Only a limited number of studies dealing with the epidemiology and therapy of central sleep apnea syndrome (CA) are available. The treatment strategies are poorly defined and not well evaluated. The aim of our present study was to treat selected CA patients with low dose acetazolamide (ACET) for a longer time period than has been done before. Previous studies were performed with high dose ACET provoking severe metabolic acidosis, not for more than 1 wk or only in obstructive apnea patients. Referred patients with suspicion of sleep-related breathing disorders (SRBD) were included in the study if, after a first selection night, their central apnea index (CAI) was > 5 or their apnea-hypopnea index (AHI) > 10 and their obstructive apnea index (OAI) < 5. Of 327 screened patients, 14 (4.3%) fulfilled these criteria. Patients were then treated with ACET (250 mg, 1 h before sleep): Polysomnography was repeated once after one single dose (N2) and twice after 1-mo chronic treatment without (N3) and with (N4) additional ACET administration. After each study night, arterial blood gases and chemical drive were measured. CAI (25.5 +/- 6.8 at N1) already decreased during N2 (13.8 +/- 5.2) and further during N3 (6.6 +/- 2.9) and N4 (6.8 +/- 2.8) p < 0.01). OAI remained unchanged. Total sleep time (TST) and sleep efficiency index (SEI) did not change significantly. The number of arousals decreased from 62 +/- 11 at N1 to 40 +/- 5 at N3 (p = 0.019).(ABSTRACT TRUNCATED AT 250 WORDS)