Human Factor: Taking Circadian Rhythm Seriously

Assuming it was 2 a.m. by the time they had made it to the hotel, had something to eat and gotten ready for bed, they would need to sleep until 10 a.m. to get the recommended eight hours of sleep. It is difficult to sleep soundly during normal waking hours, and by about 7 a.m. they would begin to hear the sounds of doors slamming and people talking in the hall as they left for breakfast or to check out. This would be followed by the noise of the service staff starting to clean the vacated rooms. The net result would be less than restful sleep.

Mark told me the crew would typically report for flight duty between 1 and 4 Pacific time that afternoon and fly up and down the West Coast, again not returning to a hotel room until the early morning hours. Mark said that by the third day, when the crew would be scheduled to fly back to the East Coast, it would be a “walking time bomb” due to lack of sleep and out-of-whack body rhythms, and that the first day back home pilots are in “zombie land trying to catch up on our sleep and get our bodies back on a normal schedule,” because everything, “sleeping, eating, even going to the bathroom, is thrown off by the disruption of our circadian rhythm.” West Coast crews on an early morning departure to the East Coast experience similar problems, and international flight crews battle even more significant effects from time zone changes.

Most people are aware that they might have trouble getting to sleep after crossing several time zones, but new information is demonstrating the pervasive and powerful effect circadian rhythms have on us. First of all, we do not have just one daily cycle. The liver has a cycle separate from the brain’s, and scientists are realizing that other organs and tissues in our bodies have their own individual cycles. The problem is that these cycles are not all affected by the same stimuli, and they do not all adjust to a new schedule at the same rate. Some can take up to two weeks to adjust to a new schedule. This leads to a kind of internal chaos, with different parts of the body that should be working together being totally out of synch and working at cross purposes.

The net result of this internal chaos is typically referred to as “jet lag” and may include:

• Fatigue.
• Difficulty in sleeping at night
and drowsiness during the day.
• Reduction in mental ability and
memory lapses.
• Irritability.
• Headaches.
• Gastrointestinal discomfort,
including upset stomach, diarrhea
or constipation.
• Coordination problems.
• Reduced physical activity.

The long-term impact on our minds and bodies may be even more devastating. Studies have demonstrated that jet lag can cause physical changes in the brain’s hippocampus and temporal lobes, and possibly lead to other ailments, including obesity, diabetes, digestive problems and even cardiovascular disease and cancer. As we get older we seem to feel the effects of jet lag more and bounce back slower.

While the impact of jet lag gets stronger as more time zones are crossed, even a one-hour time change can make a difference, as shown by studies that found a spike in heart attacks the week after changing to daylight saving time. Even a shift of one hour can affect our mood and ability to concentrate. Studies show that people working during the night or off their normal time zone schedule are more likely to make mistakes. People who work the night shift for extended periods never seem to completely adapt to the circadian shift required, sleeping about three hours less than they do at night and not sleeping as well.

This means that general aviation pilots can’t ignore the effects of changing time zones. I used to regularly take off from Arizona early in the morning in my Twin Comanche and land that same evening in Pennsylvania or Florida. During the summer that is a three-hour time zone shift. Pilots also might fly after a long trip on an airline. I have read several accident case studies that started out, “The pilot had returned from vacation the previous day (or night).” If that trip had involved crossing time zones, the pilot would have been experiencing the same effects as an airline pilot who had crossed several times zones the previous day. If it were a “red eye” flight, the effects of changing time zones would be exacerbated by lack of sleep.

As with fatigue in general, the problem is that we can and do continue to operate while suffering from the effects of time zone disruptions. Mark said, “It is only because of rigid training standards and flight crew standardization that crews are able to struggle back to the East Coast on that third day.” The danger of operating in that manner is that pilots have nothing in reserve to handle an unanticipated threat. Every once in a while a pilot or crew is pushed over the edge by delays, illness, personal stress or other factors, and we read about the results in a National Transportation Safety Board accident report.

Entire books have been written about how to reduce the effects of time zone changes using special diets, lights or schedules; however, most are not backed up by scientific studies and are too complicated for the average person to follow on a regular basis, especially a pilot with frequently changing schedules. There are a few sleep aids approved by the FAA for pilots, but they are approved only for occasional use (one to two times per week) and the FAA requires the pilot to wait at least 12 hours before flying an airplane. Since one common side effect is memory loss, I personally am not comfortable using this method.

After years of lobbying by airline pilots for a more realistic schedule to reduce the negative effects of fatigue and time zone changes, the FAA has recently come out with Advisory Circular 120-100, Basics of Aviation Fatigue and two InFOs (Information for Operators): Fatigue Risk Management Plans (FRMP) for Part 121 Air Carriers — Part 1 (No. 10013) and Part 2 (No. 10017) along with a supplement (No. 10017SUP).

While the InFOs are required only for Part 121 operators, they also provide excellent guidance for charter and corporate operators, and the advisory circular covers the latest research on circadian rhythm as it applies to pilots and flight operations. Here are a few of the more important tips for any pilot who is preparing for a flight across one or more time zones:

• Carefully consider the departure and arrival time zones and time of day and develop a plan to reduce any negative effects.
• After takeoff, set your watch to your destination's time to begin adjusting to that time zone.
• On short stays it may be possible to maintain your normal eating and sleeping schedule while at the destination, eliminating any impact on your mind or body. If this is not possible, begin to adjust your schedule a day or two before the trip. If you are planning a flight from the West Coast to the East Coast, get up an hour earlier each day for several days prior to the trip. If you're headed in the other direction, stay up later and sleep later for several days before the flight. Adjust your eating schedule in the same manner.
• Stay well hydrated by drinking plenty of water and avoiding alcohol and caffeine.
• Eat light meals that are higher in protein.
• Immediately switch over to the new schedule on arrival. Unless you have an early morning flight the next day, stay up until the local bedtime and get plenty of sunlight the next morning.
• Melatonin may help you get to sleep and speed your brain's adjustment to the new time zone, but it does not reduce other effects of time zone changes in the body.
• On extended trips, try to allow extra time to adjust at the destination. West-to-east trips typically require about one