Sleep apnea can increase blood sugar and fat levels, stress hormones, and blood pressure, even if it’s left untreated for just a few days, according to the Johns Hopkins University School of Medicine. The study also produced additional support for the use of continuous positive airway pressure (CPAP) to keep the airway open in treating obstructive sleep apnea (OSA), which affects 20% to 30% of adults.
“This is one of the first studies to show real-time effects of sleep apnea on metabolism during the night,” said Johnathan Jun, MD, assistant professor of medicine at the school and senior author of the study.
OSA has been associated with risks for diabetes and heart disease, yet there has been no consensus on whether it causes these disorders or if it is just a marker of obesity, which predisposes patients to diabetes and heart disease. Also, previous metabolic studies of patients with OSA usually collected data while participants were awake, obtaining a snapshot of its aftermath, not the actual sleep period when OSA occurs.
To better understand how OSA affects metabolism, the researchers measured free fatty acids in the blood, glucose, insulin, and the stress hormone cortisol while participants slept in a sleep laboratory at the Johns Hopkins Bayview Medical Center. The participants’ brainwaves, blood oxygen levels, heart rates, and breathing, along with eye and leg movements, were recorded each night of the study.
The researchers drew blood samples from 31 patients with moderate to severe OSA and a history of regular CPAP use for 2 nights. They drew these samples every 20 minutes starting at 9 p.m. and ending at 6:40 a.m. Each participant spent one night at the lab with CPAP or after CPAP had been stopped for 2 nights, in random order, separated by one to 4 weeks.
The average age of all participants was 50.8 years, and the average body mass index indicated obesity, a common characteristic of those with sleep apnea. Two-thirds of the study group was male, and a quarter had a history of non-insulin dependent diabetes. Also, 22.6% of the participants were African American, 9.7% were Asian, 64.5% were Caucasian, and 3.2% were Hispanic.
The researchers found that CPA withdrawal caused recurrence of OSA associated with sleep disruption, elevated heart rate, and reduced blood oxygen. CPAP withdrawal also increased levels of free fatty acids, glucose, cortisol, and blood pressure during sleep. The more severe the OSA, the more these parameters increased.
Furthermore, glucose increased the most in patients with diabetes. Increases in fatty acids, glucose, and cortisol all have been linked to diabetes. The researchers also found that blood pressure increased and the arteries showed signs of stiffness in the morning without CPAP. Over time, increased blood pressure and vascular stiffness can contribute to cardiovascular disease.
According to Jun, the study was limited by comprising people with severe OSA and obesity, limiting the ability to apply its findings to all OSA patients. The researchers also did not compare CPAP use to a sham CPAP control group to exclude a potential placebo effect. But Jun said that the study does provide further evidence that sleep apnea isn’t just a manifestation of obesity, diabetes, and cardiovascular disease, but that that it can directly aggravate these conditions.
The researchers are recruiting more patients to answer more questions about who is most vulnerable to the impacts of OSA. Meanwhile, they note that the study emphasizes the importance of CPAP therapy for OSA to prevent its metabolic and cardiovascular consequences. They also urge such patients to contact a sleep specialist who can assist them with CPAP use or who can recommend alternative therapies.
The study, “Obstructive Sleep Apnea Dynamically Increases Nocturnal Plasma Free Fatty Acids, Glucose, and Cortisol During Sleep,” was published by The Journal of Clinical Endocrinology & Metabolism.
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