Objective: This longitude study was completed in an urban elderly population to explore the prevalence, incidence rates, and outcome of elderly dementia and depression in 1990s and to see any possible change since 1980s.
Method: A total of 1,593 subjects, aged 60(+), were enrolled in 1997 from Beijing urban communities. MMSE, PAS, GDS, ADL, HAMD, DDDS, ICD-10, and HIS were used as screening, evaluating or differentiating tools for dementia and depression. All subjects were re-interviewed in 1999; 40 dementia and 25 depression identified in 1997 had follow-up interviewed for their outcome from 1998-2002. MMSE score was reanalyzed for MCI identification.
Result: Among the 1,593 enrolled, 22 cases were diagnosed as Alzheimer's disease (AD), 15 vascular dementia (VD), and 3 mixed dementia(MD), making the dementia prevalence rates of 2.51% for those of 60(+) and 3.22% for 65(+) in 1997. In 1999, 1,443 subjects (included 40 dementia and 25 depression) completed the re-interview and made dementia annual average incidence rates of 0.89% for those of 60(+) and 1.13% for 65(+). No significant difference either in prevalence or in incidence was found in the comparison with that of 1980s.
In follow-up studies on the 40 demented, accumulative-mortality rates by each year were found as 20%, 42.5%, 55%, 60%, and 72.5% respectively. Among these 22 AD cases by 2002, 15 died, 2 became worse, 3 stayed the same, 1 had changed diagnosis to "pseudodementia," and 1 missed. For the 15 VD cases, 12 died, 2 stayed the same, and 1 missed. And for the 3 MD cases, 2 died and 1 stayed the same. The average duration of these 29 died-demented was 5.34 years. Their cause of death was unspecific. The data shows a depression prevalence of 1.57% for 60(+), 1.78% for 65(+) in 1997, with a minimum average annual incidence of 1.28% for 60(+), and 1.57% for 65(+) in 1999. Correlation factor analysis show only their health status was associated with the depression prevalence and incidence rates.
In follow-up of the 25 depressed, 4 relapsed, 1 remained depressive state and rediagnosed as dysthymia, 2 developed as dementia, 8 died, 7 remained normal states without relapse, and 4 were missing. A MMSE score reanalysis for 1336 non-demented in 1997 showed 117 had 1.5 SD lower score and cognitive decline score 1 and over then were identified as MCI, making a MCI incidence rate of 8.76%. Among these 117 cases, 9 became senile dementia in 1999, with a MCI dementia incidence rate of 7.69%, 4 times higher than the dementia incidence rate investigated in 1999.
Conclusion: This study showed the prevalence and incidence rates of dementia in Beijing did not change significantly since 1980s. MCI may be a predictive factor to the development of dementia. The incidence and prevalence rates of elderly depression were significantly changed with their health status. Both dementia and depression elderly had a poor prognosis.
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