Continuous Positive Airway Pressure to Improve Milder Obstructive Sleep Apnea

Impact of CPAP on Functional Outcomes in Milder Obstructive Sleep Apnea (CATNAP)

The purpose of this study is to determine whether functional status improves in individuals with milder obstructive sleep apnea (OSA) following continuous positive airway pressure (CPAP) treatment.

BACKGROUND:

OSA is characterized as mild, moderate, or severe, according to the number of respiratory disturbances per hour of sleep (RDI), as defined by the American Academy of Sleep Medicine. CPAP is the primary treatment for sleep apnea. The column of pressure delivered to the upper airway by this device immediately eliminates the respiratory disturbances when it is applied. There is evidence from randomized controlled studies that CPAP also improves functional status, and the key manifestation of OSA, including excessive daytime sleepiness, in individuals with severe OSI (i.e., RDI greater than 30). However, there has been limited research exploring improvement in functional status in individuals with less severe OSA (i.e., those with mild OSA and RDI of 5-15 or moderate OSA and RDI of 16-30). The large placebo effect that has been reported in controlled studies of OSA-associated functional outcomes mandates the need for a placebo in studies evaluating the true impact of this treatment. Results from the three randomized controlled studies in milder OSA that have examined this issue have been equivocal, principally because of serious methodological limitations. It remains unclear whether CPAP treatment improves daily functioning in those with milder OSA (RDI 5-30). This is a critical issue as this level of disease severity represents the largest segment of OSA and comprises 15% of the U.S. population.

DESIGN NARRATIVE:

Using Granger's model of functional assessment, this study will examine whether functional status improves in participants with milder OSA following CPAP treatment. The study will employ a randomized, placebo-controlled, parallel study design, and will use a sham CPAP device as the placebo in participants with significant daytime sleepiness. The study will test the hypothesis that the change in functional status (measured by the Functional Outcomes of Sleep Questionnaire) after 8 weeks of treatment will be greater for participants treated with active CPAP compared to the placebo. Secondary aims of the study include examining whether CPAP also improves daytime sleepiness, and determining whether CPAP can reduce nocturnal blood pressure to lower the risk for stroke and hypertension linked to OSA.

Inclusion Criteria

• Newly diagnosed with OSA on overnight polysomnogram (PSG) with RDI between 5 and 30
• Score of greater than 11 on the Epworth Sleepiness Scale (ESS) on two administrations of the instrument (performed at prescreening and screening), each completed on a different day to avoid sporadic values and confirm the presence of excessive daytime sleepiness
• Stable medical history and no change in medications, including hypertension medications, in the 3 months prior to study entry
• Stable psychiatric history and no change in psychotropic medications in the 3 months prior to study entry
• Has access to a telephone

Exclusion Criteria

• Diagnosis of another sleep disorder in addition to OSA based on PSG, e.g., periodic limb movement disorder (greater than 10 limb movements per hour of sleep with arousal); central sleep apnea (greater than 5 or more central apneas); insomnia; sleep hypoventilation syndrome; or narcolepsy
• Previous treatment for sleep apnea with nasal CPAP, oral appliance, home oxygen therapy, uvulopalatopharyngoplasty, tracheotomy, or other surgery for OSA
• Oxygen or bi-level CPAP required for treatment of OSA
• Unable to return for study instructions or follow-up testing
• Medically unstable condition (e.g., heart attack, congestive heart failure, Cheyne-Stokes breathing, unstable angina, uncontrolled thyroid disease, unstable diabetes, depression or psychosis, ventricular arrhythmias, cirrhosis, or recently diagnosed cancer) in the 3 months prior to study entry
• Regular use (greater than 3 times per week) of sedative, hypnotic, or alerting medications (such as Modafinil) in the 3 months prior to study entry
• Chronic nasal congestion that would prevent the use of a nasal mask, in the 3 months prior to study entry
• History of automobile accidents due to excessive daytime sleepiness
• Employed in transportation-related safety sensitive occupation such as an airline pilot, truck driver, or train engineer
• Night shift worker regularly experiencing jet lag, or a history of irregular work schedules in the 6 months prior to study entry
• Regular use of alcohol as determined by answering yes to one or more of the questions on the CAGE questionnaire (i.e., alcohol dependent)
• Recent or recurring history of substance abuse leading to tolerance or dependence
• Pregnant; women must either be postmenopausal or confirmed not pregnant by a urine pregnancy test
• Unable to perform study tests, e.g., inability to communicate verbally; inability to write and read in English; less than a 5th grade reading level (evaluated using Flesch-Kincaid assessment); visual impairment; hearing impairment; cognitive impairment (e.g., previous head injury); or upper extremity motor deficit (e.g., previous stroke or spinal cord injury)
• Residing with an individual who is currently using CPAP treatment