CPAP Benefits in Metabolic Syndrome

December 14, 2011

December 14, 2011 (New Delhi, India)—Three months of treatment with continuous positive airway pressure (CPAP) was associated with improvements in many different components of the metabolic syndrome in a new study in patients with both metabolic syndrome and obstructive sleep apnea.

In the study, published in the December 15 issue of the New England Journal of Medicine [1], CPAP therapy was associated with a decrease in both systolic and diastolic blood pressure, lipids, glycated hemoglobin, body mass index, and abdominal fat.

Lead investigator, Dr Surendra Sharma (All India Institute of Medical Sciences, New Delhi) told heartwire he was excited about these results. He said: "Currently, we use medicines for the treatment of metabolic syndrome. The message of this study is that, if metabolic syndrome is associated with obstructive sleep apnea, then CPAP should be the first-line of treatment." He added: "Ours is the first evidence-based study with positive results and gives a ray of hope for patients that have obstructive sleep apnea with metabolic syndrome."

In the paper, the authors explain that 70–80% of patients with obstructive sleep apnea also have metabolic syndrome, and that obstructive sleep apnea is known to be an independent risk factor for hypertension and insulin resistance. While CPAP is an established treatment for symptomatic obstructive sleep apnea, its effect on metabolic syndrome is not clear. Few studies of this issue have been conducted, and studies that have been carried out have shown conflicting results.

Sharma et al therefore designed a double-blind, placebo-controlled, randomized, crossover trial in 99 patients who received 3 months of CPAP or sham CPAP, with a 1-month washout period between interventions.

Results showed that CPAP therapy was associated with significant reductions in systolic and diastolic blood pressure; glycated hemoglobin; triglycerides; LDL, non-HDL, and total cholesterol; body mass index; and both visceral and subcutaneous fat compared with sham CPAP.

CPAP Therapy and Changes in End Points

Variable Difference with CPAP
Abdominal circumference, cm –0.73
Systolic blood pressure, mmHg –3.86
Diastolic blood pressure, mmHg –2.49
Glycated hemoglobin, % –0.21
Triglycerides, mg/dL –18.65
Total cholesterol, mg/dL –13.26
LDL cholesterol, mg/dL –9.55

CPAP=continuous positive airway pressure

Following CPAP therapy, 14 patients (20%) no longer met the criteria for metabolic syndrome, with the specific criterion resolved being blood pressure (five patients), fasting blood glucose (two patients), triglycerides (two patients), HDL cholesterol (three patients), triglycerides and HDL cholesterol (one patient), and triglycerides, HDL cholesterol, and fasting blood glucose (one patient).

Sharma told heartwire that the cessation of airflow in obstructive sleep apnea leads to nocturnal oxygen desaturation, release of sympathetic hormones, and endothelial dysfunction, all of which result in metabolic abnormalities. "These can be prevented by CPAP," he added.

On the reduction in BMI and abdominal fat observed in the study, the authors suggest that this could have been caused by a decrease in daytime sleepiness and a consequent increase in physical activity after CPAP use at night. "Although a direct effect of CPAP therapy on fat reduction is debatable, 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," they wrote.

Sharma said the benefits seen in this study should translate into a significant reduction in cardiovascular risk. He recommends that patients with obstructive sleep apnea be screened for metabolic syndrome and, in addition to lifestyle modifications, weight reduction, and dietary modifications, they should receive CPAP therapy. But, he stressed, patients need to be counseled before CPAP to enhance compliance rates.

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