Good Sleep Quality and Progressive Increments in Vigilance During Extended Night Shifts: A 14-Day Actigraphic Study in Underground Miners.

Abstract

Assess the change in sleep and vigilance of underground miners during long periods of extended shifts. Seventy miners worked 14 consecutive 12-hour day and/or night shifts. Also, they wore an actigraph and completed a visual analog scale for vigilance four times per shift. Linear regression models with mixed effects were used. Sleep efficiency was higher during day shifts than during night shifts (86,5 vs 85.5, P < 0.05) but sleep duration did not differ (6:34 vs 6:44, n.s.). Mean vigilance level at Time 3 (02h00) was significantly lower than that at Time 1 (19h00) during the first 10 night shifts whereas mean vigilance level at Time 4 (05h30) remained significantly lower for the 14 night shifts. Underground miners exhibit good sleep quality despite evidence of limited circadian adaptation in terms of nighttime vigilance.