1gs at ine Be
2 Schedules.

Day Schedule £ é
Mean 44 3°
so i 1.0
2-2-5 Schedule A nN a F N
Mean 2.0 21 22 ha
sO La wh is 1S
2 Schedule 4 A M t ¢
Mean 18 08 29 24
sD he co ua Da
Table 9

Means and Standard Deviations for Stanford Sleepiness Scale Ratings of the Drive Home from
Work by Day of the Week for the Straight Day, 2-2-1, and 2-1-2 Schedules

Bayt Gay 2 Day 3 Day 4 Day 5
Day Scnedule E E E £ £
Mean 32 38 36 42 in
so “3 4 14 Le 2
2-2-1 Schedule & _
Mean 24 Le
sD ie is
2-1-2 Schedue a Mt E £
Mean 2.8 28 34
sD ag us is

Stanford Sleepiness Scale
Subje
the beginning of the work de

ive ratings of sleepiness were recorded for the straight day pears to be ner to: the
and the drive home — first three d the week, both a the begins

from work. Higher ratings indicated greater sleepi- the workday and cn the drive home

ng of

than the other

ness. Tables § and 9 presenr rhe means and standard two groups A 3 (Schedule) x $ ‘Day? x 2 (Rauing?
deviations of the SSS ratings for the beginning of the herween groups, repeated measures MANOVA was

workday and for the drive home, respectively, foreach — computed for SSS rarings. The realts of the MANOWA
group by day of the week. for SSS ratings are presented in Table 16
Figure 3 reves that sleepiness is consistently rated he MANOVA fur SSS ratings revealed significant

higher for the drive home from work than for the main effects for Day. F ~6.63, p<.l and Rat
beginning of the workday for each group. Inaddition, ing, E{1,21<22.08, p-.01. The MANOWA revealed

ii

suninmgiigemmemeiminemimanipaiatiies cose ceed

ADA294159


schedule i.e., weekly $-dey rotation of day, efternoon,

und night shifts (Saldivar, Hoffmann, & Melon,
Schroedes, Rosa, and Wiet (1995) found chat
ation wes greatest before che first afternoon

sleep
shift (8.35 hours), declined to 5.75 hours before the
second day shift, and fell co 3.75 hours before the
night shift. In a laboratory study invesciguiing the 2-
2-1. Della Rocco and Cruz (19953 found a similar
partern of decline in total sleep time across the five

ys of the 2-2-1 schedule from 7.6 and 6.4 hours

d.

prior to the ewo afternoon shifts to 5.8 and 6.6 hours
prior ro the two morning shifts to 3.7 hours prior to
the night shift. In addition, che data in the lab-based
study indicated that the sleep/wake cycle was di
rupted on the 2-2-i as compared to a straight day
schedule. The only significant sleep loss in the sched-

ule occurred just prior co the night shift, bur changes
of wo to four hours in asleep and awake times were
found at several points in the schedule. Despite fairly
in this
study, performance was mainly affected on the night

continuous disruption of the sleep/wake cycl

shift. Sleep quality ratings also declined over the
course of the 2-2-1 week, with the lowest ratings given
for the afternoon sleep before the nigh: shift. On the
other hand, Saldivar et al. (1
2-1 resulzed
particularly

showed thar the 2-

fewer ratings of poor quality sleep.
fh regard to the nigh shift, than the
straight-five rotation. Finally, in one study of job
attitudes of ATCSs (Smith, 1973), the 2-2-1 was
clearly the preferred rotation schedule even among
the most senior group of controllers.

The current study was initiated in response to 2
request by the Miami Air Route Traffic Control
Center (ARTCC) Quality Through Partnership (QTP}
team to investigate a reported problem of sleepiness
on the night shift. In an effort to understand more
about sleep patterns associated with counterclock-
wise, capidty rotating schedules, ewo cypes of rora-
tions were compared to 2 straight day schedule. The
first of these was a 2-2-1 (afternoons, early mornings,
night) schedule. which involved two quick-turn-
arounds of 8 hours cach and a night shift at the end of
the week. The second schedule was a 2-1-2 (aiter-
noons, mid-day, early mornings), which involved rvo
quick-turn-arounds of 12 hours each and did not
include a night shift. The straight day schedule in-

te

€5 Dior es

0800. These turee schedules allowed !

sono! !) wocounterclockwise rapidly

he cor

rotating sched-

ules and a straight early morning schedule
ft, and 3) 8-hour

with and without a aight si
hour quick-turn-arounds.

Because of the restrictions of the experime:
prozocol in the laboratory-based study of the 2-2-1
and a young ATC work force, Della Rocco and Cruz

{1995} speculated thar the disruptions observed in the

leboratory might be exacerbated in data from the
ATC work force. The 2-2-1 and 2-1-2, then,
were hypothesized to result in phase shifts of
and awak: ondin:
arounds i

ac

sleep

times corre: to the quick-turn-
cach schedule. They were also hypoth-
esized co resulr in less sleep over the course of the week
than the straight day schedule. In addition, the 2-1-2
was expected to be less disruptive to the sleep/wake
cycle than the 2-2-1 because 1) the 2-1-2 did not
contain a night shift and 2} the quick-turn-arounds

k

were four hours lenger than in the 2-2-1 schedule.
METHOD

Participants

Ninety-five volunteers from the Miami ARTCC
complered daily log books over a period of two weeks.
ses based
: 1} a full 5-day work week

Twenty-four were selected for these ana’

upon the following criter
of data was reported and 2) che schedule for that work
week corresponded to either a 2-2-1 (n=8)}, a 2-1-2

(ne

), ora straight day schedule (n=8}. More partici-
pants were not included because of a holiday thac
occurred during the data collection period thar re-
salted in schedules not meeting one or both of the
criteria, Of the 24 selected participants, 18 (75%)
were male and six (25%) were female: 20 were Cauc:
sian, three were Hispanic, and one w:

Asian/Pacific
Islander. The average age of chese participants wes
32.9 years isd-7.9).

Twenty-three of the 24 participants were Air Trak

fic Control Specialists, and one participant was from
the Airway Facilities work force. Of the 23 ATCSs, 14
{60.9%} were Full Performance Level (FPL), eight
{34.8%} were Developmentals (in training), and one
(4.39%) was an Area Supervisor. The average

ADA294159



wath 9 perspective. Eagles Chi

rentice Hall.

Barton. J. & Fotkard, S. (1993! Advancing versus
delaying shift systems. Ergonomics, 36 (1-3), 59
64.

Creisler, C., Moore-Ede, M.. & Coleman, R. (1982)
Rotating shift work schedules that disrupt sleep
are improved by applying circadian principles.
Science, 217, 460-463.

Della Rocco, P. & Cruz, C. (1995). Shift werk, age and
performance: 1. Sleep/wake cych in laboratory-
based investigation of the 2 shift schedule
used in air traffic contro! facilities. (DOT/FAA!
AM-95/in press). Washingron, DC: Federal Avia-
tion Administration, Office of Aviation Medicine.

Folkard, S. (1989, July). Shiftwork—a growing occupa-
tional hazard. Occupational Health, pp. 182-186.

Folkard, $. (1992). Is there a ‘best compromise’ shift
system? Ergonomics, 35{12), 1453-1463.

Gander, P., Myher, G.. Graeber, R., Andersen, H., &
Lauber, J. (1989). Adjustment of sleep and the
circadian temperature rhythm after flights across
nine time zones. Aviation, Space, and Environmen-
ual Medicine, 60, 733-743.

Hoddes, E., Zazcone, V., Smythe, E., Phillips, R.. &
Dement, W’. (1973}. Quantification of sleepiness:
A new approach. Pachophysiology, 10(4), 431-
436.

Knauth, P. (1993). The design of shift systems. Ergo-
nomics, 36 (1-3), 15-28.

Knauth, P. & Rurenfranz. J. (1982). Development of
criteria for the design of shiftwork systems. Journal
of Human Ergology, 13 (supplement}, 155-164.

stration, Office of Aviat!

. & Holley, 2. (1990). Shiftwork and safety in
aviation. In A. Scott (Ed.), Occupational) Medicine:
Sucte of the Art Reviews, § (2): 343-377. Philadel-
phia, PA: Hanley & Beifus.

Rosa, R., Bonnez, M., Bootzin, R., Eastman, C., Monk,
T., Penn, P., Tepes, D., & Walsh. J. (1990}
intervention factors for promoting adjust
nightwork and shifwork, In A. Sco:
pational Medicine: State of the Art R.
391-414, Philadelphia. PA: Hanley & Belfis,

Saidivar, j., Hoffman, $., & Melton, C. (197
air traffic controllers (DOT/FAA/:
Washington, DC: Federal Aviation Ad:
tion, Office of Aviation Medicine.

Schroeder, D., Rasa, R., & Witt, L. (1995). Effects of
8- vs. 10-hour work schedules on the perfor-
mance/alertness of air traffic control specialists
(DOT/FAA/AM-95/in press), Washington, DC:
Federal Aviation Administration, Office of Avia-
tion Medicine.

Price,

Smith, R. (1973). Job attitudes of air traffic controllers:
A comparison of three air traffic control specialties
(DOT/FAA/AM-73-2). Washingron, DC: Fed-
eral Aviation Administration, Office of Aviation
Medicine.

Taub, J. & Berger, R. (1973). Performance and mood
following variations in the length and timing of
sleep. Psychophysiology, 10(6}, 559-570.

Toothaker, L. (1991). Multiple comparisons for re-
searchers, Newbury Park: Sage Publications.

‘Turek, F. (1986). Circadian principles end design of
rotating shift work schedules. American Journal of
Physiology. 251, RG36-R638.

Wilkinson, R. (1992). How fast should the night shift
rotate! Ergonomics, 35(12), 1425-1446.

U.S. GOVERNMENT PRINTING OFFICE: 1995 . 668-057/90127

ADA294159


Deg $
Degrees of

Sums of

reedom Squares F
Scredule 2 36.07 8.22*
Between Subjects 21 46.05
Day 4 131.28
Schedule by Day 8 85.72
Within Subjects 84 77.35
*p<.05
mep<.01
c} Day 3 was the first quick-turn- around for both

the 2-2-1 and 2-1-2. TST for Day 3 of the 2-1-

2 (M-7.6 hours) was significantly longer than

for the 2-2-1 (M-=5.1 hour: 4.78. p<.05 and
the straight day 2.58, pe.05.
There was no difference in TST for Day 3
between the 2-2-1 and the straight day sched-
ules.

d) The fourth day for all of the schedules was an

.2 hours),

early morning shift and was the second quick-
turn-atound for the 2-1-2. There was, however,
no difference in TST on any of the comparisons

dules.

among s
¢) Finally. PST on Day 5. was significantiy lower
for the 2-2-1 schedu 2.4 hours} than for
the straight day (M-*.6 hours). :=6.01, p<.05,
2-1-2 schedule (M=5.9 hours), (-6.46.
fi in TST for Day

5 between the 2-1-2 and straight day schedules.

2. Comparisons of Schedule Effect (Between
Groups)

Although mean TST over the course of the work
week was lowest for the 2. schedule (M= 5.7 hours),
it was not significantly lower than the mean TST for
the straight day schedule (M=6.0 hours). The 2-1-2
schedule obtained the greatest mean TST over the
work week (M=7.0 hours), and this was significantly
higher than both the 2-2-1, (21}=3.93, p<.05, and
the straight day schedule, ¢(21}=2.90, p<.05.

~

a) Within the straight day schedule. no significant
differences were revealed from one day to the
BONE

b} Within the 2-2-1 schedule, TSTs for Day

hours), Day 3
=5.1 hours} were

U(7}=6,00, p<.05; and 1 9.37, ps. 05, respec-
tively. In addition, TST within tite 2-2-1 for the
two afternoons, Days } and 2, was signific:
higher than for the wwo carly mornings, Day 3.
}=5.86, p<.05 and, 0(7}=4.44, p<.05, respec-
and Day 4, £(7}=6.44, p<.05 and
13, pe.85, respectively.
y. within the 2-1-2
3 was significantly hi
1(7)=6.38, p<.05, or Day 5, {7)=7.67,

<)

Asleep and Awake Times

To test the hypothesis that the 2-2-1 and 2-1-2
schedules would result in phase shifts in the sleep/wake
cycfe, the average Asleep and Awake Times were com-
puted, and che changesover the schedule were examined.
Again, only the sleep periods prior ta each workday were
included in the analyses. Tables 4 and $ present the
means and standard deviations for Asleep and Awake
Times, respectively, for each group by day of the week.

ADA294159


i ftom those devel-

i Space Admin-

In the logbooks, volunteers were asked to disein-
Setweea “In bed” and “asleep” 2

wees “awake” and “arise” times. TST »as computed

s and be-

ference between reported Asleep and Awake
ong awakenings during the sleep period (30
es or longer) were subtracted from TST. SORs
ed responses to the following scales: 1) “Fall-

ing asleep,” from Not Difficult (1) to Difficuls (5); 2)
5 e

“My sleep was,” from Not Deep (i} to Deep (3); 3)
“Arising was,” from Not Difficult (1) te Difficuls (8);
and 4) “I now feel,” from Not Rested (1) 20 Rested (5).
Responses were recoded so that high scores on each
question indicaied better sles quality. Responses to
all four questions were then summed, with a possible
high SQR score of 20. Sleepiness was rated for the
start of the workday and the drive ho:
using the SSS, which instruc:

e from work

d participants to select
from seven statements ranging from, “Feeling active
and vital; wide awake,” (13 to
sleep onset soon; losing struggle te remain awake,”

{7).

“Almost in reveric;

Procedure

The ARTCC facility management provided one
hour of administrative time daily during the week of
May 24, 1993, for data collection. Management and
labor representatives jointly briefed employees thar
this study had been requested by the QTP team in
response to ATCS complaints of sleepiness on the
night shift. Two sets of data were collected: 1) fog-
books and 2) a shift work questionnaire. The log-
books were completed daily over a two-week period.
The questionnaire was completed on-site and data
will be reported in a separate study. Logbooks and
participant ID cards were number-coded to ensure
anonymity, and. for this same reason, the on-site
tesearchers did not approach the volunteers at the
facility either to check or collect logbooks.

To improve the accuracy «° the self-report data,
volunteers were instructed to make entries in their

logbooks at the time the event{s) occurred (i.e., to log

meals at the time of the meai and to log sleep inforsna-

back regarding their own data was provided t9 partici-

pants upon request.

Design and Data Analysis

‘This study was a pwo-way mixed-mode design
one berweea-groups factor and one repeated-mea-
sures factor for the following dependent variables:
Asleep Time, TST, and SQR. The
een-groups factor was Schedule Type. The within-

%

ime, Awak

jects, repeated-measures factar was Day of the
study. In the analysis of the SSS ratings, an additi
repeated-measures factor, Rating (pre- and post-work}
was included resulting in a three-way mixed-model
design. The SPSSx version 4.1 for VAX/VM5
MANOVA procedure for repeated measures was em-

na

ployed for the analyses in this study.

Multiple comparisons procedures (MCPs) were
conducted utilizing the procedures for repeated mea-
sures described by Toor!

et (1991) when significant
interactions or main effects resulted from the
MANOVA. Paired t-tests were used for the MCPs for
both the within-subjects comparisons across Day (and
Rating in the case of the SSS measure) and the within-

subjects cell mean comparisons. Results of the t-tests
for repeated-measure compatisons were compared to
a Dunn’s critical value with parameters df=}{n-1} and
C=K{(K-1}/2, where J equaled the number of beeween-
subject groups, n equaled the number of subjects per
group, and K equaled the number of repeated mea-

surements for computation of ai' pairwise compari-
sons. For fewer than all pairwise comparisons, C
equaled the number of planned comparisons. Be-
tween-group MCPs involved a t statistic based on
paired group means. The resulting statistic was com-
pared toa Tukey critical value with paramcters, df=J{n-
1} and number of means=}. Finaliv. for cell mean
comparisons between groups. a t statistic to test
means for Groups at Trials was compured using 2
pooled variance estimate, where MSWCELL=
(SS SS yr a igd J(n-1)=(k- 1] (n-1)). The resule-

Berween,

EAS REA Se I eR _

ADA294159

i
|
i
:



rasa rt

working for une PAA was 7.1 years.

of years

icipation im the stu

voluntary, and i

Scheduies

The schedules investigated in this study included
straight days and wo counterclockwise, rapidiy ro
¢ schedules, the 2-2-1 and she 2-1-2 The 2-2-1
schedule involved wo. noon (A) shif
followed by two cacly morning {E) shifis, followed by
a night (N) shift. The 2-1-2 schedule involved work-
ing two A shifts. followed by a single mid-day (M}
shift, followed by two F shiits. For purposes of this
report, E shifts generally began between 0600 and
0860, M shifts began between 0800 and 300, Achifts
began berween 1300 and 1600, and N shifts began
after 2100. The 24 volunteers represented in this
study reported work schedules chac conformed, fer
the most parr, ta one of these schedule types. The
straight day group generally worked all E shifts, Three
volunteers, however, had exceptions within their sched-

is,

king nwo afte

ules; Two worked one M shife during the week and

another worked three M shifts during the week. All of

A shift, Six

rather shan . Sixt
sample worked 8-hour days; theo 2
iwa dave off, fellowes
zwo days off, followed

hour days (five days wi
four days with three days off}. Due to che small sanz
size, the 8- vs. 9-hour comparisons were nut con
ducted. Table 1 provides the following
dule: 1) shift nype for each day of the

orm:

f

on each sch

efor each sh
mes within

week, 2) the approximate starz

(computed by averaging all start ¢ a
group and rounding to the nearest half hour}, 3} the
range of shift start times worked by the volunteers in
each group. and 4) the approximate number of hours

off herween $

Measures

Five subjective measures of sleep and sleepiness
were anatyzed: 1) Asleep Time, 2} Awake Time, 3)
Total Sleep Time (TST), 4} Sleep Quulity Racings

1973), SSS satings were given for the star of the w

day and the drive home from work. Data were col-

Table 1
Work Schedules

Day t Day 2
Straight Day $_hedule
Shik Type ia E
Approximate Stari Time 073¢ o700
Range of Stan Times 0630-100) 0630-0005
Approximate Hours Oft
Between Shitts Vb hrs. 1 brs.
2-2-4 Schedule
Shift Type A A
Approximate Start Time 1430 1330
Range of Stan Times T3HKETECO 1900.1 665
Approximate Hours Of!
Between Shits 16 hrs. 8 hrs.

2-1-2 Schedule

Shift Type A
Approximate Stat Time 3430
Range of Stan Times 1330-1500
Approximate Hours Off

Between Shitts 16 brs. 12 burs.

1250-1406

Day 3 Day 4 Day 5
— t
0636 0630

3639-0700

93-0645

8 hes.
M E
1030 v700 700
0955-1106 0630-0700 9690-0
12 hrs. Vb brs.

ADA294159

RT PET EE ETE EET TER I TES


ADA294159


Mean Total Steep Ting (Har

ca

3

|
on
j
5

Day of tne Week

Figure 1.
Schedules.

Mean Total Sleep Time by Day of the Week for the Straight Day, 2-2-1, and 2-7-2

2-2-1 and 2-1-2 schedules. as compared to the straight
day schedule.

Total Sleep Time

To test the hypothesis that working the 2-2-1 and
2-1-2 schedules would result in sleep loss, as com-
pared to the straight day schedule, TST was computed
for the sleep periods prior to each day of the work
week. Table 2 presents the means and standard devia-
tions of TST for each group by day of the week.

Figure } presents data for the mean TST by day of
the week for each shift schedule, Data revealed 1} a
consistent average TST for the straight dav schedule
across the work week, 2) equal or greater TST for the
2-1-2 on each day of the work week, and 3} two
relatively large decreases in TST for the 2-2-1 corre-
sponding to each quick-rurn-around. A 3 (Schedule)
x 5 (Day) between groups, repeated measures
MANOVA was computed for TST. The results of the
MANOVA “or TST are presented in Table 3.

The MANOVA for TST sevealed a significant
Schedule by Day interaction, F(8,84)=11.64, p<.01
and significant main effects for Schedule,
F£(2,21)=8.22, p<.05 and Day, E(4,84)-35.64. p<.01.
Multiple comparisons of TST revealed the following:

1. Comparisons of Schedule by Day Interaction
(Between Groups)
a) The first two days of the schedule showed no
difference in TST between the 2-2-1 and the 2-
1-2 schedules. On Day 1, TST for both the 2-
2-1 (M=8.3 hours} and 2-1-2 (M-+8.2 hours)
schedules (afternoon shifts for both) was ercater

than for Day 1 of the straight day schedule
(M=6.2 hours}, 223.86, p<.05 and 2=3.63, p<.05,

respectively
b) TST fer Day 2 hours}, bur
not the 2-1-2. was significantly longer than fo:

Day 2 of the straight day schedule (M-6.3

hours), £+2.53, pe.05.

ADA294159


(ecreonreeg
i a |
is J

f

is

GO)

A)

sclay its
in

cprmoved

|

Final Report

U.S. Department
of Transportation

Federal Aviation
Administration

id, Virginia 22161,

19950515 072

ADA294159



1 phase shifts in

each day to the next

by compa:

le reve.
the straight day schedule. no significant
differences in Aweke ‘Time were found from
» the next.

he 2-2-1 «chedule, advances in Awak

one d

Time corresponded to both quick-tmrn-arounds.
?

Awake Time on Day 3 (M=0540) was approsi-

mately 2.5

3, 2(7)=4.23, p<.05, and Awake Vime

hours earlier chan on Day 2

on Day 5 (M=1843) was approximately 10.25

hours carlier than on Day 4 (M-04
35.02, p<.05
-2 schedule, Awake Time on

we
a

nthe 2-
Day 2 (M=0754) was approximately .5-hour
earlier than on Day 1 (M=0828), 1(7)=3.60,
p<.05. and Awake Time on Day 4 (M=0540}
was approximately two hours easlier than on
Dey 3 (M-0744), ¢(7)= 10.37, p<.95. The tran-
sition from Day 1 co Day 2 was not a quick-
turn-around, but the cransitton from Day 3 to
Day 4 was the quick-turn-around from the

mid-day co the early morning shift.

Table 6

veers in the 2-2

-1 group, was used for these iwe missing
ndard devia-

ratings. Tabie 6 presents the means
ons of SQRs k
2 presents a line graph of the SQR averages.

reach group by day of the week

Figure 2 presents data for combined SQR:s by day

ofthe week forall schedules. A 3 (Schedulel x $
between MANOVA
computed for SQRs. The results ofthe MANOVA are
presented in Table ?.

‘The MANOVA for SQRs revealed a sign’
effect for Day, E(4,84)=2.83, p<.05. Planned

soups, repeated measures

cant
mai
multiple comparisons wit

-subjects revealed no sig-
nificant differences between Days. Analyses of each of
the SQR questions were conducted. The MANOVAs
for cach of the questions in the combined SQR re-

sulted in Day main effects for ratings of how difficult
it was to arise, E(4,84}=3.29,p<.05, and how rested
the person felt, F(4,84)=3.17.2<.05. Neither of these
ratings resuited in significance differences for compari-
sons berween days, although the iatings tended to
decline towards the end of the week.

Means and Standard Deviations for Combined Sleep Quality Ratings by Day of the Week for the

Straight Day, 2-2-1, and 2-1-2 Schedules.

Day t Day 2
Day Schedu'e E t
Mean 13.6 13.2
3D 3.2 3.2
1 Scheduie A A
Mean 15.4 149
so 3.2 3.5
2-1-2 Scheduie A A
Mean 74.4 15.2
sO a0 3a

Day 3 Day 4 Day 5
E E E
125 124 13.5
28 24 3.4
E E N
14.8 14.6 124
3.2 3.7 26
M E
15.1 13.0

as
nw

ADA294159



Day i Day 2
Dav Schecule E E
Mean 2220
SL. 14
2 nedale A
Mean 2415 2454
so ae we
hedule :
2415
13

is EN
2348 1621
0.8 13

M
2405 2340
GR Ga

Means ard Standard Deviations for Awake Times by Gay of the Week for the Straight Day, 2-2-1,

Table 5
and 2-7-2 Schedules.
Day 1 Day 2

Day Schedule é F
Mean: 0534 asd
sD 1.0 13

2-21 Schedule A A
Mean 08350 0817
sD 1.6 13

2-1-2 Schedule A A
Mean 0628 0754
sD 1.6 4

Day 3 Day 4 Day 5

E C
O54 0434 0447
a9 OF 0
E N
540 1843
Lo 6.5 W
M —
O744 0524
OF 65

A3 (Schedule) x 5 (Day) between groups. repeated
measures MANOVA was computed for Asleep Time.
Results ofthe MANOVA revealed a significant Sched-
ule by Day interaction. E(8,84)-45.91, p<.01 and
significant main effects fur Schedule. £(2,21}=14.5,
ps.0l and Day, F(4,84)=53.95, p<.G1. Planned mul-
tiple comparisons (to assess potential phase shifts i
Asleep Time by comparing each day to the ne:

in
cach schedule) revealed che following:
1) Within che straight day schedule, no significant

differencesin As
day to the next.

jeep Time were found from one

2) Within the 2-2-1 schedule, only the quick-rurn
around from the early morning w the night
shift revealed a significant difference of 7

hours between the Asleep Times for Day 4
348) and Day $ (M=1621), (7)=12.13.

p<.05.
Within the 2-1-2 schedule, no significant dif-
ferences in Asleep Time from one day to the

next were found.

wy

AB (Schedule! x 5 (Day? between groups, repeated
easures MANOVA was computed for Awake Time.
Results of the MANOVA revealed a significant Sched-

ADA2941

OT
ey



ca: values with paramerers, dfs,

(k-1}f(n-1), and number of means=].

A3 Schedule) x 5 (Day) model was used for the
“ TST, and
cep Time and
Awake Time were computed comparing each day to
the next. This resulted in 2 total of four comparisons
each sched h seven degrees of free-
dom and a Dunn's critical value of 3.34, Multiple
Ts and SQRs included: 1) a be-
tween-groups comparison of Schedule with 21 de-
grees of freedom anda Tukey cr:
awithin-subjects comparison of the repeated measure
with 21 degrees of freedom anda Dun

of 3.16 fur all possible pairwis

of Asleep

annaed comparisons for

¢ type w

comparisons for T.

al value of 2.

* critical value

comparisons of Day;
3) cell meen comparisons between groups with a
critical v: 45 computed as h; and 4) cell mean
comparisons within subjects with seven degrees of
freedam and a Dunn’s critical value of 4.03 for all
possible pairwise comparisons.

ue of 2

Table 2

Means and Standard Deviations for Total Sleep Time

Day, 2-2-1, and 2-1-2 Schedules.

parisons for

comparison o

comparison: of the repeated measu!

with 21 degrees
of freedom and a Dunn’s critical value of 3.16 fer ai
possibie pairwise comparisons of Dey; 3) cell mean
comparisons between groups with a cri
2.45 compuied as h; and 4) 25 planned cell mean
comparisons within groups with seven degrees af

1 value of

freedom and ¢ Dunn’s critical value of 4.78,
RESULTS

The results of the analyses of the followi

dent measures are pr:
Asleep and Awake Times, Sleep Quality Ratings
iSQR). and Stanford Sleepiness Scale (SSS) ratings.
Each of the denendent measures were assessed in
icrms of potential sleep/wake cycle disruption of the

nted: Total Sleep Yim:

Day 1 Day 2
Day Schedule E £
Mean 6.2 6.3
3D 1.3 1.3
2-2-1 Schedule A
Mean 77
$D wi
2-1-2 Schedule a
Mean 8.2
SD 17

Day 3 Day 4 Bay $
ia E £
6.2 5.6 3.6
1.0 4.0 Li
€ E N
5.4 5.4 2.4*
O7 08 C8
M E E
7.6 6.0 3.9
0.7 08 OQ?

° The TST listed for Day 5 represents steep taken on Day 4 in the afternoun priar to the night shift,

ADA294159



an unavoidable condition in mai

wo.

's that require 24-hour operation, inclu
rt Traffic Control (ATC). Shift sched:
with various cheracteristics have evolved among in-
duane ve arcormmodear mime Mahe. Some He
molar characteristics in shift schedule designs include
permanent vs, rorating schedules, slow vs. rapid retae
tions, and delaying (clockwisc} vs. advancing (coun-

terclockwise) rorations (Knauth, 1993). Each kind of

desig:

shift schedule system has its own set of benefits and
problems.

Akerstedt (1990} reported that disturbed sleep is
perhaps the most dramatic effect of shift werk on any
dule, Sleep duizticn on the night and morning
shifts is rccduced by one to four hours in shift workers
on rotating schedules. Sleep duration for day workers
has becn reported ro be generally longer than for shift

si

workers, with dey workers getting about 7.5 to 8.5
hours of sleep per night, and shift workers getring
about 5to 7 hours of sleep per night (Anch, Browman,
Mitler & Walsh. 1988).

Rapidly rotating schedule systems involve working
no more than two or three consecutive days on the

y argue that in rapidly rotating sched-
ale designs, delaying shift systems are to be preferred
io advancing ones (Folkard, 1989; Knauth &
Rutenfranz, 1982; Czeisler, Moore-Ede, & Coleman,
1982). A delaying system rotates in a clockwise fash-
jon such chat work start cimes are progressively later
An advancing system, on the
other hand, rotates in 2 counterclockwise fashion such

across the work wee

that work start times are progressively cazlier across
the work week. Delaying systems effectively stretch
out the work week, while advancing schedules com-
press it.

The primary complaint against the counterclock-
wise rotation is thar it results in “quick-rurn-arounds”
at each shift change, which require employees to
return to work after a relatively shore time off. These
quick-turn-arounds are thought to result in shortened

better

ag systems are pucportediy

because the endogenous body clock kas 2 c! fe
whGark vias Kppning Gey é
tation to delays easier (Rosa et al, /290), Akerstede /

990) and Barton and Folkard (1993) concede, how-

ever, thet despite the many claime that a delaying

system should be preferred to an advancing one, there H
very Hele empirical evidence of this. Turek (1986) i
ggested chat sleep would be disrupted similarly |
{advanced once, delayed once, and not changed once} i
regardless of whether the shift rotation involved 2

delay or an advance. Researchers have suggested that

maintaining consistent timing of sleep and wakeful-

ness may be more important than quantity of sleep
(Anch, Browman, Mitler & Walsh, 1988; Taub & i
Berger, 1973}. Therefore, it is important to examine
work schedules as they affect sleep timing. j
Air Traffic Control Specialists (ATCSs) work rela- i
vely unique variations of counterclockwise. rapidly i

rotating-schedules. This circumstance provided an
opportunity to examine the interaction of schedule
characteristics and sleep patterns. The schedules in

i

use at ATC facilities have relatively recently been
modified, in some cases, to allow for 9- or even 10-
hour days as part of an alternate work schedule.
Because of the safety-related nature of ATC, and
potential problems associated with rotating schedules
(Wilkinson, 1992), it is important to understand the
effects of these schedules on sleep.

Some data were available on ene of che unique shift
schedules in use at ATC facilities known as the “2-2- i
1.” The 2-2-1 is a schedule of two afternoon shifts
followed by two morning shifts followed by a night .
shift (Price & Holley, 1990). A characteristic sleep :
pattern has been teported for the 2-2-1 that has °
generally been shown to result in reductions in sleep
duration across the work week and to result in less
sleep, per day, on the average than a “straight-five”

perc)
i j :

A-/

ADA294159


| Soneduls Type A
|oSraight Dey e224 o212!

Q
g
8,
Ca

Stanford Sleepiness Scaie Ratings

1B 2s 20 3s 83 48 40 8S
Time of Rating

Figure 3. Stanford Sleepiness Scale Ratings for both the start of the workday (5) and the drive
frome (D) by day of the week for the straight day, 2-2-1, and 2-1-2 schedules.
Table 19
MANOVA Summary Table for Stanford Sleepiness Scale Ratings
Degrees of Sums of

Source of Variation Freedom Squares Mean Squares F

Schedule 2 14.53 7.27 1.42
Between Subjects 21 136.45 6.50

Day 4 21.69 5.42 6.637*

Schedule by Day 8 9.63 1.20 1.47
Within Subjects B4 68.68 6.82

Rating 1 50.42 50.42 22.08**

Schedule by Rating 2 0.23 9.12 0.05
Within Subjects 21 47.95 2.28

Day by Rating 4 5.13 1.28 1.75

Schedule by Day by Rating 8 5.60 0.70 0.95
Within Subjects 84 61.68 0.73

sp<.0t

no significant differences in SSS ratings due to Sched- examining the main effect for Day indicated that Day 5

ule, The simple main effect fer Rating indicated thatthe — (M=3.4) was rated higher than Day 1 (M=2.6).

start of the workday (M=2.4) was rated lower on average (21) =3.89, p<.05; Day 2 (M=
than the drive home (M:

7). U2} =3 98, p<.05;

8, p<.05.

Multiple comparisons and Day 3 (M=2.7), 1(21)=3.

1 2D =

12

ADA294159



beginning to lose incerest in remaining awake.” No
more than two people en any day of any other sched-

rated their sleepiness on the drive home at 5 o|
ater. The 2-1-2 schedule had the fewest number of
igs of S or higher on the drive home, suggestirg

cha: fewer people experienced extreme sleepiness on

this schedule. While statistical analysis of these data
did not reveal significant differences between groups,
the ratings of extreme sleepiness for the drive home

after the night shift on the 2-2-1, along with com-

ments in the logbooks referring to falling asleep whi

driving and falling asleep on breaks during the night
shift. suggest thar sleepiness is a problem in the 2-2-
1 schedule.

The data from this study suggest that at least one of
the counterclockwise, rapidly rorating schedules, the
2-1-2, may improve in some ways on a straight day
schedule of early morning start times. Specifically, it
resulted in ne less sleep than rhe straight day schedule,
only one phase shift in Awake Time, no poorer sleep
quality than the straight day schedule, and fewer
ratings of extreme sleepiness on the dsive home than
the straight day schedule. This schedule provided 12
hours off between shifts and did not include a night
shift. Ir also compressed the work week, providing
approximately 8 additional hours off between werk
weeks as compared to a straight day schedule. ‘The

benefits of this schedule mey indicate that counter-
clockwise, rapid rotations. ver se, should not be dis-
missed as less desirable than clockwise rotations. In
fact, Wilkinson (1992). in his critical review of
idly rotating schedules, allowed that rapid rotations
could be used to cover che morning and afternoon
shifts. Indeed, the rev "ts of this study may indicate

that the problems associated with counterclockwise.
rapid rocations have more to do with working the
night shift and easly morning work start rimes chan
with quick-turn-arounds,

The 2-2-1 schedule resulted in: 1} na less sleep over
the course of the work week than the straight day
schedule, 2) only one phase shift in Awake Time, and
3) no poorer sleep quality rhan the straight day sched-
ule. Both quick-turn-arounds in this schedule in-
volved only 8 hours off between shifts, but only the
sleep before the night shift and the number of ratings
of extreme sleepiness on the drive home from the

nigh

‘ira
hel

lack of disruption
schedule supports argume
-2-1 allows f

Bartanowiez (1986) that the
four of the five shifts within normal waking h

and, therefore, should resulz in minimal disruption of

the sleep/wake cycle allowing people co remain €

adapted. These researchers further argued that the

longer period of time off between work weeks would

provide ample time for employees to recover from any
sleep debt created by the quick-turn-arounds.
The findings in this study add empi

largely theores

ical dara ro the

cal body of literature regarding coun-
terclockwise, rapidly rotating shift schedules. ‘the
implications of these findings should be tempered by
a aumber of factors. First, the early morning start
times for the straight day schedule sesulced in < con-
tral group with a lower amount of sleep than expected
for a siraight day schedule. Falkard’s (1989) sugges-
tion that early starr times for the morni

g shift could
result in similar sleep debe to that seen for the night
shift was supported here. Second, chis study excluded
people who traded
leave. or otherwise altered their se
thar it did nor conform to a full 2-2-1, 2-1-2, or
straight day work week. In doing so, this study may
have focused on participants with particularly stable
sleep patterns and potentially excluded individuals

1ifts, cook annual leave or sick

redute in such a way

who do nar cope well with either rorating schedules or
early morning shifts. Third, the sample size in this
study was smalf. Further empirical study of counter-
clockwise, rapidly rotating shift schedules should be
done before generalizing these findings to other popu-
lations ot advocating their use.

This reporz represents the first of several to report
data collected in this field study. Other data will be
reported in a separate srudy, including date from a
shift work questionnaire that focused on health, work
schedules, sleep patcerns, life style, and earing habirs.
Future rescarch is necded to address the effects of
counterclockwise, rapidly rotating schedules, along
with carly morning start times in both retating and
non-rotating schedules and effective counter-mea-
sures to help people cope with sleepiness and fatigue

on the night shift and on the drive home from the
ight

ADA294159



6, Pertorring Orgarization Cox

6 Cagewation Repo

j
i
i
‘

[= Patomng Grganzation Nemes end Adaress
i FAA Civil Aeromedical Institute

3. Work Unt No. (RAIS)

P.O. Box 25082
Oklehoma City, OX 73125

1. Cotkoct or Sram No

cnet eege neeetuneenenfcas cure nome =

Type Of Report ana Period Covers

12. Sponsoring Agency rams ana Address

FAR Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, SW.
Washington, DC 20591

14 Sposscring Agency Code:

[YS Supplemental Notas

16 Abshoct

This study was part of @ xesearch
IATC) environment .
scheézles in use
eep/wake cycle.
before 98951. and
g schedules, the
esleep and awake
Data were collected in siaily logbooks by ai

“anal yzea an terns of
and sie

Total sleep time on the 2-2-1 sche
approximately & hours before the two afternc! on
early morning S, to 2.4 hours before the midr

the 2 2 schedule decreased from 7.5-& hours before the
midday sHifz to approximate € hours before
sleep time on the straight aay sh
of the week. The least amount
the ang before the
Disruptions in ng of sleep were limit
associated with rotations into the early morn
schedules and

Jeep: ness on home, how

han any other sh

type.
foilowi

18. Disteoutior Statement

Document is available to the
through the National Pechnic

°F Key Words
Air Traffic Contz
Shift Work, Sleep/Wake Cycle,

Specialists,

{

Sleepiness, Sleep Quality Information Service, . i

Virginia 22161 |

19 Securty Classit fof mis epoty "| «2 Sacurty Cossf. (of hs page) | 21. No. of Pages we |

i Unclassified Unclassified 18 !
Form DOTF 1700.7 (8-72) Reproduction of cormpieted page authonzed

SAA

ADA294159


is document

ADA294159



Sleep Quality Ratings

Day of the Week

Figure 2. Combined Sleep Quality Ratings by day of the week for the straight day, 2-2-1, and 2-1-

2 schedules.

Tabie 7
MANOVA Summary Table for Combined Sieep Quality Ratings

Degrees of Sums of
Source of Variation Freedom Squares Mean Squares
Schedule 2 18.53
Between Subjects 21 22.69
Day of Schedule 4 14.28
Schedule by Day 8 6.94
Within Subjects 84 3.05
*p<.05

10

Fe a
ADA294159



ight day schedule and two variations of counter-
clockwise, repidly rotating shift schedules, the 2-2-1
and the 2-1-2, were analyzed in terms of subjectively
reported cotal sleep time (TST), Asleep and Awake
Times, and ratings of sleep qualiry and sleepiness.

it was hypothesized that beth the 2-2-1 and 2-1-2
schedules would result in less TST oves the course of
the work week chan the straight day schedule. Resules
of the analysis of TST, however, indicated that the 2-
1-2 schedule resulted in greater TST over the course
of the work week than either of the other ewe sched-
ules, The 2-2-1 resulted in an average TST over the
course of the week that was nor significantly different
from the straight day schedule. ‘Thus, rapidly rorating
schedules in this study resulted in as much, or more,
TST for the week than the straight day schedule.

The straight day group obtained about 6 houis of
sleep per night throughout the week (ranging from
5.6 to 6.3 hours). Saldivar et al. (1977) also seported
that employees on the day week of the straight-5
schedule obtained 6 hours of sleep per nighz. These
sleep durations are much lower than the 7.5 to 8.5
hours of sleep per night that Anch et al. (1988)
reported for day workers.

The amount of sleep obtained by the 2-2-1 group
showed a characteristic decline fror- approximately &
hours before the two afternoon shifts to 5 hours before
the two early morning shifts to 2.4 hours before the night
shift. Studies by Saldivar ct al. (1977), Schroeder et al.
(1995), and Della Rocco and Cruz (1995) have all
reported similar patterns for the sleep obsained on the 2-
2-1 schedule, with declines in sleep duration associated
with each quick-turn-around and with most people
choosing to sleep in the afternoon prior to che aight shift.
In this study, however, the 2.4 hours of sleep before the
night shift is notably lower than the 3.5 to 2.75 hours
reported in previous studies.

The amount of sleep obtained per night by the 2-1-2
group generally declined across the work week from
approximately 7.5 to 8 hours before the first three days
of the schedule (two afternoons and a mid-day) to 6

13

pattern €

second ouick-tum-around,
orning shift, resulted in a decline in sleep d:

nin all three schedules, the average amoun: of
sleep obtained before an early morning shift was only

a straight schedule or a rapidly rotating one. Thus, the
least amount of sleep was obtained before early morning
shifts and before the night shift.

Disruptions in che timing of sleep may be as impor-
tant to performance as sleep duration, It was hypoth-
esized that disruptions in both Asleep and Awake Times
would correspond to the quick-turn-arounds within the
2-1-2 and 2-2-1 schedules, but that the disruption would
be greater for the 2-2-1 (8-hour quick-rurn-arounds)
because of shorter turn-around time than for the 2-1-2
(12-hour quick-turn-arounds). This hypothesis was only
partially supported. Asleep times were relatively stable
for both schedules, and Awake Times were significantly
shifted only once by 2.5 hours in the 2-2-1 (nat includ-
ing the shortened sleep obtained prior tc the night shift)
and by 2 hours in the 2-1-2 . Both of these alterations in
Awake Time corresponded with a quick-turn-around to
an early morning shif.

Subjective measures of sleep quality indicated no
difference in ratings due to schedule type. The ratings
appeared to decline toward the end of the week,
indicating a pattern of poorer sleep. This finding was
similar ¢o previous studies (Della Rocco & Cruz,
1998; Saldivar et al., 1977)

Subjective measures of sleepiness indicated no dif-
ce in ratings due to schedule type. Volunteers on
ail schedules rated theniselves as more sleepy at the
erd ct the day than at the beginning of the day and
moie siecpy on the iast da: of the work week than the
first caree days of the worx week. Examination of
individual volunteei s ratings, however, revealed that
seore catnugs of extreme sleepiness were given by
volunieers on the 2-i-1 schedule for the drive home
after the night shift than on any other day orany other
schedule. Of the eigh: volunteers in the 2-2-1 group,
three rated the drive home after the night shift at (6}
“Sleepy; woozy; picfe. to be lying down; fighting
sleep,” and three others at (5) “Foggy; slowed down;

ADA294159