Table 4.

Field studies of sleep inertia

Study	N	Mean age	Design	Factor	Subj	Obj	Time before testing	Findings
Horne J and Moseley R 2011 [1]	20	21; men	randomized to awakening at 0300 or 0730	Time of waking, sleep length, delay before testing		enemy attack test	5 min in the 0300 group; 60 min for 0730	8/10 of the 0300 group failed versus 3/10 at 0730
Howard ME et al 2010 [90]	8	31.0	Randomized, crossover test of 30 min nap at 1945 or 0400 versus no nap during night shift	0400 nap versus no nap (SI not tested for 1945 nap)	KSS	PVT	Right away	No effect of napping on PVT median RT. Authors report study under-powered.
Purnell MT et al 2002 [52]	24	34.8; men	Counter-balanced crossover design of 20 min nap or break (0100 to 0300)	nap versus no nap	VAS fatigue	visual RT, VVT	30 min	No reported sleep in ½ of cases. Fatigue & VVT worse with nap on 1 of 2 nights. Visual RT unaffected.
Signal TL et al 2009 [91]	28	35	4 conditions: 40 min nap or break at 0030 or 0230	time of nap; nap versus no nap		PVT	average 53–57 min	No evidence for SI by the time of testing.
Smith SS et al 2007 [92]	9	45.7	Randomized, crossover test of 30 min nap break versus continued work (0200 to 0300)	nap versus no nap	VAS sleepy, task load index	PVT	10–30 min	Napping improved sleepiness at 0300 and had no effect on PVT.
Smith-Coggins et al 2006 [2]	49	30	Randomized to 40 min nap or continued work at 0300	nap versus no nap	KSS	PVT, PM, IV place	up to 20 minutes	No effect on PVT, IV place, or KSS. PM worse after nap.

Abbreviations: IV place=CathSim intravenous line insertion, KSS=Karolinska sleepiness scale, min=minutes, n=number analyzed, obj=objective measures, SI=sleep inertia, subj=subjective measures, RT=reaction time, PVT=psychomotor vigilance task, RT=reaction time, VAS=visual analog scale, VVT=visual vigilance task