Objective To explore whether the patientsaged over 65 years with obstructive sleep apnea hypopnea syndrome (OSAHS) are able to tolerate continuous positive airway pressure (CPAP)while compared with patientsaged less than 65 years.And to investigate the factors that affectcompliance to CPAP in OSAHSpatients.Methods A total of 147 OSAHSpatients diagnosed with overnight polysomnography (PSG) were divided into two groups≥65 years old group (n=46),<65 years old group (n = 101 ).Clinical data and PSG parameters were included in a computerized database.The pressure level of CPAP,the duration of respirator use were followed up.Results Compared with <65 years old group,there were higher prevalences of COPD (16% vs.4%,P=0.02),cardiovascular disease (23% vs.10%,P=0.04),apnea (43% vs.26%,P=0.03),regular alcohol consumption (61% vs.38%,P=0.007) and lower incidence of snoring (31% vs.54%,P= 0.03),shorter total sleeping time (378 min vs.423 min,P=0.001),longer wake after sleep onset periods (162 min vs.115 min,P=0.004),lower sleepefficiency (69% vs.77%,P<0.001),higher percentage of stage 1 sleep (29% vs.20%,P=0.001),lower percentage of stage 3-4 sleep (6% vs.9%,P=0.016) and rapid eye movement (REM) sleep (12% vs.15%,P=0.001) in ≥65 years old group.The percentages of acceptance to CPAP at 3 months,6 months,1 year,2 years and 3 years were 91%,89%,84%,82% and 82% respectively in ≥65 years old group,and were 92%,86%,81%,72% and 67% in <65 years old group.Average use time of CPAP were (5.1±1.5) h/night in ≥65 years old group,and were (3.9±1.2) h/night in <65 years old group (P=0.022).By analysis of multivariate logistic regression,a high pressure CPAP was associated with higher objective CPAP compliance in OSAHSpatients.Conclusions Compliance to CPAP in older OSAHSpatients is not decreased when compared to younger adults.A high CPAP pressure is the only significant independent predictor of better CPAP compliance.