The findings add to the debate over whether Alzheimer's disease in its preclinical stages could lead to sleep-disordered breathing and explain the increased prevalence of sleep-disordered breathing in older people.

The study enrolled 68 cognitively normal elderly patients (mean age, 71.4), who underwent two nights of home monitoring for sleep-disordered breathing and were tested for at least one indicator of Alzheimer's disease.

The researchers used FDG-PET to evaluate glucose metabolism, Pittsburgh Compound B (PiB) PET to measure amyloid load, and MRI to measure hippocampal volume.

The group only found a significant association between Alzheimer's and sleep-disordered breathing when they examined body weight, according to lead author Dr. Ricardo Osorio, a research assistant professor at NYU. Patients with a body mass index (BMI) less than 25 and sleep-disordered breathing had biomarkers of Alzheimer's risk, such as increased P-tau and T-tau in the cerebrospinal fluid, hippocampal atrophy, and glucose hypometabolism in Alzheimer's-vulnerable regions.

Among obese patients with BMI greater than 25, glucose hypometabolism at FDG-PET was also found in the medial temporal lobe, but it was not significant in other Alzheimer's-vulnerable regions.

Osorio and colleagues hope to conduct a two-year longitudinal study to test their hypothesis that very early-stage brain injury associated with these Alzheimer's biomarkers can lead to sleep-disordered breathing. The goal of the study would be to clarify any causality between sleep-disordered breathing and preclinical Alzheimer's disease in elderly patients.

The current study will be presented this week at the American Thoracic Society (ATS) conference in Philadelphia.