Morning Light Treatment to Improve Glucose Metabolism

This is a pilot study to determine whether light treatment can improve glucose metabolism in people with prediabetes. Individuals will be asked to complete a baseline session with one-week of at-home sleep monitoring followed by a 24-hour stay in the clinical research unit. During this stay, we will sample saliva in the evening to measure melatonin to estimate the timing of the internal biological clock ("circadian phase") and then we will perform a 3-hour oral glucose tolerance test in the morning to estimate markers of glucose metabolism, including insulin sensitivity. The participants will then be given a light device and instructed on its use. They will use the device for four weeks and visit our laboratory every week for a check-in. At the end of the four weeks, they will repeat the 24-hour stay in the clinical research unit.