• Changes in sleep and waking EEG measures [ Time Frame: During 3-week chronic sleep restriction segment of inpatient study ] [ Designated as safety issue: No ]
• frequent measures of performance, attention, alertness, and memory [ Time Frame: During 3-week chronic sleep restriction segment of inpatient study ] [ Designated as safety issue: No ]
• measures of cardiovascular and metabolic function [ Time Frame: During 3-week chronic sleep restriction segment of inpatient study ] [ Designated as safety issue: No ]

• Changes in sleep and waking EEG measures
• frequent measures of performance, attention, alertness, and memory
• measures of cardiovascular and metabolic function

The purpose of this study is to examine the consequences of chronic sleep restriction on nighttime sleep, daytime alertness, performance and memory functions, and metabolic and cardiovascular function, and to determine if the consequences of chronic sleep restriction differ between healthy young and older adults.

It has long been recognized that sleep patterns change with age. A common feature of aging is the advance of the timing of sleep to earlier hours, often earlier than desired. Polysomnographically-recorded sleep in older people shows an increased number of awakenings, a reduction of stages 3 and 4 (SWS) sleep, and a flattening of REM sleep distribution throughout the night. These age-related changes are found in even healthy individuals who are not taking medications and who are free from sleep disorders. In addition to these sleep disturbances, many older individuals curtail their sleep voluntarily, reporting similar rates of sleep restriction (sleeping less than 7 or less than 6 hours per night) as young adults. Whether voluntary or not, insufficient sleep has medical, safety and metabolic consequences. In fact, converging evidence in young adults suggests that sleep restriction per se may impair metabolism, and that reduced sleep duration is associated with weight gain, obesity, diabetes, cardiovascular disease, and mortality.

The study begins with 21 days of outpatient study in which the participants will be required to sleep for 10 hours each night in order to ensure they are well-rested. This will be followed by a 39-day inpatient study. The study will begin with 3 "sleep satiation" days during which all participants will be scheduled to sleep for 12 hours per night and have a 4 hour nap each afternoon. This is followed by 3 baseline days in which the participants will follow the same sleep-wake schedule they were following at home. Following this, the participant will undergo 3 weeks of chronic sleep restriction while living on a non-24-hour schedule. The participant will live on a schedule that is equivalent to 5.6 hours of sleep per 24 hours. Following these 3 weeks, the participant will be scheduled to again sleep for 10 hours per night for 10 nights.

• Aging
• Sleep Deprivation
• Metabolic Syndrome

• Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, Ronda JM, Silva EJ, Allan JS, Emens JS, Dijk DJ, Kronauer RE. Stability, precision, and near-24-hour period of the human circadian pacemaker. Science. 1999 Jun 25;284(5423):2177-81.
• Dijk DJ, Duffy JF, Riel E, Shanahan TL, Czeisler CA. Ageing and the circadian and homeostatic regulation of human sleep during forced desynchrony of rest, melatonin and temperature rhythms. J Physiol. 1999 Apr 15;516 ( Pt 2):611-27.
• Dijk DJ, Shanahan TL, Duffy JF, Ronda JM, Czeisler CA. Variation of electroencephalographic activity during non-rapid eye movement and rapid eye movement sleep with phase of circadian melatonin rhythm in humans. J Physiol. 1997 Dec 15;505 ( Pt 3):851-8.
• Boivin DB, Czeisler CA, Dijk DJ, Duffy JF, Folkard S, Minors DS, Totterdell P, Waterhouse JM. Complex interaction of the sleep-wake cycle and circadian phase modulates mood in healthy subjects. Arch Gen Psychiatry. 1997 Feb;54(2):145-52.
• Dijk DJ, Duffy JF, Czeisler CA. Circadian and sleep/wake dependent aspects of subjective alertness and cognitive performance. J Sleep Res. 1992 Jun;1(2):112-7.
• Duffy JF. Increased sleep disruption, reduced sleepiness in older subjects? Sleep. 2005 Nov 1;28(11):1358-9. No abstract available.
• Klerman EB, Davis JB, Duffy JF, Dijk DJ, Kronauer RE. Older people awaken more frequently but fall back asleep at the same rate as younger people. Sleep. 2004 Jun 15;27(4):793-8.
• Duffy JF, Czeisler CA. Age-related change in the relationship between circadian period, circadian phase, and diurnal preference in humans. Neurosci Lett. 2002 Feb 1;318(3):117-20.
• Dijk DJ, Duffy JF, Czeisler CA. Age-related increase in awakenings: impaired consolidation of nonREM sleep at all circadian phases. Sleep. 2001 Aug 1;24(5):565-77.
• Dijk DJ, Duffy JF, Czeisler CA. Contribution of circadian physiology and sleep homeostasis to age-related changes in human sleep. Chronobiol Int. 2000 May;17(3):285-311. Review.
• Pavlova MK, Duffy JF, Shea SA. Polysomnographic respiratory abnormalities in asymptomatic individuals. Sleep. 2008 Feb 1;31(2):241-8.
• Silva EJ, Duffy JF. Sleep inertia varies with circadian phase and sleep stage in older adults. Behav Neurosci. 2008 Aug;122(4):928-35.
• Münch MY, Cain SW, Duffy JF. Biological Rhythms Workshop IC: sleep and rhythms. Cold Spring Harb Symp Quant Biol. 2007;72:35-46.

Inclusion Criteria:

• Healthy

Exclusion Criteria:

• Chronic or acute medical condition
• Medication use
• Depression
• History of psychiatric illness
• Sleep disorder