BACKGROUND: At present, central cholinergic neuron system is regarded the most major structural basis of cognitive function. Changes in structure of cholinergic neuron system of brain and receptor expression after brain injury can cause cognitive impairment.OBJECTIVE: To comparatively observe the intelligence quotient (IQ), latent period and wave amplitude of P300 event-related potential and the difference of activity of acetylcholinesterase (AChE) in blood and cerebrospinal fluid between patients with type 2 diabetes mellitus and with non-diabetes mellitus, and analyze the correlation of IQ of cognitive impairment patients with diabetes mellitus with AChE activity, latent period and wave amplitude of P300 event-related potential in cerebrospinal fluid.DESIGN: Correlation analysis of contrast observation.SETTING: Department of Endocrinology, Affiliated Hospital of Binzhou Medical College.PARTICIPANTS: Totally 32 patients with type 2 diabetes mellitus who received the treatment in the Department of Endocrinology, Affiliated Hospital of Binzhou Medical College between April 2004 and April 2005 were recruited, serving as diabetes mellitus group. They, including 19 male and 13 female, aged 49 to 73 years, with disease course of 4 to 11 years, all met the diagnostic criteria of diabetes mellitus revised by World Health Organization in 1999. Another 30 patients with non-diabetes mellitus who homeochronously underwent lumbar anesthesia in the Department of Surgery and Department of Gynecology were recruited, serving as non-diabetes mellitus group. The 30 patients included 18 male and 12 female,and their age ranged from 46 to 71 years. Informed consents of detected items were obtained from the involved patients.METHODS: ① Evaluation,on IQ: The IQ of involved subjects was evaluated with Chinese Version of the Wechsler Adult Intelligence Scale revised by Gong Yao-xian (WAIS-RC). WAIS-RC included 6 verbal subscales and 5 performance subscales. The test scores of the 11 subscales integrated into the scores of the whole scale, and the scores on the WAIS-RC included verbal IQ (VlQ), performance IQ (PIQ) and full scale IQ (FIQ). FIQ ≤79 scores indicated Iow IQ and FIQ≤69 indicated intelligence impairment. ②Detection of P300 wave: P300 wave was detected with evoked potential instrument (MYTOPRO, Italian),and data of latent period and amplitude of P300 event-related potential were automatically shown by computer. ③ Detection of AChE activity in blood and cerebrospinal fluid: Activity of AChE of blood and cerebrospinal fluid was measured with biochemical methods by using CORNING-560 autoanalyzer. ④Correlation analysis: Correlation of FIQ with AChE of cerebrospinal fluid and P300 wave of patients with type 2 diabetes mellitus was analyzed. T test was used in intergroup comparison and linear correlation analysis for relevant treatment.MAIN OUTCOME MEASURES: ① Comparison of IQ, latent period and wave amplitude of P300 wave as well as the activity of AChE between two groups. ② Analysis on the correlation of FIQ of patients with type 2 diabetes mellitus with AChE of cerebrospinal fluid and P300 wave.RESULTS: Thirty-two patients with diabetes mellitus and 30 non-diabetes mellitus participated in the result analysis. ① Comparison of IQ, latent period and wave amplitude of P300 wave as well as the activity of AChE between two groups: The scores of VIP, PIQ and FIQ of patients with type 2 diabetes mellitus were (97.4±10.4), (92.6±8.4) and (95.2±9.7) scores, respectively; and those of patients with non-diabetes mellitus were (104.7±9.6),(102.5±8.5)and(102.7±8.9) scores, respectively, and P ＜ 0.05-0.01 was set in intergroup comparison. The latent period of P300 wave at points Fz , Cz and Pz of patients with type 2 diabetes mellitus was (370.8±41.8),(371.5±39.1)and (375.1 ±43.1) ms, respectively, and that of patients with non-diabetes mellitus was (332.1±28.3),(335.7±29.4)and(339.7±27.3) ms, respectively, and P ＜ 0.01 was set in intergroup comparison; Wave amplitude of P300 of patients with type 2diabetes mellitus was (8.6±4.1),(8.6±4.0) and (7.7±4.0) μV, respectively and that of patients with non-diabetes mellitus was (11.9±4.1),(11.5±4.4) and (10.9±5.0) μV, respectively , and P ＜ 0.05-0.01 was set in intergroup comparison; The level of AChE in blood and cerebrospinal fluid of patients with type 2 diabetes mellitus was (235.61±50.34)and (17.89±4.46) μkat/L, respectively, which was significantly higher than that of patients with non-diabetes mellitus [(205.03±44.15)and (14.63±0.48) μ kat/L, respectively], and P ＜ 0.05-0.01 was set in the intergroup comparison. ② Correlation of FIQ value of patients with type 2 diabetes mellitus with AChE of cerebrospinal fluid and P300 wave: The value of FIQ was significantly negatively correlated with the AChE activity of cerebrospinal fluid (/=-0.588 1, P ＜ 0.01 ), significantly negatively correlated with the latent period at points Fz, C and Pz of P300 wave (r= -0.700 5, -0.689 4,-0.688 5, P ＜ 0.01 ), and significantly positively correlated with the amplitude at points Fz , Cz and Pz of P300 wave(r= 0.607 4,0.616 1,0.592 0,P ＜ 0.01 ).CONCLUSION: (① Cognitive impairment of patients with type 2 diabetes mellitus might be related to the increase of activity of AChE in cerebrospinal fluid. ② Combined application of examination of P300 wave and evaluation of IQ is more useful in deciding the state of cognitive function of patients with type 2 diabetes mellitus.