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The Effects of Coffee and Napping on Nighttime Highway Driving: A Randomized Trial

Pierre Philip, MD, PhD; Jacques Taillard, PhD; Nicholas Moore, MD, PhD; Sandrine Delord, PhD; Cédric Valtat, CRA; Patricia Sagaspe, PhD; and Bernard Bioulac, MD, PhD
[+] Article and Author Information

From Centre Hospitalier Universitaire de Bordeaux and Université Victor Segalen, Bordeaux, France.


Acknowledgments: The authors thank Autoroutes du Sud de la France for allowing the use of their highways for the research, Nestlé for providing the coffee and decaffeinated coffee, GIE RE PSA (Groupement d'Intérêt Économique Recherche Peugeot Société Anonyme) Peugeot Citroën Renault for helping in the administrative coordination of the project, and T. Spector and C. Gilbert for managing the Groupe Opérationnel 3 (GO 3) (PREDIT [Programme de Recherche et d'Innovations dans les Transports Terrestres]).

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Pierre Philip, MD, PhD, Clinique du Sommeil, CHU Pellegrin, Place Amélie Raba Léon, Unité Mixte de Recherche CNRS 5543, 33076 Bordeaux, Cedex, France; e-mail, pierrephilip@compuserve.com.

Current Author Addresses: Drs. Philip, Taillard, and Bioulac and Mr. Valtat: Clinique du Sommeil, CHU Pellegrin, Place Amélie Raba Léon, Unité Mixte de Recherche CNRS 5543, 33076 Bordeaux, Cedex, France.

Dr. Moore: Department of Pharmacology, Université Victor Segalen, INSERM U657, 33076 Bordeaux, Cedex, France.

Drs. Delord and Sagaspe: Laboratoire de Psychologie, Université Victor Segalen, 33076 Bordeaux, Cedex, France.

Author Contributions: Conception and design: P. Philip, J. Taillard, N. Moore, S. Delord, B. Bioulac.

Analysis and interpretation of the data: P. Philip, J. Taillard, N. Moore, S. Delord, C. Valtat, B. Bioulac.

Drafting of the article: P. Philip.

Critical revision of the article for important intellectual content: P. Philip, J. Taillard, N. Moore.

Final approval of the article: P. Philip, J. Taillard, N. Moore, S. Delord, C. Valtat, P. Sagaspe, B. Bioulac.

Provision of study materials or patients: P. Sagaspe.

Statistical expertise: P. Sagaspe.

Obtaining of funding: P. Philip, P. Sagaspe.

Administrative, technical, or logistic support: C. Valtat, P. Sagaspe.

Collection and assembly of data: P. Philip, J. Taillard, S. Delord, C. Valtat, B. Bioulac.


Ann Intern Med. 2006;144(11):785-791. doi:10.7326/0003-4819-144-11-200606060-00004
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All participants completed the study and all driving sessions. No protocol deviations occurred.

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Figure 2.
Self-evaluation of sleepiness at the wheel during the driving sessions.PPP

The score was based on a 100-mm visual analogue scale with scores ranging from 0 (“not at all sleepy”) to 100 (“very sleepy”). Values for the daytime driving session are absolute values (95% CI), and values for the 3 test periods are mean individual differences from the daytime period (95% CI). Greater values indicate worse results. All 3 nighttime conditions (coffee, placebo, or nap) were worse than the daytime condition (   < 0.05 [analysis of variance]). Sleepiness was worse during the placebo condition than in either countermeasure condition (caffeine,   < 0.004; nap,   < 0.034).

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Figure 1.
Self-evaluation of fatigue before the driving sessions.P

The score was based on a 100-mm visual analogue scale with scores ranging from 0 (“not at all tired”) to 100 (“very tired”). Values for the daytime driving session are absolute values (95% CI), and values for the 3 test periods are mean individual differences from the daytime period (95% CI). Greater values indicate worse results. All 3 nighttime conditions (coffee, placebo, or nap) were worse than the daytime condition (   < 0.05 [analysis of variance]) but did not differ from each other.

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Comments

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In response
Posted on June 6, 2006
Chakrapani Prakash
Community Medical Center, Toms River, NJ 08755
Conflict of Interest: None Declared

A physician who practices in today's environment, is likely to work with physician extenders like very qualified RNs, Physician's Assistants and Hopsitalists. The demands for 'scut work' are less in real world than in an Intern's world. A realistic test would be to challenge them with 'panic numbers' like abnormal electrolytes, arterial blood gases, coagulopathies; or abnormal X rays like free air in the abdomen, or pneumothorax or abnormal EKG; after 24 -36 hours of sleep deprivation, since these are typically the issues that the tired future Intern will likely face at 2 am when he is on ER call for his group. I will certainly favor a mid-day 'power nap' of 15 minutes to recharge the batteries. Chakrapani Prakash, MD FACP

Conflict of Interest:

None declared

Other factors explaining nighttime driving performance
Posted on June 12, 2006
Andrew J. Yee
Massachusetts General Hospital Cancer Center, Boston, MA
Conflict of Interest: None Declared

Philip and colleagues (1) have validated the conventional wisdom that coffee and napping improve nighttime highway driving performance with their real-life study. Their study raises several questions. First, an alternative factor affecting the ability to drive at night is nighttime visual acuity. One of the twelve study participants (participant number 7) was egregiously the worst under all three nighttime test conditions: 13 line crossings with coffee (3.1 SD worse than the mean), 17 line crossings with placebo (1.8 SD worse than the mean), and 8 line crossings with napping (2.0 SD worse than the mean). In contrast, during the day, his driving ability was comparable to the rest of the test subjects. Cataract disease, retinitis pigmentosa, and vitamin A deficiency are several conditions that may decrease nighttime visual acuity. While these disorders would certainly be highly unusual in a young healthy male and while there may be a large range in what is considered "normal" driving ability, it may be of interest to exclude these conditions as factors, given this participant's consistently poor performance, rather than attributing it to simply fatigue. Nevertheless, when this driver is excluded from the analysis, an informal analysis of the remaining 11 subjects using paired t-tests with Bonferroni correction for multiple comparisons yields findings similar to the overall conclusions of the trial.

Secondly, while the number of line crossings may be viewed as a proxy for driving performance, it would be of interest to know how many times the professional copilot had to intervene as a consequence. While potentially subjective, this may better capture the relevance of each line crossing, especially since the participants were instructed to drive at high speeds averaging 80 miles per hour.

Finally, it would informative to know what measures the professional copilot driver used to stay awake for the study. Napping, coffee, or another intervention, like modafinil?

References

1. Philip P, Taillard J, Moore N, et al. The effects of coffee and napping on nighttime highway driving: a randomized trial. Ann Intern Med. 2006;144(11):785-91.

Conflict of Interest:

None declared

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Summary for Patients

Coffee and Napping Improve Nighttime Highway Driving

The summary below is from the full report titled “The Effects of Coffee and Napping on Nighttime Highway Driving. A Randomized Trial.” It is in the 6 June 2006 issue of Annals of Internal Medicine (volume 144, pages 785-791). The authors are P. Philip, J. Taillard, N. Moore, S. Delord, C. Valtat, P. Sagaspe, and B. Bioulac.

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