Impact Of Working Hours In Worker’S Postural Control.

Abstract

Shift work, working hours, overtime, and insufficient rest time are factors that interfere with sensory-motor integration and consequently with postural control. PURPOSE: The purpose of this study was to verify the changes in postural control of workers undertaking different shift systems and working hours. METHODS: Thirty-two night workers were included, 12 bus drivers (42±8y) who worked eight-hours in a 5-consecutive-night system, with two days off, and 20 polysomnography technicians (35±7y) who worked in a 12x36h night-system, that is, 12 hours working and 36 hours off. All participants wore wrist actigraphs for four days. On the fourth day, before and after shift, they fulfilled the Karolinska Sleepiness Scale and were evaluated in a force platform for measures of postural control performance, standing as still as possible for 30 seconds with eyes-opened. Analyzes of Variance were used to compare the variables before and after shift, and statistical significance set at 5%. RESULTS: A significant and average increase of 2.15±1.59 points in the KSS was observed after-night shift for workers, as well as an increase of 0.15±0.03cm in mean sway amplitude. ROC curve analysis evidenced that an increase of at least 0.17cm in mean sway amplitude discriminates sleepy and non-sleepy individuals (scores greater than 7 in the KSS) with 72% sensitivity and 86% specificity. CONCLUSION: Our findings suggest that longer working hours may have a negative impact in postural control, independently of age, and with an additive effect of body mass index. Shift system (5x2 days or 12x36 hours) is more important in determining the level of impairment in postural control than is working hour’s duration per se and, therefore, future investigations should be aimed. Financial Support: CAPES, CNPQ, CEMSA, CEPE.