A 56-year-old woman with diabetes, hypertension, and hyperlipidemia is found to have an A1C of 11 despite her best attempts at diet and faithfully taking her metformin and glyburide. The patient mentions that she has been unable to exercise much, partially due to severe fatigue and sleepiness in the daytime. On examination she is obese, has a full appearing posterior pharynx, clear lungs, a normal heart examination, and trace bilateral edema. Reflexes and skin are normal. Her TSH is 2.0 m/L (normal). The patient asks if there is anything else that can be done before adding another oral agent or switching to insulin. What is the best next step?