Sleep apnea-hypopnea syndrome (SAHS) has a high prevalence and is associated with adverse cardiovascular consequences in elderly Veterans. Positive airway pressure therapy is deemed cumbersome and often associated with non-adherence to therapy. This proposal will investigate whether alternative therapies can be developed by modulating specific physiologic mechanisms of ventilatory control. Specifically, the investigators will study whether interventions with sustained hyperoxia (Aim 1), finasteride (Aim 2) and acetazolamide (Aim 3) will reduce breathing instability during sleep by reducing chemoresponsiveness and/or increasing cerebrovascular reactivity (CVR) in order to alleviate sleep disordered breathing in the elderly with sleep apnea. The proposed aims will also allow us to delineate key mechanisms of breathing instability in the elderly. The investigators envision that the results obtained from this project will ultimately allow us to develop novel alternative therapies for sleep apnea in the elderly. We will also compare CVR in young vs older adults