Mild hypohydration increases the frequency of driver errors during a prolonged, monotonous driving task

Physiol Behav. 2015 Aug 1;147:313-8. doi: 10.1016/j.physbeh.2015.04.028. Epub 2015 Apr 16.


The aim of the present study was to examine the effect of mild hypohydration on performance during a prolonged, monotonous driving task.

Methods: Eleven healthy males (age 22±4y) were instructed to consume a volume of fluid in line with published guidelines (HYD trial) or 25% of this intake (FR trial) in a crossover manner. Participants came to the laboratory the following morning after an overnight fast. One hour following a standard breakfast, a 120min driving simulation task began. Driver errors, including instances of lane drifting or late breaking, EEG and heart rate were recorded throughout the driving task

Results: Pre-trial body mass (P=0.692), urine osmolality (P=0.838) and serum osmolality (P=0.574) were the same on both trials. FR resulted in a 1.1±0.7% reduction in body mass, compared to -0.1±0.6% in the HYD trial (P=0.002). Urine and serum osmolality were both increased following FR (P<0.05). There was a progressive increase in the total number of driver errors observed during both the HYD and FR trials, but significantly more incidents were recorded throughout the FR trial (HYD 47±44, FR 101±84; ES=0.81; P=0.006) CONCLUSIONS: The results of the present study suggest that mild hypohydration, produced a significant increase in minor driving errors during a prolonged, monotonous drive, compared to that observed while performing the same task in a hydrated condition. The magnitude of decrement reported, was similar to that observed following the ingestion of an alcoholic beverage resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit), or while sleep deprived.

Keywords: Cognitive function; Dehydration; Fluid balance; Road traffic accident.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Accidents, Traffic / psychology
  • Accidents, Traffic / statistics & numerical data
  • Adolescent
  • Adult
  • Automobile Driving*
  • Body Mass Index
  • Cognition Disorders / etiology
  • Dehydration / blood
  • Dehydration / complications*
  • Dehydration / urine
  • Electroencephalography
  • Electrooculography
  • Humans
  • Male
  • Osmolar Concentration
  • Psychomotor Disorders / blood
  • Psychomotor Disorders / etiology*
  • Psychomotor Disorders / urine
  • Time Factors
  • Urine / physiology
  • Water-Electrolyte Balance / physiology*
  • Young Adult