The purpose of this study is to determine whether treating sleep apnea with continuous positive airway pressure would result in improvements in cognition in patients with Alzheimer's disease.

Patients with sleep disordered breathing (SDB) experience nighttime sleep fragmentation and often become hypoxic during the night. The fragmentation and hypoxemia can frequently result in daytime impairments including impairments in cognitive functioning. The state-of-the-art treatment for SDB is Continuous Positive Airway Pressure (CPAP). Many SDB patients who are successfully treated with CPAP show improvement in memory and other cognitive functions. Data have shown that there is a strong relationship between SDB and dementia with patients with Alzheimer's Disease (AD) having a high rate of SDB. This proposal will examine whether treating SDB with CPAP in patients with AD will result in improvement in cognitive functioning. The specific aims are to assess whether patients with mild AD and SDB will tolerate CPAP and be compliant with treatment; to examine the effect of CPAP treatment on SDB in patients with mild AD and SDB; to examine the effect of CPAP treatment on cognitive functioning in patients with mild AD and SDB; to examine whether improvement is greater after six weeks of CPAP treatment than after three weeks of treatment. Since caregivers are often disturbed by the patients poor sleep, we will also evaluate the effect of the patients' treatment on their caregivers. Specifically, the secondary aims are to evaluate whether caregivers feel that CPAP improves the patient's sleep and to evaluate whether caregivers feel that their own sleep improves as the patient's sleep improves. Patient identified as having mild AD and SDB will have an extensive neuropsychological battery. Half will be randomized to CPAP treatment and the other half to shamCPAP. After three weeks neuropsychological tests will be repeated. The shamCPAP will be switched to CPAP and the CPAP group will remain on CPAP for an additional three weeks. Neuropsychological tests will again be repeated. The long-term goal of this line of research is to find a new approach that might improve the quality of life, delay the dementing process, postpone institutionalization and save millions of dollars in nursing care costs.

Inclusion Criteria:

• Mild probable Alzheimer's disease (diagnosed according to the National Institute of Neurological and Communicative Disorders & Stroke-Alzheimer's Disease and Related Disorders Association [NINCDS-ADRDA] criteria).
• Mini Mental Status Exam score between 20 and 27
• Respiratory disturbance index >15 (i.e., 15 apneas plus hypopneas per hour of sleep) - Between the ages of 50-85 years
• Stable health
• reliable caregiver
• English speaking
• Patients will be allowed to continue acetylcholinesterase inhibitors, psychotropic medications, memory enhancers, health food supplements, etc. as long as they have been stable on the same dose for at least two months prior to participation and agree to continue on this dose for the duration of the study.

Exclusion Criteria:

• Currently receiving treatment for sleep apnea.
• Apneas primarily central in origin; narcolepsy or other sleep disorders
• Medication known to influence sleep (i.e. sedative hypnotics, narcotics) will be excluded if the dose can not remain stable and unchanged for the duration of the study.
• Bronchospastic and symptomatic chronic obstructive pulmonary disease as indicated by regular use of bronchodilators, steroids, history of carbon dioxide retention, waking hypoxemia (PaO2 <60 mmHg or SpO2 <92 % by pulse oximetry), or use of supplemental oxygen.
• Symptomatic coronary or cerebral vascular disease (history of myocardial infarction, angina, stroke, or transient ischemic attacks), history of life-threatening arrhythmias, cardiomyopathy, history of psychosis, or current alcohol or drug abuse
• Current diagnosis of active uncontrolled seizure disorder
• Any other advanced, severe and unstable disease of any type that may put the subject at special risk or interfere with primary and secondary variable evaluations
• Change in any medication within one month of participation.