老年人轻度认知损害的发病率及向痴呆或阿尔茨海默病的转化率:基于人群的队列研究

背景:老年人轻度认知损害已成为目前阿尔茨海默病临床研究的新热点。目前国内有多少轻度认知损害对象发展为阿尔茨海默病还是一个未知数。目的:分析老年人轻度认知损害的发病率及向痴呆和阿尔茨海默病的转化率。设计:以诊断为依据的队列研究。单位:解放军白求恩国际和平医院干部病房二科。对象:为2001-08/2001-09对石家庄市26个部队干休所60岁及以上的离退休干部进行基线调查时诊断为轻度认知损害的216例患者和2302名认知正常受试者。方法:轻度认知损害的诊断参考美国精神障碍诊断与统计手册第4版轻度神经认知损害研究用诊断标准。痴呆的诊断采用美国精神病学会的精神障碍诊断和统计手册第四修订版(DSM-IV)标准。阿尔茨海默病采用美国神经病学、语言障碍和卒中-老年性痴呆和相关疾病学会标准。对216例轻度认知损害患者和2302名认知正常受试者进行为期3年的队列研究。主要观察指标:认知正常受试者轻度认知损害的平均年发病率、认知正常受试者和轻度认知损害患者阿尔茨海默病的平均年发病率以及轻度认知损害患者与认知正常受试者比较转化为阿尔茨海默病的相对危险性(RR)和95%可信区间。结果:轻度认知损害组与认知正常组均每年随访1次,共随访3年。216例轻度认知损害患者死亡7例,实际随访209例,随访率96.8%。2302名认知正常者死亡36例,实际随访2266例,随访率98.4%。①认知正常的老年人轻度认知损害的平均年发病率为4.8%,痴呆和阿尔茨海默病的平均年发病率分别为1.3%和0.8%;②轻度认知损害患者痴呆和阿尔茨海默病的平均年发病率分别为8.1%和5.6%;男性和女性轻度认知损害患者痴呆和阿尔茨海默病的平均年发病率差别无显著性(P>0.05)。③随着文化程度的提高,轻度认知损害患者痴呆(趋势χ2=5.57,P=0.02)和阿尔茨海默病(趋势χ2=4.92,P=0.03)的发病率有降低的趋势;认知正常受试者痴呆(趋势χ2=23.1,P<0.001)和阿尔茨海默病(趋势χ2=18.0,P<0.001)的发病率亦有降低的趋势。④随着年龄的增长,轻度认知损害患者痴呆(趋势χ2=14.6,P<0.01)和阿尔茨海默病(趋势χ2=13.9,P<0.01)的平均年发病率有增高的趋势;认知正常受试者痴呆(趋势χ2=32.3,P<0.01)和阿尔茨海默病(趋势χ2=23.8,P<0.01)的平均年发病率亦有增高的趋势。⑤轻度认知损害转化为痴呆或阿尔茨海默病的相对危险性分别为认知正常者的6.4倍和7.4倍。结论:老年轻度认知损害患者转化为痴呆的危险性远远大于认知正常的老年人。应加强对老年轻度认知损害患者这一痴呆高危人群的监测。

Incidence rate of mild cognitive impairment and the conversion rates into dementia or Alzheimer disease among elderly people: A population-based cohort study

BACKGROUND: Mild cognitive impairment (MCI) in elderly people is becoming increasingly a new hot spot for the clinical study of Alzheimer disease at present, and it is still unknown how many cases of MCI will convert into Alzheimer disease. OBJECTIVE: To analyze the incidence rate of mild cognitive impairment and the conversion rates into dementia and Alzheimer disease among elderly people.DESIGN: A prospective cohort study based on diagnosis. SETTING: Second Department of Cadre's Ward, Bethune International Peace Hospital of Chinese PLA.PARTICIPANTS: The subjects were 216 MCI patients and 2 302 subjects with normal cognition selected in the baseline investigation to the retired cadres aged 60 years and above, in 26 military cadres' sanatoriums of Shijiazhuang city between August and September 2001.METHODS: The MCI diagnosis was according to the MCI diagnostic standard in Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM-Ⅳ), and the diagnosis of dementia was according to the standard in DSM-Ⅳ revised by American Psychiatric Association. Alzheimer disease was diagnosed according to the standards of National Institute of Neurological and Communicative Disorders and Stroke/the Alzheimer Disease and Related Disorders Association (NINCDS-ADRDA). All the 216 MCIpatients and 2 302 subjects with normal cognition were enrolled in the 3-year cohort study. MAIN OUTCOME MEASURES: The incidences of MCI among subjects with normal cognition; the annual conversion rates into Alzheimer disease in MCI patients and subjects with normal cognition; the relative risks (RR) and 95% confidence interval (95% CI) of MCI and normal cognition developing into Alzheimer disease. RESULTS: The MCI group and normal cognition group were followed up once every year for 3 years. Of the 216 MCI patients, 7 died, and 209 were followed up actually, and the follow-up rate was 96.8%. Of the 2 302 subjects with normal cognition, 36 died, and 2 266 were followed up actually,and the follow-up rate was 98.4%. ① In the elderly subjects with normal cognition, the annual incidence of MCI was 4.8%, and those of dementia and Alzheimer disease were 1.3% and 0.8 respectively. ② The annual in cidence rates of dementia and Alzheimer disease in MCI patients were 8.1% and 5.6% respectively, which were insignificantly different between males and females (P ＞ 0.05). ③ The incidence rates of dementia and Alzheimer disease showed a descending trend with the elevation of educational level in both the MCI patients (trend x2 =5.57, P=0.02; trend x2 =4.92, P=0.03) and the subjects with normal cognition (trend x2 =23.1, P＜ 0.001; trend x2 =18.0, P ＜ 0.001). ④ The annual incidence rates of dementia and Alzheimer disease showed an ascending trend with aging in both the MCI patients (trend x2 =14.6, P ＜ 0.01; trend x2 =13.9, P ＜ 0.01) and the subjects with normal cognition (trend x2 =32.3, P ＜ 0.01; trend x2=23.8, P ＜ 0.01). ⑤ The relative risks of the conversion into dementia and Alz heimer disease in MCI patients were 6.4 and 7.4 times as many as those in the subjects with normal cognition.CONCLUSION: The risks of conversion into dementia and Alzheimer disease in elderly MCI patients are far higher than those in elderly people with normal cognition. It should be reinforced to monitor elderly MCI patients, who are the of high risk group of dementia.