Effects of a modified shift work organization and traffic load on air traffic controllers' sleep and alertness during work and non-work activities.

A 'compressed' shift schedule (substitution of a rest day by a shift, shortening the duration of work breaks) was introduced for a better fit with aircraft traffic load. Thereafter, the company asked for a survey assessing the effects of the compressed shift system. Air traffic controllers (ATCOs) completed retrospectively a specific questionnaire assessing the effects of shift schedule (modified vs. initial) and of traffic load on fatigue, alertness (on-shift, upon awakening, during daily non-work activities), and sleep (duration, satisfaction). Work organization had marginal and unexpected effects, which might indicate ATCOs' disapproval of the intervention. Traffic load affected sleep satisfaction and alertness during work and non-work activities. Specific effects of shift included reduced sleep time prior to morning shifts compared to night shifts, whereas alertness and fatigue were rated at comparable levels for both shifts. Results suggest that shiftwork features which favor sleep loss across a work cycle have deleterious consequences on alertness and increase the need for recovery, which are further enhanced by traffic load.