Objective To evaluate the emotional and cognitive status in patients with obstructive sleep apnea syndrome （OSAS）

using neuropsychological tests and evoked-related potential （P3）. Methods Sixteen patients diagnosed of OSAS were tested by Hamilton rating scale for anxiety （HRSA） and Hamilton rating scale for depression （HRSD）. Other three groups

OSAS patient group （n=21）

snoring group （n=21）

and control group （n=21）

were administered polysomnography （PSG）

auditory evoked event-related potential （P3）

and clinic memory test. The results were analyzed using general linear model （GLM） analysis and Post Hoc test. Results Twelve OSAS patients’ scores of HRSA and HRSD were beyond the normal range

26.42 ±4.48 and 22.08 ±3.97 respectively. The auditory P3 latency in OSAS group was 363.1 ±22.9 ms （Fz）

368.57 ±28.03 ms （Cz）

in snoring group 336.57 ±31.08 ms （Fz）

339.81 ±31.76 ms （Cz）

in control group 340.8 ±28.7 ms （Fz）

338.29 ±29.21 ms （Cz）. There were significant differences between OSAS group and snoring group

as well as control group （P< 0.05）. No significant difference was seen between snoring group and control group. No significant difference was noted in P3 amplitude among three groups. Memory quotient （MQ） reduced in snoring group compared with control group. Conclusions Emotional disturbances are common clinical features in OSAS patients. Abnormal auditory P3 latency indicates the cognitive dysfunction in OSAS patients. Nocturnal hypoxaemia may play an important role on it. Snorers should be monitored because of the tendency to develop cognitive impairment.