- Email: [email protected]
Prevalence of Dementia-Associated Disability Among Chinese Older Adults: Results from a National Sample Survey
Prevalence of Dementia-Associated Disability Among Chinese Older Adults: Results from a National Sample Survey Ning Li, Ph.D., Lei Zhang, Ph.D., Wei Du, Ph.D., Lihua Pang, Ph.D., Chao Guo, M.B.B.S., Gong Chen, Ph.D., Xiaoying Zheng, Ph.D.
Objective: Due to rapid population aging and a tidal wave of dementia, dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China and little was known about the magnitude of dysfunction and disability caused by dementia. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults. Methods: We used the second China National Sample Survey on Disability, comprising 2,526,145 persons from 771,797 households. Identification for dementia was based on consensus manuals. Standard weighting procedures were used to construct sample weights considering the multistage stratified cluster sampling survey scheme. Population weighted numbers, weighted prevalence, and the odd ratios (ORs) were calculated. Results: The prevalence rate of dementia-associated disability was 4.64% (95% CI: 4.26e5.01) and it accounted for 41.03% of mental disability among Chinese older adults. Urban residence (OR: 1.33 [1.12e1.57]), older age (80þ years) (OR: 4.12 [3.38e.03]), illiteracy (OR: 1.79 [1.27e2.53]), and currently not married (OR: 1.15 [1.00e1.32]) were associated with increased risk of dementia-associated disability. Compared with those with mental disability of other causes and those with other types of disabilities, older adults with dementia-asscoiated disability were more likely to have severe or extreme difficulty in daily activities and social functions. Conclusion: Countermeasures are warranted to obtain a more precise overview of dementia in China, and strategies on enhancing early identification, treatment, and rehabilitation should be developed for people with dementia. (Am J Geriatr Psychiatry 2015; 23:320e325) Key Words: Dementia, disability, Chinese population, older adults
D
ementia, as one of the most common diseases in the older adults,1 affects more than 24.3 million people in the world—and this number will double by
2040.2 The prevalence rates of dementia range from 2.8% to 63.0% in difference regions of the world.3 The prevalence rates are higher among developed
Received March 4, 2014; revised June 3, 2014; accepted June 4, 2014. From the Institute of Population Research, Peking University, China. Send correspondence and reprint requests to Xiaoying Zheng, Ph.D., Institute of Population Research/WHO Collaborating Center on Reproductive Health and Population Science, Peking University, Beijing 100871, China. e-mail: [email protected] Ning Li and Lei Zhang made equal contributions to this paper. Ó 2015 American Association for Geriatric Psychiatry http://dx.doi.org/10.1016/j.jagp.2014.06.002
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Li et al. regions, but the developing regions have the largest number of people with dementia.2 In 2001, more than 60% of demented people lived in developing countries and this number will rise to 71.2% in 2040.2 There are approximately 6 million people with dementia in developing countries of the west-Pacific region, and these developing countries will experience a rapid growth of dementia (314%e336%) in the next 20 years.2 Dementia results in the loss of cognitive function and is a leading cause of disability among older adults of all races and regions.4 Dementia has become the most important independent contributor to disability for older adults in low- and middle-income countries.5 Dementia contributed 11.2% of years lived with disability in people aged 60 years and older.6 It was estimated that the global societal cost of dementia was US$ 422 million in 2009.7 Dementia brings a huge burden on individuals, families, and societies, and has been established as a major challenge worldwide.8 In China, approximately 5 million people have dementia.2 Prevalence rates of dementia in Chinese older adults range from 1.37% to 8.19%,2,9e15 and there has been a significant increase in the prevalence of dementia since 1980s.9 More women are affected by dementia than men,10,13,14 more rural elders have dementia than their urban counterparts,16 and the prevalence of dementia is higher among the oldest old.15 Due to rapid population aging in China17 and the increase of dementia in developing countries worldwide,5,18 dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China, however, and the current literature lacks findings based on national data. Additionally, little is known about the magnitude of dysfunction and disability caused by dementia in China. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults.
Survey on Disability (CNSSD). This survey was conducted from April 1 to May 31, 2006. The survey used a stratified, multiphased, and cluster probability sampling. A total of 734 counties (cities or districts), 2,980 towns (townships or streets), and 5,964 communities were selected from 31 provinces, autonomous regions, and municipalities directly under the Central Government in China. The target population of the survey was the non-institutionalized community population, and 2,526,145 persons in 771,797 households were investigated. In this study, information of respondents aged 65 years and older was used. Details of the survey sampling procedures have been described elsewhere.19 Interviewers and Interviewing Procedures
METHODS
Initially, pre-survey investigation was conducted to determine the number of households, population, and suspected disabled people in the sampling community. After that, face-to-face interviews were conducted to collect information from every family member in the selected households. The CNSSD survey focused on disability and its aim was to describe the prevalence of disability, its associated factors, and the characteristics of people with disabilities in China. Therefore, participants were first screened for disabilities, and those suspected to be disabled were then examined and diagnosed by doctors. People with disability caused by dementia were our study subjects in this article (i.e., dementia-associated disability). Approximately 50,000 survey assistants who conducted pre-survey investigation, 20,000 interviewers who conducted the screen scale, as well as 6,000 doctors of various specialties who made the diagnosis of disabilities and their causes participated in the CNSSD survey. During the survey, the diagnosis of disabilities and their causes, treatment, and rehabilitation suggestions, as well as the information of local hospitals and other health facilities, were provided to people diagnosed as disabled. This survey was approved by the State Council of China, and all respondents gave consent to receive the interview and clinical examination.
Sample
Measures
Data for this study are derived from a national sample survey, the second China National Sample
Demographic information such as age, sex, residence location, education level, marital status, and
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Dementia-Associated Disability Among Chinese Elderly family annual income were collected. The definition and classification of disability followed the WHO International Classification of Functioning, Disability, and Health.20 In the CNSSD survey, people with mental disability were defined as those who had mental disorders lasting more than one year; which manifested in cognitive, affective, and behavior disorders; and limited and restricted the patients’ daily life and social function.20 Dementia as well as other mental disorders were diagnosed according to the International Statistical Classification of Diseases, 10th Revision.21 Mental disability was classified into four degrees (mild, moderate, severe, and extremely severe) using WHO-DAS II,22 and the six domains (cognition, mobility, self-care, getting along, life activities, and participation) of function in WHO-DAS II were assessed as none, mild, moderate, severe, or extreme difficulty. Data Analysis Allowing for the complex sampling design, we used standard weighting procedures calculating the inverse probability of inclusion for an individual survey respondent in the multistage sampling frame.23 Descriptive statistics were used to present the population-weighted numbers and prevalence rates of dementia-associated disability by various demographic characteristics. Multivariable logistic regression models were used to calculate the adjusted odd ratios (ORs) and 95% confidence interval (CI). The Taylor series linearization method was used to estimate variance and its corresponding 95% CI.24 We used the c2 test to examine the difference on proportions of people with severe or extreme difficulty in daily activities and social functions among people with dementia-associated disability, people with mental disability of other causes, and people with other disabilities. The procedures SURVEYFREQ and SURVEYLOGISTIC of the SAS 9.1 package were used to perform the data analyses.25 We set p values less than 0.05 as statistically significant.
RESULTS
TABLE 1. Prevalence of Dementia-Associated Disability in Chinese Older Adults of the 2006 China National Sample Survey on Disability (CNSSD) Weighted Number Number (N) Sex Male Female Residence location Rural Urban Age range, years 65e69 70e74 75e79 80þ Education level Illiterate Elementary school Junior high school Senior high school and above Marital status Currently not married Currently married Annual family income per capita Higher than national average Equal to or lower than national average Region East Middle West
Weighted Prevalence Rate (%)
466 742
225,943 376,792
3.67 (3.26e4.07) 5.51 (4.97e6.05)
709 499
399,124 203,610
4.45 (3.98e4.92) 5.05 (4.44e5.67)
207 261 299 441
105,293 128,010 145,666 223,765
2.28 3.32 5.80 11.10
(1.92e2.64) (2.84e3.79) (4.99e6.61) (9.72e12.48)
771 291 81 65
403,210 140,155 35,354 24,015
5.81 3.47 3.19 2.63
(5.25e6.37) (2.98e3.96) (2.39e3.98) (1.85e3.41)
633 575
329,568 273,166
6.46 (5.82e7.11) 3.46 (3.09e3.82)
238
101,123
4.54 (3.80e5.29)
970
501,611
4.66 (4.25e5.07)
751 184 273
347,086 111,881 143,767
6.38 (5.73e7.04) 2.77 (2.27e3.26) 4.09 (3.34e4.84)
(weighted 130,033,417) were older adults aged 65 years and older. There were 1,208 (weighted 602,734) people with dementia-associated disability and the prevalence rate was 4.64% (95% CI: 4.26e5.01). Dementia-associated disability accounted for 41.03% of mental disability among Chinese older adults (2,846; weighted 1,468,917). As shown in Table 1, prevalence rate of dementia was higher among women (c2 ¼ 46.03, df ¼ 1, p <0.001), oldest old (c2 ¼ 501.37, df ¼ 3, p <0.001), illiterate population (c2 ¼ 88.02, df ¼ 3, p <0.001), people currently not married (c2 ¼ 117.16, df ¼ 1, p <0.001), and people in eastern China (c2 ¼ 132.80, df ¼ 2, p <0.001).
Prevalence Rate of Dementia-Associated Disability
Factors Associated with Dementia-Associated Disability
The total survey population was 2,526,145 (weighted 1,309,468,507) persons and 250,752
We used a multivariable logistic regression model to investigate factors associated with dementia-associated
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TABLE 2. Odds Ratios and 95% Confidence Intervals for Factors Associated with Dementia-Associated Disability in Chinese Older adults of the 2006 China National Sample Survey on Disability (CNSSD) OR (95% CI) Sex Male Female Residence location Rural Urban Age range, years 65e69 70e74 75e79 80þ Education level Senior high school and above Junior high school Elementary school Illiterate Marital status Currently married Currently not married Annual family income per capita Higher than national average Equal to or lower than national average a
pa 0.06
1 1.16 (0.99e1.34) 0.001 1 1.33 (1.12e1.57) <0.001 1 1.37 (1.12e1.67) 2.28 (1.89e2.76) 4.12 (3.38e5.03) <0.001 1 1.30 (0.89e1.91) 1.39 (0.98e1.96) 1.79 (1.27e2.53) 0.04 1 1.15 (1.00e1.32) 0.35 1 0.92 (0.77e1.10)
Wald c2 tests, df ¼ 1.
disability in Chinese older adults. Sex, residence location, age range, education level, marital status, and annual family income per capita were used as predictor variables. Urban residence (OR: 1.33 [1.12e1.57]), older age (80þ) (OR: 4.12 [3.38e5.03]), illiteracy (OR: 1.79 [1.27e2.53]), and currently not married (OR: 1.15 [1.00e1.32]) were associated with increased risk of dementia-associated disability (Table 2).
Daily Activities and Social Functions of Chinese Older Adults with Dementia-Associated Disability Compared with older adults with nonedementiaassociated disabilities, older adults with dementiaassociated disability were more likely to have severe or extreme difficulty in understanding and communicating (c2 ¼ 5234.12, df ¼ 2, p <0.001), physical movement (c2 ¼ 698.09, df ¼ 2, p <0.001), self-care (c2 ¼ 1183.77, df ¼ 2, p <0.001), getting along with people (c2 ¼ 6613.94, df ¼ 2, p <0.001), life activities (c2 ¼ 1626.27, df ¼ 2, p <0.001), and participation in society (c2 ¼ 1038.74, df ¼ 2, p <0.001) (Table 3).
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DISCUSSION This study revealed a prevalence rate of 4.64% for dementia-associated disability in Chinese older adults. The prevalence rate was much lower than the estimated rates of dementia in other countries3 as well as the estimates of studies conducted in China.2,9,13 The low prevalence rate reported in this study could be mainly attributed to the method of case ascertainment in the survey—that is, all the survey participants were first screened for disability and only those suspected of being disabled were examined and diagnosed for dementia. Thus, subjects who had dementia but didn’t meet the diagnosis of disability were not identified. In accordance with previous studies,1,5,26,27 we found that lower educational attainment had a mild effect on higher prevalence of dementia-associated disability. This relationship might be explained by other factors like childhood deleterious socioeconomic or environmental influences28 and the compensatory strategies that delay detection of the disease.29 This cross-sectional study did not reveal the causal relationship between education and dementia, however, and further studies are still needed. This study also revealed that older age was a strong predictor for higher prevalence of dementia-associated disability, which was similar to many studies.15,30,31 Though more women were affected by dementia than men, there was no significant statistical difference. Our findings differ from some previous findings32,33 in that urban residents were more likely to have dementia-associated disability than their rural counterparts in China. This finding may be attributable to differences in diagnoses—that is, dementia and dementia-associated disability may have different prevalent patterns in rural and urban populations. It is also possible that the prevalence of disability caused by different dementia subtypes may vary in rural and urban areas. Some studies reported different prevalence rates and prevalent patterns of Alzheimer disease and vascular dementia in rural and urban area in China.32,34 Diagnoses of dementia subtypes were not collected in the survey, however, and this study failed to further analyze the prevalence of different dementia subtypes. Another explanation could be that doctors in
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Dementia-Associated Disability Among Chinese Elderly
TABLE 3. Weighted Numbers and Proportions of People with Severe or Extreme Difficulty in Daily Activities and Social Functions in Chinese Older Adults of the 2006 China National Sample Survey on Disability (CNSSD) Daily Activities and Social Functions Understanding and communicating Physical movement Self-care Getting along with people Life activities Participation in society a
People with Dementia-Associated Disabilitya (Weighted Numbers and Proportions) 379,311 208,227 259,460 350,660 451,846 311,678
(62.93) (34.55) (43.05) (58.18) (74.97) (51.71)
People with Mental Disability of Other Causes 303,765 96,803 131,391 367,531 508,327 354,810
(35.07) (11.18) (15.17) (42.43) (58.69) (40.96)
People with Other Disabilities 2,839,678 3,765,870 3,961,501 2,406,852 11,068,666 7,473,029
(7.72) (10.24) (10.77) (6.54) (30.08) (20.31)
pb <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
People with multiple disabilities were not included in any group. Wald c2 tests, df ¼ 2.
b
urban China were more sophisticated and skilled than those in rural area, thus more people with dementia-associated disability were identified in urban areas than in rural areas. This study revealed that people with disabilities caused by dementia were more likely to have difficulties in daily activities and social functions than either those with mental disability of other causes and those with other disabilities. The results were similar to findings from previous studies that dementia was the major cause of functional dependence and decline in function among older adults35,36 and that dementia is an important predictor of functional disability.37,38 This probably is due to the fact that dementia not only impaired the patients’ cognitive function,1 but also affected their physical abilities.39,40 This study has several limitations. First of all, as we mentioned earlier, further diagnoses of dementia subtypes were not collected in the survey—this impedes further analyses for different subtypes of dementia. Secondly, the study findings may only represent the small number of people with dementiaassociated disability, and many demented patients without disabilities may not have been identified in the survey. Therefore, the current results may underestimate the overall population health burden of dementia and findings should be interpreted with caution. In conclusion, more than 60,000 older adults with dementia-associated disability were identified in this study and the demented population in Chinese older adults was underestimated. This study does provide a snapshot of Chinese older adults with
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dementia-associated disability, however, and the figure presented here is only a small proportion of people suffering from dementia in China. Considering the fast growing numbers of older adults17 and the increase of dementia in China,5,18 dementia will bring a heavy burden to the Chinese health system as well as the social security system in the next few decades. Countermeasures are warranted to help control the impact of dementia on Chinese society. First of all, more studies are needed to obtain a precise overview of dementia in China, and to reveal the prevalence rate of dementia, its social and economic burden, as well as its associated factors in China. Secondly, intervention programs aimed at early identification and treatment for dementia should be developed. Thirdly, as this study showed that people with dementia-associated disability suffered from severe impairment in daily activities and social functions, rehabilitation and care for demented people in senior homes and communities should be enhanced and training programs to cultivate more professional caregivers are essential. This study was supported by the State Key Development Program of Basic Research of China (973No. 2007CB511901), Yang Zi Program of MOE, State Key Funds of Social Science Project (Research on Disability Prevention Measurement in China, No. 09&ZD072), and the National Department Public Benefit Research Foundation by Ministry of Health P. R. China (No. 201302008). The authors have no conflicts of interest to report.
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Li et al. References 1. Ritchie K, Lovestone S: The dementias. Lancet 2002; 360: 1759e1766 2. Ferri CP, Prince M, Brayne C, et al: Global prevalence of dementia: a Delphi consensus study. Lancet 2005; 366:2112e2117 3. Mukadam N, Sampson EL: A systematic review of the prevalence, associations and outcomes of dementia in older general hospital inpatients. Int Psychogeriatr 2011; 23:344e355 4. Fratiglioni L, De Ronchi D, Agüero-Torres H: Worldwide prevalence and incidence of dementia. Drugs Aging 1999; 15: 365e375 5. Sousa RM, Ferri CP, Acosta D, et al: Contribution of chronic diseases to disability in elderly people in countries with low and middle incomes: a 10/66 Dementia Research Group populationbased survey. Lancet 2009; 374:1821e1830 6. WHO: World Health Report 2003—shaping the future. Geneva, World Health Organization, 2003 7. Wimo A, Winblad B, Jönsson L: The worldwide societal costs of dementia: Estimates for 2009. Alz Dement 2010; 6:98e103 8. Berr C, Wancata J, Ritchie K: Prevalence of dementia in the elderly in Europe. Eur Neuropsychopharmacol 2005; 15:463e471 9. Dong M, Peng B, Lin X, et al: The prevalence of dementia in the People’s Republic of China: a systematic analysis of 1980e2004 studies. Age Aging 2007; 36; 619e624 10. Li S, Yan F, Li G, et al: Is the dementia rate increasing in Beijing? Prevalence and incidence of dementia 10 years later in an urban elderly population. Acta Psychiatr Scand 2007; 115:73e79 11. Tang M, Ma C, Huang X, et al: The prevalence of dementia in urban and rural areas in Guangzhou [in Chinese]. Chinese Journal of Nervous and Mental Diseases 2007; 33:340e344 12. Tang Z, Meng C, Chen B: Epidemiology of dementia in Beijing [in Chinese]. Chinese Journal of Epidemiology 2003; 24:734e761 13. Zhang Z, Zahner G, Roman G, et al: Dementia subtypes in China: prevalence in Beijing, Xian, Shanghai, and Chengdu. Arch Neurol 2005; 62:447e453 14. Zhou B, Hong Z, Zeng J, et al: Comparison of the features between Alzheimer’s disease and vascular dementia [in Chinese]. Chinese Journal of Clinical Neurosciences 2002; 10:13e15 15. Zhou D, Wu C, Qi H, et al: Prevalence of dementia in rural China: impact of age, gender and education. Acta Neurol Scand 2006; 114:273e280 16. Chen R, Ma Y, Wilson K, et al: A multicentre community-based study of dementia cases and subcases in older people in China—the GMS-AGECAT prevalence and socio-economic correlates. Int J Geriatr Psychiatry 2011; 27:692e702 17. Flaherty JH, Liu ML, Ding L, et al: China: the aging giant. J Am Geriatr Soc 2007; 55:1295e1300 18. Sabat SR: Dementia in developing countries: a tidal wave on the horizon. Lancet 2009; 374:1805e1806 19. Zheng X, Chen G, Song X, et al: Twenty-year trends in the prevalence of disability in China. WHO Bulletin 20011; 89: 788e797 20. WHO: International Classification of Functioning, Disability, and Health (ICF). Geneva, World Health Organization, 2001 21. WHO: The ICD-10 Classification of Mental and Behavioral Disorders: Diagnostic Criteria for Research. Geneva, World Health Organization, 1993
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22. WHO: The World Health Organization Disability Assessment Schedule Phase II Field Trial Instrument. Geneva, World Health Organization, 1999 23. Lohr S: Sampling: design and analysis. Pacific Grove, CA, Duxbury Press, 1999 24. Korn E, Graubard B: Analysis of Health Surveys. New York, Wiley, 1999 25. SAS Institute Inc: Statistical Analysis Software (SAS) Version 9.1. Cary, NC, SAS Institute Inc, 2002 26. Karp A, Kareholt I, Qiu C, et al: Relation of education and occupationebased socioeconomic status to incident Alzheimer’s disease. Am J Epidemiol 2004; 159:175e183 27. De Ronchi D, Berardi D, Menchetti M, et al: Occurrence of cognitive impairment and dementia after the age of 60: a population-based study from Northern Italy. Dement Geriatr Cogn Disord 2005; 19:97e105 28. Hall KS, Gao S, Unverzagt FW, et al: Low education and childhood rural residence: risk for Alzheimer’s disease in African Americans. Neurology 2000; 54:95e99 29. Stern Y, Alexander GE, Prohovnik I, et al: Inverse relationship between education and parietotemporal perfusion deficit in Alzheimer’s disease. Ann Neurol 1992; 32:371e375 30. Yamada T, Hattori H, Miura A, et al: Prevalence of Alzheimer’s disease, vascular dementia and dementia with Lewy bodies in a Japanese population. Psychiatry Clin Neurosci 2001; 55:21e25 31. Qiu C, De Ronchi D, Fratiglioni L: The epidemiology of the dementias: an update. Curr Opin Psychiatry 2007; 20:380e385 32. Ma C, Tang M, Guo Y, et al: The prevalence of dementia in the urban and rural aged in Guangzhou [in Chinese]. Chinese Journal of Psychiatry 2005; 38:227e230 33. Zhang Z, Wei J, Hong X, et al: Prevalence of dementia and major subtypes in urban and rural communities of Beijing [in Chinese]. Chinese Journal of Neurology 2001; 34:199e203 34. Zhou B, Hong Z, Huang M, et al: Prevalence of dementia in Shanghai urban and rural area [in Chinese]. Chinese Journal of Epidemiology 2001; 22:368e371 35. Agüero-Torres H, Fratiglioni L, Guo Z, et al: Dementia is the major cause of functional dependence in the elderly: 3-year follow-up data from a population-based study. Am J Public Health 1998; 88:1452e1456 36. Agüero-Torres H, von Strauss E, Viitanen M, et al: Institutionalization in the elderly: the role of chronic diseases and dementia. Cross-sectional and longitudinal data from a population-based study. J Clin Epidemiol 2001; 54:795e801 37. McGuire LC, Ford ES, Ajani UA: Cognitive function as a predictor of functional disability in later life. Am J Geriatr Psychiatry 2006; 14:36e42 38. Sauvaget C, Yamada M, Fujiwara S, et al: Dementia as a predictor of functional disability: a four-year follow-up study. Gerontology 2002; 48:226e233 39. Desai AK, Grossberg GT, Sheth DN: Activities of daily living in patients with dementia: clinical relevance, methods of assessment and effects of treatment. CNS Drugs 2004; 18:853e875 40. Suh GH, Ju YS, Yeon BK, et al: A longitudinal study of Alzheimer’s disease: rates of cognitive and functional decline. Int J Geriatr Psychiatry 2004; 19:817e824
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Objective: Due to rapid population aging and a tidal wave of dementia, dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China and little was known about the magnitude of dysfunction and disability caused by dementia. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults. Methods: We used the second China National Sample Survey on Disability, comprising 2,526,145 persons from 771,797 households. Identification for dementia was based on consensus manuals. Standard weighting procedures were used to construct sample weights considering the multistage stratified cluster sampling survey scheme. Population weighted numbers, weighted prevalence, and the odd ratios (ORs) were calculated. Results: The prevalence rate of dementia-associated disability was 4.64% (95% CI: 4.26e5.01) and it accounted for 41.03% of mental disability among Chinese older adults. Urban residence (OR: 1.33 [1.12e1.57]), older age (80þ years) (OR: 4.12 [3.38e.03]), illiteracy (OR: 1.79 [1.27e2.53]), and currently not married (OR: 1.15 [1.00e1.32]) were associated with increased risk of dementia-associated disability. Compared with those with mental disability of other causes and those with other types of disabilities, older adults with dementia-asscoiated disability were more likely to have severe or extreme difficulty in daily activities and social functions. Conclusion: Countermeasures are warranted to obtain a more precise overview of dementia in China, and strategies on enhancing early identification, treatment, and rehabilitation should be developed for people with dementia. (Am J Geriatr Psychiatry 2015; 23:320e325) Key Words: Dementia, disability, Chinese population, older adults
D
ementia, as one of the most common diseases in the older adults,1 affects more than 24.3 million people in the world—and this number will double by
2040.2 The prevalence rates of dementia range from 2.8% to 63.0% in difference regions of the world.3 The prevalence rates are higher among developed
Received March 4, 2014; revised June 3, 2014; accepted June 4, 2014. From the Institute of Population Research, Peking University, China. Send correspondence and reprint requests to Xiaoying Zheng, Ph.D., Institute of Population Research/WHO Collaborating Center on Reproductive Health and Population Science, Peking University, Beijing 100871, China. e-mail: [email protected] Ning Li and Lei Zhang made equal contributions to this paper. Ó 2015 American Association for Geriatric Psychiatry http://dx.doi.org/10.1016/j.jagp.2014.06.002
320
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Li et al. regions, but the developing regions have the largest number of people with dementia.2 In 2001, more than 60% of demented people lived in developing countries and this number will rise to 71.2% in 2040.2 There are approximately 6 million people with dementia in developing countries of the west-Pacific region, and these developing countries will experience a rapid growth of dementia (314%e336%) in the next 20 years.2 Dementia results in the loss of cognitive function and is a leading cause of disability among older adults of all races and regions.4 Dementia has become the most important independent contributor to disability for older adults in low- and middle-income countries.5 Dementia contributed 11.2% of years lived with disability in people aged 60 years and older.6 It was estimated that the global societal cost of dementia was US$ 422 million in 2009.7 Dementia brings a huge burden on individuals, families, and societies, and has been established as a major challenge worldwide.8 In China, approximately 5 million people have dementia.2 Prevalence rates of dementia in Chinese older adults range from 1.37% to 8.19%,2,9e15 and there has been a significant increase in the prevalence of dementia since 1980s.9 More women are affected by dementia than men,10,13,14 more rural elders have dementia than their urban counterparts,16 and the prevalence of dementia is higher among the oldest old.15 Due to rapid population aging in China17 and the increase of dementia in developing countries worldwide,5,18 dementia has become an urgent public health issue in China. Few large-scale surveys on dementia have been conducted in China, however, and the current literature lacks findings based on national data. Additionally, little is known about the magnitude of dysfunction and disability caused by dementia in China. In this study, using national sample survey data, we aimed to describe the prevalence rate of dementia-associated disability, its associated factors, and daily activities and social functions of people with dementia-associated disability in Chinese older adults.
Survey on Disability (CNSSD). This survey was conducted from April 1 to May 31, 2006. The survey used a stratified, multiphased, and cluster probability sampling. A total of 734 counties (cities or districts), 2,980 towns (townships or streets), and 5,964 communities were selected from 31 provinces, autonomous regions, and municipalities directly under the Central Government in China. The target population of the survey was the non-institutionalized community population, and 2,526,145 persons in 771,797 households were investigated. In this study, information of respondents aged 65 years and older was used. Details of the survey sampling procedures have been described elsewhere.19 Interviewers and Interviewing Procedures
METHODS
Initially, pre-survey investigation was conducted to determine the number of households, population, and suspected disabled people in the sampling community. After that, face-to-face interviews were conducted to collect information from every family member in the selected households. The CNSSD survey focused on disability and its aim was to describe the prevalence of disability, its associated factors, and the characteristics of people with disabilities in China. Therefore, participants were first screened for disabilities, and those suspected to be disabled were then examined and diagnosed by doctors. People with disability caused by dementia were our study subjects in this article (i.e., dementia-associated disability). Approximately 50,000 survey assistants who conducted pre-survey investigation, 20,000 interviewers who conducted the screen scale, as well as 6,000 doctors of various specialties who made the diagnosis of disabilities and their causes participated in the CNSSD survey. During the survey, the diagnosis of disabilities and their causes, treatment, and rehabilitation suggestions, as well as the information of local hospitals and other health facilities, were provided to people diagnosed as disabled. This survey was approved by the State Council of China, and all respondents gave consent to receive the interview and clinical examination.
Sample
Measures
Data for this study are derived from a national sample survey, the second China National Sample
Demographic information such as age, sex, residence location, education level, marital status, and
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Dementia-Associated Disability Among Chinese Elderly family annual income were collected. The definition and classification of disability followed the WHO International Classification of Functioning, Disability, and Health.20 In the CNSSD survey, people with mental disability were defined as those who had mental disorders lasting more than one year; which manifested in cognitive, affective, and behavior disorders; and limited and restricted the patients’ daily life and social function.20 Dementia as well as other mental disorders were diagnosed according to the International Statistical Classification of Diseases, 10th Revision.21 Mental disability was classified into four degrees (mild, moderate, severe, and extremely severe) using WHO-DAS II,22 and the six domains (cognition, mobility, self-care, getting along, life activities, and participation) of function in WHO-DAS II were assessed as none, mild, moderate, severe, or extreme difficulty. Data Analysis Allowing for the complex sampling design, we used standard weighting procedures calculating the inverse probability of inclusion for an individual survey respondent in the multistage sampling frame.23 Descriptive statistics were used to present the population-weighted numbers and prevalence rates of dementia-associated disability by various demographic characteristics. Multivariable logistic regression models were used to calculate the adjusted odd ratios (ORs) and 95% confidence interval (CI). The Taylor series linearization method was used to estimate variance and its corresponding 95% CI.24 We used the c2 test to examine the difference on proportions of people with severe or extreme difficulty in daily activities and social functions among people with dementia-associated disability, people with mental disability of other causes, and people with other disabilities. The procedures SURVEYFREQ and SURVEYLOGISTIC of the SAS 9.1 package were used to perform the data analyses.25 We set p values less than 0.05 as statistically significant.
RESULTS
TABLE 1. Prevalence of Dementia-Associated Disability in Chinese Older Adults of the 2006 China National Sample Survey on Disability (CNSSD) Weighted Number Number (N) Sex Male Female Residence location Rural Urban Age range, years 65e69 70e74 75e79 80þ Education level Illiterate Elementary school Junior high school Senior high school and above Marital status Currently not married Currently married Annual family income per capita Higher than national average Equal to or lower than national average Region East Middle West
Weighted Prevalence Rate (%)
466 742
225,943 376,792
3.67 (3.26e4.07) 5.51 (4.97e6.05)
709 499
399,124 203,610
4.45 (3.98e4.92) 5.05 (4.44e5.67)
207 261 299 441
105,293 128,010 145,666 223,765
2.28 3.32 5.80 11.10
(1.92e2.64) (2.84e3.79) (4.99e6.61) (9.72e12.48)
771 291 81 65
403,210 140,155 35,354 24,015
5.81 3.47 3.19 2.63
(5.25e6.37) (2.98e3.96) (2.39e3.98) (1.85e3.41)
633 575
329,568 273,166
6.46 (5.82e7.11) 3.46 (3.09e3.82)
238
101,123
4.54 (3.80e5.29)
970
501,611
4.66 (4.25e5.07)
751 184 273
347,086 111,881 143,767
6.38 (5.73e7.04) 2.77 (2.27e3.26) 4.09 (3.34e4.84)
(weighted 130,033,417) were older adults aged 65 years and older. There were 1,208 (weighted 602,734) people with dementia-associated disability and the prevalence rate was 4.64% (95% CI: 4.26e5.01). Dementia-associated disability accounted for 41.03% of mental disability among Chinese older adults (2,846; weighted 1,468,917). As shown in Table 1, prevalence rate of dementia was higher among women (c2 ¼ 46.03, df ¼ 1, p <0.001), oldest old (c2 ¼ 501.37, df ¼ 3, p <0.001), illiterate population (c2 ¼ 88.02, df ¼ 3, p <0.001), people currently not married (c2 ¼ 117.16, df ¼ 1, p <0.001), and people in eastern China (c2 ¼ 132.80, df ¼ 2, p <0.001).
Prevalence Rate of Dementia-Associated Disability
Factors Associated with Dementia-Associated Disability
The total survey population was 2,526,145 (weighted 1,309,468,507) persons and 250,752
We used a multivariable logistic regression model to investigate factors associated with dementia-associated
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TABLE 2. Odds Ratios and 95% Confidence Intervals for Factors Associated with Dementia-Associated Disability in Chinese Older adults of the 2006 China National Sample Survey on Disability (CNSSD) OR (95% CI) Sex Male Female Residence location Rural Urban Age range, years 65e69 70e74 75e79 80þ Education level Senior high school and above Junior high school Elementary school Illiterate Marital status Currently married Currently not married Annual family income per capita Higher than national average Equal to or lower than national average a
pa 0.06
1 1.16 (0.99e1.34) 0.001 1 1.33 (1.12e1.57) <0.001 1 1.37 (1.12e1.67) 2.28 (1.89e2.76) 4.12 (3.38e5.03) <0.001 1 1.30 (0.89e1.91) 1.39 (0.98e1.96) 1.79 (1.27e2.53) 0.04 1 1.15 (1.00e1.32) 0.35 1 0.92 (0.77e1.10)
Wald c2 tests, df ¼ 1.
disability in Chinese older adults. Sex, residence location, age range, education level, marital status, and annual family income per capita were used as predictor variables. Urban residence (OR: 1.33 [1.12e1.57]), older age (80þ) (OR: 4.12 [3.38e5.03]), illiteracy (OR: 1.79 [1.27e2.53]), and currently not married (OR: 1.15 [1.00e1.32]) were associated with increased risk of dementia-associated disability (Table 2).
Daily Activities and Social Functions of Chinese Older Adults with Dementia-Associated Disability Compared with older adults with nonedementiaassociated disabilities, older adults with dementiaassociated disability were more likely to have severe or extreme difficulty in understanding and communicating (c2 ¼ 5234.12, df ¼ 2, p <0.001), physical movement (c2 ¼ 698.09, df ¼ 2, p <0.001), self-care (c2 ¼ 1183.77, df ¼ 2, p <0.001), getting along with people (c2 ¼ 6613.94, df ¼ 2, p <0.001), life activities (c2 ¼ 1626.27, df ¼ 2, p <0.001), and participation in society (c2 ¼ 1038.74, df ¼ 2, p <0.001) (Table 3).
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DISCUSSION This study revealed a prevalence rate of 4.64% for dementia-associated disability in Chinese older adults. The prevalence rate was much lower than the estimated rates of dementia in other countries3 as well as the estimates of studies conducted in China.2,9,13 The low prevalence rate reported in this study could be mainly attributed to the method of case ascertainment in the survey—that is, all the survey participants were first screened for disability and only those suspected of being disabled were examined and diagnosed for dementia. Thus, subjects who had dementia but didn’t meet the diagnosis of disability were not identified. In accordance with previous studies,1,5,26,27 we found that lower educational attainment had a mild effect on higher prevalence of dementia-associated disability. This relationship might be explained by other factors like childhood deleterious socioeconomic or environmental influences28 and the compensatory strategies that delay detection of the disease.29 This cross-sectional study did not reveal the causal relationship between education and dementia, however, and further studies are still needed. This study also revealed that older age was a strong predictor for higher prevalence of dementia-associated disability, which was similar to many studies.15,30,31 Though more women were affected by dementia than men, there was no significant statistical difference. Our findings differ from some previous findings32,33 in that urban residents were more likely to have dementia-associated disability than their rural counterparts in China. This finding may be attributable to differences in diagnoses—that is, dementia and dementia-associated disability may have different prevalent patterns in rural and urban populations. It is also possible that the prevalence of disability caused by different dementia subtypes may vary in rural and urban areas. Some studies reported different prevalence rates and prevalent patterns of Alzheimer disease and vascular dementia in rural and urban area in China.32,34 Diagnoses of dementia subtypes were not collected in the survey, however, and this study failed to further analyze the prevalence of different dementia subtypes. Another explanation could be that doctors in
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Dementia-Associated Disability Among Chinese Elderly
TABLE 3. Weighted Numbers and Proportions of People with Severe or Extreme Difficulty in Daily Activities and Social Functions in Chinese Older Adults of the 2006 China National Sample Survey on Disability (CNSSD) Daily Activities and Social Functions Understanding and communicating Physical movement Self-care Getting along with people Life activities Participation in society a
People with Dementia-Associated Disabilitya (Weighted Numbers and Proportions) 379,311 208,227 259,460 350,660 451,846 311,678
(62.93) (34.55) (43.05) (58.18) (74.97) (51.71)
People with Mental Disability of Other Causes 303,765 96,803 131,391 367,531 508,327 354,810
(35.07) (11.18) (15.17) (42.43) (58.69) (40.96)
People with Other Disabilities 2,839,678 3,765,870 3,961,501 2,406,852 11,068,666 7,473,029
(7.72) (10.24) (10.77) (6.54) (30.08) (20.31)
pb <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
People with multiple disabilities were not included in any group. Wald c2 tests, df ¼ 2.
b
urban China were more sophisticated and skilled than those in rural area, thus more people with dementia-associated disability were identified in urban areas than in rural areas. This study revealed that people with disabilities caused by dementia were more likely to have difficulties in daily activities and social functions than either those with mental disability of other causes and those with other disabilities. The results were similar to findings from previous studies that dementia was the major cause of functional dependence and decline in function among older adults35,36 and that dementia is an important predictor of functional disability.37,38 This probably is due to the fact that dementia not only impaired the patients’ cognitive function,1 but also affected their physical abilities.39,40 This study has several limitations. First of all, as we mentioned earlier, further diagnoses of dementia subtypes were not collected in the survey—this impedes further analyses for different subtypes of dementia. Secondly, the study findings may only represent the small number of people with dementiaassociated disability, and many demented patients without disabilities may not have been identified in the survey. Therefore, the current results may underestimate the overall population health burden of dementia and findings should be interpreted with caution. In conclusion, more than 60,000 older adults with dementia-associated disability were identified in this study and the demented population in Chinese older adults was underestimated. This study does provide a snapshot of Chinese older adults with
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dementia-associated disability, however, and the figure presented here is only a small proportion of people suffering from dementia in China. Considering the fast growing numbers of older adults17 and the increase of dementia in China,5,18 dementia will bring a heavy burden to the Chinese health system as well as the social security system in the next few decades. Countermeasures are warranted to help control the impact of dementia on Chinese society. First of all, more studies are needed to obtain a precise overview of dementia in China, and to reveal the prevalence rate of dementia, its social and economic burden, as well as its associated factors in China. Secondly, intervention programs aimed at early identification and treatment for dementia should be developed. Thirdly, as this study showed that people with dementia-associated disability suffered from severe impairment in daily activities and social functions, rehabilitation and care for demented people in senior homes and communities should be enhanced and training programs to cultivate more professional caregivers are essential. This study was supported by the State Key Development Program of Basic Research of China (973No. 2007CB511901), Yang Zi Program of MOE, State Key Funds of Social Science Project (Research on Disability Prevention Measurement in China, No. 09&ZD072), and the National Department Public Benefit Research Foundation by Ministry of Health P. R. China (No. 201302008). The authors have no conflicts of interest to report.
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