The purpose of this study is to determine if deficient sleep and/or disruption with the body's internal clock ("circadian rhythms") are associated with diabetes risk. This study is being done to look at the possible relationships between sleep and risk of diabetes by examining sleep in the home and diabetes risk in the laboratory.

Inclusion Criteria:

1. Ages 21-50 years
2. BMI <40 kg/m2.
3. No major illness.
4. No history of psychiatric, endocrine, cardiac or sleep disorders,
5. Premenopausal, non-pregnant women.
6. Those with dyslipidemia and hypertension will be included if these conditions are controlled by a stable treatment, such as lipid-lowering or antihypertensive medications (except beta blockers).

Exclusion criteria include:

1. Persons with diabetes.
2. Persons with diagnosed sleep disorders or apnea-hypopnea index>15.
3. History of cardiovascular event or disease (excluding controlled hypertension).
4. Major psychiatric disorder or other major illness.
5. Persons taking medications, including but not limited to antidepressants and hypnotics (but excluding lipid-lowering drugs and anti-hypertensive medications as mentioned above).
6. Persons regularly taking medication that affects melatonin such as beta blockers and exogenous melatonin.
7. Anyone who tests positive for common drugs of abuse.
8. People with color blindness.
9. People who have had Lasik eye surgery.
10. People who work night shifts.
11. Participants who travel across multiple time zones will be studied only after they have remained in the Central Time Zone (or Indiana) for one month prior to the study.

This study will recruit a total of 100 African Americans (AA) and 100 non-Hispanic whites (WH) with equal numbers of men and women in each group completing the entire study. Ages will be 21-50 years and body mass indices (BMI) will be <40 kg/m2.

During study participation, approximately 2 weeks.

Definitions do not differ.

Study sample was lower than anticipated.