submission - Independent Pilots Association

e\rernal en\rronrrcnt around the24 hour da¡' \circa--about: dies-4a¡')is callcd ci¡cadian rh¡-thm
entralnfT¡€nt.
AJrhough o¡her internal a¡rd cxternal factors do ptay a role, thc light-dark cycle is the major
enrrainrncnt factor for most of the animal kingdom. For huma¡s. though, thc Light-dark cycle is
fett to be a rclativcly weak svnchronizarion of
","*:ffiîïïil#iffit;täneåsons'
inæ nsiry requ ired for c i¡cadia¡¡ sync hronizari on
rstimatæ re.ngc from 120G250O lt¡¡ (Reinbcrg &'
re adcquacy of indoor tigbting. Sccon( man is
ht cyclc.
Sociat environnrcnt appcafs to play a fûoFe important rolc i¡ cntrainrænt sæial factors tbu can
rhythrlts includc tcmPcrarurË. flight duty, stess,
I & Wcgmann, 1987). Exercisc or activity dso
ption. Ferrcr et al. (1995) ci¡e evidcnce ¡hat
rts to shift work changes regardless of irs
ically frt and cxcrcisc rcgularly havc highcr
als, and those with high circadian rh¡hm
er et d., 1995). This belps to cxplain u'hy age'
to incre¿scd sleep diffrcultics' poor adjusÙn€n¡ to
night uork a¡d transnæridian flighs in thosc over 50'
Back oi the CtocX Operations, Circedian Rh¡'thm ¡nd Performance
There rs a subsrantiaJ bod¡ of research th¡r sho*'s de.'rea:sed pe rformance during night shifts as
compared uirh day shifts. The reasons for tlus decrcased prformance tn;lude:
o CLrcadran Pressure
to sleep when the rndir idual is anemPting to *ork
o Cúcadian pressure ro be awake when the i¡dividual is anempting to sleep
o Time s,nce a*ake r¡ay bc substa¡rrial if the individual is up alJ dav bcfore rePonin-E for the
nigbt shift.
.Cumularivcsleepdebtincreasethroughoutrheshift.
Rese¿rch conducted by Monk et al. (1989) indicates that subjecute alenness is under ¡he control
of the endogenous ciróadia¡ pacemaker and one's sleep-wakc cycle (tinrc since a*'alte). \åften
tirne si¡ce au,ake is tong and coincides with rhe circadian lo*'there is a very sharP drop in
alerness, a s¡ong tendÃc¡'ro slecp a¡rd a significant drop in performancc (Perelli, 1980)'
Alenness is relatively higb when the ci¡cadian rh¡rhm is ne¿¡ the acrophæc and tinre since a\[alie
is small. Nfonli (1996).r!u.t that this c¡cle is consistent with the NTSB (1994) frnding of a peak
accident rare occurring irithe evening. The srrength of the ci¡cadian clcle is substa¡tial Alerstedt
Literoture Retiev'
Poge 23