Iv.

Miscellaneous Observations.

1. Controllers tended to report a better quality of sleep as the
number of hours of sleep increased, indicating an interaction of quality
and quantity.

2. Approximately half the controllers on each rotation schedule were
satisfied with their work schedules. Controllers on both rotation pat-
terns who indicated a preference for a schedule other than the one being
worked tended to prefer a schedule with few or no midshifts,.

3. The difference between the number of hours of annual leave taken
during the 5-week period by controllers working the 5-day rotation
schedule (4,9 hours) and the number taken by controllers working the
2-2-1 rotation schedule (4.5 hours) was not statistically significant.
The amount of annual leave taken during the 5-week period on the evening
shift was slightly, but not significantly, greater than the amount taken
on the day shift or midshift of both rotation schedules,

4. Controllers working the 5-day rotation schedule averaged 7.5
hours of sick leave during the 5-week period and controllers working the
2-2-1 rotation schedule averaged 7.3 hours, The difference was not
statistically significant.

Discussion.

The purpose of this study was to compare the sleep patterns of air
traffic controllers working the 2-2-1 rotation schedule and those working
the 5-day rotation schedule and, from the comparison, draw conclusions
that would be helpful in determining problem areas that might possibly
arise from working those schedules, Initially, FAA management's concern
related to the question of whether controllers working the 2-2-1 rota-
tion schedule had sufficient time between shifts to obtain adequate rest
before reporting to work. Of particular concern was the short time (9-10
hours) between some shifts on the 2-2-1 rotation schedule. Previous
studies conducted by this laboratory (1,3) showed that statistically
significant biochemical differences between the 2-2-1 and the 5-day rota-
tion schedules indicated the 2-2-1 rotation schedule was the less stress-
full of the two rotations. The results of the present study generally
support the conclusions reached in those earlier studies,

Controllers working the 2-2-1 rotation schedule averaged significantly
less sleep during the workweek than did controllers on the 5-day rotation
schedule, and it is clear that this is due to the little time the 2-2-1
controllers spent sleeping just prior to the midshift. The amount of
sleep differed only slightly when the first 4 days of the workweek were
considered (12 minutes more sleep per night by 5-day controllers in con-
nection with the day shift). However, the average amount of sleep
reported for the workweek by controllers on either rotation schedule is
not out of line with values reported by other investigators for shift

12


Age Male Female

How long a controller including military and training time?

How long a controller at this facility?

Journeyman?

Trainee?

Supervisor?

What shift rotation pattern do you prefer?

What shift rotation pattern do you presently work?

Bedtime Arising time Date of arising
Begin ATC work (Date and Time) End ATC work (Date and Time)

Overtime (if any) from to Leave (if any) from to

Type of leave Regular days off (yes or no)

Remarks

Physical complaints On duty

Off duty

Sleep quality: Good Average Poor Estimated hours of sleep

Trouble going to sleep. None Slight Moderate Considerable

How do you feel? Well rested Moderately rested Slightly rested

Not at all rested . Reasons for inadequate sleep. Be specific.

Figure 1. Sample of sleep log kept by controllers for 5 weeks.
The biographical data are not repeated on subsequent

pages of the log.





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Quality of Sleep. There was no significant difference in the
reported quality of sleep obtained by controllers on the two schedules
in terms of percentage of responses of "good," "fair," and "poor"
(Table 2). However, the percentage of responses of "poor" quality of
sleep was greater on the 5-day rotation schedule than on the 2-2-1
rotation schedule. This difference is most apparent when a comparison
is made of the percentage of "poor" responses from controllers on the
midshift of the 2-2-1 rotation schedule with that from controllers on
the 5-day rotation schedule.

The quality of sleep obtained by controllers on the 2-2-1 rotation
schedule on their days off was significantly better than that obtained by
controllers on the 5-day rotation schedule, as evidenced by a greater
number of responses of "good" sleep (p < .01) and fewer responses of
"poor" sleep (p < .01).

Age, Quantity, and Quality of Sleep. A within-age-group comparison
of the amount of sleep obtained by controllers on the two rotation
schedules shows that significant differences occurred with greater fre-
quency in the 3l- to 35-year age group (Table 3). Within this age group
the number of responses from controllers on the 2-2-1 rotation schedule
indicating sleep of less than 4 hours (p < .01) was greater than that
from controllers on the 5-day rotation schedule, In the 31- to 35-year
age group, controllers on the 5-day rotation schedule reported sleeping
6-8 hours a percentage of time greater (p < .01) than that reported by
controllers on the 2-2-1 rotation schedule. It is noteworthy that there
were no significant differences with regard to quantity of sleep in the
over-41 age group on either shift rotation schedule.

Insofar as quality of sleep is concerned (Table 4), controllers who
were over 41 years of age seemed to fare better on the 2-2-1 rotation
schedule than did their counterparts on the 5-day rotation schedule.
This is evidenced by the fact that they reported a significantly greater
(p <= .01) number of "good" responses for quality of sleep than did con-
trollers on the 5-day rotation schedule.

Complaints. "Fatigue," "weakness," and "somnolence" were the most
frequent on-duty complaints given by controllers on the midshift, fol-
lowed by those same complaints in decreasing order of frequency on day
and evening shifts. The high incidence of upper respiratory complaints
might be related to the winter weather (Table 5). Postduty complaints
(Table 6) followed the same response pattern as shown in Table 5 for
on-duty complaints.

Reasoas for Unsatisfactory Rest. The reasons given most frequently
for unsatisfactory rest following the day shift were "nonspecific" oa the
5-day rotation schedule and "work related" on the 2-2-1 rotation schedule
(Table 7). On both rotation schedules, "“i11lness" ranked first as the
reason given for unsatisfactory rest following the evening shift and
“york related" and "noise" were indicated most often in connection with
the midshift (day sleep).



TABLE 1. Comparison of Average Number of Hours Slept
in Connection With the Various Shifts (and Days Off)

on the Two Rotation Schedules

Shift Rotation Schedule
5-Day 2-2-1
Day 6.0 5.8 *
Evening 7.4 7.6
Mid 5.2 3.5 **
Days Off 7.7 7.9
Average, 5-day workweek 6.4 6.1 **
Average, 7-day week 7.1 7.0
* p< .05
*k p< .01


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Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
FAA-AM-77-5
4. Title and Subtitle 5, Report Date
February 1977
SLEEP IN AIR TRAFFIC CONTROLLERS 6. Performing Organization Code

[8. Performing Organization Report No.

7. Author's)

J. T. Saldivar, S. M. Hoffmann, and C, E. Melton

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aeromedical Institute
P. 0. Box 25082 TT. Contract or Grant No.
Oklahoma City, Oklahoma 73125

TS. Type of Report and Period Covered

12. Sponsoring Agency Name ond Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W. 14. Sponsoring Agency Code
Washington, D.C. 20591 FAA

15. Supplementary Notes

Work was performed under Tasks AM-C-75-PHY-71 and AM-C-76-PHY-71.

16, Abstroct

Data obtained from sleep logs maintained for a period of 5 weeks by 185 air
traffic controllers indicate that on a weekly basis there is no significant
difference in the amount of sleep obtained by controllers working the 2-2=1
rotation pattern and that obtained by those on the 5-day rotation pattern.
Controllers working the 2-2-1 rotation pattern slept significantly less prior
to the midshift than they did before the evening and day shifts. On both the
2-2-1 and 5-day rotation patterns, the most sleep obtained was on the evening
shift followed by the day shift and midshift respectively. Approximately half
the controllers indicated satisfaction with their present shift rotations;
however, preferences indicate that they would prefer to work a shift rotation
that excluded the midshift.

Age and experience do not appear to be related to pattern of sleep or amount
of sleep obtained. "Fatigue," "weakness," and "somnolence" were complaints
most often expressed on the midshift on both rotation patterns. Reasons most
often given for not sleeping were "work related" and "illness" by controllers
on the 2-2-1 rotation pattern and "work related" and "nonspecific" by those on

the 5-day rotation pattern.

18. Distribution Stotement

17. Key Words

Air Traffic Controllers Document is available to the public

Sleep Patterns through the National Technical Information
Stress Service, Springfield, Virginia 22151.

Shift Rotation

19. Security Classif. (of this report) 20. Security Classif, (of this page) i No. of Pages | 22. Price

Unclassified Unclassified 15

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized



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Tit.

work-rest schedules. An investigation into the matter was indicated,

not only to determine problem areas that might affect job performance

and hence compromise air safety, but also to contribute to a data base
from which short- and long-term effects of shift rotation work on the

health of the controller can be determined.

Method.

Data were collected by means of a survey conducted with the coopera-
tion of the Professional Air Traffic Controllers Organization (PATCO),
Letters requesting controller volunteers to participate for 5 weeks
in the study were forwarded through PATCO's Director of Labor Relations
to each of 35 PATCO representatives in ARTCC's in the contiguous United
States. Sleep logs (Fig. 1) were distributed by PATCO to controller
volunteers. Completed sleep logs were returned to PATCO for forwarding
to the Stress Physiology Research Unit, FAA Civil Aeromedical Institute,
for processing and analysis; thus, complete anonymity of controller
volunteers was insured.

One hundred and eighty-five completed questionnaires were returned.
Thirty-two of the respondent controllers (average age 33 years, 9.4
years experience) worked the 2-2-1 rotation schedule, and 132 (average
age 34 years, 9.7 years experience) worked the 5-day rotation schedule.
Differences in age and experience between controllers on the two rotation
schedules were not statistically significant. Twenty-one controllers
worked rotation schedules different from the 2-2-1 and 5-day rotation
schedules; data from this group are not reported,

From each of the 185 questionnaires, 534 entries were made into the
Hewlett-Packard 2100 Executive Computer System for data processing and
analysis. This total of 98,790 entries related to age, number of years
of experience, rotation schedule and shift worked, quantity and quality
of sleep, on- and off-duty complaints, and reasons for not sleeping.
Entries were arranged into subsets of information for ease of handling.

Results.

Quantity of Sleep. On the basis of a 7-day week (including 2 days
off), the average amount of sleep obtained by controllers on the 2-2-1
rotation schedule did not differ significantly from that obtained by
controllers working the 5-day rotation schedule (Table 1). However,
when the 5-day workweek (not including 2 days off) was considered, the
amount of sleep obtained on the two rotation schedules was significantly
different. On the average, controllers working the 5-day rotation
schedule obtained 18 minutes more sleep per 24-hour period (p < .01) than
did controllers working the 2-2-1 rotation schedule. The difference was
clearly caused by the small amount of sleep obtained by controllers on
the 2-2-1 rotation schedule prior to the midshift. On both rotation
schedules, the greatest amount of sleep was obtained in association with
the evening shift, while the least amount of sleep was associated with
the midshift.


workers. Bjerner (4), in his study, indicated that shift workers as a
group average about 6,5 hours of sleep per 24 hours while rotating shift
workers averaged somewhat less when on the night shift (about 5.5 hours).
Wyatt and Marriott (5) concluded that 37 percent of the nightworkers in
their study reported less than 6 hours. of sleep per 24 hours.

It is generally true that the midshift has the least traffic, hence
the least workload. Characteristically, air traffic volume is low early
in the midshift and becomes higher during the last hours of the shift.
Usually, the first 1 or 2 hours of the day shift overlap the last 1 or 2
hours of the midshift. As on other shifts, controllers rarely engage in
a full 8 hours of controlling traffic. It is common for a controller to
be relieved after the first half of the shift and reassigned to a
noncontrol function. During peak traffic density late in the midshift,
the newly arrived day-shift controllers provide relief.

For the above reasons, excessive workload and prolonged hours at a
control position cannot be considered the primary stressful factors on
the midshift. An assessment of the complaints made by the controllers
indicates that work underload causing boredom, fatigue, and sleepiness is
the principal stressor. From the physiological point of view, these are
valid complaints. A change from daywork to nightwork is contrary to a
number of cyclic biological functions, some of which are body temperature,
appetite, elimination, and sleepiness (6). In the case of controllers
on the 2-2-1 rotation schedule, a disruption of circadian periodicity is
not considered a serious problem because they are effectively doing day-
work and sleeping at night. The data suggest that the controllers do
not always take full advantage of the time available to them for rest.
They relate that the amount of sleep they get is adequate for them to
perform at an acceptable level of competence and that a short rest fol-
lowing the midshift allows them to continue their day-wakefulness,
night-sleep routine with minimum disruption of their sleep pattern (1).
Their contention is supported by studies (7) that have shown performance
can be kept at an acceptable level by subjects on a rigorous schedule of
4-hour work periods and 2-hour rest periods maintained for 15 consecutive
days.

The 5-day rotation schedule presents a problem of a more serious
nature than does the quick turnaround of the 2-2-1 rotation schedule,
particularly insofar as midshift work is concerned. The workweek is
sufficient in length to allow some controllers to undergo some degree
of circadian rephasal. Once this has occurred, the time necessary for
them to readjust to a routine of daywork and night sleep consumes most
of their 2 days off. Consequently, they report returning to work tired.

It seems reasonably clear from the data presented in this report
that the midshift of either rotation schedule is the shift that presents
the most problems insofar as quantity and quality of sleep are concerned.
Considering only the midshift on both rotation schedules, it is noteworthy
that even though the 2-2-1 controllers reported less sleep in connectioa

13



References

Melton, C. E., J. M. McKenzie, R. C. Smith, B. D. Polis, E. A. Higgins,
S. M. Hoffmann, and J. T. Saldivar: Physiological, Biochemical, and
Psychological Responses in Air Traffic Control Personnel: Comparison
of the 5-Day and 2-2-1 Shift Rotation Patterns, FAA Office of Aviation
Medicine Report No. AM-73-22, 1973.

Ray, J. T., 0. E. Martin, Jr., and E, A. Alluisi: Human Performance
as a Function of the Work-Rest Cycle, a Review of Selected Studies.
Publication No. 882, National Academy of Sciences ~ National Research
Council, Washington, D.C., 1951, pp. 26-32.

Melton, C. E., R. C. Smith, J. M. McKenzie, J. T. Saldivar, S. M.
Hoffmann, and P. R. Fowler: Stress in Air Traffic Controllers:
Comparison of Two Air Route {Traffic Control Centers on Different
Shift Rotation Patterns, FAA Office of Aviation Medicine Report No.
AM-75-7, 1975.

Bjerner, B., A. Holm, and A. Swinssen: Om Natt-Och Skiftarbete,

Statens Offeatliga Utredningar, Stockholm, 1948, p. ol.

Wyatt, S., and R. Marriott: Night Work and Shift Changes, BRIT. J.
INDUSTR. MED., 10:164, 1953.

Murrell, K. F. H.: Ergonomics, Chapman and Hall, London, 1969, pp.
430-441.

Adams, 0. S., and W. D. Chiles: Human Performance and the Work-Rest
Schedule. In Bennett, E., J. Degan, and J. Spiegel (Ed.), Human
Factors_in Technology, McGraw-Hill Book Co., Inc., New York, 1963,
pp. 39-64.

Dille, J. R.: Unpublished observations.

15



SLEEP IN AIR TRAFFIC CONTROLLERS

Introduction.

Since World War II, there has been a steady increase in the number
of operations handled by the U.S. air traffic control (ATC) system.
Advances in systems tend to make the controller's task somewhat easier
from an operational point of view; however, the same cannot be said
about the work schedules at most ATC facilities.

At air route traffic control centers (ARTCC), separation of air-
craft is a 24-hour operation requiring continuous monitoring by air
traffic personnel. To make the necessary coverage equitable, personnel
are required to work rotating shift schedules. It then becomes imperative
from management's viewpoint to determine what impact these rotating
schedules might have on air safety and the health of controllers. Such
determinations cannot be made simply and directly because the physiologi-
cal, psychological, and social variables are numerous, complex, and inter-
acting. Shift work demands adaptability; the ability of controllers to
function optimally in their jobs is dependent, in part, oa how well they
adapt to their work schedules.

The two most common shift rotation schedules in effect at ATC
facilities are the 2-2-1 rotation schedule (two evening shifts, two day
shifts, and one midshift followed by 2 days off) and the the 5-day rotation
schedule (usually five evening shifts, 2 days off, five day shifts, 2
days off, five midshifts, 2 days off, and then the cycle begins again).

In studies conducted at Houston Intercontinental Tower during 1970-71,
Melton et al. (1) compared the physiological, biochemical, and psychologi-
cal responses of controllers working these two rotation schedules. In
those studies, it was found that the level of biochemical and physiologi-
cal stress was significantly lower in several respects when controllers
worked the 2-2-1 rotation schedule than it was when they worked the 5-day
rotation schedule. In addition, the amount of sleep was not greatly
different on the two rotation schedules except that controllers slept
significantly less prior to working the midshift on the 2-2-1 rotation
schedule than at any other time.

While controllers generally maintain that they experience no adverse
physiological or psychological effects from working the 2-2-1 rotation
schedule, this opinion is not generally shared by management. The
managerial position is perhaps justified in view of the large number
of publications (2) relating to effects oa job performance by various



Figure 1.

Table

Table

Table

Table

Table

Table

Table

1.

4.

5.

LEGENDS OF FIGURE AND TABLES

Sample of sleep log (page 1) kept by controllers for 5 weeks.
The biographical data are not repeated on subsequent pages of
the log.

Comparison of Average Number of Hours Slept in Connection With
the Various Shifts (and Days Off) on the Two Rotation Schedules

Comparison of Sleep Quality in Connection With Various Shifts
oa the Two Rotation Schedules

Within-Age-Group Comparisons of Hours Slept in Connection With
the Two Rotation Schedules

Within-Age-Group Comparisons of Sleep Quality in Connection With
the Two Rotation Schedules

Comparison of On-Duty Physical Complaints for Each Shift on the
Two Rotation Schedules

Comparison of Postduty Physical Complaints for Each Shift (and
Days Off) on the Two Rotation Schedules

Comparison of Reasons for Unsatisfactory Rest for Each Shift
(and Days Off) on the Two Rotation Schedules


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with the midshift than did the 5-day controllers, the former reported a
higher percentage of "good" and a lower percentage of "poor" day sleep.
In addition, the 2-2-1 controllers reported more and better sleep on
their days off than did the 5-day controllers, a further indication that
the 5-day controllers have more trouble readjusting to a day-work,
night-sleep routine.

Comparisons of sick and annual leave usage on the two rotation
schedules showed that there were no significant differences in amount
of leave taken. However, in another study, Dille (8) found that sick
leave usage among ARTCC controllers on a 5-day rotation schedule was
slightly less (60 hours per person per year) than that for 2-2-1 con-
trollers (73 hours per person per year).

The data reported here indicate that the 2-2-1 rotation schedule is

not a more disruptive routine than is the 5-day rotation schedule as far
as quantity and quality of sleep are concerned,

14