CPAP Reduced Metabolic Syndrome in OSA Patients

BY MARY ANN MOON
Elsevier Global Medical News

Continuous positive airway pressure therapy improved several components of metabolic syndrome along with obstructive sleep apnea in patients who had both disorders, according to a report in the New England Journal of Medicine.

In most cases, only one component of the metabolic syndrome improved significantly after CPAP, but that improvement was significant enough to “reverse” the syndrome, said Dr. Surendra K. Sharma of All India Institute of Medical Sciences, New Delhi, and his associates.

No particular component stood out as being the most responsive to CPAP; statistically significant improvements were seen in systolic blood pressure (BP), diastolic BP, total cholesterol, non-HDL cholesterol, LDL cholesterol, triglycerides, glycated hemoglobin, body mass index, and visceral and subcutaneous fat. “These results suggest a significant clinical benefit that will lead to a reduction in cardiovascular risk,” they noted.

To examine the effect of CPAP on components of metabolic syndrome, the researchers recruited 86 patients aged 30-65 years who had moderate or severe OSA. All the patients reported excessive daytime somnolence. A total of 75 study patients (87%) had metabolic syndrome, and the remainder had some of the components of metabolic syndrome.

These patients were randomly assigned to undergo either CPAP or sham CPAP for 3 months, followed by a washout period of 1 month. They then crossed over to receive the other intervention for 3 months. The sham CPAP was not discernible to the study subjects or the investigators.

Metabolic syndrome resolved in 14 (20%) of the study subjects after CPAP. This was due to decreased BP in five; decreased fasting blood glucose in two; decreased triglycerides in two; increased HDL cholesterol in three; improved triglycerides plus HDL cholesterol in one; and improved triglycerides, HDL cholesterol, and fasting blood glucose in one, Dr. Sharma and his colleagues said. Symptoms of the syndrome developed in three patients who did not have metabolic syndrome at the start of the study.

Overall, CPAP was associated with a mean decrease in systolic BP of 3.9 mm Hg, a mean decrease in diastolic BP of 2.5 mm Hg, a mean decrease in total cholesterol of 13.3 mg/dL, and a mean decrease in triglycerides of 18.7 mg/dL.

CT scans revealed a significant decrease in both visceral and subcutaneous fat, which was accompanied by a decrease in BMI. “These findings could be secondary to a decrease in daytime somnolence and a consequent increase in physical activity” (N. Engl. J. Med. 2011;365:2277-86).

In a subgroup analysis involving only the 51 subjects who were most compliant with CPAP, with a mean use of at least 5 hours every night, the improvements in components of the metabolic syndrome were even greater. In particular, systolic BP decreased by 5.6 mm Hg and diastolic BP decreased by 3.3 mm Hg. This subgroup of patients also showed significant improvement in carotid intima-media thickness.

This study was funded by Pfizer. All investigators reported having no financial conflicts of interest. They received technical support from ResMed Corp. in designing a sham CPAP machine.

COMMENTARY
Dr. Paul Selecky, FCCP, comments: We have known for some time that successful CPAP use for OSA has resulted in a decrease in insulin resistance and improvement in other parameters of diabetes management. Similar results have been found in improving hypertension. Adding improved metabolic syndrome to the list is therefore not surprising, but is important information nonetheless. These findings emphasize yet one more benefit that can come from the CPAP treatment of OSA.