Feb 3, 2008

Adapting to night shifts -- helping shiftworkers adapt and avoid shiftworker maladaptation

Adapting to nighttime or daytime work requires synchronization of your biological clock (which controls your circadian rhythms) to the work schedule. Maladaptation results if your biological clock is not adjusted to the work schedule. To adapt the biological clock, shiftworkers must be exposed to daylight (or bright artificial light of 1,000 lux or more) both upon awakening and
throughout their active periods (for example, during work hours).

Also, shiftworkers must avoid bright light from approximately three hours prior to the end of their long sleep period.

The only way to fully adapt to nightshift schedules is to reset the biological clock so that energy peaks during nighttime. Work must take place under artificial light (of at least 1000 lux) that mimics daylight. Although this is a far lower level than actual daylight, it will seem far brighter than normal indoor lighting which is typically in the 300-400 lux range. Sleep must take place in a dark and noise-free environment for approximately seven to eight hours. Failure to control daylight and/or light exposure is a significant contributor to fatigue and shiftwork maladaptation.
Maladaptation to shiftwork schedules and lack of energy-restoration sleep can result in persistent sleepiness, low energy, lack of motivation, and depression; in performance degradation during duty hours; and in increased safety risk.

Other health effects such as increased incidence of cardiovascular disease, gastrointestinal disorders, and sleep disorders have been historically documented in populations subjected to shiftwork maladaptation. The combined effects of disrupted sleep and biological clock disorganization can lead to endurance degradation, jet-lag-like symptoms, irritability, depression, and, in extreme cases, psychosis.

Optimizing Adaptation to Shiftwork
Optimizing shiftworker rest, while preventing shift lag (inadequate adjustment to shiftwork schedules), can contribute significantly to shiftworker adaptation to work and life aboard a maritime vessel.

Listed below are some recommendations that can prevent shift schedules from inducing short and disrupted sleep periods and shift lag.

Avoid allowing staff to work more than 12 hours in a 24-hour period. Count
these 24 hours from the time shiftworkers wake up from their longest daily sleep
period (not naps).

Total Adaptation to Night Work
  • Provide bright-light exposure (e.g., fluorescent bulbs of at least 1000 lux) during the work period. Note: This artificial-light exposure can only be implemented in environments where night vision is not required for performing normal duties (so, for instance, ambulance drivers who will need to be able to drive in the dark at night should not be exposed to bright artificial lighting between calls).
  • Provide nightshift staff with small-size meals that promote energy and alertness (high protein, low fat, low sugar, low starch, no dairy products or turkey).
  • Adjust meal times so nightshift personnel can eat a brunch on waking (at approximately 1:00 pm), including brewed coffee and breakfast foods, if desired.
  • Adapt the cafeteria services to accommodate crewmember needs. This accommodation supports both safety and crew morale.

Partial Adaptation to Night Watch or Work Schedules
When bright lights cannot be used in the work environment, stick to the following recommendations:

  • Reduce the duration of the shift in order to minimize the impact of endurance degradation on safety. Promote exercise in the evening hours.
  • Allow shiftworkers from any shift ending in the morning hours to retire prior to sunrise, and to sleep at least seven to eight hours free of noise and with absolutely no interruptions.
  • Overtime should be scheduled to occur after wake-up time (e.g., from 2:00 pm to 6:00 pm), whereas leisure activities should be scheduled for the evening hours.

Source: http://www.uscg.mil/hq/g-m/cems/PDF/light_management.pdf.

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