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Sleep Habits, Alertness, Cortisol Levels, and Cardiac Autonomic Activity in Short-Distance Bus Drivers: Differences Between Morning and Afternoon Shifts

Diez, Joaquín J. MD; Vigo, Daniel E. MD, PhD; Pérez Lloret, Santiago MD, PhD; Rigters, Stephanie MD; Role, Noelia BSc; Cardinali, Daniel P. MD, PhD; Pérez Chada, Daniel MD

Journal of Occupational and Environmental Medicine: July 2011 - Volume 53 - Issue 7 - p 806–811
doi: 10.1097/JOM.0b013e318221c6de

Objective: To evaluate sleep, alertness, salivary cortisol levels, and autonomic activity in the afternoon and morning shifts of a sample of short-distance bus drivers.

Methods: A sample of 47 bus drivers was evaluated. Data regarding subjects and working characteristics, alertness (psychomotor vigilance task), sleep habits (Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Actigraphy), endocrine stress response (salivary cortisol), and autonomic activity (heart-rate variability) were collected.

Results: Sleep restriction was highly prevalent. Drivers in the morning shift slept 1 hour less than those in the afternoon shift, showed lower reaction time performance, a flattening of cortisol morning-evening difference, and higher overweight prevalence.

Conclusions: The differences found between morning and afternoon shifts point out to the need of the implementation of educational strategies to compensate the sleep loss associated with an early workschedule.

Supplemental digital content is available in the text.

From the Departamento de Fisiología (Dr Diez), Universidad Austral, Buenos Aires, Argentina; Departamento de Fisiología (Drs Vigo and Pérez Lloret), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina; Departamento de Docencia e Investigación (Drs Vigo and Cardinali), Facultad de Medicina, Universidad Católica Argentina, Buenos Aires, Argentina; Departamento de Neumonología (Dr Pérez Chada), Hospital Universitario Austral, Buenos Aires, Argentina; Laboratorio Hidalgo (Ms Role), Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (Drs Vigo, Pérez Lloret, and Cardinali), Buenos Aires, Argentina; and Faculteit der Geneeskunde (Dr Rigters), Universiteit van Amsterdam, Amsterdam, The Netherlands.

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Address correspondence to: Daniel Pérez Chada, MD, Departamento de Neumonología, Hospital Universitario Austral, Av Juan D. Perón 1500, 1635-Derqui—Pilar, Argentina (

©2011The American College of Occupational and Environmental Medicine