A blue-enriched light intervention counteracts the alertness decrement among mine workers on extended 12-hour night shift periods.

OBJECTIVE: Assess whether a blue-enriched light intervention improves nocturnal alertness and daytime sleep of night workers.

METHODS: Thirteen miners performing 12-hour night shifts for 12 consecutives nights were exposed to a baseline and a blue-enriched light condition. All subjects wore an actigraph and completed a Psychomotor Vigilance Task at the beginning and at the end of each shift. Data was analyzed with linear mixed models.

RESULTS: In the blue-enriched light condition, the daily increase in median RT, mean RT, slowest 10% of RT, and fastest 10% of RT was lower than that observed in the baseline condition between day 1 and 12 (p ≤ 0.05).

CONCLUSIONS: The addition of blue-enriched light during a long period of extended night shifts counteracts most of the daily decline in nocturnal alertness observed in the standard lighting condition, irrespectively of sleep duration and sleep efficiency.