CHICAGO—Evidence that cerebral ischemia may be exacerbated by sleep apnea was presented at the 15th Annual Meeting of the Associated Professional Sleep Societies.

Other topics discussed at the meeting included a description of the frequency of gastroesophageal reflux disease (GERD) in obstructive sleep apnea (OSA) patients, as well as the effect of surgically induced weight loss on pharyngeal anatomy and sleep-disordered breathing.

New approaches to the diagnosis and treatment of obstructive sleep disorders were also covered. Modafinil was evaluated for its efficacy in reducing daytime sleepiness and improving vigilance and memory. Researchers also found that they were able to use a single night for the diagnosis and treatment of OSA, which they thought could help reduce both time and costs.

ISCHEMIC BRAIN DISEASE RELATED TO SLEEP APNEA

Investigators from Brown University School of Medicine have observed evidence of cerebral ischemia (white matter hyperintensities) on magnetic resonance images of patients with sleep apnea. They found that those patients with a severe form experience more serious small-vessel ischemic brain disease than do patients with only minimal apnea.

Aloia and coworkers measured hyperintensities in eight patients with severe or minimal apnea; the two groups were similar in age, body mass index, and gender. All four patients with severe OSA, and two of the four patients with minimal OSA, had hypertension requiring treatment with one medication.

Greater white matter hyperintensities were seen in the severe group than the minimal group. The investigators acknowledged that the mechanism underlying the development of white matter hyperintensities is not completely understood, but they suggested that their evidence indicates that sleep apnea contributed to hypertension-associated brain abnormalities.

GERD AND SLEEP DISORDERS MAY NOT BE RELATED

No positive correlation exists between the incidence of OSA and GERD, according to Kim and coworkers from the Eastern Virginia Medical School.

They administered a GERD questionnaire to 294 patients with sleep disorders; a score of 15.5 or higher on the questionnaire was considered evidence of GERD. All patients also underwent polysomnography; the OSA syndrome was diagnosed when the respiratory disturbance index score was 10 or higher.

The researchers found that although GERD was present in 23% of the patients studied, there was no relationship between GERD and the presence of apnea or its severity. They suggested that the high frequency of GERD in this population may have been related to misinterpretation of GERD symptoms as OSA symptoms.

Kim and colleagues also theorized that the pathophysiology of GERD might be different in patients with sleep disorders than it is in the general population.

WEIGHT REDUCTION IMPROVES SLEEP-DISORDERED BREATHING

Weight loss aided by gastroplasty improves sleep-disordered breathing, according to research presented by Fogel and associates. They also demonstrated that a reduction in weight correlates with increased pharyngeal lumen, decreased fat in the upper airway, and decreased lung-volume dependence on pharyngeal airway size.

The researchers examined eight patients before and after gastroplasty. The subjects underwent standard polysomnography, and pharyngeal anatomy was assessed by spiral computed tomography at three lung volumes: functional residual capacity, total lung capacity, and residual volume.

Fogel and associates found that after weight loss, both the minimal pharyngeal area cross-section and pharyngeal airway volume increased, while the volume of pharyngeal fat pads decreased. Reductions were also seen in the lung-volume dependence of the pharyngeal airway. Concurrently, apnea/hypopnea indexes (AHI) for these patients dropped from an average of 54 events preoperatively to 25 postoperatively.

The researchers concluded that anatomical changes were the main effect of weight reduction. Furthermore, they said, these changes made breathing easier with less need for dilator muscle use.

SUCCESSFUL TREATMENT FOR DAYTIME SOMNOLENCE

Modafinil may be an effective treatment for daytime sleepiness, daytime vigilance, and memory impairment in patients with OSA. To define the use of this central non-amphetamine awakening substance, Schiza and associates designed a randomized, double-blind study with 34 male and 16 female subjects who took modafinil or placebo for 12 weeks. Patients kept sleep/wake diaries, and measurements of arterial blood pressure were taken daily. Sleep laboratory examination took place before assignment to modafinil or placebo and again at the end of the study.

The medication was well tolerated and was significantly more successful than placebo in reducing daytime sleepiness. Objective and subjective assessments of daytime vigilance and memory were improved; however, nighttime sleep and respiration remained unchanged.

The researchers concluded that modafinil might be useful as an adjunctive therapy for daytime sleepiness.

NEW DIAGNOSTIC METHOD FOR SLEEP APNEA

Guo and coworkers from Beijing Chaoyang Hospital concluded that in a single night’s stay at a sleep laboratory, it may be possible to both confirm the diagnosis of OSA and establish the optimal level of continuous positive airway pressure (CPAP).

The investigators observed 288 patients with OSA during two nights in a sleep laboratory; during the first night, they were given titrated CPAP treatment. During the second night, a two-part protocol was employed; the hours from 22:00 to 02:00 were used to diagnose OSA, and the hours from 02:00 to 06:00 were used for CPAP titration.

The researchers found that a reliable OSA diagnosis could be made with the split-night evaluation, especially in patients with an AHI of 20 or greater. Once that diagnosis was made, CPAP titration could be used to find an appropriate pressure for continued treatment.

Guo and coworkers stated that this might be helpful in reducing overall costs for treatment and diagnosis. However, they warned that the accuracy of CPAP titration during the split-night protocol was lower in patients with an initial AHI of less than 20.

—Owen McCarthy

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