BACKGROUND: The differential diagnosis between depressive pseudodementia and Alzheimer disease (AD) is a clinical problem, and it is more difficult to diagnose depression in AD.OBJECTTVE: To analyze the incidence and characters of depression in AD patients, and investigate the correlative factors.DESIGN: A randomized controlled study.SETTING: Beijing Geriatrics Hospital.PARTICIPANTS: From October 2005 to July 2006, 34 patients with probable AD were selected from the Department of Dementia, Beijing Geriatrics Hospital according to National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer Disease and Related Disorders Association (NINCDS-ADRDA) criteria for AD. There were 16 males and 18 females, aged 63-85 years. Meanwhile, 30patients with other chronic neurological disorders (CND) were selected from our hospital as the CND control group, there were 16 males and 14 females, aged 55-85 years, including 18 cases of cerebrovascular sequela, 9 of Parkinson disease and 3 of migraineurs. Another 30 patients with chronic physical diseases(CPD) were enrolled as the CPD control group, there were 15 males and 15 females, aged 57-83 years,including 15 cases of chronic bronchitis, 8 of hypertension and 7 of diabetes mellitus. Besides, 30 physical examinees were enrolled as the healthy control group, including 15 males and 15 females, aged 55-80 years.All the subjects were informed and agreed with the detection.METHODS: ① All the subjects underwent the Hamilton rating scale for depression (HAMD) (24 items)assessment, and the total score ＜ 8 points was regarded as no depression, 8-20 as mild depression, 20-35 as moderate depression, ≥ 35 as severe depression. ② All the AD patients were assessed with Cell scale for depression in dementia (CSDD) (19 items), and the total score ＜ 8 points was regarded as no depression, and ≥ 8 as depression. CSDD consisted of five subscales, including mood-related signs, behavioral disturbance,cyclic functions, ideational disturbance and physical signs, which were scored as 0-2 points respectively, and the abnormal rate of each factor was observed, the abnormal rate was the percentage of number of patients suffering from the symptoms in the subscales to the total number of patients. ③ The cognitive function of the AD patients was assessed with Mini-mental status examination (MMSE) (the total score ranged 0-30 points; ≤17 in illiterate, ≤ 20 in primary school and ≤ 24 in middle school and higher was regarded as cognitive deficit)and the daily living ability of the AD patients was assessed with ADL.MATN OUTCOME MEASURES: ① HAMD scores in all the groups; ② CDSS scores and abnormal rate of factors in AD patients; ③ MMSE score and activity of daily life (ADL) score in AD patients; ④ Correlation between depression and correlative factors in AD patients.RESULTS: All the 124 subjects were involved in the analysis of results. ① The HAMD average score of the AD group was significantly higher than those of the CND, CPD and healthy control groups [(12.7±3.2), (5.5±2.5),(3.4±1.3), (2.6±1.7) points, P＜ 0.01]. ② In the AD group, the CDSS average score was (5.8±4.3) points,41.2% (14/34) met the criteria for depression. The abnormal rates in order were 44% (15/34) for mood-related signs, 32% (11/34) for behavioral disturbance, 24% (8/34) for cyclic function, 12% (4/34) for ideational disturbance and 12% (4/34) for physical signs. ③ The factors of age, course, MMSE score and ADL score were finally excluded after a multiple regression (P＞ 0.05). There was a negative correlation between CSDD score and onset age (P ＜ 0.05), sex was also obviously correlated with CSDD score (P ＜ 0.05).CONCLUSrON: The incidence of depression in AD is much higher with various manifestations. Female patients are the susc and earlier onset age is the risk factor for the presence of depression in AD.