Influence of caffeine and caffeine withdrawal on headache and cerebral blood flow velocities

Repeated caffeine intake suppresses cerebral grey matter responses to chronic sleep restriction in an A1 adenosine receptor-dependent manner: a double-blind randomized controlled study with PET-MRI

Evidence has shown that both sleep loss and daily caffeine intake can induce changes in grey matter (GM). Caffeine is frequently used to combat sleepiness and impaired performance caused by insufficient sleep. It is unclear (1) whether daily use of caffeine could prevent or exacerbate the GM alterations induced by 5-day sleep restriction (i.e. chronic sleep restriction, CSR), and (2) whether the potential impact on GM plasticity depends on individual differences in the availability of adenosine receptors, which are involved in mediating effects of caffeine on sleep and waking function. Thirty-six healthy adults participated in this double-blind, randomized, controlled study (age = 28.9 ± 5.2 y/; F:M = 15:21; habitual level of caffeine intake < 450 mg; 29 homozygous C/C allele carriers of rs5751876 of ADORA2A, an A2A adenosine receptor gene variant). Each participant underwent a 9-day laboratory visit consisting of one adaptation day, 2 baseline days (BL), 5-day sleep restriction (5 h time-in-bed), and a recovery day (REC) after an 8-h sleep opportunity. Nineteen participants received 300 mg caffeine in coffee through the 5 days of CSR (CAFF group), while 17 matched participants received decaffeinated coffee (DECAF group). We examined GM changes on the 2nd BL Day, 5th CSR Day, and REC Day using magnetic resonance imaging and voxel-based morphometry. Moreover, we used positron emission tomography with [18F]-CPFPX to quantify the baseline availability of A1 adenosine receptors (A1R) and its relation to the GM plasticity. The results from the voxel-wise multimodal whole-brain analysis on the Jacobian-modulated T1-weighted images controlled for variances of cerebral blood flow indicated a significant interaction effect between caffeine and CSR in four brain regions: (a) right temporal-occipital region, (b) right dorsomedial prefrontal cortex (DmPFC), (c) left dorsolateral prefrontal cortex (DLPFC), and (d) right thalamus. The post-hoc analyses on the signal intensity of these GM clusters indicated that, compared to BL, GM on the CSR day was increased in the DECAF group in all clusters  but decreased in the thalamus, DmPFC, and DLPFC in the CAFF group. Furthermore, lower baseline subcortical A1R availability predicted a larger GM reduction in the CAFF group after CSR of all brain regions except for the thalamus. In conclusion, our data suggest an adaptive GM upregulation after 5-day CSR, while concomitant use of caffeine instead leads to a GM reduction. The lack of consistent association with individual A1R availability may suggest that CSR and caffeine affect thalamic GM plasticity predominantly by a different mechanism. Future studies on the role of adenosine A2A receptors in CSR-induced GM plasticity are warranted.

Effects of caffeine on cerebral blood flow

OBJECTIVE

The objective of the present study is to evaluate whether, after caffeine ingestion, there are variations in blood velocity of the middle cerebral arteries in clinically healthy young people as well as to evaluate whether this variation is dependent on the administered dose.

METHODS

We used transcranial Doppler ultrasonography to record blood velocities of the middle cerebral arteries in three groups of 15 clinically healthy young adults each: no caffeine, a45 mg, and 120 mg of caffeine groups. Transcranial Doppler ultrasonography provided simultaneous bilateral velocity of the middle cerebral arteries measurements while participants performed functional tests (hyperventilation and hypoventilation orders) and three cognitive activities (test 1, short-term memory; test 2, solving a vocabulary problem; and test 3, solving a math problem) each in 31-s tests with 1-min rests between them. Participants were assessed before and 30 min after caffeine ingestion.

RESULTS

There was a significant decrease in mean velocity, peak systolic velocity, end-diastolic velocity, and heart rate after high caffeine intake, except in hyperventilation, which was only observed in peak systolic velocity. With the intake of a lower dose, significant decreases were seen with hypoventilation and with test 1. In hyperventilation, there was only a significant decrease in end-diastolic velocity and heart rate; in test 2, it was found in mean velocity and peak systolic velocity; and in test 3, only in heart rate.

CONCLUSION

With this study, we conclude that caffeine influences the cardiovascular system acutely, interfering with the velocity of the middle cerebral arteries, causing its decrease. We also conclude that this acute effect causes vasodilation of the cerebral arteries, more accentuated with higher doses of caffeine.

Weekend Headaches in School-Age Children

Children commonly encounter primary headaches, with various factors playing a role in their onset. The daily routine notably contributes to the occurrence of primary headaches in children. This study aims to profile children experiencing headaches on weekends (WH) in comparison to those primarily having headaches midweek (MWH). Out of 109 children visiting a pediatric headache clinic, 60 prospectively filled out questionnaires regarding their headaches. The average age was 11.8 years, and 63% were of female sex. Most of the children suffered from migraine headaches (60%), while the rest suffered from tension-type headaches (TTH, 15%), mixed headaches (17%), or undetermined headaches (8%). None of the children suffered from a headache only on the weekend. In contrast, 14 (23%) children suffered from a headache exclusively in midweek. Children with learning difficulties were similarly distributed between the WH and the MWH groups (48% and 52%, respectively). Children without learning difficulties suffered significantly more from MWH compared to WH (79% vs. 21%, respectively). In conclusion, children did not suffer from WH alone. Self-reported triggers were not significantly different in WH and MWH patients. Proper profiling of headache types and triggers may lead to more accurate management of these patients.

Migraine without aura

Migraine without aura is the commonest form of migraine in both children and adults. The diagnosis is made by applying the International Classification of Headache Disorders Third Edition subsection for migraine without aura (ICHD-3 subsection 1.1). Attacks in patients with migraine without aura are characterized by their polyphasic presentation (prodrome, headache phase, postdromal phase). The symptomatology of attacks is diverse and heterogeneous, with most common symptoms being photophobia, phonophobia, nausea, vomiting, and aggravation of pain by movement. The clinician and researcher who wants to learn about migraine without aura needs to be able to apply the ICHD-3 criteria with its specific symptomatology to make a correct diagnosis, but also needs to be aware about the plethora of symptoms patients may experience. In this chapter, the reader will explore the clinical phenotypical features of migraine without aura.

Caffeine consumption as a risk factor for childhood and adolescence migraine

BACKGROUND

Caffeine consumption is a risk factor for chronic daily headache but few studies have addressed relationships between pediatric patient caffeine levels and headache severity. We examined associations between serum and urine caffeine levels and headache severity in childhood and adolescent migraine cases.

METHODS

Levels of caffeine and caffeine metabolites in serum and urine samples were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The Wilcoxon rank-sum test was used for comparisons of age, sleep time, headache severity, caffeine consumption, and caffeine detection. Spearman's rank correlation coefficient (ρ) was calculated for associations. Correlations where ρ ≥ 0.3 and differences where p < 0.05 were considered statistically significant.

RESULTS

Of the 40 patients studied, 34 declared caffeine consumption and six declared no caffeine consumption. These two groups did not differ significantly in any of the above clinical parameters. Liquid chromatography-tandem mass spectrometry analysis of both serum and urine samples revealed nine caffeine-negative (level <0.0625 μM) and 31 caffeine-positive cases. The Headache Impact Test-6 (HIT-6) score was higher (p = 0.033) for the caffeine-positive group versus the caffeine-negative group. Caffeine was detected by LC-MS/MS in the serum and/or urine of three of the six patients who declared no caffeine consumption. No significant correlations were observed among age, sleep times, headache severity score, or levels of caffeine and caffeine metabolites.

CONCLUSION

Thirty one of 40 (77.5%) cases of childhood/ adolescence migraine showed serum and urine caffeine positivity based on LC-MS/MS. The HIT-6 score, a measure of headache severity, was significantly higher for caffeine-positive versus caffeine-negative cases. Symptoms of childhood/adolescence migraine were exacerbated by caffeine consumption.

Time to Recover From Daily Caffeine Intake

Caffeine elicits widespread effects in the central nervous system and is the most frequently consumed psychostimulant worldwide. First evidence indicates that, during daily intake, the elimination of caffeine may slow down, and the primary metabolite, paraxanthine, may accumulate. The neural impact of such adaptions is virtually unexplored. In this report, we leveraged the data of a laboratory study with N = 20 participants and three within-subject conditions: caffeine (150 mg caffeine × 3/day × 10 days), placebo (150 mg mannitol × 3/day × 10 days), and acute caffeine deprivation (caffeine × 9 days, afterward placebo × 1 day). On day 10, we determined the course of salivary caffeine and paraxanthine using liquid chromatography-mass spectrometry coupled with tandem mass spectrometry. We assessed gray matter (GM) intensity and cerebral blood flow (CBF) after acute caffeine deprivation as compared to changes in the caffeine condition from our previous report. The results indicated that levels of paraxanthine and caffeine remained high and were carried overnight during daily intake, and that the levels of paraxanthine remained elevated after 24 h of caffeine deprivation compared to placebo. After 36 h of caffeine deprivation, the previously reported caffeine-induced GM reduction was partially mitigated, while CBF was elevated compared to placebo. Our findings unveil that conventional daily caffeine intake does not provide sufficient time to clear up psychoactive compounds and restore cerebral responses, even after 36 h of abstinence. They also suggest investigating the consequences of a paraxanthine accumulation during daily caffeine intake.

Caffeine supplementation in the hospital: Potential role for the treatment of caffeine withdrawal

Caffeine use in the population is widespread. Caffeine withdrawal in the hospital setting is an underappreciated syndrome with symptoms including drowsiness, difficulty concentrating, mood disturbances, low motivation, flu-like symptoms, and headache. Withdrawal may occur upon abstinence from chronic daily exposure at doses as low as 100 mg/day and following only 3-7 days of consumption at higher doses. There are limited data investigating how caffeine withdrawal contributes to hospital morbidity. Some studies suggest caffeine withdrawal may contribute to intensive care delirium and that caffeine may promote wakefulness post-anesthesia. Caffeine supplementation has also shown promise in patients at risk of caffeine withdrawal, such as those placed on nil per os (NPO) status, in preventing caffeine withdrawal headache. These data on caffeine supplementation are not entirely consistent, and routine caffeine administration has not been implemented into clinical practice for patients at risk of withdrawal. Notably, caffeine serves a therapeutic role in the hospital for other conditions. Our review demonstrates that caffeine is largely safe in the general population and may be an appropriate therapeutic option for future studies, if administered properly. There is a need for a randomized controlled trial investigating in-hospital caffeine supplementation and the population that this would best serve.

Lifestyle Modifications to Help Prevent Headache at a Developmental Age

Headache is the world's seventh most significant cause of disability-adjusted-life in people aged between 10 and 14 years. Therapeutic management is based on pharmacological approaches and lifestyle recommendations. Many studies show associations between each migraine-promoting lifestyle, behavioral triggers, frequency, and intensity of headaches. Nevertheless, the overall aspects of this topic lack any definitive evidence. Educational programs advise that pediatric patients who suffer from migraines follow a correct lifestyle and that this is of the utmost importance in childhood, as it will improve quality of life and assist adult patients in avoiding headache chronicity, increasing general well-being. These data are important due to the scarcity of scientific evidence on drug therapy for prophylaxis during the developmental age. The "lifestyle recommendations" described in the literature include a perfect balance between regular sleep and meal, adequate hydration, limited consumption of caffeine, tobacco, and alcohol, regular physical activity to avoid being overweight as well as any other elements causing stress. The ketogenic diet is a possible new therapeutic strategy for the control of headache in adults, however, the possible role of dietary factors requires more specific studies among children and adolescents. Educational programs advise that the improvement of lifestyle as a central element in the management of pediatric headache will be of particular importance in the future to improve the quality of life of these patients and reduce the severity of cephalalgic episodes and increase their well-being in adulthood. The present review highlights how changes in different aspects of daily life may determine significant improvements in the management of headaches in people of developmental age.

Ultraprocessed Food: Addictive, Toxic, and Ready for Regulation

Past public health crises (e.g., tobacco, alcohol, opioids, cholera, human immunodeficiency virus (HIV), lead, pollution, venereal disease, even coronavirus (COVID-19) have been met with interventions targeted both at the individual and all of society. While the healthcare community is very aware that the global pandemic of non-communicable diseases (NCDs) has its origins in our Western ultraprocessed food diet, society has been slow to initiate any interventions other than public education, which has been ineffective, in part due to food industry interference. This article provides the rationale for such public health interventions, by compiling the evidence that added sugar, and by proxy the ultraprocessed food category, meets the four criteria set by the public health community as necessary and sufficient for regulation—abuse, toxicity, ubiquity, and externalities (How does your consumption affect me?). To their credit, some countries have recently heeded this science and have instituted sugar taxation policies to help ameliorate NCDs within their borders. This article also supplies scientific counters to food industry talking points, and sample intervention strategies, in order to guide both scientists and policy makers in instituting further appropriate public health measures to quell this pandemic.

Secondary Headache: Current Update

PURPOSE

The purpose of this paper is to review some of the causes of secondary headache particularly focusing on the subcategories of secondary headache in the International Classification of Headache Disorders, 3rd edition, the clinical features of these headaches, and their associated features and management.

OVERVIEW

Headache attributed to trauma or injury to the head and/or neck, headache attributed to cranial or cervical vascular disorder, headache attributed to non-vascular intracranial disorder, headache attributed to a substance or its withdrawal, headache attributed to infection, headache attributed to disorder of homeostasis, and headache or facial pain attributed to disorder of the cranium, neck, eye, ears, nose, sinuses, teeth, mouth, or other facial or cervical structure are discussed in this paper.

DISCUSSION

Headache is a common symptom of multiple medical conditions. Although a minority of headache patients have a secondary basis for their headaches, it is important to identify clinical features of secondary headache disorders including both the headache and non-headache features of the condition, diagnose the secondary etiology correctly, and treat them appropriately.

The Ambiguous Role of Caffeine in Migraine Headache: From Trigger to Treatment

Migraine is a chronic disorder, and caffeine has been linked with migraine for many years, on the one hand as a trigger, and on the other hand as a cure. As most of the population, including migraineurs, consume a considerable amount of caffeine daily, a question arises as to whether it influences their headaches. Indeed, drinking coffee before a migraine attack may not be a real headache trigger, but a consequence of premonitory symptoms, including yawning, diminished energy levels, and sleepiness that may herald a headache. Here, we aim to summarize the available evidence on the relationship between caffeine and migraines. Articles concerning this topic published up to June 2020 were retrieved by searching clinical databases, and all types of studies were included. We identified 21 studies investigating the prevalence of caffeine/caffeine withdrawal as a migraine trigger and 7 studies evaluating caffeine in acute migraine treatment. Among them, in 17 studies, caffeine/caffeine withdrawal was found to be a migraine trigger in a small percentage of participants (ranging from 2% to 30%), while all treatment studies found caffeine to be safe and effective in acute migraine treatment, mostly in combination with other analgesics. Overall, based on our review of the current literature, there is insufficient evidence to recommend caffeine cessation to all migraine patients, but it should be highlighted that caffeine overuse may lead to migraine chronification, and sudden caffeine withdrawal may trigger migraine attacks. Migraine sufferers should be aware of the amount of caffeine they consume and not exceed 200 mg daily. If they wish to continue drinking caffeinated beverages, they should keep their daily intake as consistent as possible to avoid withdrawal headache.

Caffeine and Primary (Migraine) Headaches-Friend or Foe?

Background: The actions of caffeine as an antagonist of adenosine receptors have been extensively studied, and there is no doubt that both daily and sporadic dietary consumption of caffeine has substantial biological effects on the nervous system. Caffeine influences headaches, the migraine syndrome in particular, but how is unclear. Materials and Methods: This is a narrative review based on selected articles from an extensive literature search. The aim of this study is to elucidate and discuss how caffeine may affect the migraine syndrome and discuss the potential pathophysiological pathways involved. Results: Whether caffeine has any significant analgesic and/or prophylactic effect in migraine remains elusive. Neither is it clear whether caffeine withdrawal is an important trigger for migraine. However, withdrawal after chronic exposure of caffeine may cause migraine-like headache and a syndrome similar to that experienced in the prodromal phase of migraine. Sensory hypersensitivity however, does not seem to be a part of the caffeine withdrawal syndrome. Whether it is among migraineurs is unknown. From a modern viewpoint, the traditional vascular explanation of the withdrawal headache is too simplistic and partly not conceivable. Peripheral mechanisms can hardly explain prodromal symptoms and non-headache withdrawal symptoms. Several lines of evidence point at the hypothalamus as a locus where pivotal actions take place. Conclusion: In general, chronic consumption of caffeine seems to increase the burden of migraine, but a protective effect as an acute treatment or in severely affected patients cannot be excluded. Future clinical trials should explore the relationship between caffeine withdrawal and migraine, and investigate the effects of long-term elimination.

Investigating the role of expectancy in caffeine withdrawal using the balanced placebo design

OBJECTIVE

This study investigated psychological influences on drug withdrawal symptomatology using a caffeine-based model.

METHODS

Using the 2 × 2 balanced placebo design caffeine dose (given caffeinated vs decaffeinated coffee) was crossed with dose expectancy (told caffeine vs. decaf) among 87 (16-hr abstinent) regular coffee consumers in a 2-day study.

RESULTS

There were effects of expectancy and pharmacology that differed depending on the measure. Those told decaf reported greater caffeine cravings than those told caffeine 45 min and 8 hr postmanipulation. There were no expectancy effects on withdrawal symptoms or cognitive performance. There were pharmacological effects on all measures. Those given decaf reported greater withdrawal symptoms and showed poorer cognitive performance 45 min and 8 hr postmanipulation, with effects for headache and flu-like symptoms first emerging 8 hr postmanipulation (i.e., 24 hr abstinence in given decaf conditions). Caffeine readministration alleviated all withdrawal symptoms and cognitive decrements within 45 min. No drug by expectancy interactions were observed.

CONCLUSIONS

These findings confirm a strong pharmacological basis for caffeine withdrawal and an important role of cognition in drug craving. Future research should investigate the role of expectancy in drug withdrawal and craving and the potential use of expectancy manipulations in symptom prevention and management.

Caffeine in the management of patients with headache

Caffeinated headache medications, either alone or in combination with other treatments, are widely used by patients with headache. Clinicians should be familiar with their use as well as the chemistry, pharmacology, dietary and medical sources, clinical benefits, and potential safety issues of caffeine. In this review, we consider the role of caffeine in the over-the-counter treatment of headache. The MEDLINE and Cochrane databases were searched by combining “caffeine” with the terms “headache,” “migraine,” and “tension-type.” Studies that were not placebo-controlled or that involved medications available only with a prescription, as well as those not assessing patients with migraine and/or tension-type headache (TTH), were excluded. Compared with analgesic medication alone, combinations of caffeine with analgesic medications, including acetaminophen, acetylsalicylic acid, and ibuprofen, showed significantly improved efficacy in the treatment of patients with TTH or migraine, with favorable tolerability in the vast majority of patients. The most common adverse events were nervousness (6.5%), nausea (4.3%), abdominal pain/discomfort (4.1%), and dizziness (3.2%). This review provides evidence for the role of caffeine as an analgesic adjuvant in the acute treatment of primary headache with over-the-counter drugs, caffeine doses of 130 mg enhance the efficacy of analgesics in TTH and doses of ≥100 mg enhance benefits in migraine. Additional studies are needed to assess the relationship between caffeine dosing and clinical benefits in patients with TTH and migraine.

Mild closed head traumatic brain injury-induced changes in monoamine neurotransmitters in the trigeminal subnuclei of a rat model: mechanisms underlying orofacial allodynias and headache

Our recent findings have demonstrated that rodent models of closed head traumatic brain injury exhibit comprehensive evidence of progressive and enduring orofacial allodynias, a hypersensitive pain response induced by non-painful stimulation. These allodynias, tested using thermal hyperalgesia, correlated with changes in several known pain signaling receptors and molecules along the trigeminal pain pathway, especially in the trigeminal nucleus caudalis. This study focused to extend our previous work to investigate the changes in monoamine neurotransmitter immunoreactivity changes in spinal trigeminal nucleus oralis, pars interpolaris and nucleus tractus solitaries following mild to moderate closed head traumatic brain injury, which are related to tactile allodynia, touch-pressure sensitivity, and visceral pain. Our results exhibited significant alterations in the excitatory monoamine, serotonin, in spinal trigeminal nucleus oralis and pars interpolaris which usually modulate tactile and mechanical sensitivity in addition to the thermal sensitivity. Moreover, we also detected a robust alteration in the expression of serotonin, and inhibitory molecule norepinephrine in the nucleus tractus solitaries, which might indicate the possibility of an alteration in visceral pain, and existence of other morbidities related to solitary nucleus dysfunction in this rodent model of mild to moderate closed head traumatic brain injury. Collectively, widespread changes in monoamine neurotransmitter may be related to orofacial allodynhias and headache after traumatic brain injury.

Longitudinal changes in cerebral blood flow velocities in different clinical courses of migraine

Objective To assess longitudinal changes in cerebral blood flow velocities (ΔCBFVs) according to the clinical course of migraine. Methods We retrospectively included migraine patients with two or more attacks per month at baseline who were followed up within 2 years with transcranial Doppler in a tertiary headache clinic. ΔCBFVs were analyzed in relation to clinical courses, defined as remission (0-1 headache days/month), persistence (2-14/month), or progression (≥15/month) in episodic migraine (EM), and conversion to EM (<15/month) and persistence (≥15/month) in chronic migraine (CM). Results A total of 166 patients (90 EM and 76 CM) were included. In EM, the remission group ( n = 30) showed a decrease in CBFV in the middle cerebral artery (MCA) and the basilar artery (BA). The progression group ( n = 10) showed increasing CBFVs in the bilateral MCAs. Patients with the persistence course ( n = 50) showed generally unchanged CBFVs. In CM, ΔCBFVs decreased in the BA and increased in the posterior cerebral artery (PCA) after conversion to EM ( n = 61), whereas they remained unchanged in the persistence group ( n = 15). In all patients, % change in headache days was positively correlated with the %ΔCBFVs of the bilateral MCAs and the BA. Conclusions CBFV changes are associated with the different clinical courses of migraine. The association is more prominent in EM than CM.

Influence of pro-algesic foods on chronic pain conditions

This paper examines current knowledge about putative "pro-algesic" dietary components, and discusses whether limiting the intake of these substances can help improve chronic pain. Although there is a common impression that numerous food components, natural and synthetic, can cause or worsen pain symptoms, very few of these substances have been investigated. This article focuses on four substances, monosodium glutamate, aspartame, arachidonic acid, and caffeine, where research shows that overconsumption may induce or worsen pain. For each substance, the mechanism whereby it may act to induce pain is examined, and any clinical trials examining the effectiveness of reducing the intake of the substance discussed. While all four substances are associated with pain, decreased consumption of them does not consistently reduce pain.

High-frequency use of over-the-counter analgesics among adolescents: reflections of an emerging difficult life, a cross-sectional study

AIMS

To examine characteristics of 15- to 16-year-old adolescents who used over-the-counter analgesics daily to weekly (high-frequency users) as compared to those who used less or no analgesics (low-frequency users). Further to analyse the differences in pain experience, lifestyle, self-esteem, school attendance and educational ambition.

METHODS

An anonymous cross-sectional questionnaire-based study. The questionnaire covered the use of over-the-counter analgesics, pain experience, sociodemographics, lifestyle factors, self-esteem, school absence and future educational plans. The study took place in the 10th grade in six junior high schools in a medium-sized town in Norway. The local sales data for analgesics and antipyretics were close to the national average. We invited 626 adolescents to participate. Of the 367 adolescents (59%) who responded, 51% were girls. Associations between the frequency of use of over-the-counter analgesic and the mentioned variables were analysed using multiple logistic regression.

RESULTS

In total, 26% (42 boys and 48 girls) used over-the-counter analgesics daily to weekly. These high-frequency users experienced more widespread pain, slept less, had more paid spare-time work, drank more caffeinated drinks, participated more often in binge drinking, had lower self-esteem, less ambitious educational plans and more frequent school absence than did the low-frequency users. These associations remained significant when controlling for gender, cultural background and self-evaluated economic status.

CONCLUSION

Adolescent, who are high-frequency users of over-the-counter analgesics, suffer more pain and have identifiable characteristics indicative of complex problems. Their ability to handle stress appears to be discordant with the kind of situations to which they are exposed. The wear and tear associated with allostatic mechanisms counteracting stress may heighten their pain experience.

Prevalence and determinants of headaches in Hawaii: the Hilo Women's Health Study

BACKGROUND

Headache frequency has been associated with ethnicity, menopause, abdominal obesity and stress.

AIM

To examine the prevalence and determinants of headaches in the multi-ethnic community of Hilo, Hawaii.

SUBJECTS AND METHODS

A random sample of 1824 women aged 16-100 was recruited by postal survey; 206 women aged 45-55 were recruited for clinical measures. Both studies queried the presence/absence of headaches during the past 2 weeks. The clinical study also examined migraines and tension headaches. Headaches were examined in relation to demographic, reproductive and lifestyle variables, stress, symptoms and anthropometric measures.

RESULTS

Headache prevalence was 47%. Japanese women were less likely to report headaches compared to women of European descent, but, after controlling for measures of stress, Japanese women were at a higher risk for headaches. Post-menopausal women were half as likely to report headaches compared with pre-menopausal women. Women with children younger than 18 were 4-times as likely to report migraines compared with women who did not have children younger than 18.

CONCLUSION

Standardized measures of daily hassles, life and job satisfaction were not associated with headaches. The relationship between headaches and having young children suggests that the everyday stress of family life is a headache risk. This may be particularly true in Hilo, Hawaii, where the value of family is culturally prioritized.

Methylxanthines and drug dependence: a focus on interactions with substances of abuse

This chapter examines the psychostimulant actions of methylxanthines, with a focus on the consequences of their excessive use. Consumption of methylxanthines is pervasive and their use is often associated with that of substances known to produce dependence and to have abuse potential. Therefore, the consequences of this combined use are taken into consideration in order to evaluate whether, and to what extent, methylxanthines could influence dependence on or abuse of other centrally active substances, leading to either amplification or attenuation of their effects. Since the methylxanthine that mostly influences mental processes and readily induces psychostimulation is caffeine, this review mainly focuses on caffeine as a prototype of methylxanthine-produced dependence, examining, at the same time, the risks related to caffeine use.

SPECT assessment of brain activation induced by caffeine: no effect on areas involved in dependence

Caffeine is not considered addictive, and in animals it does not trigger metabolic increases or dopamine release in brain areas involved in reinforcement and reward. Our objective was to measure caffeine effects on cerebral perfusion in humans using single photon emission computed tomography with a specific focus on areas of reinforcement and reward. Two groups of nonsmoking subjects were studied, one with a low (8 subjects) and one with a high (6 subjects) daily coffee consumption. The subjects ingested 3 mg/kg caffeine or placebo in a raspberry-tasting drink, and scans were performed 45 min after ingestion. A control group of 12 healthy volunteers receiving no drink was also studied. Caffeine consumption led to a generalized, statistically nonsignificant perfusion decrease of 6% to 8%, comparable in low and high consumers. Compared with controls, low consumers displayed neuronal activation bilaterally in inferior frontal gyrus-anterior insular cortex and uncus, left internal parietal cortex, right lingual gyrus, and cerebellum. In high consumers, brain activation occurred bilaterally only in hypothalamus. Thus, on a background of widespread low-amplitude perfusion decrease, caffeine activates a few regions mainly involved in the control of vigilance, anxiety, and cardiovascular regulation, but does not affect areas involved in reinforcing and reward.

Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption

Caffeine, a widely consumed adenosine A(1) and A(2A) receptor antagonist, is valued as a psychostimulant, but it is also anxiogenic. An association between a variant within the ADORA2A gene (rs5751876) and caffeine-induced anxiety has been reported for individuals who habitually consume little caffeine. This study investigated whether this single nucleotide polymorphism (SNP) might also affect habitual caffeine intake, and whether habitual intake might moderate the anxiogenic effect of caffeine. Participants were 162 non-/low (NL) and 217 medium/high (MH) caffeine consumers. In a randomized, double-blind, parallel groups design they rated anxiety, alertness, and headache before and after 100 mg caffeine and again after another 150 mg caffeine given 90 min later, or after placebo on both occasions. Caffeine intake was prohibited for 16 h before the first dose of caffeine/placebo. Results showed greater susceptibility to caffeine-induced anxiety, but not lower habitual caffeine intake (indeed coffee intake was higher), in the rs5751876 TT genotype group, and a reduced anxiety response in MH vs NL participants irrespective of genotype. Apart from the almost completely linked ADORA2A SNP rs3761422, no other of eight ADORA2A and seven ADORA1 SNPs studied were found to be clearly associated with effects of caffeine on anxiety, alertness, or headache. Placebo administration in MH participants decreased alertness and increased headache. Caffeine did not increase alertness in NL participants. With frequent consumption, substantial tolerance develops to the anxiogenic effect of caffeine, even in genetically susceptible individuals, but no net benefit for alertness is gained, as caffeine abstinence reduces alertness and consumption merely returns it to baseline.

The effect of daily caffeine use on cerebral blood flow: How much caffeine can we tolerate?

Caffeine is a commonly used neurostimulant that also produces cerebral vasoconstriction by antagonizing adenosine receptors. Chronic caffeine use results in an adaptation of the vascular adenosine receptor system presumably to compensate for the vasoconstrictive effects of caffeine. We investigated the effects of caffeine on cerebral blood flow (CBF) in increasing levels of chronic caffeine use. Low (mean = 45 mg/day), moderate (mean = 405 mg/day), and high (mean = 950 mg/day) caffeine users underwent quantitative perfusion magnetic resonance imaging on four separate occasions: twice in a caffeine abstinent state (abstained state) and twice in a caffeinated state following their normal caffeine use (native state). In each state, there were two drug conditions: participants received either caffeine (250 mg) or placebo. Gray matter CBF was tested with repeated-measures analysis of variance using caffeine use as a between-subjects factor, and correlational analyses were conducted between CBF and caffeine use. Caffeine reduced CBF by an average of 27% across both caffeine states. In the abstained placebo condition, moderate and high users had similarly greater CBF than low users; but in the native placebo condition, the high users had a trend towards less CBF than the low and moderate users. Our results suggest a limited ability of the cerebrovascular adenosine system to compensate for high amounts of daily caffeine use.

Caffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG, and subjective effects

RATIONALE

Although the subjective effects of caffeine abstinence, acute and chronic administration, and tolerance are well described, the corresponding neurophysiological effects are not.

OBJECTIVES

Caffeine withdrawal, acute caffeine effects, caffeine tolerance, and net beneficial effects of chronic caffeine administration were investigated using cerebral blood flow velocity, quantitative electroencephalography (EEG), and subjective effects.

MATERIALS AND METHODS

Sixteen regular caffeine users participated in this double-blind, within-subject study during which they received acute caffeine and placebo challenges (1) while maintained on 400 mg caffeine daily for > or =14 days and (2) while maintained on placebo for > or =14 days. Blood flow velocity was determined for the middle (MCA) and anterior (ACA) cerebral arteries using pulsed transcranial Doppler sonography. EEG was recorded from 16 scalp sites. Subjective effects were assessed with questionnaires.

RESULTS

Acute caffeine abstinence (evaluated 24 h after placebo substitution) increased mean, systolic, and diastolic velocity in the MCA and ACA and decreased pulsatility index in the MCA. Acute caffeine abstinence increased EEG theta and decreased beta 2 power. Acute caffeine abstinence also increased measures of Tired, Fatigue, Sluggish, and Weary and decreased ratings of Energetic, Friendly, Lively, and Vigor. Acute caffeine effects were demonstrated across a wide range of measures, including cerebral blood flow, EEG, and subjective effects. Tolerance and "complete" tolerance were observed on subjective but not physiological measures. Chronic caffeine effects were demonstrated only on the measure of EEG beta 2 power.

CONCLUSION

Acute caffeine abstinence and administration produced changes in cerebral blood flow velocity, EEG, and subjective effects. Tolerance to subjective but not physiological measures was demonstrated. There was almost no evidence for net effects of chronic caffeine administration on these measures. Overall, these findings provide the most rigorous demonstration to date of physiological effects of caffeine withdrawal.

Caffeine and headaches

Caffeine is the most widely consumed psychostimulant drug in the world. With intermittent exposures, caffeine may act as a mild analgesic for headache or as an adjuvant for the actions of other analgesics. Chronic repetitive exposures to caffeine increase the risks for development of analgesic-overuse headache, chronic daily headache, and physical dependency. Cessation of caffeine use after chronic exposures leads to a withdrawal syndrome with headache as a dominant symptom. At dosages achieved by common dietary intake, caffeine acts as a potent antagonist of central and peripheral nervous system adenosine receptors. The complex effects of caffeine on headache disorders suggest important roles for adenosine in these disorders and in the induction of caffeine dependency.

Weekend migraine

It is a general belief that migraine attacks are prone to occur on days off. Only a few studies, however, have addressed this issue. The objective of this study was to investigate the periodicity of migraine with respect to weekly (circaseptan) variations. Eighty-nine females of fertile age who had participated in a previous questionnaire-based study volunteered to record in detail every migraine attack for 12 consecutive months. Eighty-four patients completed recordings for a mean of 311 days (s.d. = 95.9, range 30-365). A total of 2314 attacks were recorded. Migraine occurrence was almost equally distributed during the week, except on Sundays, when there were significantly fewer attacks (t = -4.42, d.f. = 83, P < 0.001). A Mantel-Haenszel estimate of the relative risk of having an attack on a holiday vs. another day, not Sundays included, was 0.64 (95% CI 0.49-0.85). Our study suggests that days off protect against migraine.

Influences of caffeine, acetazolamide and cognitive stimulation on cerebral blood flow velocities

Assessment of cerebral blood flow velocities (CBFV) can be used as a non-invasive tool to evaluate specific drug effects, like caffeine (CAF), acetazolamide (AA) as well as cognition. Their influences on each others CBFV were evaluated in detail, using a randomized, double-blind, double-dummy, placebo-controlled three-fold cross-over study design in 18 right-handed healthy male volunteers. CBFV (maximal, mean, minimal) and pulsatility index of both middle cerebral arteries were recorded by transcranial Doppler ultrasound simultaneously, during a verbal memory test, oral CAF, intravenous AA or placebo. AA led to increase in CBFV of 25-32%. Caffeine resulted in decreased V(mean) and V(min) of 10-13%. Cognitive stimulation resulted in a slight increase of CBVF of about 4%, but was overruled by effects of AA and CAF. We conclude that pharmacological effects can easily be assessed by TCD during clinical pharmacological studies of vasoactive drugs. However intraindividual variability and effects of neuropsychological stimulation needs to be taken into account.

A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features

RATIONALE

Although reports of caffeine withdrawal in the medical literature date back more than 170 years, the most rigorous experimental investigations of the phenomenon have been conducted only recently.

OBJECTIVES

The purpose of this paper is to provide a comprehensive review and analysis of the literature regarding human caffeine withdrawal to empirically validate specific symptoms and signs, and to appraise important features of the syndrome.

METHODS

A literature search identified 57 experimental and 9 survey studies on caffeine withdrawal that met inclusion criteria. The methodological features of each study were examined to assess the validity of the effects.

RESULTS

Of 49 symptom categories identified, the following 10 fulfilled validity criteria: headache, fatigue, decreased energy/activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded. In addition, flu-like symptoms, nausea/vomiting, and muscle pain/stiffness were judged likely to represent valid symptom categories. In experimental studies, the incidence of headache was 50% and the incidence of clinically significant distress or functional impairment was 13%. Typically, onset of symptoms occurred 12-24 h after abstinence, with peak intensity at 20-51 h, and for a duration of 2-9 days. In general, the incidence or severity of symptoms increased with increases in daily dose; abstinence from doses as low as 100 mg/day produced symptoms. Research is reviewed indicating that expectancies are not a prime determinant of caffeine withdrawal and that avoidance of withdrawal symptoms plays a central role in habitual caffeine consumption.

CONCLUSIONS

The caffeine-withdrawal syndrome has been well characterized and there is sufficient empirical evidence to warrant inclusion of caffeine withdrawal as a disorder in the DSM and revision of diagnostic criteria in the ICD.

Medications and substances as a cause of headache: a systematic review of the literature

Medication- or substance-induced headache is probably an underrecognized entity with numerous etiologies, including prescribed medication, over-the-counter medication, illicit drugs, anesthetic agents, foods, food additives, beverages, vitamins, inhaled substances, and substances used in diagnostic procedures. The author performs a systemic review of the literature to provide an exhaustive description of the relationship between medications and substances and headaches of various types, along with pathophysiologic mechanisms whenever possible. Suggestions for improved identification of this phenomenon and its avoidance are provided. More scientific evaluation of substances and their possible association with headache is required with almost all substances indicated herein.

Dietary caffeine consumption and withdrawal: confounding variables in quantitative cerebral perfusion studies?

PURPOSE

To evaluate the effects of dietary caffeine intake and withdrawal on cerebral blood flow (CBF), as determined from a randomized, blinded, placebo-controlled study.

MATERIALS AND METHODS

Twenty adults (16 men, four women; age range, 24-64 years) categorized as low (mean, 41 mg/d) or high (mean, 648 mg/d) caffeine users underwent quantitative flow-sensitive alternating inversion-recovery perfusion magnetic resonance (MR) imaging twice: 90 minutes after a dose of caffeine (250 mg) on one day and after a dose of placebo on another day (randomized counterbalanced design). Doses were preceded by 30 hours of caffeine abstinence to induce withdrawal in high caffeine users. Quantitative CBF maps were gray matter (GM)-white matter (WM) segmented and subjected to region-of-interest analysis to obtain mean CBF in WM, anterior circulation GM (AGM), and posterior circulation GM (PGM). By using two-way repeated-measures analysis of variance, regional CBF data were tested for within-subject differences between caffeine and placebo and for between-subject differences related to dietary caffeine habits. Linear regression was used to determine whether dietary caffeine use predicts CBF or CBF response to caffeine.

RESULTS

Caffeine reduced CBF (P < or =.05) by 23% (AGM, PGM) and 18% (WM) in all subjects. Postplacebo (withdrawal) CBF in high caffeine users exceeded that in low users (P < or =.05) by 31% (AGM) and 32% (WM) (PGM, not significant). Mean postcaffeine CBF reduction in AGM was 26% in high users versus 19% in low users (P < or =.05; PGM and WM, not significant). Increasing caffeine consumption predicted higher CBF (P < or =.05) in all regions: r = 0.79 (AGM), 0.57 (PGM), and 0.76 (WM). Dietary caffeine use did not predict CBF response to caffeine.

CONCLUSION

Dietary caffeine consumption and withdrawal are potential confounding variables in cerebral perfusion and functional MR imaging.

The diet factor in pediatric and adolescent migraine

Diet can play an important role in the precipitation of headaches in children and adolescents with migraine. The diet factor in pediatric migraine is frequently neglected in favor of preventive drug therapy. The list of foods, beverages, and additives that trigger migraine includes cheese, chocolate, citrus fruits, hot dogs, monosodium glutamate, aspartame, fatty foods, ice cream, caffeine withdrawal, and alcoholic drinks, especially red wine and beer. Underage drinking is a significant potential cause of recurrent headache in today's adolescent patients. Tyramine, phenylethylamine, histamine, nitrites, and sulfites are involved in the mechanism of food intolerance headache. Immunoglobulin E-mediated food allergy is an infrequent cause. Dietary triggers affect phases of the migraine process by influencing release of serotonin and norepinephrine, causing vasoconstriction or vasodilatation, or by direct stimulation of trigeminal ganglia, brainstem, and cortical neuronal pathways. Treatment begins with a headache and diet diary and the selective avoidance of foods presumed to trigger attacks. A universal migraine diet with simultaneous elimination of all potential food triggers is generally not advised in practice. A well-balanced diet is encouraged, with avoidance of fasting or skipped meals. Long-term prophylactic drug therapy is appropriate only after exclusion of headache-precipitating trigger factors, including dietary factors.

Leisure sickness: a pilot study on its prevalence, phenomenology, and background

AIM

To explore the prevalence, phenomenology, and background of leisure sickness, i.e., the condition of people developing symptoms of sickness during weekends and/or vacations.

METHOD

In order to obtain an estimate of its prevalence, a representative Dutch sample consisting of 1,128 men and 765 women was asked to indicate to what extent they recognized themselves in our description of weekend and vacation sickness. For the investigation of the phenomenology and background of this condition and the characteristics of the patients suffering from it, questionnaire data were collected in new samples consisting of 114 cases and 56 controls. Questions referred to symptoms, onset, duration, appreciation of weekend and vacation activities, and appraisal of work and workload.

RESULTS

In the case of male respondents, 3.6 and 3.2% recognized themselves in the description of the weekend and the vacation syndrome, respectively, compared with 2.7 and 3.2% women. Most frequently reported symptoms were headache/migraine, fatigue, muscular pains, and nausea. In addition, viral infections (flue-like, common cold) were often reported in relation to vacations. Cases had generally suffered from leisure sickness for over 10 years and the onset was associated with stressful conditions. They attributed their condition to difficulties with the transition from work to nonwork, stress associated with travel and vacation, as well as workload and personality characteristics. There were no significant group differences in the appreciation of weekend and leisure activities or lifestyle during days off. Most striking differences were found with respect to experienced workload, sense of responsibility, and inability to relax.

CONCLUSION

Leisure sickness is a relatively common condition. Specific lifestyle factors or leisure activities seem to be less relevant for its development. Concerning risk factors, the data tend to point to high workload and person characteristics, namely, the inability to adapt to the nonworking situation, a high need for achievement, and a high sense of responsibility with respect to work. Future studies should be designed for testing specific hypotheses concerning the underlying mechanisms and evaluating the effectiveness of psychological and/or physical activity interventions.

Topographic quantitative EEG response to acute caffeine withdrawal: a comprehensive analysis of multiple quantitative variables

Most previous studies of the neurophysiological effects of caffeine have focused on the effects of caffeine ingestion, and few studies have examined the effects of caffeine withdrawal. This open study evaluated the quantitative EEG (QEEG) changes occurring during a 4-day period of abstinence in subjects who habitually consume 300 mg or more of caffeine daily. Thirteen subjects underwent QEEG studies during their usual caffeine consumption (baseline) and on days 1, 2, and 4 of a 4-day period of caffeine abstinence. Ten of the subjects underwent a second QEEG on day 4 that consisted of a period of recording after reinstitution of caffeine. A comprehensive analysis of multiple quantitative variables was performed for each study during the abstinence period and compared to the variables obtained at baseline for each subject. Changes occurring during caffeine abstinence included: 1) increases in theta absolute power over all cortical areas, 2) increases in delta absolute power over the frontal cortex, 3) decreases in the mean frequency of both the alpha and beta rhythm, 4) increase in theta relative power and decrease in beta relative power, and 5) significant changes in interhemispheric coherence. Most of these changes tended to return to pre-abstinence baseline levels rapidly after resumption of caffeine consumption. The caffeine withdrawal state affects a number of neurophysiological variables. Further investigation of the neurophysiological aspects of caffeine withdrawal using placebo controlled double blind assessment methods is warranted.

Measuring caffeine-induced changes in middle cerebral artery blood velocity using transcranial Doppler in patients recovering from ischaemic stroke

Acute ingestion of caffeine is known to reduce cerebral blood flow in normal volunteers and in certain patient groups. There is no evidence that this causes problems in the normal population. However, there may be implications if a similar reduction occurs in patients recovering from an ischaemic stroke, in whom local blood flow has already been reduced. Transcranial Doppler provides a non-invasive method for measuring changes in middle cerebral artery (mca) blood velocity. A method for obtaining consistent. reliable measurements was developed and used in a double blind, randomized, crossover study on 20 patients (18 M, 2 F; mean age 70) recovering from ischaemic stroke in the mca territory. Middle cerebral artery blood velocity was measured bilaterally using transcranial Doppler before and after 250 mg caffeine (equivalent to about two cups of filter coffee) or matched placebo. Caffeine caused an average 12% reduction in blood velocity compared to placebo in the hemisphere affected by the stroke (95%c CI 8%-16%, p < 0.00001), and a 12% reduction in the non-affected hemisphere (95% CI 6%-18%, p < 0.001). The clinical implications are unclear at present, and imaging techniques will be required to establish whether caffeine does reduce flow to hypo-perfused regions.

Toward a rational understanding of migraine trigger factors

The typical migraine patient is exposed to a myriad of migraine triggers on a daily basis. These triggers potentially can act at various sites within the cerebral vasculature and the central nervous system to promote the development of migraine headache. The challenge to the physician is in the identification and avoidance of migraine trigger factors within patients suffering from migraine headache. Only through a rational approach to migraine trigger factors can physicians develop an appropriate treatment strategy for migraine patients.

Reversal of caffeine withdrawal by ingestion of a soft beverage

Followlng regular use, acute cessation of caffeine is associated with a characteristic withdrawal syndrome. Despite this, caffeine remains popular with its consumers. The aim of this study was to examine the physiologic and psychologic effects of small caffeine doses, administered in the form of a market-leading soft drink, on healthy women who were acutely withdrawn from caffeine. After 48-h abstinence and overnight fast, 11 healthy (22 to 40 years) female volunteers, all regular caffeine users (daily consumption 143 to 773 mg) consumed using a double-blind. randomized, controlled cross-over design either 2 tins of regular or caffeine-free Diet Coke. On both visits a Mars bar was eaten to prevent hypoglycaemia. Thus, the caffeine load was 76 or 10 mg respectively. Following ingestion of regular Diet Coke, there was a l0% fall in middle cerebral artery velocity (95% CI [6%-l4%], p < 0.005 versus caffeine free) and improvement in feelings of pleasure (p < 0.046) and energy (p < 0.037). Intellectual function (4-choice reaction time) was unaffected by caffeine status. On both visits, ingestion of Diet Coke induced a pressor response (maximum rise in systolic pressure +15+/- 2 mm Hg with caffeine and +l2 +/- 2 mm Hg with caffeine-free beverage, both p < 0.001 compared with baseline). In conclusion, in women acutely withdrawn from caffeine, ingestion of a popular soft beverage containing modest amounts of caffeine is associated with demonstrable physiologic and psychologic effects.

Caffeine can affect velocity in the middle cerebral artery during hyperventilation, hypoventilation, and thinking: a transcranial Doppler study

This study examined possible caffeine-mediated changes in blood flow velocity in the middle cerebral artery (VMCA) induced by tests of cerebrovascular responsiveness. Transcranial Doppler (TCD) sonography provided simultaneous bilateral VMCA measures while healthy college students hypoventilated, hyperventilated, and performed cognitive activities (short-term remembering, generating an autobiographical image, solving problems), each in 31-second tests. VMCA measures were obtained from the same persons, in separate testing sessions, when they were noncaffeinated and under two levels of caffeine: a smaller amount (from a cola, 45 mg/12 oz) and a larger amount (from coffee, 117 mg/8 oz). Compared with the no-caffeine control condition, a smaller amount of caffeine had no significant effects on global VMCA, but a larger amount suppressed VMCA by 5.8%. Time-course analyses showed that VMCA (1) followed a triphasic pattern to increase over baselines during hypoventilation regardless of caffeine condition, (2) slowed below baselines during hyperventilation (with the degree of slowing attenuated under caffeine), and (3) increased over baselines during all cognitive activities (ranges 3.8-6.9%). It is concluded that a large amount of caffeine can suppress VMCA, and this possibility should be anticipated when TCD is used to assess cerebral hemovelocity.

Are we dependent upon coffee and caffeine? A review on human and animal data

Caffeine is the most widely used psychoactive substance and has been considered occasionally as a drug of abuse. The present paper reviews available data on caffeine dependence, tolerance, reinforcement and withdrawal. After sudden caffeine cessation, withdrawal symptoms develop in a small portion of the population but are moderate and transient. Tolerance to caffeine-induced stimulation of locomotor activity has been shown in animals. In humans, tolerance to some subjective effects of caffeine seems to occur, but most of the time complete tolerance to many effects of caffeine on the central nervous system does not occur. In animals, caffeine can act as a reinforcer, but only in a more limited range of conditions than with classical drugs of dependence. In humans, the reinforcing stimuli functions of caffeine are limited to low or rather moderate doses while high doses are usually avoided. The classical drugs of abuse lead to quite specific increases in cerebral functional activity and dopamine release in the shell of the nucleus accumbens, the key structure for reward, motivation and addiction. However, caffeine doses that reflect the daily human consumption, do not induce a release of dopamine in the shell of the nucleus accumbens but lead to a release of dopamine in the prefrontal cortex, which is consistent with caffeine reinforcing properties. Moreover, caffeine increases glucose utilization in the shell of the nucleus accumbens only at rather high doses that stimulate most brain structures, non-specifically, and likely reflect the side effects linked to high caffeine ingestion. That dose is also 5-10-fold higher than the one necessary to stimulate the caudate nucleus, which mediates motor activity and the structures regulating the sleep-wake cycle, the two functions the most sensitive to caffeine. In conclusion, it appears that although caffeine fulfils some of the criteria for drug dependence and shares with amphetamines and cocaine a certain specificity of action on the cerebral dopaminergic system, the methylxanthine does not act on the dopaminergic structures related to reward, motivation and addiction.

The best defense against hypoglycemia is to recognize it: is caffeine useful?

Caffeine, 1,3,7trimethylxanthine, is used by 80% of the adult population of the world in its various forms. Even the simple pleasure of consuming this socially acceptable drug has implications for the person with diabetes mellitus. Caffeine may increase an individual's sensitivity to hypoglycemia through the combined effects of reducing substrate delivery to the brain via constriction of the cerebral arteries, whilst simultaneously increasing brain glucose metabolism and augmenting catecholamine production. This article summarizes the evidence supporting the hypothesis that caffeine influences the perception of and physiological response to hypoglycemia. Under laboratory conditions, acute ingestion of caffeine markedly enhances the symptomatic and sympathoadrenal responses to hypoglycemia in both healthy volunteers and patients with type 1 diabetes. Recently a study of free-living people with type 1 diabetes showed that caffeine consumption increased the awareness of hypoglycemia. Caffeine has been associated with a number of negative effects and addiction. Most serious of these associations are ischemic heart disease and hypertension, the relationships have not been clearly established and the evidence to date is controversial. Thus we conclude that in modest doses, caffeine may be a useful adjuvant therapy for patients with hypoglycemia unawareness. For once here is a therapy which is inexpensive, safe, and remarkably popular with its consumers.