AGRONOMY

Coffee berry borer Hypothenemus hampei (Coleoptera: Curculionidae): searching for sustainable control strategies

Jaramillo, J.; Borgemeister, C.; Baker, P.

The coffee berry borer Hypothenemus hampei (Ferrari) is the most serious pest of the world's most valuable tropical export crop. Since the last review on this insect was published six years ago, many new studies have contributed to an improved insight into the biology and ecology of the beetle, and have indicated new avenues for integrated and biological control. The latest developments in research, both laboratory and field, on the pest, its natural enemies and their implications for integrated control of H. hampei are summarized, with a particular focus on the situation in The Americas. Lately, the global coffee industry has changed radically; it has suffered a long cycle of lowest-ever world market prices caused by overproduction and technological change. At the same time, the advent of sustainable certification schemes has had a major impact on the industry. The role of integrated pest management and biological control of H. hampei in an era of changes in the coffee industry is discussed.

Source : Bull Entomol Res, vol. 96 (3), pp 223 - 233

Construction and characterization of a Coffea canephora BAC library to study the organization of sucrose biosynthesis genes

Leroy, T.; Marraccini, P.; Dufour, M.; Montagnon, C.; Lashermes, P.; Sabau, X.; Ferreira, L. P.; Jourdan, I.; Pot, D.; Andrade, A. C.; Glaszmann, J. C.; Vieira, L. G.; Piffanelli, P.

The first bacterial artificial chromosome (BAC) library of Robusta coffee (Coffea canephora) was constructed, with the aim of developing molecular resources to study the genome structure and evolution of this perennial crop. Clone 126, which is highly productive and confers good technological and organoleptic qualities of beverage, was chosen for development of this library. The BAC library contains 55,296 clones, with an average insert size of 135 Kb per plasmid, therefore representing theoretically nine haploid genome equivalents of C. canephora. Its validation was achieved with a set of 13 genetically anchored single-copy and 4 duplicated RFLP probes and yielded on average 9 BAC clones per probe. Screening of this BAC library was also carried out with partial cDNA probes coding for enzymes of sugar metabolism like invertases and sucrose synthase, with the aim of characterizing the organization and promoter structure of this important class of genes. It was shown that genes for both cell wall and vacuolar forms of invertases were probably unique in the Robusta genome whereas sucrose synthase was encoded by at least two genes. One of them (CcSUS1) was cloned and sequenced, showing that our BAC library is a valuable tool to rapidly identify genes of agronomic interest or linked to cup quality in C. canephora.

Source : Theor Appl Genet, vol. 111 (6), pp 1032 - 1041

Germination of coffee seeds and its significance for coffee quality

Selmar, D.; Bytof, G.; Knopp, S. E.; Breitenstein, B.

Besides genotypic characteristics, the crucial factor that determines coffee quality is the mode of post-harvest treatment, i.e., the wet and dry processing. Up to now, the resulting characteristic flavour differences between these differentially processed coffees were attributed exclusively to differences in starting material. However, as these quality differences are still evident, even when identical coffee samples were processed by the two methods in parallel, the differences must be created by metabolic processes in the coffee beans themselves. Based on expression studies of the germination-specific isocitrate lyase and the resumption of cell cycle activity, monitored by the abundance of beta-tubulin, we evidence that germination is initiated in coffee seeds during the course of standard coffee post-harvest treatments. The extent and nature of the germination processes depend on the processing method. The coherence of metabolic events, substantial differences in the chemical composition of the coffee beans, and the generation of specific coffee qualities establishes the basis for a quite novel approach in coffee research.

Source : Plant Biol (Stuttg), vol. 8 (2), pp 260 - 264

PROCESSING

Fundamentals of spray freezing of instant coffee

MacLeod, C. S.; McKittrick, J. A.; Hindmarsh, J. P.; Johns, M. L.; Wilson, D. I.

Freezing kinetics of coffee solution droplets were investigated using a unique combination of freezing equipment and DSC, where freezing behaviour was related to system parameters such as composition, freezing temperature and gas flow rate. Data were used to verify a simple model of the cooling process, and scanning electron microscopy was utilised to relate freezing parameters to developed microstructure. Freezing of single 2 mm droplets of coffee solution in cold moving air down to -15 C was examined for 50 wt% coffee solutions using a novel temperature monitoring apparatus, and in a similar device within NMR spectrometer. Heat transfer measurements and modelling confirmed that droplet internal temperatures were almost uniform, which was consistent with the microstructures generated. Nucleation temperature, degree of recalescence, freezing temperature, and extent of freezing and freeze concentration were determined as fundamental parameters. The mode of nucleation was dependent on concentration, cooling rate and air temperature.

Source : J Food Eng, 2006 vol. 74 (4), 451-461

CHEMISTRY

Characterization by LC-MS(n) of four new classes of p-coumaric acid-containing diacyl chlorogenic acids in green coffee beans

Clifford, M. N.; Marks, S.; Knight, S.; Kuhnert, N.

LC-MS4 has been used to detect and characterize in green coffee beans 15 quantitatively minor p-coumaric acid-containing chlorogenic acids not previously reported in nature. These comprise 3,4-di-p-coumaroylquinic acid, 3,5-di-p-coumaroylquinic acid, and 4,5-di-p-coumaroylquinic acid (Mr 484); 3-p-coumaroyl-4-caffeoylquinic acid, 3-p-coumaroyl-5-caffeoylquinic acid, 4-p-coumaroyl-5-caffeoylquinic acid, 3-caffeoyl-4-p-coumaroyl-quinic acid, 3-caffeoyl-5-p-coumaroyl-quinic acid; and 4-caffeoyl-5-p-coumaroyl-quinic acid (Mr 500); 3-p-coumaroyl-4-feruloylquinic acid, 3-p-coumaroyl-5-feruloylquinic acid and 4-p-coumaroyl-5-feruloylquinic acid (Mr 514); and 4-dimethoxycinnamoyl-5-p-coumaroylquinic acid and two isomers (Mr 528) for which identities could not be assigned unequivocally. Structures have been assigned on the basis of LC-MS4 patterns of fragmentation.

CONCLUSIONS : Forty-five chlorogenic acids have now been characterized in green Robusta coffee beans.

Source : J Agric Food Chem, vol. 54 (12), pp 4095 - 4101

Coffee antioxidant properties: effects of milk addition and processing conditions

Dupas, C. J.; Marsset-Baglieri, A. C.; Ordonaud, C. S.; Ducept, F.-M. G.; Maillard, M. N.

In the human diet, coffee is the major source of caffeoyl-quinic acids, known to be powerful antioxidants. The aim of this study was to assess the effect of usual coffee consumption, such as the addition of milk, and of processing conditions, such as spray-drying, on beverage antioxidant power and potential polyphenol bioavailability impairments. When 25% milk was added to coffee, up to 40% of coffee chlorogenic acid was found to be bound to dairy proteins, using an ultrafiltration technique. However, neither milk addition nor spray-drying had a significant effect on beverage antioxidant power, evaluated using 2,2-diphenyl-1-pycrylhydrazyl (DPPH), 2-2'-azobis (2-amidinopropane) dihydrochloride (AAPH), and total antioxidant capacity (TAC) tests. Also, these interactions tended to decrease during in vitro gastric and intestinal digestion, thus suggesting that interactions between chlorogenic acid and milk proteins in coffee and milk beverage may not have any significant effect on coffee antioxidant power before and after consumption.

Source : Journal of Food Science, 2006 vol. 71 (3), pp S253 - S258

Evolution in Caffeoylquinic Acid Content and Histolocalization During Coffea canephora Leaf Development

Mondolot, L.; LA Fisca, P.; Buatois, B.; Talansier, E.; DE Kochko, A.; Campa, C.

Background and Aims Caffeoylquinic acids are cinnamate conjugates derived from the phenylpropanoid pathway. They are generally involved in plant responses to biotic and abiotic stress and one of them, chlorogenic acid (5-O-caffeoylquinic acid, 5-CQA), is an intermediate in the lignin biosynthesis pathway. Caffeoylquinic acids, and particularly 5-CQA, are accumulated in coffee beans, where they can form vacuolar complexes with caffeine. Coffea canephora beans are known to have high caffeoylquinic acid content, but little is known about the content and diversity of these compounds in other plant parts. To gain new insights into the caffeoylquinic acid metabolism of C. canephora, caffeoylquinic acid content and in situ localization were assessed in leaves at different growth stages. * Methods HPLC analyses of caffeoylquinic acid content of leaves was conducted in conjunction with detailed histochemical and microspectrofluorometrical analysis. * Key Results and Conclusions HPLC analyses revealed that caffeoylquinic acid content was 10-fold lower in adult than in juvenile leaves. The most abundant cinnamate conjugate was 5-CQA, but dicaffeoylquinic acids (particularly in juvenile leaves) and feruloylquinic acids were also present. Using specific reagents, histochemical and microspectrofluorometrical analysis showed that caffeoylquinic acids (mono- and di-esters) were closely associated with chloroplasts in very young leaves. During leaf ageing, they were found to first accumulate intensively in specific chlorenchymatous bundle sheath cells and then in phloem sclerenchyma cells. The association with chloroplasts suggests that caffeoylquinic acids have a protective role against light damage. In older tissues, their presence in the leaf vascular system indicates that they are transported via phloem and confirms their involvement in lignification processes. In accordance with the hypothesis of a complex formation with caffeine, similar tissue distribution was observed for alkaloids and this is further discussed

Source : Ann Bot (Lond), vol. 98 (1), pp 33 - 40

Characterization of galactomannan derivatives in roasted coffee beverages

Nunes, F. M.; Reis, A.; Domingues, M.-R. M.; Coimbra, M. A.

Galactomannans from Arabica roasted coffee infusions were purified, using 50% ethanol precipitation, anion exchange chromatography and phenylboronic acid-immobilized Sepharose chromatography, and characterized. Specific enzymic hydrolysis of the beta-(1<right arrow>4)-D-mannan backbone showed that the galactomannans of roasted coffee infusions are high mol. wt. supports of low mol. wt. brown compounds. Also, the mol. wt. of the brown compounds linked to the galactomannans was found to increase with an increasing degree of the coffee roasting (light and dark roasts (5 and 10% DM losses) were studied). Reaction of galactomannans during coffee roasting were inferred from the detection of specific chemical markers by GC-electron impact MS and/or electrospray ionization tandem MS. Maillard reaction, caramelization, isomerization, oxidation and decarboxylation pathways were identified by detection of Amadori compounds, 1,6-beta-anhydromannose, fructose, glucose, mannonic acid, 2-ketogluconic acid and arabinonic acid at the reducing end of the obtained oligosaccharides. The implication of these competing reaction pathways is discussed and related to the structural changes of the galactomannans present in the roasted coffee infusions.

Source : J Agr Food Chem, 2006 vol. 54 (9), pp 3428 - 3439

COFFEE & HEALTH

Consumption of coffee is associated with reduced risk of death attributed to inflammatory and cardiovascular diseases in the Iowa Women\'s Health Study

Andersen, L. F.; Jacobs, D.-R. Jr; Carlsen, M. H.; Blomhoff, R.

Coffee is the major source of dietary antioxidants. The association between coffee consumption and risk of death from diseases associated with inflammatory or oxidative stress has not been studied. OBJECTIVE: We studied the relation of coffee drinking with total mortality and mortality attributed to cardiovascular disease, cancer, and other diseases with a major inflammatory component. DESIGN: A total of 41,836 postmenopausal women aged 55-69 y at baseline were followed for 15 y. After exclusions for cardiovascular disease, cancer, diabetes, colitis, and liver cirrhosis at baseline, 27,312 participants remained, resulting in 410,235 person-years of follow-up and 4265 deaths. The major outcome measure was disease-specific mortality. RESULTS: In the fully adjusted model, similar to the relation of coffee intake to total mortality, the hazard ratio of death attributed to cardiovascular disease was 0.76 (95% CI: 0.64, 0.91) for consumption of 1-3 cups/d, 0.81 (95% CI: 0.66, 0.99) for 4-5 cups/d, and 0.87 (95% CI: 0.69, 1.09) for > or =6 cups/d. The hazard ratio for death from other inflammatory diseases was 0.72 (95% CI: 0.55, 0.93) for consumption of 1-3 cups/d, 0.67 (95% CI: 0.50, 0.90) for 4-5 cups/d, and 0.68 (95% CI: 0.49, 0.94) for > or =6 cups/d.

CONCLUSIONS: Consumption of coffee, a major source of dietary antioxidants, may inhibit inflammation and thereby reduce the risk of cardiovascular and other inflammatory diseases in postmenopausal women

Source : Am J Clin Nutr,  vol. 83 (5), pp 1039 - 1046

Effects of coffee consumption on glucose tolerance, serum glucose and insulin levels -a cross-sectional analysis

Bidel, S.; Hu, G.; Sundvall, J.; Kaprio, J.; Tuomilehto, J.

Coffee has several metabolic effects that could reduce the risk of type 2 diabetes. Our objective was to examine the effects of coffee consumption on glucose tolerance, glucose and insulin levels. RESEARCH DESIGN AND METHODS: A subsample of subjects aged 45 to 64 years in 1987 and in 1992 from the population-based FINRISK study (12,287 individuals) was invited to receive the standard oral glucose tolerance test at baseline. Plasma samples were taken after an overnight fast, and a two-hour oral glucose tolerance test was administered. Fasting and two-hour plasma glucose and insulin were measured in 2434 subjects with data on coffee use and potential confounders. RESULTS: After adjustment for potential confounding factors (age, body mass index, systolic blood pressure, occupational, commuting and leisure time physical activity, alcohol and tea drinking, smoking), coffee consumption was significantly and inversely associated with fasting glucose, two-hour plasma glucose, and fasting insulin in both men and women. Coffee consumption was significantly and inversely associated with impaired fasting glucose, impaired glucose regulation, and hyperinsulinemia among both men and women and with isolated impaired glucose tolerance among women.

CONCLUSIONS: In this cross-sectional analysis, coffee showed positive effects on several glycemia markers.

Source : Horm Metab Res, vol. 38 (1), pp 38 - 43

Coffee and type 2 diabetes: from beans to beta-cells

van Dam, R. M.

Coffee consumption has been associated with improved glucose tolerance and a lower risk of type 2 diabetes in diverse populations in the U.S., Europe, and Japan. This review discusses the strength of the evidence, relevant mechanisms, possible implications, and directions for further research. The finding that higher consumption of decaffeinated coffee was associated with a lower risk of type 2 diabetes suggests that coffee constituents other than caffeine play a role. Coffee is a source of several compounds that improved glucose metabolism in animal studies, including the chlorogenic acids and lignans. Further research on phytochemicals in coffee may lead to the identification of novel mechanisms for effects of diet on the development of type 2 diabetes. In addition, knowledge on effects of coffee components may aid in the development or selection of types of coffee with improved health effects. Longer-term randomized intervention studies that test the effects of coffee consumption on glucose tolerance are warranted. Physical activity and weight management should be the mainstay of public health strategies to prevent type 2 diabetes. For individual choices regarding coffee consumption, potential effects of coffee on various health outcomes should be considered.

Source : Nutr Metab Cardiovasc Dis, vol.16 (1), pp 69 - 77

The glucose intolerance induced by caffeinated coffee ingestion is less pronounced than that due to alkaloid caffeine in men

Battram, D. S.; Arthur, R.; Weekes, A.; Graham, T. E.

Although acute alkaloid caffeine (CAF) ingestion results in an impaired glucose tolerance, chronic coffee (RCOF) ingestion decreases the risk of developing type 2 diabetes. This study examines the hypothesis that CAF ingestion impairs glucose tolerance to a greater extent than RCOF and that the ingestion of decaffeinated coffee (DECAF) results in a positive effect. Eleven healthy males underwent 4 double-blinded randomized trials. Each trial included the ingestion of either: 1) CAF in capsule form (4.45 mg/kg body weight), 2) RCOF (4.45 mg/kg body weight caffeine), 3) dextrose (placebo, PL) in capsule form, or 4) DECAF (equal in volume to the RCOF trial), followed 1-h later by a 2-h oral glucose tolerance test. Blood samples were collected at baseline (-30), 0 (time of treatment ingestion), 60 (initiation of oral glucose tolerance test), 75, 90, 120, 150, and 180 min. Area under the curve for glucose and insulin were higher (P < or = 0.05) following CAF than both PL and DECAF and, although a similar trend (P = 0.07) was observed following RCOF compared with DECAF, the effect was less pronounced. Interestingly, DECAF resulted in a 50% lower glucose response (P < or = 0.05) than PL, suggesting that the effects of PL and DECAF on glucose tolerance are not the same.

CONCLUSIONS : These findings suggest that the effects of CAF and RCOF are not identical and may provide a partial explanation as to why acute CAF ingestion impairs glucose tolerance while chronic RCOF ingestion protects against type 2 diabetes.

Source : J Nutr, vol.136 (5), pp 1276 - 1280

Coffee drinking and risk of preterm birth - No risk induced by low consumption

Chiaffarino, F.; Parazzini, F.; Chatenoud, L.; Ricci, E.; Tozzi, L.; Chiantera, V.; Maffioletti, C.; Fedele, L.

The association between coffee drinking before and during the 3 trimesters of pregnancy and the risk of preterm birth of babies normal for gestational age (NGA) or small for gestational age (SGA) was investigated. This case-control study, conducted in University clinics of North Italy, included 502 women who delivered at <37 wk of gestation. The controls included 1966 women who gave birth at term (<greater than or equal to>37 wk of gestation) to healthy infants on randomly selected days at the hospitals where cases had been identified. There was an inverse association for coffee consumption in the 3rd trimester of pregnancy in SGA cases compared to NGA (heterogeneity test between odd ratio (OR): chi12 = 5.6811, P < 0.05). In comparison with not drinkers, all the OR of overall intake of caffeine were close to unity for both SGA and NGA preterm birth.

CONCLUSIONS : These findings indicate that, compared with no consumption, a low consumption of coffee during pregnancy may not have significant effects on preterm birth.

Source : European Journal of Clinical Nutrition, 2006 vol. 60(5), pp 610 - 613

Coffee antioxidant properties: effects of milk addition and processing conditions

Dupas, C. J.; Marsset-Baglieri, A. C.; Ordonaud, C. S.; Ducept, F.-M. G.; Maillard, M. N.

In the human diet, coffee is the major source of caffeoyl-quinic acids, known to be powerful antioxidants. The aim of this study was to assess the effect of usual coffee consumption, such as the addition of milk, and of processing conditions, such as spray-drying, on beverage antioxidant power and potential polyphenol bioavailability impairments. When 25% milk was added to coffee, up to 40% of coffee chlorogenic acid was found to be bound to dairy proteins, using an ultrafiltration technique. However, neither milk addition nor spray-drying had a significant effect on beverage antioxidant power, evaluated using 2,2-diphenyl-1-pycrylhydrazyl (DPPH), 2-2'-azobis (2-amidinopropane) dihydrochloride (AAPH), and total antioxidant capacity (TAC) tests. Also, these interactions tended to decrease during in vitro gastric and intestinal digestion, thus suggesting that interactions between chlorogenic acid and milk proteins in coffee and milk beverage may not have any significant effect on coffee antioxidant power before and after consumption.

Source : Journal of Food Science,  2006 vol. 71 (3), pp S253 - S258

Coffee and health: a review of recent human research

Higdon, J. V.; Frei, B.

This article reviews recent research on the benefits and risks of coffee consumption in humans. Coffee components that may affect human health are discussed; these include caffeine, cafestol and kahweol, chlorogenic acid and micronutrients. Studies on the potential health benefits of coffee, together with possible mechanisms, are outlined in relation to type-2 diabetes; Parkinson's disease; suicide risk; colorectal cancer; and hepatic injury, cirrhosis and hepatocellular carcinoma. Health risks described include: cardiovascular disease; cancer; osteoporosis and hip fracture; mineral (e.g. iron, zinc) deficiencies. The special risk groups of women of childbearing age (i.e. in relation to conception, pregnancy and lactation), children and older adults are discussed. Adverse effects specifically relating to caffeine are discussed, including acute toxicity and overdose, adverse reactions, withdrawal and drug interactions.

Source : Critical Reviews in Food Science and Nutrition,  2006, vol. 46 (2), 101-123

Coffee, cirrhosis, and transaminase enzymes

Klatsky, A. L.; Morton, C.; Udaltsova, N.; Friedman, G. D.

A minority of persons at risk develop liver cirrhosis, but knowledge of risk modulators is sparse. Several reports suggest that coffee drinking is associated with lower cirrhosis risk. METHODS: We studied 125 580 multiethnic members of a comprehensive prepaid health care plan without known liver disease who supplied baseline data at voluntary health examinations from 1978 to 1985. Subsequently, through 2001, 330 of them were diagnosed with liver cirrhosis. Review of medical records confirmed the diagnosis of cirrhosis and ascertained probable etiology. The association of coffee drinking with cirrhosis was estimated by Cox proportional hazards models with 7 covariates. We also did a cross-sectional analysis of baseline aspartate aminotransferase and alanine aminotransferase levels, studied by logistic regression. RESULTS: In the cohort study, relative risks of alcoholic cirrhosis (199 subjects) for coffee drinking (vs none) were less than 1 cup per day, 0.7 (95% confidence interval [CI], 0.4-1.1); 1 to 3 cups, 0.6 (95% CI, 0.4-0.8; P<.001); and 4 or more cups, 0.2 (95% CI, 0.1-0.4; P<.001). For 131 subjects with nonalcoholic cirrhosis, relative risks were less than 1 cup, 1.2 (95% CI, 0.6-2.2); 1 to 3 cups, 1.3 (95% CI, 0.8-2.1); and 4 or more cups, 0.7 (95% CI, 0.4-1.3). These relative risks for coffee drinking were consistent in subsets. Tea drinking was unrelated to alcoholic or nonalcoholic cirrhosis. In the cross-sectional analyses, coffee drinking was related to lower prevalence of high aspartate aminotransferase and alanine aminotransferase levels; for example, the odds ratio of 4 or more cups per day (vs none) for a high aspartate aminotransferase level was 0.5 (95% CI, 0.4-0.6; P<.001) and for a high alanine aminotransferase level, 0.6 (95% CI, 0.6-0.7; P<.001), with stronger inverse relations in those who drink large quantities of alcohol.

CONCLUSION: These data support the hypothesis that there is an ingredient in coffee that protects against cirrhosis, especially alcoholic cirrhosis.

Source : Arch Intern Med, vol. 166 (11), pp 1190 - 1195

Changes in caffeine intake and long-term weight change in men and women

Lopez-Garcia, E.; Dam, R.-M. van; Swapnil, Rajpathak; Willett, W. C.; Manson, J. E.; Hu, F. B.

The long-term effects of caffeine intake on wt. have not been examined prospectively. This study sought to assess the relationship between caffeine intake and 12-yr wt. change. A prospective study was conducted of 18 417 men and 39 740 women, with no chronic diseases at baseline, who were followed from 1986 to 1998. Caffeine intake was assessed repeatedly every 2-4 yr. Wt. change was calculated as the difference between the self-reported wt. in 1986 and in 1998. Participants reported a change in caffeine intake that varied across quintiles, from decreases of 296 and 342 mg/day to increases of 213 and 143 mg/day in men and women, respectively. Age-adjusted models showed a lower mean wt. gain in participants who increased their caffeine consumption than in those who decreased their consumption, but the differences between extreme quintiles were small: -0.43 kg (95% confidence interval (CI): -0.17, -0.69) in men and -0.41 kg (95% CI: -0.20, -0.62) in women. After adjustment for potential confounders and baseline, as well as change in total energy intake and other nutrients and foods, the differences remained similar for men and diminished slightly for women (men: -0.43 kg; 95% CI: -0.17, -0.68; women: -0.35; 95% CI: -0.14, -0.56). An increase in coffee and tea consumption was also associated with less wt. gain. In men, the association between caffeine intake and wt. was stronger in younger participants (P for interaction < 0.001); in women, the association was stronger in those who had a body mass index (kg/m2) <greater than or equal to>25, who were less physically active, or who were current smokers (P for interaction < 0.001).

CONCLUSIONS : It is concluded that increases in caffeine intake may lead to a small reduction in long-term wt. gain.

Source : American Journal of Clinical Nutrition, 2006 vol. 83 (3), pp 674 - 680

The effects of coffee and napping on nighttime highway driving: a randomized trial

Philip, P.; Taillard, J.; Moore, N.; Delord, S.; Valtat, C.; Sagaspe, P.; Bioulac, B.

Sleep-related accidents often involve healthy young persons who are driving at night. Coffee and napping restore alertness, but no study has compared their effects on real nighttime driving performances. OBJECTIVE: To test the effects of 125 mL of coffee (half a cup) containing 200 mg of caffeine, placebo (decaffeinated coffee containing 15 mg of caffeine), or a 30-minute nap (at 1:00 a.m.) in a car on nighttime driving performance. DESIGN: Double-blind, randomized, crossover study. SETTING: Sleep laboratory and open highway. PARTICIPANTS: 12 young men (mean age, 21.3 years [SD, 1.8]). MEASUREMENTS: Self-rated fatigue and sleepiness, inappropriate line crossings from video recordings during highway driving, and polysomnographic recordings during the nap and subsequent sleep. INTERVENTION: Participants drove 200 km (125 miles) between 6:00 p.m. and 7:30 p.m. (daytime reference condition) or between 2:00 a.m. and 3:30 a.m. (coffee, decaffeinated coffee, or nap condition). After intervention, participants returned to the laboratory to sleep. RESULTS: Nighttime driving performance was similar to daytime performance (0 to 1 line crossing) for 75% of participants after coffee (0 or 1 line crossing), for 66% after the nap (P = 0.66 vs. coffee), and for only 13% after placebo (P = 0.041 vs. nap; P = 0.014 vs. coffee). The incidence rate ratios for having a line crossing after placebo were 3.7 (95% CI, 1.2 to 11.0; P = 0.001) compared with coffee and 2.9 (CI, 1.7 to 5.1; P = 0.021) compared with nap. A statistically significant interindividual variability was observed in response to sleep deprivation and countermeasures. Sleep latencies and efficiency during sleep after nighttime driving were similar in the 3 conditions. LIMITATIONS: Only 1 dose of coffee and 1 nap duration were tested. Effects may differ in other patient or age groups.

CONCLUSIONS: Drinking coffee or napping at night statistically significantly reduces driving impairment without altering subsequent sleep.

Source: Ann Intern Med, vol. 144 (11), pp 785 - 791

The effect of caffeine on cognitive task performance and motor fatigue

van Duinen, H.; Lorist, M. M.; Zijdewind, I.

In everyday life, people are usually capable of performing two tasks simultaneously. However, in a previous study we showed that during a fatiguing motor task, cognitive performance declined progressively. There is extensive literature on the (positive) effects of caffeine on cognitive and motor performance. These effects are most pronounced under suboptimal conditions, for example during fatigue. However, little is known about the effects of caffeine on cognitive performance during a fatiguing motor task. OBJECTIVE: This study was aimed to investigate whether a moderate dose of caffeine could attenuate the decline in cognitive performance during a fatiguing motor task. METHODS: The study consisted of a placebo and a caffeine (3 mg/kg) session. A total of 23 subjects completed these sessions in a semi-randomized and double-blind order. In each session, subjects performed maximal voluntary contractions of the index finger, a choice reaction time (CRT) task and a dual task consisting of a fatiguing motor task concomitantly with the same CRT task. After the fatiguing dual task, the CRT task was repeated. RESULTS: Caffeine improved cognitive task performance, in both the single and dual task, as shown by decreased reaction times together with unchanged accuracy. Cognitive performance in the dual task deteriorated with increasing fatigue. However, the decrease in cognitive performance in the beginning of the dual task, as observed in the placebo condition, was partly prevented by caffeine administration (i.e., no increase in reaction times). We found no effects of caffeine on motor parameters (absolute force, endurance time or electromyographic amplitude).

CONCLUSIONS: Caffeine improved cognitive performance. This effect also extends under demanding situations, as was shown by the performance during the dual task, even during progressive motor fatigue

Source : Psychopharmacology (Berl), vol.180 (3), pp 539 - 547