Morning Light Treatment to Improve Glucose Metabolism

Inclusion Criteria: 34 subjects (50% female, age 40-65 y)

Subjects will be:

- Prediabetic (HbA1c 5.7% to <6.5%)

- obese (BMI>30 kg/m2)

- have significant circadian misalignment (social jet lag ≥ 2 h, associated with higher
BMI [2] and higher HbA1c [3])

- be free of moderate to severe obstructive sleep apnea (apnea-hypopnea index<15).

The laboratory sessions will occur during women's follicular phase or women will be
postmenopausal (≥6 months since last menses).

Subjects will be scheduled to participate ≥ 1 month from travel outside the central time
zone, and during a time with minimal special events.

Exclusion Criteria:

- Women who are pregnant, planning on becoming pregnant, or are breastfeeding.

- Women on oral contraceptives or hormone replacement therapy will be excluded (alters
OGTT and melatonin).

- Men and women who have a child at home that does not sleep through the night will be
excluded.

- Adults unable to consent, individuals who are not yet adults (infants, children,
teenagers), pregnant women, and prisoners are also excluded.

- History of any form of diabetes, including use of diabetes medications

- Age outside 40-65 years (we will not enroll anyone older than 65 years because of a
reduced response to light).

- Smokers

- Shift workers

- Failed urine drug test (drugs of abuse, nicotine)

- Eye disease/photosensitizing medications

- Sleep medications, diagnosed sleep disorders (history of treatment may affect glucose
metabolism),

- Daily beta-blocker, NSAID or melatonin use (confounds DLMO)

- History of psychiatric disorders (confounds effect of light treatment, per relevant
items from Mood Disorder, Psychotic Screening and Substance Use Disorders Modules of
the Structured Clinical Interview for DSM-IV Axis I Disorders - Non-Patient Edition
(SCID-IV/NP) to screen for schizophrenia, bipolar depression, substance abuse,
suicidal ideation, obsessive compulsive disorder, PTSD), depressive symptoms using the
Center for Epidemiologic Studies - Depression (CES-D) scale

- Irregular menses

- History of cardiovascular disease (excluding hypertension), endocrine, kidney,
gastrointestinal or liver disorder, seizures, and cancer.