Time zone and circadian disruption

FAID Quantum has been developed by InterDynamics for any industry where workers are routinely required to operate across multiple time zones.  The aviation industry, in particular Long Haul and Ultra-Long Haul operations, is exposed to higher frequency rates of trans-meridian adjustment, and this factor is considered to result in higher levels of fatigue exposure for aircrews.

FAID Quantum users can use work hours in both UTC and local time as its inputs to predict the effect on fatigue and performance of different duty periods or work schedules, taking into account rest time and the number of time zones crossed.  FAID Quantum models human biology and is best used as a statistically significant indicator of general human response, but not as a predictor of an individual’s condition. This is true of all models given that variations in sleep requirements and tolerances do exist within the human population.

The following has been determined by the aviation industry in the USA (See reference below) – An aircrew’s level of alertness at any time depends upon the complex interaction between a number of variables. In particular, five variables need to be considered:

1. Time on task, including flight time and duty period duration
2. Time awake, since last sleep, when beginning the duty period
3. The extent of circadian disruption caused by transiting multiple time zones, and working at night
4. How quickly the pilot returns to home base – the speed of transition
5. Individual sleep debt, be it acute and/or chronic

Use of FAID Quantum can provide a metric that reports the effect of Items 1, 2, 3 and 4 on the individual’s and group of individual’s indicative exposure to fatigue.

Customisations for reading client data sources, crew augmentation to meet client rules and sleep quality adjustments are available.

Battelle Memorial Institute, JIL Information Systems. (1998). An overview of the scientific literature concerning fatigue, sleep, and the circadian cycle. Prepared for the Office of the Chief Scientific and Technical Advisor for Human Factors, Federal Aviation Administration, Washington, DC. Read the Full Text.

View the system requirements.

How FAID Quantum accounts for circadian disruption caused by trans-meridian changes

Research into the way we adapt to time zone changes is not yet conclusive, but there are some principles that are generally agreed. Crossing time zones of 1-3 hours is generally understood to have a relatively small impact on performance. It is also thought that faster adjustment takes place after westward flights, compared with eastward flights.

Longer haul operations are known to experience larger effects. Eastward travel takes, on average, two thirds as many days as the number of time zones crossed to adapt. So a time zone transit of 9 hours eastwards takes 6 days to adjust. The adaptation to westward travel takes, on average, half as many days as the number of time zones crossed.

These principles are embodied within FAID Quantum.  The method used for calculating the hours of work fatigue score when time zone changes apply is to calculate the individual hours of work fatigue score for each hour of duty based on the individual’s current ‘body clock’.

An individual’s initial ‘body clock’ is based on their starting time zone from the first duty in the work schedule, which is established using the difference between UTC and local time where the first duty commenced. Adjustments to the ‘body clock’ are then made taking into account the rest time and number of time zones crossed.

The FAID Standard BMM

In the FAID Standard BMM the researchers chose to implement rates that differ by direction of travel.  Adjustment begins at the end of the duty, and the magnitude of adjustments is as follows:

• 1.5 time zones per day when traveling in an Easterly direction
• 2 time zones per day when traveling in a Westerly direction

There are additional rules and exceptions for adjustments being made:

1. There is no adjustment to an individual’s ‘body clock’ when the second of two consecutive duties involves a return to the starting time zone of the first duty in the work schedule and either:
   a. the rest period between the two duties is less than 36 hours, or
   b. the time zone difference is three hours or less, and the rest period between the duties is less than 48 hours.
2. Any duty performed at the rest period location will not prevent rule one (above) being applied. The quickest adjustment to the target time zone will be selected beyond 10 time zone changes (which is not always the direction of travel).

When analysing a work schedule, a work history of 15 days is recommended to best correct an individual’s current body clock before the start of the Analysis Period.

When displaying analysis results, if there is a difference of more than three hours between the starting time zone of a duty and the previous duty’s ending time zone, then no FAID Score Outputs will be displayed for 15 days after the end time of the previous duty. This action is to provide time for the circadian sleep/wake rhythm adaptation to the new time zone, in response to the absent time zone movement information