CPAP improves glycemic control in diabetics

• Diabetes • Dec 23, 08

Continuous positive airway pressure (CPAP) therapy, primarily used as a treatment for obstructive sleep apnea, improves glycemic (blood sugar) control during sleep in patients who also have type 2 diabetics, according to a report in the Journal of Clinical Sleep Medicine.

The average decrease in nocturnal glucose level in diabetic patients was about 20 mg/dL. “The decrease was small in those with good glycemic control and much greater in those whose control was poor,” Dr. Arthur Dawson from Scripps Clinic, La Jolla, California, told Reuters Health. This finding “suggests that treating obstructive sleep apnea could have a major impact on the management of those type 2 diabetics who, for whatever reason, cannot get their glucose levels down to the optimal range.”

Obstructive sleep apnea, one of the most common types of sleep disorders, is characterized by loud snoring and the cessation of breathing during sleep due to blockage of the airways. This results in continuous arousals during the night, leading to sleep deprivation and daytime fatigue.

CPAP is a method of respiratory ventilation in which a gentle continuous stream of air is delivered through a pliable mask worn over the nose during sleep. This keeps the airways open and prevents the episodes of oxygen deprivation (apnea) and subsequent arousal at night.

Dawson and colleagues used a continuous glucose monitoring system to measure glucose levels during polysomnography recordings of sleep in 20 patients with type 2 diabetes and moderate-to-severe sleep apnea. This was conducted before and after 4 to 13 weeks of CPAP therapy.

After CPAP treatment, patients had an increase in total sleep time with less time awake after sleep onset, the authors report, as well as less time in stage 1 sleep and more time in stage 3 through 4 sleep and REM. They also had significantly fewer arousals with treatment.

The average glucose levels during sleep were lower and less variable with CPAP treatment than before CPAP, the researchers note.

The average sleeping glucose levels decreased in 10 of 11 patients whose levels were greater than 100 mg/dL, but did not decrease in the 9 patients with levels less than 100 mg/dL.

The average 24-hour glucose level also decreased significantly during CPAP treatment, the investigators say, but the change in average daytime glucose (from 7 a.m. to 11 p.m.) was not statistically significant.

The improvement in sleeping glucose level also did not correlate significantly with the apnea-hypopnea index, the report indicates.

“All of the diabetics in our study had at least moderate, and most of them severe, sleep apnea and so would have been treated with CPAP even if they were not diabetic,” Dawson explained. “A more interesting question is whether diabetics with mild obstructive sleep apnea should be treated, but our study doesn’t apply to that group.”

“We are now doing a study on diabetics with obstructive sleep apnea who are regular users of CPAP to see the effect on glucose levels of a single night of withdrawal from CPAP,” Dawson said.

SOURCE: Journal of Clinical Sleep Medicine, December 15, 2008.