The Effects of Coffee and Napping on Nighttime Highway Driving

A Randomized Trial

6 June 2006 | Volume 144 Issue 11 | Pages 785-791

Background: 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.

Editors' Notes Context The effectiveness of coffee drinking and napping to maintain alertness during nighttime driving is unknown. Contribution Twelve healthy young men drove 125 miles on a straight highway in 4 sessions: 1 session during daylight and 3 sessions from 2:00 a.m. to 3:30 a.m. An hour before the nighttime driving sessions, participants drank decaffeinated coffee (placebo) or caffeinated coffee or took a 30-minute nap. The principal outcome was crossing the line between the lanes. The proportion of participants with no or 1 line crossing was 13%, 66%, and 75% after placebo, nap, and caffeinated coffee, respectively. Implications Drinking coffee or napping reduces impaired nighttime driving. —The Editors

 

Author and Article 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{at}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.

Read all Rapid Responses

In response

Chakrapani Prakash

Annals Online, 7 Jun 2006 [Full text]

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