Individual differences affecting caffeine intake. Analysis of consumption behaviours for different times of day and caffeine sources

Caffeine Consumption in Polish Adults: Development and Validation of a Polish Questionnaire for Assessing Caffeine Intake

Objective: Caffeine is one of the oldest natural substances consumed by people. Its consumption in Poland has not been well described. The aim of this study was to design and validate an online food frequency questionnaire (FFQ) on caffeine intake and to use it to estimate caffeine consumption in Polish adults.Method: The FFQ was prepared and validated in a pilot study. The intake assessment was conducted in 2019-2020 on 372 respondents, aged 18 to 60 years. The FFQ included products such as coffee, tea, energy drinks, and carbonated drinks, as well as supplements and chocolate.Results: We showed good repeatability of the FFQ and it was considered a valid tool. The mean total caffeine intake among all participants was 426.7 mg ± 283.4 mg/day of all sources; in women, it was 446.4 mg ± 306.2 mg/day, while in men, it was 394.1 ± 236.4 mg/day. Forty-three percent of the respondents consumed more than 400 mg of caffeine/day. Coffee was the main source of caffeine and contributed to 65% of total caffeine consumption. Women consumed 90% more green tea than men (p < 0.01). Overweight and obese people have 20% greater total caffeine intake (p = 0.01) and consumed 20% more coffee (p = 0.02) and 30% more black tea (p = 0.01) than people of normal weight.Conclusions: Average caffeine consumption among Polish adults slightly exceeds the safe consumption dose established by the European Food Safety Authority. Body weight status can differentiate caffeine intake.

Differences in Dietary Intake, Eating Occasion Timings and Eating Windows between Chronotypes in Adults Living with Type 2 Diabetes Mellitus

Chronotype studies investigating dietary intake, eating occasions (EO) and eating windows (EW) are sparse in people with type 2 Diabetes mellitus (T2DM). This analysis reports data from the CODEC study. The Morningness-Eveningness questionnaire (MEQ) assessed chronotype preference. Diet diaries assessed dietary intake and temporal distribution. Regression analysis assessed whether dietary intake, EW, or EO differed by chronotype. 411 participants were included in this analysis. There were no differences in energy, macronutrient intake or EW between chronotypes. Compared to evening chronotypes, morning and intermediate chronotypes consumed 36.8 (95% CI: 11.1, 62.5) and 20.9 (95% CI: -2.1, 44.1) fewer milligrams of caffeine per day, respectively. Evening chronotypes woke up over an hour and a half later than morning (01:36 95% CI: 01:09, 02:03) and over half an hour later than intermediate chronotypes (00:45 95% CI: 00:21; 01:09. Evening chronotypes went to sleep over an hour and a half later than morning (01:48 95% CI: 01:23; 02:13) and an hour later than intermediate chronotypes (01:07 95% CI: 00:45; 01:30). Evening chronotypes' EOs and last caffeine intake occurred later but relative to their sleep timings. Future research should investigate the impact of chronotype and dietary temporal distribution on glucose control to optimise T2DM interventions.

Sustainable coffee capsule consumption: Understanding Italian consumers' purchasing drivers

Introduction

Coffee is among the most appreciated beverages by consumers globally. Single serve coffee market expands and is highly profitable, but coffee in capsules (CIC) raises a major issue of environmental sustainability. The coffee industry aims to expand the CIC sales and to reduce capsule environmental impact and waste. To better define a sustainability-oriented strategy, the coffee industry needs to understand how to approach different socio-economic consumer groups. Thus, this study aims to explore consumers' perception and awareness of sustainable CIC, with specific attention on consumers' socio-economic characteristics.

Methods

The study interviewed a sample of 261 Italian consumers. Data elaboration includes four main steps: a cluster analysis leading to three socio-economic groups, a factor and structural equation modeling to confirm the factors and the relation between CIC sustainability and quality factors, and a multinomial logistic regression to examine the factors that drive the likeliness of consumers' willingness to purchase sustainable CIC.

Results

Results support that all groups of consumers value sustainability attribute as main CIC purchasing decision driver. The sustainability factor does not show any significance on the explanation of the CIC quality factor. Consumer perception of the CIC sustainability is not affected by age, income, level of education, and gender.

Conclusion

This study provides preliminary insights for sustainable CIC production and consumption.

Relationship between chronotype and consumption of stimulants

Consumption of some stimulants may lead to health problems. The aim of the study was to identify a potential correlation between extreme chronotypes and the tendency to use various stimulants. The preferred time of consumption was also checked, both on working and nonworking days. The study was conducted in January 2020 using the CAWI method. 306 people took part in the survey. To determine the chronotype of the surveyed people, the polish version of MEQ questionnaire (Morningness - Eveningness Questionnaire) was used. Because 178 respondents were intermediate types, 128 people participated in the second part of the study, including 68 owls and 60 larks. Activity preferences during the day of respondents were checked and compared with data about the quantity and frequency of using stimulants like coffee, energy drinks, alcohol and cigarettes. Chi-square test was used for testing relationships. The time periods for taking stimulants differed between groups and were associated with activity during the day. It has been shown that people with evening chronotype use more energy drinks (p = .009), alcohol drinks (p = .013) and cigarettes or e-cigarettes (p = .021), especially in the group of respondents aged ≥30. Social jet lag was statistically higher in the group of owls and larks; however, consumption of stimulants depended on age and chronotype, not social jet lag. People with the morning chronotype are less likely to use stimulants. Owls showed a greater and more frequent use of energy drinks, alcohol and cigarettes, especially those older than 30 years. Assessing eveningness among people aged more than 30 may be helpful in characterizing an overall risk profile.

Coffee Consumption and All-Cause, Cardiovascular, and Cancer Mortality in an Adult Mediterranean Population

We assessed the association between usual coffee consumption and all-cause, cardiovascular (CV), and cancer mortality in an adult population in Spain, taking into account both the amount and type of coffee consumed. We used baseline data on coffee consumption and other personal variables, and the number of deaths during an 18-year follow-up period, for 1567 participants aged 20 years and older from the Valencia Nutrition Study in Spain. Total, caffeinated, and decaffeinated coffee consumption was assessed using a validated food frequency questionnaire. Cox regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). During the 18-year follow-up period, 317 died; 115 due to CV disease and 82 due to cancer. Compared with no-consumption, the consumption of ≤1 cup per day and >1 cup per day of coffee was associated with a lower risk of all-cause mortality, HR = 0.73 (95% CI: 0.56–0.97) and HR 0.56 (95% CI: 0.41–0.77), respectively. A lower cancer mortality was observed among drinkers of more than 1 cup per day compared with nondrinkers, HR 0.41 (95% CI 0.20–0.86). Regarding the type of coffee, only the overall consumption of caffeinated coffee was associated with lower all-cause mortality at 12 and 18 years of follow-up, HR = 0.66 (95% CI:0.46–0.94) and HR = 0.59 (95% CI: 0.44–0.79), respectively. In conclusion, this study suggests that the moderate consumption of coffee, particularly caffeinated coffee (range 1–6.5 cups per day), is associated with a lower all-cause and cancer mortality after a long follow-up period. No significant association was found between coffee consumption and CVD mortality.

Relationships between use of dietary supplements, caffeine and sensation seeking among college students

Objective: Caffeine and dietary supplement (DS) use by college students is not well-documented. Given reported associations between energy drink consumption and sensation seeking, we used the Sensation Seeking Scale Form V (SSS-V) to assess relationships between sensation-seeking, caffeine, and DS use. Participants: Data from 1,248 college students from five US institutions were collected from 2009 to 2011. Methods: Linear regression was used to examine relationships between scores on the SSS-V and caffeine and DS use, demographic, and lifestyle characteristics. Results: Male sex, nonHispanic race-ethnicity, higher family income, tobacco use, consuming caffeinated beverages, more than 400 mg caffeine per day, and energy drinks with alcohol at least 50% of the time, were significantly associated with higher total SSS-V scores (P < 0.001). Those using protein DSs had higher total, disinhibition, and boredom susceptibility SSS-V scores (Ps < 0.001). Conclusions: Results demonstrate a positive correlation between sensation-seeking attitudes and habitual caffeine, energy drink, and DS consumption.

Is it the Taste or the Buzz? Alexithymia, Caffeine, and Emotional Eating

BACKGROUND

Alexithymia, a relatively stable personality trait characterized by difficulties identifying and describing feelings and externally oriented thinking, has been linked to both substance use disorders and eating disorders. In nonclinical samples, alexithymia is associated with heavier consumption of alcohol and caffeine. Both are psychoactive drugs, but unlike most drugs they are typically consumed in the context of palatable and calorie-rich products.

OBJECTIVES

Given the association of alexithymia with disordered eating, the present study evaluated the hypothesis that heavier consumption of caffeine by those with high levels of alexithymia may be motivated by the palatable and caloric aspects of common caffeine products rather than by drug-seeking.

METHODS

There were 224 participants aged 17-63 years who completed instruments assessing demographics, alexithymia, emotional eating, caffeine consumption, alcohol consumption, negative moods, and reward sensitivity.

RESULTS

As predicted, alexithymia was positively related to emotional eating as well as consumption of caffeine and alcohol, and alexithymia was a significant predictor of caffeine intake in regression models. However, there was no indication of mediation by emotional eating.

CONCLUSIONS

Alexithymia is characterized by deficient emotion regulation and negative moods, hence use of drugs and/or foods to regulate emotions, combined with poor interoceptive awareness, may account for excessive consumption of drugs or foods as alternative emotion regulation strategies in those with high levels of this trait.

Gray’s Personality Dimensions and Reasons for Voluntary Sleep Deprivation Among College Students

Tendency toward healthy and health-risk behavior is associated with external factors, and healthy lifestyle affects its quality. Activation of Behavioral Inhibition System (BIS) and Behavioral Activation System (BAS) and its association with sleeping habits provides insight into the correlates of voluntary sleep deprivation. Aim of the study was to evaluate the relationship between BIS/BAS activity and reasons for voluntary sleep deprivation among young adults and to assess benefits and costs of decreasing sleep duration. Participants were 223 college students. The instruments used were the BIS/BAS Scale, Pittsburgh Sleep Quality Index and a newly developed survey. Statistical analysis wasconducted using Mann-Whitney’s U-test and Spearman’s rho correlation. Increased BIS activity is positively correlated with the frequency of foregoing sleep to study (r = 0.19; p < 0.01), while activation of BAS Fun Seeking is associated with more frequent voluntary sleep deprivation due to work (r = 0.18; p < 0.05), social life (r = 0.34; p < 0.01), and participation in various types of entertainment (p = 0.24; p < 0.01). Analysis yielded a positive correlation between BAS activity and the amount of perceived benefits of cutting down sleep (p = 0.26; p < 0.01 for BAS Fun Seeking and p = 0.25; p < 0.01 for BAS Reward Responsiveness) and the magnitude of BIS activation and the number of perceived losses (r = 0.19; p < 0.01). Individuals with a higher BAS activity in the Reward Responsiveness subscale more often report choosing sleep deprivation voluntarily (r = 0.14; p < 0.5). The quality of sleep is related to BIS/BAS activation. The reasons for voluntary sleep deprivation differ depending on the level of BAS/BIS activation.

Coffee Drinking and Associated Factors in an Elderly Population in Spain

Coffee consumption is highly prevalent worldwide, and many studies have reported positive and inverse associations of coffee with many diseases. However, factors associated with coffee consumption remain poorly characterized in some populations, such as the elderly. This study aimed to assess the factors associated with total, caffeinated and decaffeinated coffee consumption in an elderly population in Spain. Data were analyzed from 903 participants, aged 65 years and above, from two population-based studies carried out in the Valencia region in Spain (Valencia Nutritional Survey (VNS) and European Eye Study (EUREYE-Study). Total, caffeinated and decaffeinated coffee consumption was assessed through two specific questions using a validated food frequency questionnaire. Information on personal characteristics, anthropometry and lifestyles was collected in personal interviews. Multinomial logistic regression analysis was used to estimate the adjusted relative risk ratios (RRR) and confidence intervals (95% CI). The prevalence of total, caffeinated and decaffeinated coffee consumption was 70%, 38% and 32%, respectively. The consumption of caffeinated coffee was positively associated with: Educational level, RRR = 1.63 (1.09–2.44); body mass index (≥30), RRR = 2.03 (1.05–3.95); tobacco smoking, RRR = 1.96 (1.13–3.39); alcohol intake [≥12 g/day category intake vs. no-alcohol intake, RRR = 6.25 (3.56–10.95)]; and energy intake (p < 0.05). Consumption of caffeinated coffee was negatively associated with: Age (≥75 years), RRR = 0.64 (0.43–0.94); and pre-existing hypertension, RRR = 0.67 (0.45–0.98). The consumption of decaffeinated coffee was positively associated with: Alcohol intake, RRR = 2.63 (1.19–4.64); pre-existing diabetes, RRR = 1.67 (1.06–2.62); and energy intake (p < 0.01). The consumption of coffee is high among elderly people in Spain. It is a novelty in this study with elderly population that tobacco smoking and alcohol drinking were the two main factors associated with higher coffee consumption. Self-reported hypertension was associated with a lower consumption of caffeinated coffee, and pre-existing diabetes was associated with a higher consumption of decaffeinated coffee. These associations should be taken into account when the health effects of coffee consumption are investigated.

Coffee consumption and purchasing behavior review: Insights for further research

This paper presents a systematic literature review of consumer research towards coffee with the objective to identify and categorize motives, preferences and attributes of coffee consumption and purchasing behavior. Research papers were analyzed in terms of main characteristics and components (study type, research methodology, sampling, and product type). The review gives a systematic overview of the heterogeneous group of concepts and approaches that have been used so far to examine consumer behavior towards coffee. Results provide a model of key determinants for coffee consumption that can be grouped into the categories, (1) personal preferences, (2) economic attributes, (3) product attributes, (4) context of consumption, and (5) socio-demographics. The findings also show that there is a strong focus on coffee sustainability.

Effects of processing parameters on the caffeine extraction yield during decaffeination of black tea using pilot-scale supercritical carbon dioxide extraction technique

In this pilot-scale study supercritical carbon dioxide (SCCO₂) extraction technique was used for decaffeination of black tea. Pressure (250, 375, 500 bar), extraction time (60, 180, 300 min), temperature (55, 62.5, 70 °C), CO₂ flow rate (1, 2, 3 L/min) and modifier quantity (0, 2.5, 5 mol%) were selected as extraction parameters. Three-level and five-factor response surface methodology experimental design with a Box-Behnken type was employed to generate 46 different processing conditions. 100% of caffeine from black tea was removed under two different extraction conditions; one of which was consist of 375 bar pressure, 62.5 °C temperature, 300 min extraction time, 2 L/min CO₂ flow rate and 5 mol% modifier concentration and the other was composed of same temperature, pressure and extraction time conditions with 3 L/min CO₂ flow rate and 2.5 mol% modifier concentration. Results showed that extraction time, pressure, CO₂ flow rate and modifier quantity had great impact on decaffeination yield.

Effects of acute and chronic caffeine on risk-taking behavior in children and adolescents

Consumption of caffeinated beverages is associated with increased risk-taking behavior. The purpose of this study was to determine if acute caffeine administration influences risk-taking behavior in a dose-dependent manner. Participants were pre- (ages 8-9) and post-pubertal (ages 15-17) children who visited the laboratory three times and consumed a beverage containing 0, 1, or 2 mg/kg of caffeine. Thirty minutes later, participants completed the balloon analogue risk task (BART), the Iowa gambling task (IGT), and a delay discounting task. The number of balloons exploded on the BART task was significantly increased after 2 mg/kg of caffeine in moderate caffeine consumers, but was decreased after 2 mg/kg of caffeine in high caffeine consumers. There were no main effects of caffeine dose on the delay discounting task or on the IGT. Post-pubertal participants showed reduced delay discounting compared with pre-pubertal participants. Finally, average daily caffeine use was significantly, positively correlated with scores on a risk-taking questionnaire. These data suggest that caffeine dose-dependently influences decision making and risk taking. More research is needed to determine the mechanism of this difference as well as the extent to which sex and pubertal phase influence these relationships.

A case-control field study on the relationships among type 2 diabetes, sleepiness and habitual caffeine intake

OBJECTIVES

The purpose of this study was to examine the possible links between type 2 diabetes, daytime sleepiness, sleep quality and caffeine consumption.

METHODS

In this case-control field study, comparing type 2 diabetic ( n=134) and non-type 2 diabetic ( n=230) participants, subjects completed detailed and validated questionnaires to assess demographic status, health, daytime sleepiness, sleep quality and timing, diurnal preference, mistimed circadian rhythms and habitual caffeine intake. All participants gave saliva under standardised conditions for CYP1A2 genotyping and quantification of caffeine concentration. Hierarchical linear regression analyses examined whether type 2 diabetes status was associated with caffeine consumption.

RESULTS

Type 2 diabetic participants reported greater daytime sleepiness ( p=0.001), a higher prevalence of sleep apnoea ( p=0.005) and napping ( p=0.008), and greater habitual caffeine intake ( p<0.001), derived from the consumption of an extra cup of coffee each day. This finding was confirmed by higher saliva caffeine concentration at bedtime ( p=0.01). Multiple regression analyses revealed that type 2 diabetes status was associated with higher self-reported caffeine consumption ( p<0.02) and higher salivary caffeine ( p<0.02). Next to male sex, type 2 diabetes status was the strongest predictor of caffeine intake. Subjective sleep and circadian estimates were similar between case and control groups.

CONCLUSIONS

Type 2 diabetic patients may self-medicate with caffeine to alleviate daytime sleepiness. High caffeine intake reflects a lifestyle factor that may be considered when promoting type 2 diabetes management.

Caffeine consumption patterns and determinants among adolescents in Serbia

BACKGROUND

The number of adolescents who use caffeine is constantly increasing. As juvenile age is vulnerable, it is reasonable to expect that they will differently perceive reason and react to caffeine use than adults, and be more prone to unwanted physiological and psychological consequences of its consumption.

AIM

Analysis of the scope and pattern of caffeine consumption among adolescents in Serbia.

STUDY DESIGN

The cross-sectional survey was implemented in the study population of 191 Serbian adolescents during 2010.

RESULTS

The median daily intake of caffeine was 95.6 mg. The major source of caffeine was brewed coffee, and the most common reasons for caffeine intake were leisure, peer influence, or habit. Only 57.6% of the subjects were aware that caffeine is present in consumed beverages. Sex affected the pattern, but not the overall level, of caffeine consumption. No association between caffeine consumption and smoking status, frequency of caffeine use in the family, or negative personal experience with caffeine effects was observed.

CONCLUSION

Our investigation provides first and rather detailed insight into caffeine-containing beverage consumption scope and pattern among Serbian adolescents. For accurate estimation and analysis of caffeine intake in this population, randomized studies with prospective longitudinal design, caffeine content measurement, and more subjects involved are warranted.

Subjective Responses to Caffeine Are Influenced by Caffeine Dose, Sex, and Pubertal Stage

Background: Our previous work has shown that there are sex differences in subjective responses to acute caffeine administration in adolescents. The purpose of this study was to determine if these sex differences are dependent on pubertal development. Materials and Methods: We examined subjective responses before and after administration of 0, 1, and 2 mg/kg of caffeine in pre- and postpubertal boys and girls (n = 112). In addition, we examined differences in subjective responses to acute caffeine in both the luteal and follicular phases of the menstrual cycle in postpubertal girls. Results: Caffeine at both doses resulted in greater changes in responses on the Addiction Research Center Inventory and the Brief Assessment of Mood States compared with placebo. Girls reported greater increases from baseline to peak in feeling different and liking the feeling than boys after 2 mg/kg of caffeine regardless of pubertal stage. Postpubertal girls also had a greater decrease from baseline in reports of feeling high and greater increases from baseline in reports of wanting more than postpubertal males. Finally, girls had greater changes (both increases and decreases) in responses on the Brief Mood Questionnaire when in the follicular phase compared with the luteal phase. This was also true for reports of feeling high and feeling different on the Drug Effects Questionnaire. None of these effects varied as a function of usual caffeine use, suggesting that differences are not the result of tolerance or sensitization. Conclusions: These results suggest that subjective responses to caffeine emerge before puberty, but sex differences may be strengthened after pubertal development.

Do gamblers eat more salt? Testing a latent trait model of covariance in consumption

A diverse class of stimuli, including certain foods, substances, media, and economic behaviours, may be described as 'reward-oriented' in that they provide immediate reinforcement with little initial investment. Neurophysiological and personality concepts, including dopaminergic dysfunction, reward sensitivity and rash impulsivity, each predict the existence of a latent behavioural trait that leads to increased consumption of all stimuli in this class. Whilst bivariate relationships (co-morbidities) are often reported in the literature, to our knowledge, a multivariate investigation of this possible trait has not been done. We surveyed 1,194 participants (550 male) on their typical weekly consumption of 11 types of reward-oriented stimuli, including fast food, salt, caffeine, television, gambling products, and illicit drugs. Confirmatory factor analysis was used to compare models in a 3×3 structure, based on the definition of a single latent factor (none, fixed loadings, or estimated loadings), and assumed residual covariance structure (none, a-priori / literature based, or post-hoc / data-driven). The inclusion of a single latent behavioural 'consumption' factor significantly improved model fit in all cases. Also confirming theoretical predictions, estimated factor loadings on reward-oriented indicators were uniformly positive, regardless of assumptions regarding residual covariances. Additionally, the latent trait was found to be negatively correlated with the non-reward-oriented indicators of fruit and vegetable consumption. The findings support the notion of a single behavioural trait leading to increased consumption of reward-oriented stimuli across multiple modalities. We discuss implications regarding the concentration of negative lifestyle-related health behaviours.

Sex differences on the acute effects of caffeine on maximal strength and muscular endurance

The aim of this study was to look at the effects of caffeine on strength performance and to examine any differences between sexes. Sixteen moderately active, resistance-trained individuals (10 males and 8 females) performed 2 trials (excluding a familiarisation trial). The effect of 5 mg/kg body mass (BM) caffeine or a placebo on bench press (BP) one repetition maximum (1RM), squat 1RM, the number of BP reps to failure at 40% 1RM (total weight lifted; TWL), pain rating (0-10) were recorded after each final successful lift. BP 1RM was significantly greater (P=0.016), with an increase of 5.91% for males and an increase of 10.69% for females. However, there was no sex difference in squat 1RM with males producing 130.3±27.8 and 134.0±28.9 kg and females producing 66.9±6.2 and 65.3±7.0 kg for placebo and caffeine, respectively. TWL tended to increase with caffeine for males from 1,246.8±704.9 to 1,545.5±920.3 kg; with females having no effect of caffeine (397.8±245.1 to 398.8±182.7kg; P=0.06). Caffeine had no effect on pain perception. This study found that 5 mg/kg BM caffeine improved BP 1RM in resistance-trained males and females. However, for TWL there was a tendency towards improvement in males only, suggesting a sex difference to caffeine ingestion for TWL.

Cardiovascular responses to caffeine by gender and pubertal stage

BACKGROUND

Caffeine use is on the rise among children and adolescents. Previous studies from our laboratory reported gender differences in the effects of caffeine in adolescents. The purpose of this study was to test the hypotheses that gender differences in cardiovascular responses to caffeine emerge after puberty and that cardiovascular responses to caffeine differ across the phases of the menstrual cycle.

METHODS

To test these hypotheses, we examined heart rate and blood pressure before and after administration of placebo and 2 doses of caffeine (1 and 2 mg/kg) in prepubertal (8- to 9-year-olds; n = 52) and postpubertal (15- to 17-year-olds; n = 49) boys (n = 54) and girls (n = 47) by using a double-blind, placebo-controlled, dose-response design.

RESULTS

There was an interaction between gender and caffeine dose, with boys having a greater response to caffeine than girls. In addition, we found interactions between pubertal phase, gender, and caffeine dose, with gender differences present in postpubertal, but not in prepubertal, participants. Finally, we found differences in responses to caffeine across the menstrual cycle in post-pubertal girls, with decreases in heart rate greater in the midluteal phase and blood pressure increases greater in the midfollicular phase of the menstrual cycle.

CONCLUSIONS

These data suggest that gender differences in response to caffeine emerge after puberty. Future research will determine the extent to which these gender differences are mediated by physiological factors, such as steroid hormones, or psychosocial factors, such as more autonomy and control over beverage purchases.

Differences between the nonselective adenosine receptor antagonists caffeine and theophylline in motor and mood effects: studies using medium to high doses in animal models

RATIONALE

Caffeine and theophylline are methylxanthines that are broadly consumed, sometimes at high doses, and act as minor psychostimulants. Both are nonselective adenosine antagonists for A1 and A2A receptors, which are colocalized with dopamine D1 and D2 receptors in striatal areas. Adenosine antagonists generally have opposite actions to those of dopamine antagonists. Although the effects of caffeine are widely known, theophylline has been much less well characterized, especially at high doses.

METHODS

Adult male CD1 mice were used to study the effect of a broad range of doses (25.0, 50.0 or 100.0mg/kg) of caffeine and theophylline on measures of spontaneous locomotion and coordination, as well as the pattern of c-Fos immunoreactivity in brain areas rich in adenosine and dopamine receptors. In addition, we evaluated possible anxiety and stress effects of these doses.

RESULTS

Caffeine, at these doses, impaired or suppressed locomotion in several paradigms. However, theophylline was less potent than caffeine at suppressing motor parameters, and even stimulated locomotion. Both drugs induced corticosterone release, however caffeine was more efficacious at intermediate doses. While caffeine showed an anxiogenic profile at all doses, theophylline only did so at the highest dose used (50mg/kg). Only theophylline increased c-Fos immunoreactivity in cortical areas.

CONCLUSION

Theophylline has fewer disruptive effects than caffeine on motor parameters and produces less stress and anxiety effects. These results are relevant for understanding the potential side effects of methylxanthines when consumed at high doses.

Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed

STUDY OBJECTIVE

Sleep hygiene recommendations are widely disseminated despite the fact that few systematic studies have investigated the empirical bases of sleep hygiene in the home environment. For example, studies have yet to investigate the relative effects of a given dose of caffeine administered at different times of day on subsequent sleep.

METHODS

This study compared the potential sleep disruptive effects of a fixed dose of caffeine (400 mg) administered at 0, 3, and 6 hours prior to habitual bedtime relative to a placebo on self-reported sleep in the home. Sleep disturbance was also monitored objectively using a validated portable sleep monitor.

RESULTS

Results demonstrated a moderate dose of caffeine at bedtime, 3 hours prior to bedtime, or 6 hours prior to bedtime each have significant effects on sleep disturbance relative to placebo (p < 0.05 for all).

CONCLUSION

The magnitude of reduction in total sleep time suggests that caffeine taken 6 hours before bedtime has important disruptive effects on sleep and provides empirical support for sleep hygiene recommendations to refrain from substantial caffeine use for a minimum of 6 hours prior to bedtime.

Adolescent caffeine consumption and self-reported violence and conduct disorder

Caffeine is the most widely used psychoactive substance in the world and currently the only one legally available to children and adolescents. The sale and use of caffeinated beverages has increased markedly among adolescents during the last decade. However, research on caffeine use and behaviors among adolescents is scarce. We investigate the relationship between adolescent caffeine use and self-reported violent behaviors and conduct disorders in a population-based cross-sectional sample of 3,747 10th grade students (15-16 years of age, 50.2 % girls) who were enrolled in the Icelandic national education system during February 2012. Through a series of multiple regression models, while controlling for background factors, Attention Deficit Hyperactivity Disorder symptoms and current medication and peer delinquency, and including measures on substance use, our findings show robust additive explanatory power of caffeine for both violent behaviors and conduct disorders. In addition, the association of caffeine to the outcomes is significantly stronger for girls than boys for both violent behaviors and conduct disorders. Future studies are needed to examine to what extent, if at all, these relationships are causal. Indication of causal connections between caffeine consumption and negative outcomes such as those reported here would call into question the acceptability of current policies concerning the availability of caffeine to adolescents and the targeting of adolescence in the marketing of caffeine products.