DENVER — Continuous positive airway pressure improved both excessive daytime sleepiness and—in a particularly encouraging finding—cognitive function in a randomized trial involving Alzheimer's disease patients with obstructive sleep apnea, investigators reported at the annual meeting of the Associated Professional Sleep Societies.
“This is preliminary, but it seems to be quite promising. If in fact we can do anything to at least slow down deterioration of cognition—if not actually improve it—then that might postpone institutionalization, which will save billions of dollars as well as improving quality of life for these patients,” observed Sonia Ancoli-Israel, Ph.D., professor of psychiatry at the University of California, San Diego.
Sleep-disordered breathing is exceedingly common in Alzheimer's disease patients. Various studies have put the prevalence of obstructive sleep apnea (OSA) in patients with dementia at 50%–90%.
Moreover, demented patients with severe OSA have significantly worse dementia and individuals with severe dementia have more sleep-disordered breathing.
“Clearly there is some association between how much one can breathe at night and how much dementia one might have. Do I think that sleep apnea causes dementia? No, I don't—but I do think that if someone is already demented and you add hypoxia and disturbed sleep on top of that, it's likely to make the dementia worse,” Dr. Ancoli-Israel explained.
She reported on 40 noninstitutionalized patients with mild to moderate Alzheimer's disease and OSA who were randomized in double-blind fashion to true continuous positive airway pressure (CPAP) or to a control group given a counterfeit respiratory assistance protocol—“affectionately known as CRAP,” she said. After 3 weeks of CRAP, patients in the control group were switched to 3 weeks of CPAP. Those already on CPAP continued on the therapy for an additional 3 weeks. A comprehensive neuropsychological test battery was administered at baseline, at 3 weeks, and after 6 weeks.
The first noteworthy finding, Dr. Ancoli-Israel said, was that these Alzheimer's disease patients—mean age 78 years—tolerated CPAP “reasonably well,” using the equipment for an average of 5 hours per night. “That's really not that different from what we see in our clinic patients.”
The patients' mean respiratory disturbance index, a measure of OSA severity, decreased in the CPAP group from a baseline of 30.4 events per hour to 7.2 after 3 weeks and 4.9 per hour after 6 weeks. No significant change was seen in the CRAP group until 3 weeks after those patients had been switched to real CPAP.
Composite neuropsychological test scores improved significantly after 3 weeks of CPAP; no further improvement was seen during the second 3 weeks on the therapy. There was no improvement in neuropsychological test scores after sham therapy, but a significant gain was documented following the switch to CPAP.
“The kinds of changes that we're seeing are actually not that different from the changes one sees when patients are put on cognition-enhancing drugs. So this might be an additional way to treat the patient,” she said.