied the use of energy drinks and the conditions associated with it among Japanese secondary school students. Participants were 236 students in grades 7-9 who completed anonymous questionnaires at home in July 2018. We measured the basic attributes and dietary, sleeping, and exercise habits. We used Chi-squared tests to compare differences between users and non-users of energy drinks. Logistic regression analyses were used to elucidate the complex association between the variables. The results showed that boys were more willing to consume energy drinks than girls. The reasons were 'feeling fatigued', 'needing to stay awake', 'for curiosity', and 'to quench one's thirst'. Among boys, the following were associated with the use of EDs. Buying their own snacks , not understanding nutritional labels on foods, high caffeinated beverage intake, late bed-times on weekdays, always waking up at about the same time, and weight. Health guidance is needed to prevent overconsumption and dependence on energy drinks. The cooperation of parents and teachers is needed to achieve these goals.

Association between coffee intake and frailty among older American adults: A population-based cross-sectional study

Objective

We aimed to investigate the association between coffee consumption and frailty in older American adults. We focused on individuals at higher frailty risk, such as women, ethnic minorities, smokers, and those with obesity and insufficient physical activity.

Methods

The data of 8,087 individuals aged over 60 years from the 2007-2018 National Health and Nutrition Examination Surveys were used for this cross-sectional study. The coffee drinks were classified into two categories: caffeinated and decaffeinated. Frailty was measured using the 53-item frailty index. Weighted binary logistic regression was used to evaluate the association between coffee intake and frailty risk. Restricted cubic spline models were used to assess the dose-response relationship between caffeinated coffee intake and frailty.

Results

Among the 8,087 participants, 2,458 (30.4%) had frailty. Compared with those who reported no coffee consumption, the odds ratios [ORs; 95% confidence intervals (CIs)] of total coffee consumption > 498.9 (g/day) were 0.65 (0.52, 0.79) in the fully adjusted model. Compared with those who reported no caffeinated coffee consumption, the ORs (95% CIs) of total coffee consumption > 488.4 (g/day) were 0.68 (0.54, 0.85) in the fully adjusted model. Compared with those who reported no decaffeinated coffee consumption, the ORs (95% CIs) of total coffee consumption > 0 (g/day) were 0.87 (0.71, 1.06) in the fully adjusted model. Nonlinear associations were detected between total coffee and caffeinated coffee consumption and frailty. In the subgroup analyses by smoking status, the association between coffee consumption and the risk of frailty was more pronounced in non-smokers (P for interaction = 0.031).

Conclusion

Caffeinated coffee consumption was independently and nonlinearly associated with frailty, especially in non-smokers. However, decaffeinated coffee consumption was not associated with frailty.

Urine caffeine metabolites are positively associated with cognitive performance in older adults: An analysis of US National Health and Nutrition Examination Survey (NHANES) 2011 to 2014

The aim of this study was to explore urine caffeine metabolites in relation to cognitive performance among 2011-2014 National Health and Nutrition Examination Survey participants aged ≥60 years. We hypothesized that urine caffeine metabolites were positively associated with cognition in older adults. Caffeine and 14 of its metabolites were quantified in urine by use of high-performance liquid chromatography-electrospray ionization-tandem quadruple mass spectrometry with stable isotope labeled internal standards. Cognitive assessment was based on scores from the word learning and recall modules. Participants were categorized based on the quartiles of caffeine and its metabolites level. The association between caffeine metabolites and each cognitive dimension was analyzed using multiple logistic regression analysis in adjusted models. Stratification analyses by gender were also performed. For CERAD test, there was a significant association between 1-methyluric acid (OR=0.62, 95% CI: 0.42 to 0.92), 7-methylxanthine(OR=0.49, 95% CI: 0.27 to 0.89), theophylline (OR=0.52, 95% CI: 0.29 to 0.92), as well as paraxanthine (OR=0.49, 95% CI: 0.27 to 0.88) and cognitive function. For animal fluency test, there was a positive association between theophylline (TP) (OR=0.44, 95% CI: 0.22 to 0.89) and cognitive function. The trend that the risk of low cognitive function decreased with increasing concentration of 1-methylxanthine (P trend=0.0229) was also observed. Furthermore, the same trend existed for 3-methylxanthine (p trend = 0.0375) in men. In conclusion, there was a significant positive association between urine caffeine metabolites and cognitive performance in older adults, particularly for theophylline, paraxanthine and caffeine; and the association might be dependent on gender.

Evaluation of Caffeine Ingested Timing on Endurance Performance based on CYP1A2 rs762551 Profiling in Healthy Sedentary Young Adults

Background

Caffeine is generally suggested to increase VO2max in endurance performance. Nevertheless, the response to caffeine ingestion does not seem to be uniform across individuals. Therefore, caffeine ingested timing on endurance performance based on the type of CYP1A2 single nucleotide polymorphism rs762551, that were classified as fast and slow metabolizers, need to be evaluated.

Methods

Thirty participants participated in this study. DNA was obtained from saliva samples and genotyped using polymerase chain reaction-restriction fragment length polymorphism. Each respondent completed beep tests under three treatments blindly: placebo, 4 mg/kg body mass of caffeine one hour, and two hours before test.

Results

Caffeine increased estimated VO2max in fast metabolizers (caffeine=29.39±4.79, placebo=27.33±4.02, p<0.05) and slow metabolizers (caffeine=31.25±6.19, placebo=29.17±5.32, p<0.05) in one hour before test. Caffeine also increased estimated VO2max in fast metabolizers (caffeine=28.91±4.65, placebo=27.33±4.02, p<0.05) and slow metabolizers (caffeine=32.53±6.68, placebo=29.17±5.32, p<0.05) in two hour before test. However, for slow metabolizers, the increasing was greater when caffeine was administered two hours before test (slow=3.37±2.07, fast=1.57±1.62, p<0.05).

Conclusion

Genetic variance may affect the optimal caffeine ingestion timing, sedentary individuals who want to enhance their endurance performance may ingest caffeine 1 hour before exercise for fast metabolizers and 2 hours before exercise for slow metabolizers.

Ergogenic Aids to Improve Physical Performance in Female Athletes: A Systematic Review with Meta-Analysis

Most intervention studies investigating the effects of ergogenic aids (EAs) on sports performance have been carried out in the male population. Thus, the aim of this systematic review and meta-analysis was to summarize the effects in the existing literature of EAs used by female athletes on performance. A literature research was conducted, and a descriptive analysis of the articles included in the systematic review was carried out. Meta-analyses could be performed on 32 of the included articles, evaluating performance in strength, sprint, and cardiovascular capacity. A random-effects model and the standardized mean differences (SMD) ± 95% confidence intervals (CI) were reported. The results showed that caffeine helped to improve jumping performance, isometric strength values, and the number of repetitions until failure. Caffeine and sodium phosphate helped to improve sprint performance. Aerobic tests could be improved with the use of taurine, caffeine, and beta-alanine. No conclusive effects of beetroot juice, polyphenols, or creatine in improving aerobic performance were shown. In terms of anaerobic variables, both caffeine and sodium phosphate could help to improve repeated sprint ability. More studies are needed in female athletes that measure the effects of different EAs on sports performance, such as beetroot juice, beta-alanine or sodium phosphate, as the studies to date are scarce and there are many types of EA that need to be further considered in this population, such as creatine and taurine.

Mitigative effect of caffeine against diclofenac-induced hepato-renal damage and chromosomal aberrations in male albino rats

BACKGROUND

Among the most commonly consumed non-steroidal anti-inflammatory drugs (NSAID) is Diclofenac (Dic), especially in low-income countries due to its high efficiency and affordable price. However, the continuous administration of Diclofenac may induce toxic effects on various body organs including the liver and kidney. Caffeine (Caf) (1,3,7-trimethylxanthine) is a pharmacologically active alkaloid type with antioxidant and anti-inflammatory actions.

AIM

The current study aims to evaluate the ameliorative effect of Caffeine against Dic-induced hepato-renal toxicity and damage.

METHODS

Twenty-four male albino rats type were assigned randomly into four groups (n = 6): (Group 1): Control group, (Group 2): Six male rats were exposed to Dic 10 mg/kg intraperitoneally (I.P) for 28 days, (Group 3): Six male rats were exposed to Caf (15 mg/kg orally) for 28 days; (Groups 4): Six male rats were exposed to Dic (10 mg/kg, i.p) + Caf (15 mg/kg, orally) for 28 days. Histopathological study and various biological parameters were estimated among the four groups including hemoglobin (Hb%) red blood cells (RBCs), Hematocrit (HT%), total leucocyte count (WBCs), lipid peroxidation (LPO), glutathione peroxidase (GPx), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine, tumor necrosis factor-α (TNF-α), and nitric oxide (NO).

RESULTS

The administration of Diclofenac resulted in significant deteriorations in the histopathological findings and estimated biological parameters. Whereas, daily Caffeine administration ameliorated Diclofenac-induced toxicity in the kidney and liver by three mechanisms including antioxidant, anti-inflammatory, and DNA damage inhibition.

CONCLUSION

The current study demonstrated the promising ameliorative and protective effects of Caffeine against Diclofenac-induced hepatic and renal injury.

Effects of Different Sources of Low-Dose Caffeine on Mood/Arousal and Cognitive Performance

In this study we investigated the effects of variously derived sources of low-dose caffeine on mood/arousal and cognitive performance. Twenty-two participants (15 men, 7 women; M age: 28.2, SD = 9.0 years) undertook five randomized, crossover trials in which they consumed either a water control (CON) or 80 mg of caffeine from one of four sources (coffee [COF], energy drink [END], capsule [CAP], and dissolvable mouth strip [STR]). We measured the participants' perceived efficacy of these varied caffeine sources pre-treatment; and we measured mood/arousal at pre-treatment, and again at 15 and 45 minutes post-treatment. We also measured choice reaction-time at 15 and 45 minutes post-treatment, and participants completed the psychomotor vigilance task (PVT) 45 minutes post-treatment. Caffeine increased participant ratings of alertness and decreased their ratings of tiredness irrespective of source (p's < .05), and all sources of caffeine decreased reaction time on the PVT (p's < .05), with ex-Gaussian distributional analysis localizing this to the tau-parameter, indicating lower variability. However, only the COF source was associated with improved 'overall mood' (p's < .05). Participants expected to perform better on the PVT with COF compared to CON, but there were no other significant associations between source expectancy and performance. In sum, a modest dose of caffeine, regardless of source, positively impacted mood/arousal and cognitive performance, and these effects did not appear to be influenced by expectations.

Evening Caffeine Did Not Improve 100-m Swimming Time Trials Performed 60 Min Post-Ingestion or the Next Morning After Sleep

The potential ergogenic benefits of caffeine (CAF) are well known within the athletic community, often leading to its use in adolescent swimming cohorts to enhance their performance. However, it has previously been reported that CAF has sleep-disturbing effects, which could be detrimental to performance over consecutive days in multiday competitions. Moreover, the effects that evening CAF ingestion has on sleep, side effects, and next-day performances are yet to be researched in trained adolescents. In a double-blind, randomized, crossover design, eight national-level swimmers (age: 18 ± 1 years, height: 1.76 ± 0.06 cm, body mass [BM]: 69.4 ± 6.4 kg) ingested a capsule containing 3 mg/kg BM CAF or a placebo 60 min before an evening 100-m swimming time trial. The next morning, sleep was analyzed (Core Consensus Sleep Diary) and 100-m time trials were repeated. Side effects were analyzed via visual analog scales throughout the study. No differences were found for swimming performance (p = .911) in the evening (CAF: 59.5 ± 7.8 s, placebo: 59.9 ± 7.9 s, g = 0.06) or morning (CAF: 59.7 ± 7.7 s, placebo: 60.2 ± 7.9 s, g = 0.07). In addition, no group differences were found for any subjective side effects (e.g., anxiety: p = .468, tachycardia: p = .859, alertness: p = .959) or sleep parameters (e.g., sleep latency: p = .395, total sleep time: p = .574). These results question the use of a standardized 3 mg/kg BM CAF ingestion strategy for 100-m swimming time trials in trained adolescents, although objective measures may be needed to confirm that CAF does not affect sleep within this cohort.

Associations between urinary caffeine and caffeine metabolites and cognitive function in older adults

BACKGROUND

The effects of caffeine on cognitive impairment have not been conclusively determined. This study aimed to objectively assess the correlation between the urinary caffeine and caffeine metabolites and cognitive decline in older adults.

METHODS

Data on urinary caffeine and caffeine metabolites and the cognitive performance of participants aged 60 years and older were extracted from the National Health and Nutrition Examination Surveys 2011-2014. Binary logistic regression and restricted cubic splines (RCS) analyses were used to evaluate the association between urinary caffeine and caffeine metabolites and cognitive performance.

RESULTS

Eight hundred twenty-seven individuals were enrolled in this cross-sectional study. We observed that 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, 1,3-dimethylxanthine, 1,7-dimethylxanthine, and 3,7-dimethylxanthine levels were significantly and inversely associated with cognitive decline. The RCS results suggested an approximately linear dose-response relationship between the aforementioned metabolites and cognitive performance. Moreover, the effects of urinary caffeine and caffeine metabolites on cognitive function assessed using the AFT were more evident in men.

CONCLUSIONS

Our study suggested that urinary caffeine and caffeine metabolite levels were associated with a reduced risk of cognitive impairment in a linear manner, especially in men.

Caffeine alters the breathing pattern during high-intensity whole-body exercise in healthy men

PURPOSE

The current study investigated the effect of caffeine on the breathing pattern during a high-intensity whole-body exercise.

METHODS

Using a randomized, crossover, counterbalanced, and double-blind design, twelve healthy men ingested either 5 mg.kg^-1 of caffeine or cellulose (placebo) one hour before performing a high-intensity whole-body exercise (i.e., work rate corresponding to 80% of the difference between the gas exchange threshold and maximal oxygen uptake) until the limit of tolerance. Ventilatory and metabolic responses were recorded throughout the trial and at task failure.

RESULTS

Caffeine ingestion increased time to task failure in relation to the placebo (368.1 ± 49.6 s vs. 328.5 ± 56.6 s, p = 0.005). Caffeine also increased tidal volume and inspiratory time throughout the exercise (p < 0.05). Compared to task failure with placebo, task failure with caffeine intake was marked by higher (p < 0.05) minute ventilation (134.8 ± 16.4 vs. 147.6 ± 18.2 L.min^-1), the ventilatory equivalent of oxygen consumption (37.8 ± 4.2 vs. 41.7 ± 5.5 units), and respiratory exchange ratio (1.12 ± 0.10 vs. 1.19 ± 0.11 units).

CONCLUSION

In conclusion, ingestion of caffeine alters the breathing pattern by increasing tidal volume and lengthening the inspiratory phase of the respiratory cycle. These findings suggest that caffeine affects the ventilatory system, which may account, in part, for its ergogenic effects during high-intensity whole-body exercises.

The Impact of Caffeine Intake on Mental Health Symptoms in Postmenopausal Females with Overactive Bladder Symptoms: A Randomized, Double-Blind, Placebo-Controlled Trial

Background: Caffeine has been associated with a dose-dependent variety of mental health changes, which have been found to precede or be a complication of overactive bladder (OAB) symptoms after menopause. The current study examines the effects of low and moderate caffeine intake on anxiety, depression, sleep, and stress in postmenopausal females with OAB. Materials and Methods: Eighty-one females were randomized in a prospective, double-blind, placebo-controlled study. Participants were allocated to 200 mg/day caffeine, 400 mg/day caffeine, and placebo capsules for 1 week each in a crossover design and evaluated using validated mental health questionnaires. Symptoms during each treatment phase were measured using Beck Anxiety and Depression Inventory, Insomnia Severity Index, and Perceived Stress Scale. Linear regression models were used to examine the impact of low (200 mg/day) and moderate (400 mg/day) dose of caffeine and placebo on mental health. Results: Fifty-six female participants finished the study. The mean age was 69.2 years (58.0-84.0 years). Two females dropped out during the treatment phase with 400 mg/day caffeine intake due to side effects associated with headaches and nausea. Moderate dose of caffeine showed a small positive effect on mental health, specifically a decrease in anxiety during 7 days of exposure (p < 0.05). Conclusions: Moderate caffeine use may decrease anxiety in postmenopausal patients with underlying OAB, whereas depression, insomnia, and perceived stress were not affected by low-to-moderate caffeine intake. Our results support that counseling efforts on moderate caffeine consumption in postmenopausal patients underline that low-to moderate caffeine intake may be appropriate and possibly beneficial unless contraindicated due to other underlying conditions. Clinical Trials Registration: clinicaltrials.gov (NCT02180048).

Caffeinated Gum Does Not Influence RPE-Regulated Cadence in Recreationally-Active College Females Regardless of Habitual Caffeine Consumption

Caffeine (CAF) has been extensively studied for its ergogenic and analgesic effects during exercise. However, the majority of these studies have been conducted in male populations. This study investigated the effects of acute CAF chewing gum on self-selected exercise intensity during a rating of perceived exertion (RPE) production trial in active females (n = 16, 21.0 ± 2.8 y). Data were also analyzed based on habitual CAF consumption level. Participants completed a V̇O_2peak trial, followed by a familiarization and two randomized, triple-blinded experimental RPE production trials on an arm ergometer [clamped resistance, blinded to self-selected cadence (CAD)] with either CAF gum (300 mg; 4.8 ± 0.7 mg/kg^-1 body mass) or placebo (PLA), at a prescribed RPE of 4 and 7 (10 min each). Self-selected CAD did not statistically differ (p > 0.05) between CAF or PLA for an RPE4 (37.7 ± 1.6 vs. 37.6 ± 1.6 rev·min^-1) or RPE7 (42.9 ± 1.6 vs. 41.2 ± 1.7 rev·min^-1), respectively. There were no statistical differences between treatment groups for any other variables, except restlessness rating which was significantly higher (3.5 vs. 2.2; p = 0.03, d = 0.64) for the CAF group compared to PLA. Secondary analysis revealed no statistical differences for any variables between habitual consumers of low (23 ± 20 mg/day) or mod/high (195 ± 93 mg/day) CAF. Our data support previous studies examining CAF in women across different testing modalities and suggest that regardless of habitual CAF consumption, females might require higher doses of CAF to replicate subjective and physiological responses commonly observed using similar RPE production protocols in male participants. These findings support the need for additional investigations into female physiological and perceptual responses following CAF ingestion.

Does Acute Caffeine Supplementation Improve Physical Performance in Female Team-Sport Athletes? Evidence from a Systematic Review and Meta-Analysis

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.

Coffee consumption and cardiovascular diseases and mortality in patients with type 2 diabetes: A systematic review and dose-response meta-analysis of cohort studies

AIMS

To evaluate the long-term consequences of coffee drinking in patients with type 2 diabetes.

DATA SYNTHESIS

PubMed, Scopus, and Web of Sciences were searched to November 2020 for prospective cohort studies evaluating the association of coffee drinking with risk of cardiovascular disease (CVD) and mortality in patients with type 2 diabetes. Two reviewers extracted data and rated the certainty of evidence using GRADE approach. Random-effects models were used to estimate the hazard ratios (HRs) and 95% CIs. Dose-response associations were modeled by a one-stage mixed-effects meta-analysis. Ten prospective cohort studies with 82,270 cases were included. Compared to those with no coffee consumption, the HRs for consumption of 4 cups/d were 0.79 (95%CI: 0.72, 0.87; n = 10 studies) for all-cause mortality, 0.60 (95%CI: 0.46, 0.79; n = 4) for CVD mortality, 0.68 (95%CI: 0.51, 0.91; n = 3) for coronary heart disease (CHD) mortality, 0.72 (95%CI: 0.54, 0.98; n = 2) for CHD, and 0.77 (95%CI: 0.61, 0.98; n = 2) for total CVD events. There was no significant association for cancer mortality and stroke. There was an inverse monotonic association between coffee drinking and all-cause and CVD mortality, and inverse linear association for CHD and total CVD events. The certainty of evidence was graded moderate for all-cause mortality, and low or very low for other outcomes.

CONCLUSIONS

Drinking coffee may be inversely associated with the risk of mortality in patients with type 2 diabetes. However, more research is needed considering type of coffee, sugar and cream added to coffee, and history of CVD to present more confident results.

REGISTRY AND REGISTRY NUMBER

The protocol of this systematic review was registered at Open Science Framework (https://osf.io/8uaf3, registered form: osf.io/xur76, registration DOI: 10.17605/OSF.IO/8UAF3).

Relationships of beverage consumption and actigraphy-assessed sleep parameters among urban-dwelling youth from Mexico

OBJECTIVE

To examine whether usual beverage intake was associated with sleep timing, duration and fragmentation among adolescents.

DESIGN

Usual beverage intake was assessed with a FFQ. Outcomes included sleep duration, midpoint (median of bed and wake times) and fragmentation, assessed with 7-d actigraphy. Sex-stratified linear regression was conducted with sleep characteristics as separate outcomes and quantiles of energy-adjusted beverage intake as exposures, accounting for age, maternal education, physical activity and smoking.

SETTING

Mexico City.

PARTICIPANTS

528 adolescents residing in Mexico City enrolled in a longitudinal cohort.

RESULTS

The mean age (sd) was 14·4 (2·1) years; 48 % were male. Among males, milk and water consumption were associated with longer weekday sleep duration (25 (95 % CI 1, 48) and 26 (95 % CI 4, 47) more minutes, in the 4th compared to the 1st quartile); and higher 100 % fruit juice consumption was related to earlier weekday sleep timing (-22 (95 % CI -28, 1) minutes in the 1st compared to the last quantile; P = 0·03). Among females, soda was associated with higher sleep fragmentation (1·6 (95 % CI 0·4, 2·8) % in the 4th compared to the 1st), and coffee/tea consumption was related to shorter weekend sleep duration (-23 (95 % CI -44, 2) minutes in the 4th compared to the 1st).

CONCLUSIONS

Among females, adverse associations with sleep were observed for caffeinated drinks, while males with higher consumption of healthier beverage options (water, milk and 100 % juice) had evidence of longer and earlier-timed sleep. Potential mechanisms involving melatonin and tryptophan should be further investigated.

The Association Between Coffee Consumption and Nonalcoholic Fatty Liver Disease in the South Korean General Population

SCOPE

To identify the cross-sectional and prospective association between coffee consumption and nonalcoholic fatty liver disease (NAFLD) among South Korean adults.

METHODS AND RESULTS

Participants are selected from the Health Examinees study. NAFLD is defined using three non-invasive indexes: fatty liver index (FLI), hepatic steatosis index, and fibrosis-4 calculator (FIB-4). In the cross-sectional analysis, higher habitual coffee consumption is associated with a lower risk for NAFLD, define using the FLI, (men, odds ratio [OR] 0.702; women, OR 0.810) compared with non-consumers. Participants who consumed coffee with sugar and creamer also have a lower risk for NAFLD, defined using the FIB-4, compared with non-coffee-consumers (men, OR 0.739; women, OR 0.807). A prospective analysis indicated that higher coffee consumption is associated with a lower incidence of NAFLD, defined using the FLI, in men (hazard ratio, 0.706). In both men and women, a lower FIB-4 index score is associated with higher coffee consumption regardless of coffee type (all p-value <0.05).

CONCLUSIONS

 Coffee consumption of >3 cups per day has a protective effect against the development of NAFLD to a certain extent, and a negative association is found between coffee consumed with sugar and creamer and the FIB-4 index score in South Korean adults.

The Effects of Caffeine on Jumping Performance and Maximal Strength in Female Collegiate Athletes

Caffeine is often used in a variety of forms to enhance athletic performance; however, research regarding caffeine's effects on strength and power in female athletes is lacking. Therefore, the purpose of this study was to analyze the acute effects of caffeine anhydrous (6 mg/kg of body mass) on jumping performance and maximal strength in female collegiate athletes. Eleven athletes (19.7 ± 0.9 yrs; 166.4 ± 10.2 cm, 67.7 ± 9.4 kg) performed two testing sessions separated by one week, and randomly received caffeine or placebo using a double-blind approach. Heart rate, blood pressure, and tympanic temperature were recorded before athletes received each condition, following 60 min of quiet sitting, and directly after performance testing. Athletes were assessed on unweighted and weighted squat jump height (SJH0, SJH20) and countermovement jump height (CMJH0, CMJH20), isometric mid-thigh pull peak force (IPF), and rate of force development from 0-200 ms (RFD200). Resting systolic blood pressure was significantly greater following caffeine administration compared to a placebo (p = 0.017). There were small, significant differences in SJH0 (p = 0.035, g = 0.35), SJH20 (p = 0.002, g = 0.49), CMJH0 (p = 0.015, g = 0.19), and CMJH20 (p < 0.001, g = 0.37) in favor of caffeine over placebo. However, there was no significant difference in IPF (p = 0.369, g = 0.12) and RFD200 (p = 0.235, g = 0.32) between conditions. Therefore, caffeine appears to enhance jumping performance, but not maximal strength in female collegiate athletes.

Gender differences and caffeine impact in adenosine-induced hyperemia

Background: Caffeine consumption before adenosine stress myocardial perfusion imaging (MPI) is known to affect the hemodynamic response and, thus, reduce the stress myocardial blood flow (MBF) and myocardial flow reserve (MFR) assessments. However, it is not clear if any gender-specific differences in the hemodynamic response following caffeine consumption exist. This study aimed to evaluate if such differences exist and, if so, their impact on MBF and MFR assessments. Methods: This study comprised 40 healthy volunteers (19 women). All volunteers underwent four serial rest/stress MPI sessions employing Rubidium-82; two sessions were acquired without controlled caffeine consumption, and two sessions following oral ingestion of either 100mg and 300mg caffeine or 200mg and 400mg caffeine. For the caffeine imaging sessions, caffeine was ingested orally 1hr before the MPI scan. Results: Increase in plasma caffeine concentration (PCC) (mg/l) following consumption of caffeine was larger in women (MPI session without caffeine vs. MPI session with caffeine: women = 0.3±0.2 vs. 5.4±5.1, men = 0.1±0.2 vs. 2.7±2.6, both p<0.001). Caffeine consumption led to reduced stress MBF and MFR assessments for men while no changes were reported for women (women (PCC<1mg/l vs PCC≥1mg/l): stress MBF = 3.3±0.6 vs. 3.0±0.8 ml/g/min, P = 0.07; MFR = 3.7±0.6 vs. 3.5±1.0, P = 0.35; Men (PCC<1mg/l vs PCC≥1mg/l): stress MBF= 2.7±0.7 vs. 2.1±1.0 ml/g/min, P = 0.005, MFR = 3.8±1.0 vs. 3.1±1.4, P = 0.018). Significant differences in the stress MBF were observed for the two genders (both p≤0.001), while similar MFR were reported (both p≥0.12). Conclusion: Associations between increases in PCC and reductions in stress MBF and MFR were observed for men, while women did not have the same hemodynamic response. Stress MBF was affected at lower plasma caffeine concentrations in men than women.

A Differential Threshold of Breakfast, Caffeine and Food Groups May Be Impacting Mental Well-Being in Young Adults: The Mediation Effect of Exercise

Diet and exercise are known to influence mental health. However, the interaction between diet, dietary practices, and exercise and its impact on the mood of young adults (YA) is poorly understood. YA are inherently at risk for mental distress. They tend to consume a low-quality diet and are generally active. The purpose of the study was to assess these relationships through validating causal loop diagrams (CLD) that describe these connections by using a system dynamic (SD) modeling methodology. Adults 18-29 years were invited to complete the Food-Mood questionnaire. The anonymous questionnaire link was distributed to several institutional listservs and via several social media platforms targeting young adults. A multi-level analysis, including machine learning techniques, was used to assess these relationships. The key findings were then built into gender based CLD, which suggest that a differential repertoire may be needed to optimize diet quality, exercise, and mental well-being. Additionally, a potential net threshold for dietary factors and exercise may be needed to achieve mental well-being in young adults. Moreover, our findings suggest that exercise may boost the enhancing effect of food groups on mental well-being and may lessen the negative impact of dietary impediments of mental well-being.

Effects of Creatine and Caffeine Supplementation During Resistance Training on Body Composition, Strength, Endurance, Rating of Perceived Exertion and Fatigue in Trained Young Adults

The primary purpose was to determine the separate and combined effects of creatine and caffeine supplementation during resistance training on body composition and muscle performance in trained young adults. Twenty-eight participants were randomized to supplement with creatine and caffeine (CR-CAF; n = 9, 22 ± 4 years; 0.1 g·kg^-1·d^-1 of creatine monohydrate + 3 mg·kg^-1·d^-1 of caffeine anhydrous micronized powder); creatine (CR; n = 7, 22 ± 4 years, 0.1 g·kg^-1·d^-1 of creatine + 3 mg·kg^-1·d^-1 of micronized cellulose), caffeine (CAF; n = 6, 19 ± 1 years, 3 mg·kg^-1·d^-1 of caffeine + 0.1 g·kg^-1·d^-1 of maltodextrin) or placebo (PLA; n = 6, 23 ± 7 years, 0.1 g·kg^-1·d^-1 of maltodextrin + 3 mg·kg^-1·d^-1 micronized cellulose) one hour prior to performing resistance training for 6 weeks. Before and after training and supplementation, fat-free and fat mass (air-displacement plethysmography), muscle thickness (elbow and knee flexors and extensors; ultrasound), muscle strength (1-repetition maximum [1-RM] for the leg press and chest press), and endurance (one set of repetitions to volitional fatigue using 50% baseline 1-RM for leg press and chest press) were assessed. There was a group x time interaction (p = 0.049) for knee extensor muscle thickness with CR experiencing an increase over time with no changes in the other groups. There were no other between group differences for any variable. In conclusion, creatine supplementation and resistance training results in a small improvement in knee extensor muscle accretion in trained young adults.

Diet, Exercise, Lifestyle, and Mental Distress among Young and Mature Men and Women: A Repeated Cross-Sectional Study

Customization of mental health therapies needs to consider the differences in degree of brain maturity between young (18–29 years) and mature (30 years or older) adults as well as brain morphology among men and women. The aim of this study was to identify the significant dietary and lifestyle contributors to mental distress in these sub-populations. Independent repeated cross-sectional sampling was performed for over a 5-year period (2014–2019) to collect data from different populations at different time-points and seasons. A backward stepwise regression analysis was used on 2628 records. Mental distress in young women was associated with high consumption of caffeine and fast-food, and it was negatively correlated with moderate-high levels of exercise as well as frequent breakfast consumption. Mature women shared several common factors with young women; however, high fruit consumption was negatively associated with mental distress. For young men, high exercise, moderate consumption of dairy, and moderate-high intake of meat were negatively associated with mental distress. In addition, high fast-food and caffeine consumption were positively associated with mental distress in young men. For mature men, strong negative associations between higher education, moderate intake of nuts and mental distress surfaced. Our results support the need to customize dietary and lifestyle recommendations to improve mental wellbeing.

Caffeine ingestion alters central hemodynamics following aerobic exercise in middle-aged men

PURPOSE

To examine the acute influence of caffeine on post-exercise central blood pressures, arterial stiffness, and wave reflection properties.

METHODS

In a double-blind randomized placebo-controlled crossover study design, ten middle-aged males (55 ± 5 year) completed two exercise trials after ingestion of caffeine (400 mg) or placebo. Measurements were taken before and 30 min post-ingestion via cuff-based pulse wave analysis (PWA) and carotid-femoral pulse wave velocity (PWV). Participants performed a 40-min cycling bout at 70% HRmax with matched workloads between trials. PWA and PWV were reassessed 30 min post-exercise.

RESULTS

Prior to exercise, compared to placebo, caffeine increased brachial systolic blood pressure (bSBP) (+ 12.3 ± 2.4 mmHg; p = 0.004), brachial diastolic blood pressure (bDBP) (+ 7.7 ± 0.9 mmHg; p = 0.011), central systolic blood pressure (cSBP) (+ 11.1 ± 2.1 mmHg; p = 0.005) and central diastolic blood pressure (cDBP) (+ 7.6 ± 1.0 mmHg; p = 0.012). PWV was higher 30 min after pill ingestion (p = 0.021 for time) with a trend for a greater increase in caffeine (p = 0.074 for interaction). bSBP (p = 0.036) and cSBP (p = 0.007) were lower after exercise but remained higher (both p < 0.001) in caffeine compared to placebo. PWV remained higher (p = 0.023) after exercise in caffeine compared to placebo but was not influenced by exercise. At rest, augmentation pressure (AP) and index (AIx) were not influenced by caffeine ingestion. Conversely, AIx was lower (p = 0.009) after exercise in placebo only.

CONCLUSION

In healthy and active middle-aged men, pre-exercise caffeine ingestion led to higher central and peripheral systolic blood pressures, PWV and AIx at 30 min post-exercise, indicating an increased left ventricular workload which may have implications for cardiovascular event risk.

Effects of Dietary Supplements on Adaptations to Endurance Training

Endurance training leads to a variety of adaptations at the cellular and systemic levels that serve to minimise disruptions in whole-body homeostasis caused by exercise. These adaptations are differentially affected by training volume, training intensity, and training status, as well as by nutritional choices that can enhance or impair the response to training. A variety of supplements have been studied in the context of acute performance enhancement, but the effects of continued supplementation concurrent to endurance training programs are less well characterised. For example, supplements such as sodium bicarbonate and beta-alanine can improve endurance performance and possibly training adaptations during endurance training by affecting buffering capacity and/or allowing an increased training intensity, while antioxidants such as vitamin C and vitamin E may impair training adaptations by blunting cellular signalling but appear to have little effect on performance outcomes. Additionally, limited data suggest the potential for dietary nitrate (in the form of beetroot juice), creatine, and possibly caffeine, to further enhance endurance training adaptation. Therefore, the objective of this review is to examine the impact of dietary supplements on metabolic and physiological adaptations to endurance training.

Energy drink intake is associated with insomnia and decreased daytime functioning in young adult females

OBJECTIVE

To investigate the association between energy drink (ED) use and sleep-related disturbances in a population-based sample of young adults from the Raine Study.

DESIGN

Analysis of cross-sectional data obtained from self-administered questionnaires to assess ED use and sleep disturbance (Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire (FOSQ-10) and the Pittsburgh Sleep Symptoms Questionnaire-Insomnia (PSSQ-I)). Regression modelling was used to estimate the effect of ED use on sleep disturbances. All models adjusted for various potential confounders.

SETTING

Western Australia.

PARTICIPANTS

Males and females, aged 22 years, from Raine Study Gen2-22 year follow-up.

RESULTS

Of the 1115 participants, 66 % were never/rare users (i.e. <once/month) of ED, 17·0 % were occasional users (i.e. >once/month to <once/week) and 17 % were frequent users (≥once/week). Compared with females, a greater proportion of males used ED occasionally (19 % v. 15 %) or frequently (24 % v. 11 %). Among females, frequent ED users experienced significantly higher symptoms of daytime sleepiness (FOSQ-10: β = 0·93, 95 % CI 0·32, 1·54, P = 0·003) and were five times more likely to experience insomnia (PSSQ-I: OR = 5·10, 95 % CI 1·81, 14·35, P = 0·002) compared with never/rare users. No significant associations were observed in males for any sleep outcomes.

CONCLUSIONS

We found a positive association between ED use and sleep disturbances in young adult females. Given the importance of sleep for overall health, and ever-increasing ED use, intervention strategies are needed to curb ED use in young adults, particularly females. Further research is needed to determine causation and elucidate reasons for gender-specific findings.

Translation and Validation of the Caffeine Expectancy Questionnaire in Brazil (CaffEQ-BR)

Caffeine is the world's most commonly used stimulant of the central nervous system. Caffeine is present in coffee and other beverages such as tea, soft drinks, and cocoa-based foods. The caffeine expectancy questionnaire was developed to investigate the effects of caffeine expectations and thus contribute to knowledge about its usage and subjective effects (response expectancies). This study aimed to evaluate caffeine expectation psychometrically in a sample of the Brazilian population. The original version of the "Caffeine Expectancy Questionnaire (CaffEQ)" was translated and validated into Brazilian-Portuguese and adapted to Brazilian culture to be used in the Brazilian adult (19-59 y) population. After the translation and back-translation processes of the original CaffEQ questionnaire, the content and semantic validation were performed by a group of experts. The Brazilian-Portuguese version of the questionnaire consists of 47 items, in seven factors, which assess subjective perceptions about the effects of caffeine. Interobserver reproducibility and internal consistency of the questionnaire were tested with a convenience sample (n = 50) of Brazilian adult consumers of caffeine sources, who completed the Brazilian CaffEQ (CaffEQ-BR) on two occasions separated by 24 h. All of the 47 questions were adequate regarding reliability, clarity, and comprehension. Psychometric properties could be replicated consistently. Appropriate internal consistency and validation were confirmed by Cronbach's alpha (α) 0.948, and an intraclass correlation coefficient of 0.976 was observed. The CaffEQ-BR was applied using a web-based platform to a convenience sample of Brazilian adults from all 27 Brazilian states (n = 4202 participants), along with measures of sociodemographic and caffeine consumption data. Factor validity was verified by confirmatory factor analysis. The seven factors presented a good fit for Root Mean Square Error of Approximation-RMSEA = 0.0332 (95% CI: 0.0290-0.0375). By confirming the validity and reliability of CaffEQ-BR, a useful tool is now available to assess caffeine expectations in the Brazilian adult population.

Determinants of energy drink consumption in adolescents: identification of sex-specific patterns

OBJECTIVES

To investigate sex differences in sociodemographic and lifestyle correlates of frequent energy drink (ED) consumption in adolescents.

STUDY DESIGN

This study was based on data collected among French-speaking Belgian adolescents aged 11-20 years (n = 8137) within the 2018 Health Behaviour in School-aged Children study.

METHODS

Multiple logistic analyses stratified by sex were performed to estimate the associations between consuming EDs more than once a week, and various sociodemographic and lifestyle characteristics.

RESULTS

Overall, 14.0% of boys and 7.6% of girls consumed ED more than once a week. For both genders, the likelihood of consuming ED more than once a week was higher among adolescents consuming soft drinks daily (vs. < daily), alcohol weekly (vs. < weekly), spending at least 5 h/day in front of screens (vs. < 5 h/day), and going to bed later than 11:30 PM (vs. ≤ 10:00 PM). Among boys, adolescents reporting at least 1 h of moderate-to-vigorous physical activity (MVPA) daily (vs. < 1 h/day MVPA) were more likely to consume ED more than once a week (adjusted odd ratio (aOR) = 1.49 (95% confidence interval [CI] 1.11-2.01)). Among girls, adolescents from low affluence families (vs. high affluence) (aOR = 2.03 (95% CI 1.19-3.48)) and immigrants (vs. natives) (2nd generation: aOR = 1.75 (95% CI 1.31-2.32); 1st generation: aOR = 1.90 (95% CI 1.20-3.03)) were more likely to consume ED more than once a week.

CONCLUSIONS

We identified different patterns of ED consumption in boys and girls. These results suggest that sex-tailored interventions could be relevant to reduce ED consumption in adolescents.

Caffeine Use and Associations With Sleep in Adolescents With and Without ADHD

OBJECTIVE

The objective of this study was to compare caffeine consumption in the morning, afternoon, and evening in adolescents with and without attention-deficit/hyperactivity disorder (ADHD) and examine associations with sleep functioning.

METHODS

Participants were 302 adolescents (ages 12-14) with (N = 140) and without (N = 162) ADHD. Adolescents wore actigraph watches to assess total sleep time and wake after sleep onset and reported on sleep-wake problems and the number of caffeinated beverages consumed per day in the morning, afternoon, and evening. Parents reported on adolescents' difficulties initiating and maintaining sleep. Chi-square tests, odds ratios, and path analyses were conducted.

RESULTS

Analyses controlled for sex, medication status, and pubertal development. Adolescents with ADHD were 2.47 times more likely to consume caffeine in the afternoon and evening than adolescents without ADHD. Path analyses indicated significant associations between afternoon caffeine use and more self-reported sleep problems for adolescents with and without ADHD, and an association between evening caffeine use and self-reported sleep problems only in adolescents with ADHD. Afternoon caffeine use was associated with parent-reported sleep problems in adolescents with ADHD only. Caffeine use was not associated with actigraphy-assessed sleep.

CONCLUSION

This is the first study to show that adolescents with ADHD consume more caffeine than peers during later times of the day. Additionally, caffeine use is more consistently associated with poorer subjective sleep functioning in adolescents with ADHD. Pediatricians and mental health professionals should assess for caffeine use in adolescents with ADHD and co-occurring sleep problems.

Regular Coffee Consumption Is Associated with Lower Regional Adiposity Measured by DXA among US Women

BACKGROUND

Coffee is among the most popular daily beverages in the United States. Importantly, coffee consumption has been associated with a lower risk of multiple health outcomes including a reduction in adiposity. DXA is a means to assess body fat and distribution.

OBJECTIVES

The aim of this study was to examine the relation between coffee consumption and DXA-assessed adiposity and adiposity distribution.

METHODS

Cross-sectional data from the NHANES were used. Participants were adults aged 20-69 y from the 2003-2004 and 2005-2006 waves. Information on coffee consumption was assessed through the FFQ (categorized as no coffee, 0 to <0.25 cup/d, 0.25 to <1 cup/d, 1 cup/d, 2-3 cups/d, or ≥4 cups/d). Both caffeinated and decaffeinated coffee consumption were included. Trunk fat and total fat percentage were measured via whole-body DXA scans. The association between coffee consumption and body fat was investigated using age-adjusted and multivariable-adjusted linear regression models which accounted for sample weights.

RESULTS

Higher coffee consumption was associated with significantly lower total body fat percentage and trunk body fat percentage in a dose-response manner (all P values < 0.05) among women. Although this dose-response relation was nonsignificant among men, men aged 20-44 y who drank 2-3 cups/d had 1.3% (95% CI: -2.7%, 0.1%) less total fat and 1.8% (95% CI: -3.3%, -0.4%) less trunk fat than those who did not consume coffee. Furthermore, the association between coffee consumption and body fat percentage exhibited for both caffeinated and decaffeinated coffee among women (all P for trend < 0.001) but not among men (all P for trend > 0.05).

CONCLUSIONS

The present study found a significant association between higher coffee consumption and lower DXA-measured adiposity. Moreover, a gender difference in this association in the general US adult population was also observed.

A low caffeine dose improves maximal strength, but not relative muscular endurance in either heavier-or lighter-loads, or perceptions of effort or discomfort at task failure in females

Background

The body of literature considering caffeine as an ergogenic aid has primarily considered typically aerobic based exercise, male participants and moderate-to large-caffeine doses. With this in mind the aim of this project was to explore the effects of a low-caffeine dose upon maximal voluntary contraction (MVC) and muscular endurance (time to task failure, TTF) at heavier-and lighter-loads.

Methods

Nineteen physically active, habitual caffeine consuming females randomly performed four testing conditions; two with a low-dose of caffeine (100 mg equating to mean = 1.5 ± 0.18 mg·kg⁻¹) and two placebo conditions, where they performed a maximal strength test (MVC) knee extension at 45° followed by a task of relative muscular endurance (sustained isometric contraction for TTF) using either heavier-(70% MVC) and lighter-(30% MVC) loads. Each participant performed each load condition following both caffeine and placebo consumption. Immediately following cessation of the muscular endurance test participants were asked to report their rating of perceived effort (RPE) and rating of perceived discomfort (RPD).

Results

Analyses revealed a significant effect for caffeine upon MVC compared to placebo (p = 0.007). We also found a significantly greater TTF for the lighter-compared to the heavier-load condition (p < 0.0001); however, there was no significant effect comparing caffeine to placebo (p = 0.2368), but insufficient precision of estimates to infer equivalence in either lighter-(p = 0.750) or heavier-load (p = 0.262) conditions. There were no statistically significant effects for caffeine compared with placebo, or lighter-compared with heavier-loads, for RPE and RPD (all p > 0.05). RPE was statistically equivalent between caffeine and placebo for both lighter-(p = 0.007) and heavier-load (p = 0.002) conditions and RPD for heavier-(p = 0.006) but not lighter-load (p = 0.136).

Discussion

This is the first study to demonstrate a positive effect on strength from a low caffeine dose in female participants. However, it is unclear whether caffeine positively impacts upon relative muscular endurance in either heavier-or lighter-loads. Further, both RPE and RPD appear to be relatively similar during isometric tasks performed to task failure independently of caffeine supplementation or load. These findings may have implications for persons wishing to avoid side-effects or withdrawal symptoms associated with larger caffeine doses whilst still attaining the positive strength responses.

Energy drink consumption, psychological distress, and suicidality among middle and high school students

BACKGROUND

Previous research has found links between energy drink consumption and mental health outcomes in youth. However, little is known about the factors that could moderate these relationships. The present study examined the associations between energy drink consumption and psychological distress, suicidal thoughts, and suicide attempts among adolescents, and tested whether sex and school type (i.e. middle vs. high school) would moderate these associations.

METHODS

Data on students in grades 7 through 12 was obtained from the 2017 Ontario Student Drug Use and Health Survey (N  =  5,538). Multivariable Poisson regression analyses were used to examine associations between energy drink consumption and mental health outcomes. Analyses were weighted and adjusted for the complex survey design.

RESULTS

Energy drink consumption was associated with greater risk of moderate to serious (adjusted incidence rate ratio (IRR) 1.19, 95% confidence interval (CI) 1.03-1.37) and serious (IRR: 1.45, 95% CI: 1.13-1.86) levels of psychological distress, suicidal thoughts (IRR: 1.98, 95% CI: 1.62-2.42), and suicide attempts (IRR: 3.67, 95% CI: 2.26-5.95). The association between energy drink consumption and mental health outcomes was much stronger among boys and middle school students.

LIMITATIONS

The cross-sectional nature of the data precludes causal inferences and there is possibility of bias related to self-reports.

CONCLUSIONS

Energy drink consumption among adolescents is strongly and differentially associated with mental health problems among male and female middle and high school students. Future research is necessary to replicate and disentangle the observed differences in more detail to inform the development of tailored interventions.

Conflicting Effects of Coffee Consumption on Cardiovascular Diseases: Does Coffee Consumption Aggravate Pre-existing Risk Factors?

Coffee is one of the most popular beverages worldwide. Its effect on health is generally regarded as beneficial in many studies. However, there are growing concerns about the adverse effect of coffee consumption on cardiovascular disease (CVD) due to the potential aggravating impact on the cardiovascular system attributed to various compounds within coffee. This review is focused on deteriorative effects of coffee consumption on CVDs with possible mechanisms. Patients with risk factors of CVDs should prudently consider heavy consumption of coffee as it may exacerbate hypertension, dyslipidemia, and atherosclerosis, and increase the odds of cardiovascular events. J-shaped or U-shaped dose-response graphs of coffee consumption and CVD parameters partially explain the inconsistency of conclusions between coffee studies on CVD, highlighting a moderate intake of coffee. Moreover, there are discrepancies in results from clinical studies elucidating considerable influences of confounding factors including gender and smoking status on outcomes of those conducted to reveal the actual impact of coffee consumption on CVDs. Physical features of subjects including genetic variations and body mass index (BMI) make it difficult to determine moderate intake of coffee for individuals in terms of caffeine metabolism. Further epidemiological studies with consideration about characteristics of the study population are needed to determine the exact effect of coffee consumption on CVD.

Acute caffeine intake increases performance in the 15-s Wingate test during the menstrual cycle

AIMS

In male athletes, caffeine is considered an ergogenic aid to increase anaerobic performance during the Wingate anaerobic test (WANT). However, information about the effect of caffeine on WANT performance in female athletes is contradictory. Furthermore, it is unknown whether the ergogenicity of caffeine is present during all the phases of the menstrual cycle. The aim of this study was to investigate the effects of caffeine intake on WANT performance during 3 phases of the menstrual cycle.

METHODS

Thirteen well-trained eumenorrhoeic triathletes participated in a double-blind, placebo-controlled, cross-over experimental trial. On 2 different days in each phase, and in randomized order, participants ingested caffeine (3 mg kg-1 ) or a placebo (cellulose). The menstrual cycle phases were individually characterized as follows: (i) early follicular; (ii) preovulatory; and (iii) midluteal. In each trial, participants performed a 15-s adapted version of the WANT.

RESULTS

In comparison to the placebo, caffeine increased peak power during the WANT in the early follicular (8.6 ± 0.8 vs 8.9 ± 0.9 W/kg, P = .04; effect size [d] = 0.45), preovulatory (8.6 ± 0.9 vs 8.9 ± 0.9 W/kg, P = .04; d = 0.23) and mid-luteal phases (8.6 ± 0.8 vs 8.9 ± 0.9 W/kg, P < .01; d = 0.52).

CONCLUSION

The ergogenic effect of caffeine on WANT peak cycling power was of a similar magnitude in the follicular, preovulatory, and mid-luteal phases. These results suggest that caffeine increases performance in the 15-s Wingate test in women athletes and it might be considered an ergogenic aid to increase anaerobic performance in eumenorrhoeic women during their menstrual cycle.

Association of Coffee, Decaffeinated Coffee and Caffeine Intake from Coffee with Cognitive Performance in Older Adults: National Health and Nutrition Examination Survey (NHANES) 2011-2014

The aim of this study was to examine the association of coffee, caffeinated coffee, decaffeinated coffee and caffeine intake from coffee with cognitive performance in older adults. we used data from the National Health and Nutrition Examination Survey (NHANES) 2011–2014. Coffee and caffeine intake were obtained through two 24-hour dietary recalls. Cognitive performance was evaluated by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) test, Animal Fluency test and Digit Symbol Substitution Test (DSST). Binary logistic regression and restricted cubic spline models were applied to evaluate the association of coffee and caffeine intake with cognitive performance. A total of 2513 participants aged 60 years or older were included. In the fully adjusted model, compared to those reporting no coffee consumption, those who reported 266.4–495 (g/day) had a multivariate adjusted odd ratio (OR) with 95% confidence interval (CI) of 0.56(0.35–0.89) for DSST test score, compared to those reporting no caffeinated coffee consumption, those who reported ≥384.8 (g/day) had a multivariate-adjusted OR (95% CI) of 0.68(0.48–0.97) for DSST test score, compared to the lowest quartile of caffeine intake from coffee, the multivariate adjusted OR (95% CI) of the quartile (Q) three was 0.62(0.38–0.98) for the CERAD test score. L-shaped associations were apparent for coffee, caffeinated coffee and caffeine from coffee with the DSST test score and CERAD test score. No significant association was observed between decaffeinated coffee and different dimensions of cognitive performance. Our study suggests that coffee, caffeinated coffee and caffeine from coffee were associated with cognitive performance, while decaffeinated coffee was not associated with cognitive performance.

Association between lifetime coffee consumption and late life cerebral white matter hyperintensities in cognitively normal elderly individuals

Coffee consumption is associated with cerebral hypoperfusion that may contribute to the development of cerebral white matter hyperintensities (WMH). We investigated the effect of lifetime coffee consumption on the volume of WMH (V_WMH) in late life, and compared the effect between men and women since caffeine clearance may be different between sexes. We enrolled 492 community-dwelling cognitively normal elderly individuals (73.4 ± 6.7 years old on average) from the Korean Longitudinal Study on Cognitive Aging and Dementia. We evaluated their patterns and amounts of coffee consumption using a study-specific standardized interview and estimated cerebral V_WMH by automatic segmentation of brain fluid-attenuated inversion recovery sequence magnetic resonance images. Higher cumulative lifetime coffee consumption was associated with higher logV_WMH in both sexes (p = 0.030). The participants who consumed more than 2 cups of coffee per day on average in their lifetime showed higher logV_WMH in late life than those who consumed less. When both sexes were analyzed separately, these coffee-logV_WMH associations were found only in women, although the volumes of brain and white matter of women were smaller than those of men. Our findings suggest that prolonged high coffee consumption may be associated with the risk of WMH in late life.

Associations Between Caffeine Consumption, Cognitive Decline, and Dementia: A Systematic Review

BACKGROUND

Epidemiologic studies have provided inconclusive evidence for a protective effect of caffeine consumption on risk of dementia and cognitive decline.

OBJECTIVE

To summarize literature on the association between caffeine and 1) the risk of dementia and/or cognitive decline, and 2) cognitive performance in individuals with mild cognitive impairment (MCI) or dementia, and 3) to examine the effect of study characteristics by categorizing studies based on caffeine source, quantity and other possible confounders.

METHODS

We performed a systematic review of caffeine effects by assessing overall study outcomes; positive, negative or no effect. Our literature search identified 61 eligible studies performed between 1990 and 2020.

RESULTS

For studies analyzing the association between caffeine and the risk of dementia and/or cognitive decline, 16/57 (28%) studies including a total of 40,707/153,070 (27%) subjects reported positive study outcomes, and 30/57 (53%) studies including 71,219/153,070 (47%) subjects showed positive results that were dependent on study characteristics. Caffeine effects were more often positive when consumed in moderate quantities (100-400 mg/d), consumed in coffee or green tea, and in women. Furthermore, four studies evaluated the relationship between caffeine consumption and cognitive function in cognitively impaired individuals and the majority (3/4 [75% ]) of studies including 272/289 subjects (94%) reported positive outcomes.

CONCLUSION

This review suggests that caffeine consumption, especially moderate quantities consumed through coffee or green tea and in women, may reduce the risk of dementia and cognitive decline, and may ameliorate cognitive decline in cognitively impaired individuals.

Ergogenic effects of caffeine on peak aerobic cycling power during the menstrual cycle

PURPOSE

Recent investigations have established that the ingestion of a moderate dose of caffeine (3-6 mg kg^-1) can increase exercise and sports performance in women. However, it is unknown whether the ergogenicity of caffeine is similar during all phases of the menstrual cycle. The aim of this investigation was to determine the ergogenic effects of caffeine in three phases of the menstrual cycle.

METHODS

Thirteen well-trained eumenorrheic triathletes (age = 31 ± 6 years; body mass = 58.6 ± 7.8 kg) participated in a double-blind, cross-over, randomised experimental trial. In the (1) early follicular (EF); (2) preovulation (PO); (3) and mid luteal (ML) phases, participants either ingested a placebo (cellulose) or 3 mg kg^-1 of caffeine in an opaque and unidentifiable capsule. After a 60-min wait for substance absorption, participants performed an incremental maximal cycle ergometer test until volitional fatigue (25 W/min) to assess peak aerobic cycling power (Wmax).

RESULTS

In comparison to the placebo, caffeine increased Wmax in the EF (4.13 ± 0.69 vs. 4.24 ± 0.71 W kg^-1, Δ = 2.7 ± 3.3%, P = 0.01), in the PO (4.14 ± 0.70 vs. 4.27 ± 0.73 W kg^-1, Δ = 3.3 ± 5.0%; P = 0.03) and in the ML (4.15 ± 0.69 vs. 4.29 ± 0.67 W kg^-1, Δ = 3.6 ± 5.1%; P = 0.01) phases. The magnitude of the caffeine ergogenic effect was similar during all of the menstrual cycle phases (P = 0.85).

CONCLUSION

Caffeine increased peak aerobic cycling power in the early follicular, preovulatory, and mid luteal phases. Thus, the ingestion of 3 mg of caffeine per kg of body mass might be considered an ergogenic aid for eumenorrheic women during all three phases of the menstrual cycle.

The Effect of Caffeine on the Velocity of Half-Squat Exercise during the Menstrual Cycle: A Randomized Controlled Trial

Recent literature confirms the ergogenic effect of acute caffeine intake to increase muscle strength and power in men. However, the information about the effect of caffeine on muscle performance in women is uncertain and it is unknown whether its ergogenicity is similar during the menstrual cycle. The goal of this investigation was to assess the effect of acute caffeine intake on mean and peak velocity of half-squat exercise during three different phases of the menstrual cycle. Thirteen trained eumenorrheic athletes (age = 31 ± 6 years; body mass = 58.6 ± 7.8 kg) participated in a double-blind, crossover and randomized experimental trial. In the early follicular (EFP), late follicular (LFP) and mid luteal phases (MLP), participants either ingested a placebo (cellulose) or 3 mg/kg/bm of caffeine in an opaque and unidentifiable capsule. In each trial, participants performed a half-squat exercise at maximal velocity with loads equivalent to 20%, 40% 60% and 80% of one repetition maximum (1RM). In each load, mean and peak velocity were measured during the concentric phase of the exercise using a rotatory encoder. In comparison to the placebo, a two-way ANOVA showed that the ingestion of 3 mg/kg/bm of caffeine increased mean velocity at 60% 1RM in EFP (Δ = 1.4 ± 2.7%, p = 0.04; ES: 0.2 ± 0.2) and LFP (Δ = 5.0 ± 10.4%, p = 0.04; ES: 0.3 ± 0.4). No other statistical differences were found for the caffeine-placebo comparison for mean velocity, but caffeine induced an ergogenic effect of small magnitude in all of the menstrual cycle phases. These results suggest that the acute intake of 3 mg/kg/bm of caffeine induces a small effect to increase movement velocity during resistance exercise in eumenorrheic female athletes. The positive effect of caffeine was of similar magnitude in all the three phases of the menstrual cycle.

Coffee Ingestion Improves 5 km Cycling Performance in Men and Women by a Similar Magnitude

Caffeine is a well-established ergogenic aid, although research to date has predominantly focused on anhydrous caffeine, and in men. The primary aim of the present study was to investigate the effect of coffee ingestion on 5 km cycling time trial performance, and to establish whether sex differences exist. A total of 38 participants (19 men and 19 women) completed a 5 km time trial following the ingestion of 0.09 g·kg^-1 coffee providing 3 mg·kg^-1 of caffeine (COF), a placebo (PLA), in 300 mL of water, or control (CON). Coffee ingestion significantly increased salivary caffeine levels (p < 0.001; ηP2 = 0.75) and, overall, resulted in improved 5 km time trial performance (p < 0.001; ηP2 = 0.23). Performance following COF (482 ± 51 s) was faster than PLA (491 ± 53 s; p = 0.002; d = 0.17) and CON (487 ± 52 s; p =0.002; d = 0.10) trials, with men and women both improving by approximately 9 seconds and 6 seconds following coffee ingestion compared with placebo and control, respectively. However, no differences were observed between CON and PLA (p = 0.321; d = 0.08). In conclusion, ingesting coffee providing 3 mg·kg^-1 of caffeine increased salivary caffeine levels and improved 5 km cycling time trial performance in men and women by a similar magnitude.

Association between caffeine intake and cognitive function in adults; effect modification by sex: Data from National Health and Nutrition Examination Survey (NHANES) 2013-2014

BACKGROUND & AIMS

The aim of this study was to evaluate the association between caffeine intake and cognitive function.

METHODS

In this cross sectional study, we used data from the 2013-2014 National Health and Nutritional Examination Surveys (NHANES). Our research subjects were 1440 adults aged ≥60 years. The individual's cognitive functions were evaluated using the Consortium to Establish a Registry for Alzheimer's disease (CERAD) Word List Learning Test, CERAD Word List Recall Test, Animal Fluency test, and Digit Symbol Substitution Test (DSST). Participants were categorized based on the quartiles of caffeine intake. In each dimension of cognitive, we calculated and used median value as cut-off point and assessed the association between each dimension (binary) and caffeine intake using multiple logistic regression analysis in different models.

RESULTS

In all of the dimensions, only the highest quartile of caffeine intakes was positively associated with the cognitive function in the crude model and also trend existed (P trend <0.05). After adjusting for potential confounders (age, sex, family income, education, marital status, history of disease, sleep disorders, thyroid problems, physical activity, social support, smoking, and some nutrients), the association was marginally significant in CERAD Word List Recall Test (P trend = 0.09), but was not significant in other dimensions of cognitive function. A statistically significant interaction was noted between caffeine intake and gender in relation to the CERAD Word List Recall Test (P = 0.02).

CONCLUSIONS

Generally, there was a weak positive association between caffeine intake and cognitive performance in older adults that modified by sex. So that, the relation was stronger among male than female.