Visit 2: Within 1-48 hours of completion of the 24-hour urine collection and before you begin treatment for your sleep disorder, you will need to bring the urine specimen to the Diabetes and Metabolic Research Center. A part of this urine will be stored (frozen) for possible testing of a hormone called aldosterone, substances filtered by the kidneys (salt and creatinine), and other potential risk factors. Also at this visit, about 2 tablespoons of blood will be drawn and stored for potential testing of a protein in the blood called renin. You should continue the dietary suggestions (e.g., liberal salt diet) given for the collection of the 24-hour urine until the blood is collected. A part of the blood drawn during this visit will also be stored (frozen) in case potential risk factors of heart rate variability are discovered in the future. This visit will last approximately 15 minutes.