The Follow-up Study Of Senile Dementia And High-risk Groups In Urban And Rural Areas Of Guangzhou

Background: Dementia and Alzheimer's disease(AD) are becoming common diseases in elderly with increasing aging rapidly in our country. AD was not easily diagnosed in its early period because its onset was gradual and the early symptoms was very mild. Its symptoms were obvious when its cognitive impairment was severe. In order to prevent or delay the development of AD, early diagnosis and treatment was very important. The mild cognitive impairment(MCI) was the most importance group which was at the greatest risk of conversion to dementia, and a lot of study about MCI had carried on at abroad. China also pay attention to the follow-up study of dementia's high-risk group, but how process that change to dementia is still not completely clear, so we carried out the follow-up study to high-risk groups based on the epidemiological investigation of dementia in guangzhou's community in 2001.Objective: We studied the natural history of the dementia and the high-risk groups in the Guangzhou area.and investigated the deficits of cognitive function, the mortality, the survival, as well as the causes of death for overall dementia and AD patients. To estimate progression to dementia of mild cognitive impairment and the other high-risk groups evaluating the relationship with the Neuropsychological examination. To study the mortality and survival rate in the high-risk group of the dementia .Method: Between Sep 2001 to Feb 2002, the prevalence (baseline) survey was carried out in 5276 residents aged 55 years or older, who belonged to the urban or rural areas that were selected by stratified random sampling method from Guangzhou, Guangdong province. The first follow-up investigation was carried out from Jul 2003 to Aug 2003 on subjects diagnosed as dementia or MCI and MMSE score below or equal to demarcation, and above demarcation of MMSE score but memory complaint by an informant needed to further check by the doctor in the baseline study. During the second follow-up phase (between Nov 2008 and dec 2008), the same subjects were investigated again.The scales and procedures used in the three surveys were exactly the same. And the diagnosis of dementia was made according to the DSM-Ⅲ-R criteria. NINCDS/AIREN criteria and Hachinski ischemia score were applicated in diagnosis of vascular dementia (VD). NINCDS-ADRDA was the criteria for diagnosis of probable AD and possible AD. Petersen's criteria was used to diagnose MCI.The severity of dementia was assessed by CDR scale.Result: 1) 838 participants aged over 55 years were recruited from population-based cohort (183 dementia, 264 mild cognitive impairment, 316 MMSE score below or equal to demarcation, and above demarcation of 75 MMSE score but memory complaint by an informant needed to further check by the doctor in 2001. The subjects were reassessed after 2 and 7years,respectively.2)It was found in the follow-up surveys that the cognitive impairment of patients with dementia and MCI was aggravated progressively. The differences of MMSE scores of subjects with MMSE score > demarcation , MMSE score≤demarcation,mild cognitive imapirment and dementia between the baseline survey and the second follow-up survey were 3.97±6.58,-0.78±-8.15,2.15±7.99,6.37±6.84,respectively (P<0.001). The decline of neuropsychological scores of patients with MCI or dementia was larger than that of other groups, and the increment of POD scores was higher in MCI or dementia patients than in the other subject. The decline of scores in cognitive function examinations was more in female,highly aged and severely demented individuals than in male,relatively young and mildly demented subjects. It was indicated by multivariate stepwise regression analysis that age (β=0.299) had significant effects on the difference of MMSE scores (p<0.001).3) MCI is not fully converted to dementia, at 7 year, 34.9% of MCI maintain the same level of cognitive function, 21.1% reversed to normal. Conversion rate to dementia in MCI group (8.07% person year) was higher than the other two groups (2.74% person year,3.80% person year). The MCI with advance aged,female,less education are at high risk of conversing to dementia. AMCI was more than VMCI, AMCI more easily progress to AD, VMCI more easily progress to VD. Age OR =1.87(95% CI:1.35-2.57)was the major risk factors for covertion of the MCI.4)The mortality of subjects with MMSE score > demarcation , MMSE score≤demarcation, MCI, and dementia were 4.60%,7.49%,7.80% and 14.28% person-year, respectively. The mortality of patients with AD, VD, and other dementia subtypes were 19.09%,25.17% and 38.24% person-year respectively. The mortality of male (5.26% person-year) and male dementia patients (26.84% person-year) were higher than the female counterparts (4.03%,18.97%person-yea) r.The mortality of patients with mild, morderate and sever dementia were 13.75,26.59 and 57.24per person-year, respectively. Age (OR=1.05,95%CI:1.03-1.08)),CDR OR=2.29,95% CI:1.67-3.15) and MMSE score(OR=0.96,95% CI:0.94-0.99)were the major risk factors for death of the elderly. The survival rate of subjects with MMSE score > demarcation , MMSE score≤demarcation,MCI, and dementia at baseline examination were 73%,58 %,54% and 19% after 7 years, respectively (p<0.001). The 50% survival duration of patients with dementia was 3.67±0.35 year(s95%CI:2.98-4.36). The survival of female patients was higher than that of male patients. The survival rate of the patients with mild, moderate and sever dementia were 30%,11% and 4 %(p<0.001) after 7 years, and the 50% survival duration of them were 5.42±0.69(95%CI:4.06-6.77),3.33±0.35(95%CI:2.65-4.01)and 0.67±0.29(95%CI:0.091-1.25)years, respectively. The disease duration of the demented patients after dementia onset was about 13-16years. The 50% survival duration from the point of disease onset in patients with AD,VD, and other dementia were 3.92±0.45(95%CI:3.04-4.79),2.83±0.77(95%CI:1.33-4.33)and 2.08±1.42(95%CI:0.00-4.85)years, respectively.Conclusion: 1) The cognitive decline of group with dementia was faster than the other groups. Their cognitive deficit was aggravated progressively. The mortality of demented patients increased with the advantage of cognitive impairment, while the survival tended to progress to the contrary direction. Among all dementia subtypes the mortality of patients with other dementia subtypes was highest and VD was higher than AD . The female dementia had more severe cognitive impairment, but the male dementia accelerated decline.2) Subjects with cognitive impairment although MMSE score > demarcation , MMSE score≤demarcation, MCI are the high risk of dementia, the conversion rates to dementia are significantly higher than normal elderly, MCI was the highest rate in conversion to dementia ,but over time, the rate would decline. Age was the major risk factors for coversion to dementia of the MCI.3) Mild cognitive impairment is a heterogeneous state, some maintain cognitive function, or even reversed to normal.