HPRU Medical Research Centre, Guildford and
1 Department of Gastroenterology, Epsom General Hospital, Epsom, UK
Received 28 February 2003; in revised form 31 March 2003; accepted 31 March 2003
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ABSTRACT |
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INTRODUCTION |
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Nevertheless, it is relatively common for people to drive having consumed a legally acceptable amount of ethanol. This has been confirmed in roadside surveys conducted in the UK between 1988 and 1990, in which 99.2% of drivers voluntarily took breath alcohol tests, revealed that 2.3% of those tested had breath alcohol results equivalent to BACs of between 40 and 80 mg/dl (the legal limit in the UK being 80 mg/dl), while only 1.2% exceeded this limit (Maycock, 1997). The concept of units (10 ml or 8 g of ethanol) has been widely publicized as a means of monitoring alcohol consumption, and labelling on spirit, wine and beer bottles has been adopted on a voluntary basis as a means of informing people how many units of alcohol they contain. However, there is clearly a need to inform the public, particularly those who drink before undertaking potentially hazardous activities such as driving, of other factors that may impact on BAC levels.
It is widely believed that champagne is more intoxicating than wine and it has been suggested that carbonated beverages speed up the emptying of the stomach into the small intestine, where alcohol is absorbed faster (Lewy, 1995). However, a thorough literature search has failed to reveal any investigation performed under controlled conditions that might provide evidence to support or refute this belief. The purpose of this study was therefore to assess the effects of champagne and degassed champagne on psychometric performance and BAC.
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SUBJECTS AND MEASURES |
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Procedure
Subjects were trained on all psychometric measures to ensure that learning effects were minimized (Parkin et al., 1997). A two-way counterbalanced crossover design was used for both studies. The minimum washout period was 7 days. A non-vintage brut champagne was used for both conditions. Champagne doses were measured out from freshly opened bottles and the wine (degassed champagne) condition consisted of the same champagne, from which the carbon dioxide (CO2) had been removed by whisking with an electric blender. Samples of both drinks were assessed with a blood gas analyser probe and were also tested for alcohol content and pH. All subjects received alcohol in a dose of 0.6 g/kg body weight, e.g. a 65 kg subject received 325 ml. The subjects were allowed 20 min to consume the drinks.
Subjects were unaware that the wine was degassed champagne. They were asked to abstain from alcohol for 24 h prior to each assessment period and were breathalysed to assess compliance. A validated psychometric test battery, comprising critical flicker fusion (CFF); a choice reaction time test (CRT) including recognition reaction time (RRT) and motor reaction time (MRT) components; a Sternberg memory task (STM); a compensatory tracking task (CTT); and rapid visual information processing (RVIP), were performed before the drinks were administered. The tests were repeated 20 and 60 min after the end of the 20-min drinking period.
Study 2 employed the same protocol (without psychometric testing) with the addition of serial blood samples taken 5, 10, 15, 20, 25, 30, 35 and 40 min after drinking, using an indwelling cannula. BAC was measured using gasliquid chromatography (Tagliaro et al., 1992).
Measures
Critical flicker fusion. CFF assesses CNS arousal. Subjects are required to discriminate flicker from fusion, and vice versa, in a set of four light-emitting diodes arranged in a 1-cm square. Individual thresholds are determined by the psychophysical method of limits on four ascending and four descending scales (Woodworth and Schlosberg, 1958). The means of the eight scales give the threshold frequency in hertz (Hz). CFF has been shown to be sensitive to a variety of psychoactive compounds, e.g. antidepressants and anxiolytics (Hindmarch, 1975
, 1994
). A lowering of the threshold indicates a reduction in CNS arousal.
Choice reaction time. CRT (Hindmarch, 1980) is used as an indicator of sensorimotor performance, assessing the ability to attend and respond to a critical stimulus (Sherwood and Kerr, 1993
). Subjects are required to extinguish one of six equidistant red lights by pressing the associated response button as quickly as possible. There are 50 trials per test. RRT (in ms) is the time between stimulus onset and the subject lifting their finger from the start button. MRT (in ms) indexes the movement component of this task.
Compensatory tracking test. CTT entails using a mouse to keep a cursor in alignment with a moving target on a computer screen. The mean difference between the centres of target and cursor in pixels is recorded, while a peripheral awareness task assesses speed of response (in ms) to a stimulus presented in the periphery of vision. CTT has been shown to be sensitive to the effects of psychotropic drugs (Subhan et al., 1986; Hindmarch and Shamsi, 2002
).
Rapid visual information processing. RVIP assesses the performance of attention mechanisms in remaining vigilant to periodically occurring events. Subjects are required to monitor a series of single digits (09) appearing on the screen at a rate of 100 digits every minute, and respond to consecutive sequences of three odd or even digits by pressing a button (Wesnes and Warburton, 1983). The response measures are the mean reaction time (in ms) and the number of valid responses.
Sternberg memory task. High-speed scanning and retrieval from short-term memory are assessed using a reaction time method (Sternberg, 1966). Subjects memorize a random series of one, three or five digits, which are followed by a series of 12 single probe digits. Subjects indicate whether each probe digit is contained within the original stimulus set. The mean reaction time and number of correct/incorrect responses to 72 trials are recorded. Performance on the STM is sensitive to psychoactive compounds (Subhan and Hindmarch, 1984
).
Statistical methods
SPSS version 10 (SPSS, Inc., Chicago, IL, USA) was used to analyse psychometric results. Owing to presence of non-uniform residuals in the results, a non-parametric test, Wilcoxons matched-pairs signed ranks test was employed. A between-treatment pairwise comparison was carried out on the maximum change from baseline for each variable, and in addition, within-treatment comparisons were used to examine the effects of time on performance for each drink. The areas under the plasma concentration time curves (AUC) of blood samples were analysed using SAS version 8.2 (SAS Institute, Cary, NC, USA) mixed procedure.
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RESULTS |
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BAC. There were significant differences between champagne and degassed champagne in AUC05 (P < 0.01), AUC010 (P < 0.01), AUC015 (P < 0.05) and AUC020 (P = 0.0274), when champagne produced a plasma concentration time curve of 203.08 compared with 167.33 mgmin/100 ml with degassed champagne. The between-drink difference in AUC025 was not significant (P = 0.0668), and there were no other significant treatment differences (Fig. 1).
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CTT. There was a significant between-treatment difference in reaction times to peripheral stimuli. Subjects were significantly slower to respond after drinking champagne (P = 0.019) than they were after drinking degassed champagne (Table 1). There was also a significant within-treatment time effect with champagne at both +20 min (P = 0.012) and +60 min (P = 0.004), but not with degassed champagne (Fig. 2
). There was no significant treatment effect on the tracking performance component of this task, but there were significant within-treatment effects. With champagne, tracking performance was significantly impaired at +60 min (P = 0.01), but not at +20 min (P = 0.06). There were no significant within-treatment effects with degassed champagne (Fig. 2
).
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STM. There were no significant between-treatment effects on reaction time or the number of correct responses. There were also no significant within-treatment effects with either degassed champagne or champagne (Table 1).
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DISCUSSION |
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The significant treatment difference revealed in the CTT test is of interest, as divided attention tasks are particularly sensitive to the effects of ethanol, with impairment regularly being reported at BACs at 20 mg/dl or below (Hindmarch et al., 1992; Roehrs et al., 1994
). Typically, ethanol impairs performance, by increasing concentration, on the main component of the task (in this case tracking), to the detriment of the secondary task (reacting to peripheral stimuli). Our results corroborate this, as the between-treatment difference was seen in the reaction time component of this task and degassed champagne had no effect on tracking error or reaction time. In addition, champagne impaired reaction time at both post-treatment assessments, but only affected tracking performance at +60 min. These findings and the results of the other tests employed are also in accordance with the results of a recent review on the effects of low BACs on performance related to car driving skills. STM and tests of psychomotor performance such as MRT, neither of which was significantly affected by either drink, are typically less sensitive to the impairing effects of ethanol than the other measures employed here, impairment rarely being detected at BACs of <60 mg/dl (Moskowitz and Fiorentino, 2000
).
Although the results of the BAC analysis show that both drinks appear to reach a similar plateau after the first 20 min, the psychometric results provide additional support for the view that champagne may produce more rapid or severe intoxication than degassed champagne or wine. The analysis of the samples of degassed champagne and champagne show that a small amount of ethanol (0.2 g/dl) may have been lost in the preparation of the degassed champagne condition and the pH value of degassed champagne was found to be 0.05 higher than that of champagne. However, these differences between the treatments are relatively minor and seem unlikely to provide a sufficient explanation of these results. It therefore appears that the high CO2 content of champagne may alter gastric emptying in a way that enhances the absorption of alcohol. Tests of gastric emptying would cast light on a possible mechanism. One possible limitation of this study is that BAC measurements were only taken for 40 min post-treatment. Further studies would be enhanced by the inclusion of additional measurements corresponding to the timing of the 60 min test battery to embrace the average peak BAC levels that occur between 45 and 90 min following ingestion (Ideström and Cadenius, 1968). The absence of a placebo arm in this study may, however, be justifiable, because the difficulty of blinding treatments could have confounded the results, if subjects had been aware of whether or not they had consumed alcohol.
Conclusion
Although, this was very much a pilot study, employing a small number of subjects, the results support the popular belief that champagne may be more intoxicating than wine, although the mechanism remains unclear. Further research into the effects of CO2 in alcoholic drinks could be of relevance to car drivers and others who wish to monitor their BACs.
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ACKNOWLEDGEMENTS |
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FOOTNOTES |
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REFERENCES |
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