This project has 6 aims.

1. To examine the impact of recurrent partial sleep loss in young, middle-aged and older men and women. Sleep will be restricted to 4 hours.
2. To test the hypothesis that extending bedtimes to allow for sleep recovery will reverse the metabolic, endocrine, and cardiovascular and neuro-behavioral alterations resulting from sleep restriction. Sleep will be extended to 12 hours following the 4 hour sleep restriction.
3. To test the hypothesis that there are age and gender differences in the total amount of sleep recovery obtained during the week of 12-hour bedtimes.
4. To test the hypothesis that there are age and gender differences in sleep capacity (the amount of time an individual can sleep per night when there is no sleep debt).
5. To test the hypothesis that sleep capacity is partly determined by baseline levels of slow-wave sleep and slow-wave activity.
6. To determine whether sleep capacity is related to sleep need by examining metabolic, endocrine, cardiovascular and neuro-behavioral changes with the amount of the individual sleep debt.

Inclusion Criteria:

• normal weight
• healthy
• age 18-75 old

Exclusion Criteria:

• sleep disorder
• irregular life habits (shift workers, travelers)
• smokers
• on medication
• consumption of > 2 alcohol or caffeinated beverages/day