Can postural control performance be an indicator of truck drivers’ sleep deprivation? Andre´ Albuquerque a , Elaine Marqueze b , Andre´ Rodacki a , Lucia Lemos b , Geraldo Lorenzi-Filho c , Fernando Louzada d and Claudia Moreno b * a Department of Physical Education, Federal University of Parana ´, Curitiba, PR, Brazil; b Environmental Health Department, School of Public Health, University of Sa ˜o Paulo, Sa ˜o Paulo, SP, Brazil; c Sleep Laboratory, Heart Institute, Pulmonary Division, University of Sa ˜o Paulo, Sa ˜o Paulo, SP, Brazil; d Physiology Department, Federal University of Parana ´, Curitiba, PR, Brazil (Received 22 August 2011; final version received 9 October 2011) Long-haul drivers work in irregular schedules due to load delivery demands. In general, driving and sleeping occur at irregular times and, consequently, partial sleep deprivation and/or circadian misalignment may emerge and result in sleepiness at the wheel. In this way, the aim of this study was to verify changes in the postural control parameters of professional drivers after one-night working. Eight male truck drivers working at night – night drivers (ND) and nine day drivers (DD) volunteered to participate in this study. The night drivers’ postural stability was assessed immediately before and after an approximately 430 km journey by two identical force platforms at departure and arrival sites. The DD group was measured before and after a day’s work. An interaction effect of time of day and type of shift in both conditions: eyes open (p 5 0.01) and eyes closed (p 5 0.001) for amplitude of mediolateral movements was observed. Postural stability, measured by force platform, is affected by a night of work, suggesting that it could be an effect of circadian and homeostatic influences over postural control. Keywords: sleep deprivation; circadian misalignment; postural control; truck drivers 1. Introduction Sleepiness impairs cognitive activities, affecting work and social life. The risk of errors and accidents in several professional categories is increased when the worker is sleepy (Folkard and Tucker 2003). Professional drivers have greater risk of accidents due to sleepiness during their work shifts that require overnight work to fulfill delivery schedule demands. Partial sleep deprivation, which can lead to excessive sleepiness, may emerge when driving and sleeping occur on an irregular basis. Irregular work schedules and short breaks between shifts cause poor and insufficient sleep, circadian misalignment and extend the wakefulness period (Akerstedt 1995a). In addition, sleepiness from sleep disorders, short sleep duration and circadian rhythm disorders could also contribute to road accidents, many of them fatal (Black *Corresponding author. Email: crmoreno@usp.br Biological Rhythm Research Vol. 43, No. 6, December 2012, 663–670 ISSN 0929-1016 print/ISSN 1744-4179 online Ó 2012 Taylor & Francis http://dx.doi.org/10.1080/09291016.2011.631789 http://www.tandfonline.com