Effect of Acetazolamide on Sleep Disordered Breathing in Lowlanders Older Than 40 Years at Altitude

Inclusion Criteria: * Healthy men and women, age 40-75 yrs, without any disease and need of medication. * Born, raised and currently living at low altitude (\<800m). * Written informed consent. * Kyrgyz ethnicity Exclusion Criteria: * Any active respiratory, cardiovascular or other disease requiring regular treatment or being otherwise relevant for tolerance of hypoxia or altitude exposure. * Any condition that may interfere with protocol compliance including current heavy smoking (\>20 cigarettes per day or \>20 pack-years with active smoking during the last 10 years), regular use of alcohol. * Allergy to acetazolamide and other sulfonamides.