Continuous positive airway pressure therapy improved several components of the metabolic syndrome along with obstructive sleep apnea in patients who had both disorders, according to a report in the Dec. 15 issue of 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.
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Continuous positive airway pressure therapy (CPAP) improved a number of components of the metabolic syndrome and obstructive sleep apnea in patients with both disorders.
No particular component stood out as being the most responsive to CPAP; statistically significant improvements were seen in systolic BP, diastolic BP, total cholesterol, non-HDL cholesterol, LDL cholesterol, triglycerides, glycated hemoglobin, weight, 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 the metabolic syndrome, the researchers recruited 86 patients aged 30-65 years from the sleep laboratory at the institute who had obstructive sleep apnea that was moderate or worse in severity. All the subjects reported excessive daytime somnolence.
A total of 75 study subjects (87%) had the metabolic syndrome, and the remainder had some of the components of the 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.
The metabolic syndrome resolved in 14 (20%) of the study subjects after CPAP. This was due to decreased blood pressure 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, with CPAP therapy. "These findings could be secondary to a decrease in daytime somnolence and a consequent increase in physical activity after CPAP use at night."
In addition, "we speculate that CPAP has a favorable effect on leptin levels, which have been shown to be elevated in patients with obstructive sleep apnea and to normalize with CPAP therapy," the investigators said (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, "suggesting a potential role for CPAP therapy in reversing endothelial damage due to obstructive sleep apnea and the metabolic syndrome," Dr. Sharma and his associates said.
Two patients could not tolerate CPAP and one could not tolerate sham CPAP within the first month of treatment, and they withdrew from the study. "Other adverse events reported included skin irritation (in 51% of all patients), nasal bridge discomfort (in 44%), nasal congestion (in 28%), headache (in 26%), and mask leaks (in 30%)."
This study was funded by Pfizer. All investigators reported having no financial conflicts of interest. The investigators received technical support from ResMed Corp. in designing a sham CPAP machine.