Johns Hopkins study adds to evidence that sleep apnea causes cardiovascular, metabolic stress

Untreated sleep apnea can contribute to a range of conditions associated with heart disease and diabetes, according to a new study conducted by Johns Hopkins Medicine researchers.

The study found increases in blood sugar, fat levels, stress hormones, and blood pressure in patients with obstructive sleep apnea—a condition that affects 20 to 30 percent of adults.

The findings, published in this month's issue of The Journal of Clinical Endocrinology & Metabolism, may help to refine the scientific debate over whether sleep apnea is just a manifestation of obesity, or in fact an active contributor to associated health problems like diabetes and heart disease.

While the link between sleep apnea and these diseases is well known, study senior author Jonathan Jun, an assistant professor at the Johns Hopkins University School of Medicine, says the new findings add to evidence that sleep apnea can directly aggravate the health problems.

The report also emphasizes the importance of CPAP, or continuous positive airway pressure, as a treatment solution. CPAP machines increase air pressure in the throat to prevent sleep apnea's effect of closing off the upper airway and interrupting breathing.

As opposed to many previous studies that collected data from participants who were already awake, the Johns Hopkins teams studied patients while they were sleeping.

"This is one of the first studies to show real-time effects of sleep apnea on metabolism during the night," Jun says.

Researchers found that withdrawing CPAP in the sleeping patients increased levels of free fatty acids, glucose, and cortisol (a stress hormone)—all conditions linked to diabetes. The more severe the sleep apnea, the more these parameters increased. The team also found increases in blood sugar and vascular stiffness, two conditions that can contribute to cardiovascular disease over time.

Jun emphasized that the study was limited in analyzing patients with severe obstructive sleep apnea and obesity. But the team is continuing to recruit patients in order to produce findings with broader applicability.

The report highlights consistent use of CPAP therapy as an important way to prevent the metabolic and cardiovascular consequences of sleep apnea. During the study, CPAP withdrawal caused recurrence of obstructive sleep apnea associated with sleep disruption, elevated heart rate, and reduced blood oxygen.

For patients with a hard time tolerating CPAP, researchers recommend working with sleep specialists who can assist with the machine or recommend alternative therapies.