More and more scientific studies are showing correlations between poor quality sleep and/or insufficient sleep with a variety of diseases, including high blood pressure, diabetes, and depression. For example, insufficient sleep can impair the body's ability to use insulin, which can lead to the development of more severe diabetes. Patients with poorly controlled diabetes and sleep apnea have improvement of blood sugar control when treated for sleep apnea. This is also found in patients with high blood pressure and sleep apnea. When the sleep apnea is treated, the blood pressure also improves. In addition, too little sleep may decrease growth hormone secretion, which has been linked to obesity.