Table 1.

Demographic and Baseline Night Sleep Characteristics of Older and Young Subjects. Mean (± SD).

	Older subjects	Young subjects	Pvalue
Age	68.1 ± 3.6	21.9 ± 3.3
Gender	3 women, 8 men	7 women, 19 men
Sleep efficiency (%)	82.0 ± 6.6	93.6 ± 3.5	<.01
Duration of slow wave sleep (Minutes)	10.13 ± 7.34	17.25 ± 6.95	<.02
Awakenings (Number)	30.3 ± 6.99	4.54 ± 4.24	<.01
Awakenings (Duration, minutes)	2.42 ± 0.76	2.04 ± 2.67	.53

Sleep efficiency in young adults is typically >90% under these laboratory conditions, while in healthy young-old adults it typically averages between 75–85%, and is often even lower in many older adults or those taking medications, with medical conditions, or with undiagnosed sleep disorders [1;2;9;22]. The amount of slow wave sleep in non-sleep-deprived young adults is typically about 15–25% of sleep time (~60–90 minutes of an 8-hour sleep episode), and this declines with age such that young-old adults often average as little as 5% slow wave sleep (10–25 minutes of an 8-hour sleep episode) [1;2;9]. The number of awakenings during sleep is typically quite low in young adults and increases with age [1], although the exact number depends on the criteria used to define an awakening.