Bronchodilator effects of caffeine in coffee. A dose-response study of asthmatic subjects

Association between coffee and caffeine intake and risk of COPD: Findings based on NHANES 2007-2012

BACKGROUND

The association between coffee and caffeine intake and the risk of COPD and lung function has not been thoroughly discussed in Americans, with subgroup and threshold effects remaining unclear.

OBJECTIVES

This study investigated the association between coffee and caffeine consumption and the risk of chronic obstructive pulmonary disease (COPD) as well as lung function utilizing data from the NHANES 2007-2012.

METHODS

We assessed the associations of coffee and caffeine consumption with the risk of COPD and lung function parameters, including FEV1 and FVC, adjusting for common demographic and disease characteristics in a cross-sectional analysis of NHANES data.

RESULTS

A total of 9763 participants were included in the study, and 592 were diagnosed with COPD. Multivariate regression models revealed positive associations between coffee and caffeine consumption and the risk of COPD and lung function. Subgroup analyses stratified by sex, DM, hypertension status, and smoking habits identified potential effect modifiers as well as inflection points from threshold effect examinations.

CONCLUSIONS

The results of this cross-sectional study indicated significant positive correlations between coffee and caffeine consumption and the risk of COPD. Additionally, positive correlations between exposure variables and FEV1 and FVC were detected. Among the stratification factors, smoking status exhibited the most potential for modifying effects. Future practices and research are needed to validate the results and explore the underlying mechanisms.

Respiratory Safety Pharmacological Testing with Single Intravenous Administration of Caffeine in Sprague-Dawley Rats

As caffeine consumption continues to increase, both positive and negative effects are becoming evident. Caffeine directly affects the cardiovascular system, including heart function and rate. Thus, understanding the current respiratory safety pharmacological responses is of utmost importance. To elucidate the respiratory safety pharmacological characteristics of caffeine, male Sprague-Dawley rats, aged 6 weeks, were intravenously administered doses of 0, 2, 6, and 20 mg/kg of caffeine. Respiratory rate, tidal volume, and minute volume were subsequently measured. In this study, we observed a significant increase in respiratory rate and minute volume, but a remarkable reduction in tidal volume following the intravenous administration of caffeine at doses exceeding 6 mg/kg. These changes were evident within the timeframe of 0.25 to 1.5 h. The data we have collected can serve as valuable foundational scientific information for future research on caffeine, encompassing absorption, distribution, metabolism, excretion, and pharmacological core-battery experiments.

Association of Coffee and Tea Consumption with the Risk of Asthma: A Prospective Cohort Study from the UK Biobank

Background: Previous observational studies investigated the relationship between coffee and tea intake and the risk of asthma, however, the conclusions were inconsistent. Further, the combined effect of coffee and tea consumption on asthma has rarely been studied. Methods: We examined associations between the self-reported intake of tea and coffee and the risk of incident asthma in a total of 424,725 participants aged from 39 to 73 years old from the UK Biobank. Cox proportional hazards models were used to estimate the associations between coffee/tea consumption and incident adult-onset asthma, adjusting for age, sex, race, smoking status, body mass index (BMI), education, and Townsend deprivation index. Results: Cox models with penalized splines showed J-shaped associations of coffee, tea, caffeinated coffee, and caffeine intake from coffee and tea with the risk of adult-onset asthma (p for nonlinear <0.01). Coffee intake of 2 to 3 cups/d (hazard ratio [HR] 0.877, 95% confidence interval [CI] 0.826−0.931) or tea intake of 0.5 to 1 cups/d (HR 0.889, 95% CI 0.816−0.968) or caffeinated coffee intake of 2 to 3 cups/d (HR 0.858, 95% CI 0.806−0.915) or combination caffeine intake from tea and coffee of 160.0 to 235.0 mg per day (HR 0.899, 95% CI 0.842−0.961) were linked with the lowest hazard ratio of incident asthma after adjustment for age, sex, race, smoking status, BMI, qualification, and Townsend deprivation index. Conclusions: Collectively, the study showed light-to-moderate coffee and tea consumption was associated with a reduced risk of adult-onset asthma and controlling total caffeine intake from coffee and tea for a moderate caffeine dose of 160.0 to 305.0 mg/day may be protective against adult-onset asthma. Further investigation on the possible preventive role of caffeine in asthma is warranted.

Antidiarrheal Effect of 80% Methanol Extract and Fractions of the Roasted Seed of Coffea arabica Linn (Rubiaceae) in Swiss Albino Mice

BACKGROUND

Globally in 2019, diarrhea was the second leading cause of mortality in children, accounting for more than half a million under-five deaths yearly. Several societies use Coffea arabica Linn for the treatment of diarrhea. However, its use is not scientifically validated.

OBJECTIVE

The study was conducted to evaluate antidiarrheal activity of 80% methanol extract and solvent fractions of roasted seed of Coffea arabica Linn in mice.

METHODS

Coffea arabica Linn seed was roasted, milled, extracted, and fractionated using hexane, ethyl acetate, and distilled water. Castor oil-induced diarrhea, enteropooling, and motility tests were conducted. Effects on onset, number of feces, weight of feces, fluid content, volume and weight of intestinal content, and motility were evaluated by administering 100 mg/kg, 200 mg/kg, and 400 mg/kg of each extract. Negative controls received 10 ml/kg of the vehicle, and positive controls received either loperamide (3 mg/kg) or atropine (1 mg/kg). Data were analyzed using one-way ANOVA followed by Tukey's post hoc test.

RESULTS

Ethyl acetate fraction at all tested doses significantly prolonged (p < 0.05) onset of diarrhea. The number and weight of feces were also reduced significantly by crude extract and ethyl acetate fraction. Reduction in fluid content was observed at 200 mg/kg and 400 mg/kg of the crude extract (p < 0.01) and aqueous fraction (p < 0.001) as well as all tested doses of ethyl acetate fraction (p < 0.001). Similarly, the crude extract, ethyl acetate fraction, and aqueous fraction showed a significant reduction in the volume and weight of intestinal content. At 400 mg/kg, the crude extract, hexane fraction, aqueous fraction, and all doses of ethyl acetate fraction showed significant antimotility activity.

CONCLUSION

The results of this study revealed that the roasted seed of Coffea arabica Linn has antidiarrheal activity.

Acute intermittent hypoxia and respiratory muscle recruitment in people with amyotrophic lateral sclerosis: A preliminary study

Respiratory failure is the main cause of death in amyotrophic lateral sclerosis (ALS). Since no effective treatments to preserve independent breathing are available, there is a critical need for new therapies to preserve or restore breathing ability. Since acute intermittent hypoxia (AIH) elicits spinal respiratory motor plasticity in rodent ALS models, and may restore breathing ability in people with ALS, we performed a proof-of-principle study to investigate this possibility in ALS patients. Quiet breathing, sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) were tested in 13 persons with ALS and 10 age-matched controls, before and 60 min post-AIH (15, 1 min episodes of 10% O₂, 2 min normoxic intervals) or sham AIH (continuous normoxia). The root mean square (RMS) of the right and left diaphragm, 2nd parasternal, scalene and sternocleidomastoid muscles were monitored. A vector analysis was used to calculate summated vector magnitude (Mag) and similarity index (SI) of collective EMG activity during quiet breathing, SNIP and MIP maneuvers. AIH facilitated tidal volume and minute ventilation (treatment main effects: p < 0.05), and Mag (ie. collective respiratory muscle activity; p < 0.001) during quiet breathing in ALS and control subjects, but there was no effect on SI during quiet breathing. SNIP SI decreased in both groups post-AIH (p < 0.005), whereas Mag was unchanged (p = 0.09). No differences were observed in SNIP or MIP post AIH in either group. Discomfort was not reported during AIH by any subject, nor were adverse events observed. Thus, AIH may be a safe way to increase collective inspiratory muscle activity during quiet breathing in ALS patients, although a single AIH presentation was not sufficient to significantly increase peak inspiratory pressure generation. These preliminary results provide evidence that AIH may improve breathing function in people with ALS, and that future studies of prolonged, repetitive AIH protocols are warranted.

Association between Caffeine Intake and All-Cause and Cause-Specific Mortality: An Analysis of the National Health and Nutrition Examination Survey (NHANES) 1999-2014 Database

Sixty-four percent of adults in America drink coffee daily, and caffeine is the main reason people tend to drink coffee habitually. Few studies have examined the association between caffeine and all-cause and cause-specific mortality. The objective of this study was to examine the association between caffeine and all-cause and cause-specific mortality using the National Health and Nutrition Examination Survey (NHANES) 1999–2014 database. The multivariate Cox proportional hazards regression model was used to examine 23,878 individuals 20 years and older. Daily caffeine intake was measured once at baseline. A total of 2206 deaths occurred, including 394 cardiovascular (CVD) deaths and 525 cancer deaths. Compared to those with a caffeine intake of <100 mg/day, the hazard ratios (HRs) for CVD mortality were significantly lower in the participants with a caffeine intake of 100–200 mg/day (HR, 0.63; 95% confidence interval [CI], 0.45–0.88), and those with a caffeine intake of >200 mg/day (HR, 0.67; 95% CI, 0.50–0.88) after adjusting for potential confounders. The HRs for all-cause mortality were significantly lower in the participants with a caffeine intake of 100–200 mg/day (HR, 0.78; 95% CI, 0.67–0.91), and those with a caffeine intake of >200 mg/day (HR, 0.68; 95% CI, 0.60–0.78). Subgroup analyses showed that caffeine may have different effects on all-cause mortality among different age and body mass index (BMI) groups. In conclusion, higher caffeine intake was associated with lower all-cause and CVD mortality.

Urinary caffeine and caffeine metabolites, asthma, and lung function in a nationwide study of U.S. adults

OBJECTIVE

Coffee intake has been inversely associated with asthma in adults. We examined the relation between urinary levels of caffeine or caffeine metabolites and asthma, lung function, and fractional exhaled nitric oxide (FeNO) in adults.

METHODS

Cross-sectional study of 2,832 adults aged 18-79 years in the US National Health and Nutrition Examination Survey (NHANES). Multivariable logistic or linear regression was used for the analysis of urinary levels of caffeine or each of its three major metabolites (paraxanthine, theobromine, and theophylline) and current asthma, lung function, and FeNO.

RESULTS

Subjects with urinary paraxanthine levels in the fourth quartile (Q4) had 53% lower odds of current asthma than those whose urinary paraxanthine levels were in the first quartile (Q1; 95% confidence = 0.22 to 1.00). Among never and former smokers, subjects with urinary theophylline levels above Q1 had 49% lower odds of current asthma than those whose urinary theophylline level was in Q1 (95% CI = 0.31 to 0.85). Among subjects without current asthma, each log₁₀-unit increment in paraxanthine level was associated with a 0.83% increment in percent predicted (%pred) FEV₁ and a 1.27% increment in %pred FVC, while each log₁₀-unit in theophylline was associated with a 1.24% increment in %pred FVC. Neither urinary caffeine nor any urinary caffeine metabolite was associated with bronchodilator response or FeNO.

CONCLUSIONS

Our findings suggest that two caffeine metabolites (theophylline and paraxanthine) may contribute to the previously reported inverse association between coffee intake and asthma in adults.

Taste Receptors: The Gatekeepers of the Airway Epithelium

Taste receptors are well known for their role in the sensation of taste. Surprisingly, the expression and involvement of taste receptors in chemosensory processes outside the tongue have been recently identified in many organs including the airways. Currently, a clear understanding of the airway-specific function of these receptors and the endogenous activating/inhibitory ligands is lagging. The focus of this review is on recent physiological and clinical data describing the taste receptors in the airways and their activation by secreted bacterial compounds. Taste receptors in the airways are potentially involved in three different immune pathways (i.e., the production of nitric oxide and antimicrobial peptides secretion, modulation of ciliary beat frequency, and bronchial smooth muscle cell relaxation). Moreover, genetic polymorphisms in these receptors may alter the patients’ susceptibility to certain types of respiratory infections as well as to differential outcomes in patients with chronic inflammatory airway diseases such as chronic rhinosinusitis and asthma. A better understanding of the function of taste receptors in the airways may lead to the development of a novel class of therapeutic molecules that can stimulate airway mucosal immune responses and could treat patients with chronic airway diseases.

Nonpharmacologic Strategies to Manage Exercise-Induced Bronchoconstriction

Pharmacologic management of exercise-induced bronchoconstriction (EIB) is the mainstay of preventative therapy. There are some nonpharmacologic interventions, however, that may assist the management of EIB. This review discusses these nonpharmacologic interventions and how they may be applied to patients and athletes with EIB.

Association Between Caffeine Intake and All-Cause and Cause-Specific Mortality: A Population-Based Prospective Cohort Study

OBJECTIVE

To assess whether caffeine intake is associated with all-cause and cause-specific mortality.

PATIENTS AND METHODS

We conducted a prospective cohort study using data from the National Health and Nutrition Examination Survey 1999-2010. Cox proportional hazards models were used to compare the multivariate-adjusted hazard ratios (HRs) of participants with a caffeine intake of 10 to 99, 100 to 199, and 200 mg/d or more with those of participants with a caffeine intake of less than 10 mg/d.

RESULTS

In total, 17,594 participants were included, and the mean ± SD and median (interquartile range) follow-up was 6.5±2.8 years and 6.4 (3.6-9.5) years, respectively; 17,568 participants (99.8%) completed the follow-up, and 1310 died. Compared with those who had a caffeine intake of less than 10 mg/d, HRs and 95% CIs for all-cause mortality were significantly lower in participants with a caffeine intake of 10 to 99 mg/d (HR, 0.81; 95% CI, 0.66-1.00; P=.05), 100 to 199 mg/d (HR, 0.63; 95% CI, 0.51-0.78; P<.001), and 200 or more mg/d (HR, 0.69; 95% CI, 0.58-0.83; P<.001). A similar association was observed in participants who consumed less than 1 cup of coffee per week, and the HR was lowest in those with a caffeine intake of 100 to 199 mg/d (HR, 0.46; 95% CI, 0.22-0.93). There was no association between caffeine intake and cardiovascular mortality, whereas the HRs for noncardiovascular mortality were significantly lower in those with a caffeine intake of 10 to 99 mg/d (HR, 0.74; 95% CI, 0.57-0.95; P=.01), 100 to 199 mg/d (HR, 0.60; 95% CI, 0.46-0.77; P<.001), and 200 or more mg/d (HR, 0.65; 95% CI, 0.53-0.80; P<.001).

CONCLUSION

Moderate caffeine intake was associated with a decreased risk of all-cause mortality, regardless of the presence or absence of coffee consumption.

The effect of dietary components on inflammatory lung diseases - a literature review

Anti-inflammatory treatment in chronic inflammatory lung diseases usually involves glucocorticosteroids. With patients suffering from serious side effects or becoming resistant, specific nutrients, that are suggested to positively influence disease progression, can be considered as new treatment options. The dietary inflammatory index is used to calculate effects of dietary components on inflammation and lung function to identify most potent dietary components, based on 162 articles. The positive effects of n-3 PUFAs and vitamin E on lung function can at least partially be explained by their anti-inflammatory effect. Many other dietary components showed only small or no effects on inflammation and/or lung function, although the number of weighted studies was often too small for a reliable assessment. Optimal beneficial dietary elements might reduce the required amounts of anti-inflammatory treatments, thereby decreasing both side effects and development of resistance as to improve quality of life of patients suffering from chronic inflammatory lung diseases.

Taste receptors in asthma

PURPOSE OF REVIEW

Although today's cornerstone therapies for asthma (inhaled bronchodilators and corticosteroids) target airway narrowing and lung inflammation, about half of treated asthmatic patients do not achieve good disease control. There is a clear need for new therapeutic approaches and novel drug targets. Recent research has unexpectedly revealed that certain taste receptors (particularly those involved in bitter taste transduction) are expressed in lung tissue.

RECENT FINDINGS

Bitter taste receptors are expressed in several cell types in the lungs (such as chemosensory cells, epithelial cells, smooth muscle cells, lymphocytes, and macrophages) and variously involved in ciliary beating, muscle relaxation, and/or inhibition of the production of inflammatory mediators. Here, we review recent research on the role of bitter taste receptors in experimental models of asthma and in asthmatics.

SUMMARY

The currently available data suggest that bitter taste receptor agonists have therapeutic potential in chronic obstructive airway diseases such as asthma.

[Taste receptors in the lungs: interesting or anecdotal?]

The receptors responsible for taste perception distinguish the four basic tastes : salty, sweet, bitter and umami. Among them, the bitter taste receptors (TAS2R) are G protein coupled receptors, including 25 subtypes identified in humans to date. Although the existence of endogenous agonists remains uncertain, the TAS2R receptors have the ability to recognize natural or synthetic molecules, as various molecules produced by bacteria, or caffeine, chloroquine, or erythromycin. The expression of these receptors, initially thought to be confined to the oral cavity, has recently been described in extra-oral tissues such as the gastrointestinal tract and the lungs. The effects in the lung tissue are essentially at three levels : TAS2R receptors expressed on the cilia of epithelial cells increase the cilia vibration frequency; the stimulation of TAS2R receptors expressed in bronchial smooth muscle cells leads to bronchial relaxation; while TAS2R receptors expressed on immune cells in the lung tissue, including macrophages, are involved in the modulation of the production of pro-inflammatory cytokines. In conclusion, in view of these complementary mechanisms, TAS2R receptors may become a pharmacological target of interest for the treatment of obstructive lung diseases.

Effects of habitual coffee consumption on cardiometabolic disease, cardiovascular health, and all-cause mortality

Coffee, after water, is the most widely consumed beverage in the United States, and is the principal source of caffeine intake among adults. The biological effects of coffee may be substantial and are not limited to the actions of caffeine. Coffee is a complex beverage containing hundreds of biologically active compounds, and the health effects of chronic coffee intake are wide ranging. From a cardiovascular (CV) standpoint, coffee consumption may reduce the risk of type 2 diabetes mellitus and hypertension, as well as other conditions associated with CV risk such as obesity and depression; but it may adversely affect lipid profiles depending on how the beverage is prepared. Regardless, a growing body of data suggests that habitual coffee consumption is neutral to beneficial regarding the risks of a variety of adverse CV outcomes including coronary heart disease, congestive heart failure, arrhythmias, and stroke. Moreover, large epidemiological studies suggest that regular coffee drinkers have reduced risks of mortality, both CV and all-cause. The potential benefits also include protection against neurodegenerative diseases, improved asthma control, and lower risk of select gastrointestinal diseases. A daily intake of ∼2 to 3 cups of coffee appears to be safe and is associated with neutral to beneficial effects for most of the studied health outcomes. However, most of the data on coffee's health effects are based on observational data, with very few randomized, controlled studies, and association does not prove causation. Additionally, the possible advantages of regular coffee consumption have to be weighed against potential risks (which are mostly related to its high caffeine content) including anxiety, insomnia, tremulousness, and palpitations, as well as bone loss and possibly increased risk of fractures.

Health beliefs, treatment preferences and complementary and alternative medicine for asthma, smoking and lung cancer self-management in diverse Black communities

OBJECTIVE

The purpose of this literature review is to characterize unconventional health beliefs and complementary and alternative medicine (CAM) for asthma, smoking and lung cancer as those that are likely safe and those that likely increase risk in diverse Black communities. These findings should provide the impetus for enhanced patient-provider communication that elicits patients' beliefs and self-management preferences so that they may be accommodated, or when necessary, reconciled through discussion and partnership.

METHODS

Original research articles relevant to this topic were obtained by conducting a literature search of the PubMed Plus, PsychINFO and SCOPUS databases using combinations of the following search terms: asthma, lung cancer, emphysema, chronic obstructive pulmonary disease (COPD), smoking, beliefs, complementary medicine, alternative medicine, complementary and alternative medicine (CAM), explanatory models, African American, and Black.

RESULTS

Using predetermined inclusion and exclusion criteria, 51 original research papers were retained. Taken together, they provide evidence that patients hold unconventional beliefs about the origins of asthma and lung cancer and the health risks of smoking, have negative opinions of standard medical and surgical treatments, and have favorable attitudes about using CAM. All but a small number of CAM and health behaviors were considered safe.

CONCLUSION

When patients' unconventional beliefs and preferences are not identified and discussed, there is an increased risk that standard approaches to self-management of lung disease will be sub-optimal, that potentially dangerous CAM practices might be used and that timely medical interventions may be delayed.

PRACTICE IMPLICATIONS

Providers need effective communication skills as the medical dialog forms the basis of patients' understanding of disease and self-management options. The preferred endpoint of such discussions should be agreement around an integrated treatment plan that is effective, safe and acceptable to both.

Caffeine for asthma

BACKGROUND

Caffeine has a variety of pharmacological effects; it is a weak bronchodilator and it also reduces respiratory muscle fatigue. It is chemically related to the drug theophylline which is used to treat asthma. It has been suggested that caffeine may reduce asthma symptoms and interest has been expressed in its potential role as an asthma treatment. A number of studies have explored the effects of caffeine in asthma, this is the first review to systematically examine and summarise the evidence.

OBJECTIVES

To assess the effects of caffeine on lung function and identify whether there is a need to control for caffeine consumption prior to either lung function or exhaled nitric oxide testing.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and the reference lists of articles (August 2009). We also contacted study authors.

SELECTION CRITERIA

Randomised clinical trials of oral caffeine compared to placebo or coffee compared to decaffeinated coffee in adults with asthma.

DATA COLLECTION AND ANALYSIS

Trial selection, quality assessment and data extraction were done independently by two reviewers.

MAIN RESULTS

Seven trials involving a total of 75 people with mild to moderate asthma were included. The studies were all of cross-over design .Six trials involving 55 people showed that in comparison with placebo, caffeine, even at a 'low dose' (< 5mg/kg body weight), appears to improve lung function for up to two hours after consumption. Forced expiratory volume in one minute showed a small improvement up to two hours after caffeine ingestion (SMD 0.72; 95% CI 0.25 to 1.20), which translates into a 5% mean difference in FEV1. However in two studies the mean differences in FEV1 were 12% and 18% after caffeine. Mid-expiratory flow rates also showed a small improvement with caffeine and this was sustained up to four hours.One trial involving 20 people examined the effect of drinking coffee versus a decaffeinated variety on the exhaled nitric oxide levels in patients with asthma and concluded that there was no significant effect on this outcome.

AUTHORS' CONCLUSIONS

Caffeine appears to improve airways function modestly, for up to four hours, in people with asthma . People may need to avoid caffeine for at least four hours prior to lung function testing, as caffeine ingestion could cause misinterpretation of the results. Drinking caffeinated coffee before taking exhaled nitric oxide measurements does not appear to affect the results of the test, but more studies are needed to confirm this.

Safety of regadenoson, an adenosine A2A receptor agonist for myocardial perfusion imaging, in mild asthma and moderate asthma patients: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Patients with reactive airways are at risk for adenosine-induced bronchoconstriction, mediated via A(2B) and/or A(3) adenosine receptors.

METHODS AND RESULTS

To examine the effects of regadenoson, a selective adenosine A(2A) receptor agonist, on airway resistance, we conducted a randomized, double-blind, placebo-controlled crossover trial in asthmatic patients with a positive adenosine monophosphate challenge test. The mean ratio of the forced expiratory volume in 1 second (FEV(1)) at each tested time point relative to the baseline FEV(1) was significantly higher after treatment with regadenoson compared with placebo from 10 to 60 minutes after treatment. One patient had a substantial but asymptomatic FEV(1) reduction (-36.2%) after regadenoson that reversed spontaneously. The most common adverse events with regadenoson were tachycardia (66%), dizziness (53%), headache (45%), and dyspnea (34%). The mean heart rate significantly increased with regadenoson (maximum of +10.4 beats/min) versus placebo.

CONCLUSIONS

In this pilot safety study of 48 patients with mild or moderate asthma who had bronchial reactivity to adenosine monophosphate, regadenoson was safe and well tolerated.

Early variable-flow nasal continuous positive airway pressure in infants < or =1000 grams at birth

OBJECTIVE

To compare the incidence of chronic lung disease (CLD) in extremely low birth weight (ELBW, < or =1000 g) infants before and after the introduction of early, preferential application of nasal continuous airway pressure (NCPAP) utilizing a variable flow delivery system.

STUDY DESIGN

A retrospective cohort study of ELBW infants 2 years prior to (Pre-early NCPAP, n=96) and 2 years following (Early NCPAP, n=75) the initiation of an early NCPAP policy.

RESULTS

There were no significant changes (Pre-early NCPAP vs Early NCPAP) in the incidences of CLD (35 vs 33%, P=0.81) or CLD or death (50 vs 43%, P=0.34). Infants in the Early NCPAP group weaned off mechanical ventilation and supplemental oxygen more rapidly than infants in the Pre-early NCPAP group (hazard ratio (HR) 1.80, P=0.002 and HR 1.69, P=0.01).

CONCLUSION

A policy of early NCPAP has not decreased the incidence of CLD despite a decrease in time to successful tracheal extubation.

Vitamin E and Beta-Carotene Supplementation and Hospital-Treated Pneumonia Incidence in Male Smokers

BACKGROUND

Vitamin E and beta-carotene affect various measures of immune function and accordingly might influence the predisposition of humans to infections. However, only few controlled trials have tested this hypothesis.

STUDY OBJECTIVE

To examine whether vitamin E or beta-carotene supplementation affects the risk of pneumonia in a controlled trial.

DESIGN AND SETTING

The Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) study, a randomized, double-blind, placebo-controlled trial that examined the effects of vitamin E, 50 mg/d, and beta-carotene, 20 mg/d, on lung cancer using a 2 x 2 factorial design. The trial was conducted in the general community in southwestern Finland in 1985 to 1993; the intervention lasted for 6.1 years (median). The hypothesis being tested in the present study was formulated after the trial was closed.

PARTICIPANTS

ATBC study cohort of 29,133 men aged 50 to 69 years, who smoked at least five cigarettes per day, at baseline.

MAIN OUTCOME MEASURE

The first occurrence of hospital-treated pneumonia was retrieved from the national hospital discharge register (898 cases).

RESULTS

Vitamin E supplementation had no overall effect on the incidence of pneumonia (relative risk [RR], 1.00; 95% confidence interval [CI], 0.88 to 1.14) nor had beta-carotene supplementation (RR, 0.98; 95% CI, 0.85 to 1.11). Nevertheless, the age of smoking initiation was a highly significant modifying factor. Among subjects who had initiated smoking at a later age (> or =21 years; n = 7,469 with 196 pneumonia cases), vitamin E supplementation decreased the risk of pneumonia (RR, 0.65; 95% CI, 0.49 to 0.86), whereas beta-carotene supplementation increased the risk (RR, 1.42; 95% CI, 1.07 to 1.89).

CONCLUSIONS

Data from this large controlled trial suggest that vitamin E and beta-carotene supplementation have no overall effect on the risk of hospital-treated pneumonia in older male smokers, but our subgroup finding that vitamin E seemed to benefit subjects who initiated smoking at a later age warrants further investigation.

Caffeine for asthma

BACKGROUND

Caffeine has a variety of pharmacological effects. It is chemically related to the drug theophylline which is used to treat asthma. Accordingly, interest has been expressed in its potential role as an asthma treatment. A number of studies have explored the effects of caffeine in asthma, this is the first review to systematically examine and summarise the evidence.

OBJECTIVES

Caffeine is a weak bronchodilator and it also reduces respiratory muscle fatigue. It has been suggested that caffeine may reduce asthma symptoms. The objective of this review was to assess the effects of caffeine on lung function and identify whether there is a need to control for caffeine consumption prior to lung function testing.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and the reference lists of articles. We also contacted study authors.

SELECTION CRITERIA

Randomised trials of oral caffeine compared to placebo in adults with asthma.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were done independently by two reviewers.

MAIN RESULTS

Six trials involving a total of 55 people were included. The studies were all of cross-over design and of high quality. In comparison with placebo, caffeine appears to improve lung function for up to two hours after consumption. Forced expiratory volume in one minute showed a small improvement up to two hours after caffeine use (standardised mean difference -0.73, 95% confidence interval -1.20 to -0.25). Mid-expiratory flow rates also showed a small improvement with caffeine and this was sustained up to four hours.

REVIEWER'S CONCLUSIONS

Caffeine appears to improve airways function modestly in people with asthma for up to four hours. People may need to avoid caffeine for at least four hours prior to lung function testing.

Sample purification for the analysis of caffeine in tobacco by gas chromatography-mass spectrometry

A commonly used additive to tobacco products is cocoa. A sensitive an selective method was developed to measure caffeine, a marker for cocoa, in tobacco by using gas chromatography-mass spectrometry (GC-MS). Tobacco components usually produce high background signals in GC-MS analysis. Therefore, a series of extraction steps were designed to effectively purify the tobacco extracts. The analytical recovery of caffeine was 100 when [trimethyl-13C3] caffeine was used as an isotope-dilution reference. A linear calibration curve was generated with caffeine concentration ranging from 0.01 to 20 micrograms/ml. The detection limit of caffeine was 0.02 microgram/ml in the final solution. This method was applied to several commercial tobacco products, of which the corresponding caffeine levels varied from below the detection limit to 125 micrograms/g.

Selected health and behavioral effects related to the use of caffeine

This paper reviews the research literature concerning health and selected behavioral effects of caffeine. Epidemiological and laboratory findings are reviewed to determine the health risks associated with both acute and chronic caffeine exposure. Common sources of caffeine, its properties, and physiological effects are considered. The relationships between caffeine and various health conditions are examined including caffeine's association with heart disease, cancer, and benign breast disease. Caffeine's possible contribution to enhanced exercise performance is discussed along with a brief overview of caffeine's effects on mental and emotional health. Over 100 references cited in this review were part of a more extensive literature base obtained from several on-line services including MEDLINE and LEXIS/NEXIS medical data bases. Other sources of relevant literature included manual searches of research journals and the use of selected references from appropriate articles. The relationship between caffeine consumption and various illnesses such as cardiovascular disease and cancer remains equivocal. Prudence might dictate that pregnant women and chronically ill individuals exercise restraint in their use of caffeine, although research suggests relatively low or nonexistent levels of risk associated with moderate caffeine consumption.

Rapid method for the routine determination of caffeine and its metabolites by high-performance liquid chromatography

Caffeine is a popular compound for phenotyping individuals for CYP4501A2, xanthine oxidase (XO) and N-acetyltransferase (NAT) utilising urinary metabolites. The analysis is complex since at least thirteen metabolites are excreted by man. Past methods have been less than satisfactory in that either not all the metabolites have been resolved and/or extractions selective for particular groups of metabolites are required prior to chromatography. We report a method for the rapid analysis of caffeine and metabolites in urine that negates the requirement for an extraction step, and also a method for plasma analysis.

Decrease of histamine induced bronchoconstriction by caffeine in mild asthma

BACKGROUND

While high doses of caffeine may affect pulmonary function and bronchial challenge tests in patients with mild asthma, the effects of lower doses (< or = 5 mg/kg) are less well documented. Specific recommendations exist for withholding theophylline, but not caffeine, before bronchoprovocation and pulmonary function testing.

METHODS

To assess the effect of a single oral dose of caffeine (5 mg/kg) on FEV1 and bronchial responsiveness to histamine a double blind, placebo controlled study was performed in eight patients with mild stable asthma.

RESULTS

While caffeine had no effect on FEV1, mean (95% confidence interval) log PC20 histamine was significantly higher 150 minutes [caffeine = 0.99 (0.2) mg/ml, placebo = 0.53 (0.29)] and 240 minutes [caffeine = 0.89 (0.24), placebo = 0.44 (0.26)] after administration of caffeine than after placebo.

CONCLUSIONS

Caffeine should be excluded from the diet for a period of more than four hours before bronchial provocation testing. The exact length of time for which it must be excluded requires further study.

Caffeine consumption decreases the response to bronchoprovocation challenge with dry gas hyperventilation

OBJECTIVE

To determine whether caffeine consumption affects bronchoprovocation challenge (BPC).

DESIGN

A prospective, double-blind, placebo-controlled, randomized, crossover trial.

PATIENTS

Eleven nonsmoking men, aged 18 to 42 years, with normal baseline spirometry and evidence of exercise-induced bronchospasm.

INTERVENTION

On three separate test days, each individual received, in random order, either placebo, 5 mg/kg caffeine, or 10 mg/kg caffeine, and then underwent BPC with eucapnic voluntary hyperventilation (EVH).

RESULTS

Caffeine (10 mg/kg) significantly reduced bronchoconstriction compared to placebo (p = 0.02). The reduction in bronchoconstriction correlated with the serum level of caffeine (p = 0.014).

CONCLUSIONS

Caffeine decreases bronchoconstriction due to EVH. Caffeine should be eliminated from diet prior to BPC.

Population characteristics and cigarette yield as determinants of smoke exposure

Relationships of population characteristics, smoking history, and cigarette yield with smoke exposure as measured by peripheral blood concentrations of thiocyanate, carboxyhemoglobin, nicotine and cotinine were sought in 170 male smokers. This population of smokers had significant elevations of serum thiocyanate, blood carboxyhemoglobin and plasma nicotine and cotinine concentrations as compared with an equal number of age- and sex-matched nonsmokers and these concentrations correlated significantly with past 24-hour cigarette consumption. Although the nicotine yield of the cigarette correlated significantly with plasma cotinine and marginally with plasma nicotine, the reduction in plasma nicotine and cotinine was not proportionate to the reduced yield of the cigarettes, suggesting that smokers partially compensate for the lower yields of their cigarettes. Blood levels of carboxyhemoglobin, nicotine and cotinine were also significantly associated with the weight of the subjects, presumably due to the relationship between weight and the volume of distribution. Univariate and multiple regression analyses provided evidence that coffee and alcohol consumption and years smoked also may be important determinants of smoke exposure.

Effect of caffeine on histamine bronchoprovocation in asthma

It was recently reported that caffeine may reduce the clinical symptoms of asthma and may prevent the clinical manifestations of this disease. The effect of caffeine on histamine responsiveness is unknown. The effect of caffeine (5 mg/kg) and placebo on histamine responsiveness (the provocation concentration causing a 20% fall in FEV1, PC20) was studied in 10 subjects with mild asthma (prechallenge FEV1 84% of predicted value). The PC20 for histamine bronchoprovocation after caffeine ingestion was 2.65 (95% confidence limits 0.99, 7.10) mg/ml. After placebo the PC20 was 1.89 (0.96, 3.71) mg/ml. It is concluded that caffeine in a dose equivalent to about three cups of coffee has a very small effect, if any, on histamine bronchoprovocation in those with mild asthma. Specific instructions about not having drinks containing caffeine before histamine challenge are therefore not necessary.