German investigators have demonstrated that continuous positive airway pressure (CPAP) treatment rapidly improves insulin sensitivity in patients with obstructive sleep apnea syndrome (OSAS). Less obese patients improved after 2 days of treatment. The researchers studied insulin sensitivity in 40 OSAS patients who had a mean apnea-hypopnea index of 43 breathing pauses per hour. Insulin sensitivity readings were taken before, 2 days after CPAP treatment started, and after 3 months of treatment. The authors said that insulin resistance seems to play a key role among the mechanisms responsible for the metabolic effects of OSAS. In fact, the presence of increased insulin resistance has repeatedly been reported in patients with OSAS. (Obstructive sleep apnea is characterized by airway collapse and cessation of breathing (airflow) for 10 seconds or more during sleep. These pauses, which can occur many times over during the night, are followed by a brief arousal and resumption of breathing.) Since the problem leads to inadequate amounts of oxygen in the blood, it can bring on deficits to the individual, including daytime sleepiness, inattention, and impaired quality of life. The standard treatment for the disorder is CPAP. This device delivers air through a mask that usually covers the mouth and nose. CPAP increases air pressure in the throat and prevents tissues in the airway from collapsing when the individual inhales. In the 31 patients the investigators followed for 3 months, they found no further significant improvement in their individual insulin sensitivity indexes; however, the positive differences from baseline measurements remained statistically significant. The study appears in the second issue for January 2004 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.