Sleep and Fatigue 11

more sleep than adults. However as people get older they sleep less but at the same time, become less flexible about when sleep is taken. Shift work becomes more difficult with age as it is much harder to reprogramme the body clock. Women tend to sleep longer than men but report more sleep problems.

Naps and Microsleeps

Naps

A nap is a short period of sleep taken at any hour. The time of day, the duration of the nap and the sleep credit/deficit of the individual will determine through which sleep stages the individual will pass. The restorative properties of naps will vary from one individual to another. Those who habitually take naps appear to gain more benefit than non-habitual nappers, who sometimes perform at a reduced level for some time after awakening from the nap.

With the increase in extended flight times there is debate about allowing a crew member to take 20 to 30 minute naps in the seat in an effort to keep him/her fresh. There would appear to be some benefit but pilots should be aware of the pitfalls. It is not unknown for one of the pilots to be taking a nap and the other pilot to fall asleep.

Pilots should also be aware that after napping it may take some minutes to collect one’s thoughts and they will have slow responses and reactions for up to 5 minutes after being roused. The minimum duration for a nap to be restorative appears to be not less than 10 minutes (Hawkins). It is strongly recommended that pilots should plan to be fully awake at least 1 hour before descent.

Microsleeps

Microsleeps are very short periods of sleep lasting from a fraction of a second to two to three seconds. Although their existence can be confirmed by EEG readings, the individual may be unaware of their occurrence which makes them particularly dangerous. They occur most often in conditions of fatigue but are of no assistance in reducing sleepiness.

Shift Work

General

Sleep loss or partial sleep is an occupational hazard of commercial aviation. There will be times when the pilot has to work when he would rather be asleep, and other times when he has to sleep when he would rather be awake. At these times sleep problems may be aggravated by circadian rhythms.

The sleep/wake cycle affects readiness for sleep, and the timing of sleep relative to the body cycle of temperature is critical in determining the duration of the sleep.

Planning ShiftWork Sleep

As an example it is assumed that one is rostered for night duty. The pilot will attempt to get some sleep during the afternoon prior to reporting for duty. However, it will be difficult to get any satisfactory sleep due to having a good sleep credit assuming a normal night’s sleep had been achieved the night before, plus an increasing body temperature does not facilitate sleep.

There are basically two options in this case:

Firstly, one could go to bed early the previous night and set the alarm for an early call so that, by the afternoon, the body will be approaching sleep deficit and be ready for sleep. The second

Sleep and Fatigue 11

211

11 Sleep and Fatigue

Fatigue and Sleep 11

alternative would be to go to bed late the previous night, sleep late, relax in the afternoon and still have a good sleep credit for the night duty.

Both solutions have limitations. In the first case, having gone to bed in the afternoon, sleep may be impossible due to outside noise, daylight entering the room or, if in a hotel, construction work or domestic work in the corridors, in which case one may go on duty with an even greater sleep deficit. The second solution will prove useless if, having prepared oneself for five to six hours duty, the trip is delayed for a few hours for technical, weather, or air traffic reasons.

Generally, it is now accepted that shift rotation should be to later shifts (early shift to late shift to night shift and so on).

Time Zone Crossing

General

Crossing time zones is a way of life for long haul aircrew, and time zone shifts can lead to cumulative sleep deprivation. Although such sleep deficits can build up, it is unlikely to go to extreme levels as the body will sleep when it needs to. Long haul pilots have constantly to adjust and readjust their circadian rhythms, and it is possible that continual disruption may incur some health penalties, particularly associated with stomach and bowel disorders. The disturbance to the normal body functions is commonly known as jet lag or circadian dysrhythmia.

Circadian Dysrhythmia (Transmeridian Desynchronisation)

The internal body rhythms become of great significance in the modern age of rapid air travel. This leads to a large discrepancy between the local time at destination and the body clock of the traveller.

For example it may be local noon for the traveller arriving in Los Angeles, but his body clock will still be based on a UK time of 2000 hours, possibly leading to an internal conflict. After a sleep the internal body clock will indicate a time to wake up when the local time is 0100 hours.

These factors are of great significance to the pilot who may have to sleep during local day hours or operate a long flight at a time when his body clock is indicating a time for sleep. In addition to this, normal rhythms of the alimentary canal (the passage along which food passes during digestion) and urinary system can cause disruption to sleep in the new time zone.

Recovery

The shifting of zeitgebers will help to resynchronize to the new local time but it is a slow process, averaging a shift of about 90 minutes for each day in the new time zone. A shift of 9 hours in local time, for example, on a flight direct from London to Los Angeles, will require about 6 days for the body to adjust to the local time. The pilot may only have 2 or 3 days before return to London and when he does return his body clock is now out of synchronisation again.

Another factor to be considered is that body systems shift their phase at different rates, so while they are shifting, they are not only out-of-phase with the local time, but out-of-phase with each other.

Effects of Direction on Recovery - East orWest, which is Best?

The effects of jet lag and its recovery will also be dependent on the direction of travel. The following two examples illustrate this phenomena.

212

Sleep and Fatigue 11

Travelling Westwards

(London - New York)

New York is 5 hours behind London so noon occurs 5 hours later. This means that an aircrew will experience a 29 hour day. However, our free-running body clock is 25 hours which means that the crew will suffer from 4 hours jet lag.

Travelling Eastwards

(New York - London)

London is 5 hours ahead of New York so noon occurs 5 hours earlier. This means that an aircrew will experience a 19 hour day. However, our free-running body clock is 25 hours which means that the crew will suffer from 6 hours jet lag.

Sleep and Fatigue 11

Figure 11.4 Jet lag after travelling westwards is less than Eastwards

RecoveryTechniques

The method of dealing with circadian dysrhythmia is a major research area in aviation. With the differences in individual pilots’ reaction to time zone changes and rates of resynchronisation there cannot be any hard and fast rules. Each individual must work out his/her own methods for dealing with the problem but there are some generally accepted techniques. See examples below.

Short Stopover - LessThan 24 Hours

If the stopover is of short duration with a rapid return to base, it may be advisable to try to maintain home time in one’s activities. For example eating breakfast at home base time rather than conforming to local time and sleeping at normal home time hours.

24 Hours - the Most Difficult Stopover

One of the worst time intervals to spend on a stopover is 24 hours. This does not allow time for two good sleep periods but is too long a period to cover with only a single sleep session. This may involve taking a limited rest period on arrival so that at a later time the body will be more ready to sleep for a longer period before call for duty. As will be seen in the example below, the options open are not easy.

Stopover - MoreThan 24 Hours

For longer stops it is recommended that you plan to readjust to the new local time as soon as possible.

213

11 Sleep and Fatigue

Sleep Planning

Fatigue and Sleep 11

To ensure that you have the maximum amount of beneficial sleep before arriving at work to fly it is recommended that you base your calculations on three simple rules:

Basic Rules

To calculate the required sleep pattern there are three simple rules:

Rule 1 1 hour’s sleep = 2 hours awake.

Rule 2 The required sleep must be taken immediately prior to the wake-up call for duty.

Rule 3 Use the “3 in 1 Rule”. (Rule 1 gives units of three hours which we can use to calculate the required amount of sleep needed.

Example

A pilot flies from London to New York (5 hours behind UTC for a 24 hour stopover. He/she arrives at the hotel room at 2100 hours local time with no sleep credits. The following duty day is scheduled to be 16 hours.

Solution 1

The pilot requires 8 hours sleep (Rule 1) for the duty day ahead and this must be taken immediately prior to the wake-up call (Rule 2). The problem is how best to organize his/her sleep pattern.

The pilot has 16 hours before he/she must go to sleep to ensure the maximum amount of credit. Using Rule 3, divide 16 hours by 3 and we find that 5 hours 20 minutes of sleep is required. This sleep could be taken as:

State	Local Time	Body Clock Time	Sleep Credits
Sleep	2100 - 0220	0200 - 0720	10 hours 40 minutes
Awake	0220 - 1300	0720 - 1800	0
Sleep	1300 - 2100	1800 - 0200	16 hours

Advantages

•The second sleep will be of good quality as sleep credit is 0 and the body temperature is decreasing for much of the time.

•Only one disruption of sleep.

Disadvantages

•First sleep period will be of mixed quality as although there is 0 credit the body temperature is on the rise for part of the time.

•Unsociable time to be awake and the temptation to sleep again prior to 1300 hours will be strong.

Another possible way to organise the 5 hour 20 minutes of sleep prior to the time when he/ she must sleep is:

214