Table 1.

Demographic and neuropsychological measures (mean ± SD)

Variable	Young (N = 16)	Older (N = 14)
Age (years)	20.5 ± 2.1	71.9 ± 6.7
Gender	8 Female	11 Female
MMSE	29.7 ± 0.4	29.4 ± 0.8
Mean bed time	0:31 ± 0:50	22:45 ± 1:04***
Mean wake time	8:33 ± 0:51	7:04 ± 1:00***
Mean prestudy time in bed (hours)	8.05 ± 0.61	8.32 ± 0.85
Mean prestudy sleep time (hours)	7.74 ± 0.61	6.85 ± 1.05*
Mean prestudy sleep latency (min)	14.7 ± 9.3	40.2 ± 56.8
Mean prestudy sleep efficiency (%)	96.3 ± 2.2	82.9 ± 13.8**
Scan time relative to prestudy wake time	1:49 ± 1:17	2:09 ± 1:00
Neuropsychological measures
Education (year)		17.5 ± 1.3
CVLT (long delay, # free recalled)		11.6 ± 3.3
WMS (visual reproduction %)		83.6 ± 13.6
Trailmaking B (s)		71.3 ± 43.3
Stroop (# correct in 60 s)		52.7 ± 12.2

CVLT denotes the California verbal learning test; WMS denotes the Wechsler memory scale.

*P < 0.05.

**P < 0.01.

***P < 0.001.