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| | Epidemiological studies in Chinese elderly | | 2005-2-22 0:36:48 Institute of Mental Health, Peking Unive Yu Xin M.D |  Epidemiological studies in Chinese elderly
There are two nation-wide surveys on mental disorders taking place in 1983 and 1992 respectively. The first study, which met with all requirements of epidemiological research, was conducted in 1982, led by Institute of Mental Health, Beijing Medical University. This study adopted standard sampling method, a survey instrument whose validity and reliability were tested, and ICD-9 used as diagnostic criteria. Twelve areas with 51982 people were involved in this study. This survey found that the life time prevalence rate of "senile dementia" was 0.29% (in 38,136 people aged 15 and above) and "mental disorders induced by cerebral vascular disease" was 0.50%. The life time prevalence of schizophrenia in 4619 people aged over 60 was 0.46% (female 0.72% vs. male 0.13%).3)
In 1993 national survey, 7000 households in 7 areas were included. There were totally 3341 people over 60. The diagnostic criteria were ICD-9. The lifetime prevalence rates of major mental disorders are: schizophrenia 9.88‰; Alzheimers disease 2.10‰; drug dependence 1.80‰; alcohol dependence 1.20‰; mental disorders induced by cerebral vascular disease 1.20‰; mood disorders 1.20‰.4)
There are also several small scope of epidemiological surveys targeting specific mental disorders in elderly conducted in China. We will give detailed explanation on dementia and mood disorders.
l Dementia:
In 1986, the first epidemiology study of age-related dementia on population aged 60 and above was conducted in China in an urban area of Beijing.5) 1090 elderly was screened by Mini Mental State Examination (MMSE), the suspected cases were interviewed by psychiatrists, DSM-III was adopted as diagnostic criterion and Dementia Differential Diagnostic Schedule (DDDS) for differential diagnosis. 14 cases of dementia for moderate and severe degree were identified. With the prevalence rate 1.28% (≥60) and 1.82% (≥65).
Table 3 listed results of other studies on prevalence rate of dementia.
Table 3: Prevalence rates of dementia in China:
Author Year Location Population Diagnostic Criteria Differential diagnostic instruments Results: Vascular dementia/ (Alzheimers disease)
Li Ge, et al 1989 Beijing, urban area 1090 (>60) DSM-III DDDS 0.83% (0.37%)
Zhang Mingyuan, et al6) 1990 Shanghai, urban area 5055 (>55) DSM-III-R NINCDS-ADRDA Hachinski Ischemic Scale >55:0.74% (1.50%)>65:1.26% (2.90)
Zhu Ziqing, et al7) 1998 Shanghai 3083 (>55) DSM-III-R NINCDS-ADRDA Hachinski Ischemic Scale (HIS) >65:1.28%(3.00%)
Wu Zhen, et al8) 1992 Beijing, urban community 966, average age: 67.8 Hesegawa Dementia Scale No 0.93% (0%)
Chen Changhui, et al.9) 1992 Beijing, urban community 5172 average age: 68.9±6.6 DSM-III DDDS 0.50% (0.2%)
Gao Zhixu, , et al.10) 1993 Shanghai, both rural and urban areas 3779rural/urbane:2560/1219 DSM-III-R Hachinski Ischemic Scale 0.85% (3.15%)
Zhang Jingli, , et al.11) 1998 Beijing, urban area 1243 DSM-III-R Hachinski Ischemic Scale 0.96% (1.37%)
Li Shuran, et al.12) 1999 Bejing, urban area 1593 ICD-10 DDDSHIS 0.94%(1.38%)
All above studies demonstrated that dementia was more prevalent in older age and illiterate group. All studies except Zhang Jingli showed that prevalence rate of vascular dementia in women was higher than that in men. Zhang Mingyuan also indicated that loss of spouse and lower economical status were more common in dementia patients.
It is very interesting to point out that 2 studies conducted in Shanghai showed a difference in the ratio of prevalence rates between vascular dementia and AD compared to studies carried out in Beijing (except Zhang Jinglis study): prevalence rate of VD was lower than that of AD in Shanghai, higher than that of AD in Beijing.
The largest epidemiological survey on dementia so far was just finished and data was not published yet. The study included 42890 elderly aged over 55 in 6 cities and provinces which represented the north, the south, and the west China. The overall prevalence of dementia was 2.9% in the population over 60 and 5.22% in the population over 65. The prevalence rate of AD was higher than that of VD in each subgroup (rural area vs. urban area; south vs. north China). It also indicated that the prevalence of VD in north China was higher than that in south China.
The epidemiological studies on dementia conducted in China so far have several problems: a) lack of comparability due to different diagnostic criteria and screening instruments applied; b) sample size was often too small; c) most of studies were conducted in urban areas and limited to Beijing or Shanghai.
A very important issue when we evaluate these epidemiological data on dementia should be considered: the homogeneity of subjects. Since China is a huge country, it has diverse geographic characteristics over the nation. The demographic features of Chinese including dialects, customs and diets vary a lot in different areas as well. Chinese are more heterogeneous than usually supposed. Some anthropologists even said that northern Chinese are decadents of Mongolians or Persians while southern Chinese are more like Malays physically. Hypertension is generally considered a risk factor of vascular dementia. An investigation on prevalence rate of hypertension in elderly in different places in China indicated that the incidence rate of hypertension in Beijing was the much higher than that in Shanghai. 13) Another study on incidence rate of hypertension also indicated that incidence rate of hypertension was higher in northern China. 14) (Beijing is located in northern China and Shanghai in the south). A possible explanation for these differences is that the salt intake is different between north and south: people in northern part of China usually take higher amount of salt in their diet than their southern counterparts. However, many other factors still need to be investigated. It is too difficult to answer all questions before further studies are carried out.
Mood disorders
Except for two national surveys on mental disorders that could offer some information about the prevalence of elderly depression, there are few studies about mood disorders in the elderly which can be defined as reliable and scientific. Li Shuran interviewed 1593 elderly people over 60 by Geriatric Depression Scale (GDS) and evaluated them later by Hamilton Rating Scale of Depression (HRDS).12) The prevalence of depression in this group of people was 1.57% according to ICD-10. This figure didnt remove all the questions that the overall prevalence of depression in China was lower than that in western countries, on the contrary, it raised more debate. Are there any culturally protective factors that can make Chinese immune to depression? Or are there some methodological problems that make Chinese researchers blind to depressed patients?
Some authors tried to explore the underneath reasons. Different diagnostic criteria may contribute to the discrepancy of prevalence rate of elderly depression. However, differences in understanding and operating diagnostic criteria may be more important since all studies implemented ICD-10 or DSM-IV. It was also frequently mentioned that Chinese (even all Asians) couldnt express themselves clearly when they were depressed. So called "masked depression" was said more common in Chinese. Several authors challenged this "myth" when they evaluated rating scales on depression such as "Psychogeriatric Assessment Scale (PAS)", "GDS" in Chinese subjects. Chinese did report a lot of somatic complaints but they could also describe their feelings openly. Possibly Chinese elderly are not as susceptible to depression as their western compartments. Relatively stable life pattern, supporting family, and friendly societal environment can be regarded as protective factors. It is worthwhile to initiate an epidemiological study in two sorts of populations: elderly in China and elderly in Chinese community in western countries in order to understand this issue better.
Summary: China has already stepped into an elderly society while Chinese geriatric psychiatry is still at its infancy. When we become aware of the severity of the problem we find we have to work with it everyday. Neurologists and geriatricians are very active in dealing with dementia and depression. They could be alliance but sometimes they are viewed as invaders into psychiatrists territory. Anyway, there is a long way to go for Chinese geriatric psychiatrists before they can be confident in their career.
Reference:
1. Chinese National Statistical Bureau: Statistical report on 1995 1% sampling survey of China.
2. Lu Zhishan. (1994) Current status of elderly and its development tendency in China. Chinese Journal of Geriatrics. 14, 194-8
3. 12 areas Epidemilological investigation on mental disorders coordinating group. (1986): The summary of prevalence rates of various mental disorders from 12 areas epidemiological investigation. Chinese Journal of Neurology and Psychiatry. 19, 80-2
4. Liu Zhiguang, Wu Huamin, Shen Yucun, et al. (1998): Epidemiological survey on mental disorders in elderly in 7 areas of China. Chinese Journal of Psychiatry. 31:126
5. Li Ge, Shen Yucun, Chen Changhui, et al. (1989): An epidemiological survey of age-related dementia in an urbane area of Beijing. Acta Psychiatr Scand. 79, 557-563
6. Zhang Mingyuan, Rober Katzman, William Liu, et al. (1990): Prevalence study on dementia and Alzheimers disease. Chinese Journal of Medicine. 70,424-8
7. Zhu Ziqing, Chen Jianxin, Zhang Mingyuan, et al. (1998): The 5 years longitude study of Alzheimers disease in Shanghai. Psychiatry of Shanghai. 10(Suppl),6-8
8. Wu Zhen, Meng Jiamei, Wang Moli.(1992): A epidemiological survey of dementia in the elderly in Changchun Street Areas of Beijing. Journal of Chinese Geriatric Medicine. 22, 131-3
9. Chen Changhui, Shen Yucun, Li Shuran et al. (1992): The investigation on prevalence rate of elderly dementia in urbane area of Beijing. Chinese Mental Health Journal. 6,49-52
10. Gao Zhixu, Liu Fugen, Fang Yongsheng, et al. (1993): A study of morbidity rate of senile dementia among aged in urban and rural areas. Journal of Neurology and Psychiatry of China. 26,209-211
11. Zhang Jingli, Zhang Honghong, Tao Guoshu, et al. (1998): An epidemiological study on senile dementia among 1390 elderly people in Haidian district, Beijing. Chinese Journal of Epidemiology.19, 18-20
12. Li Shuran, Chen Changhui, Zhang Weixi, et al. (1999): The prevalence of dementia and depression of the elderly in the urban community in Beijing. Chinese Mental Health Journal. 13(5), 266-268
13. Wang Wenzhi, Fang Xianghua, Wu Shengping, et al. (1996): A community-based survey on hypertension in the elderly in seven cities of China. Chinese Journal of Geriatrics. 15, 332-5
14. Wu Xigui, Wu Yangfeng, Zhou Beifan, et al. (1996): The incidence of hypertension and associated factors in 10 population groups of China. National Medical Journal of China. 76,24-9
(Edited by Shuping,Tan)
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Ministry of Health, (2003) No.013
ICP:No.040657