Personal light dosimetry in permanent night and day workers

Area of Science:

• Occupational Health
• Chronobiology
• Environmental Light Exposure

Background:

• Shift work is common and associated with circadian rhythm disruption.
• Understanding light exposure patterns is crucial for mitigating negative health effects of shift work.

Purpose of the Study:

• To quantify and compare light exposure in night and day shift workers.
• To investigate the relationship between light exposure and subjective state in night workers.

Main Methods:

• Photopic vision-calibrated photocells were worn on spectacles by 12-hour shift workers (day and night).
• Light exposure was measured over 48 hours on work days and 48 hours on days off.
• Correlations between light exposure and subjective state (alertness, mood) were analyzed.

Main Results:

• Both day and night watches had low light exposure, with night watches significantly lower.
• On work days, night workers averaged 13 min above 1,500 lx vs. 52 min for day workers.
• On days off, night workers averaged 3 min above 1,500 lx vs. 89 min for day workers.
• Night workers showed a tendency for light avoidance on days off.
• High negative correlations were found between subjective state acrophases and light exposure in night watches.

Conclusions:

• Permanent night workers experience substantially reduced light exposure, potentially due to light avoidance.
• This low light exposure may exacerbate desynchronization between subjective state, sleep, and activity patterns.
• Interventions to increase light exposure for night workers could be beneficial for circadian alignment.