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The research on the status, rehabilitation, education, vocational development, social integration and support services related to intellectual disability in China
Research in Developmental Disabilities 31 (2010) 1216–1222
Contents lists available at ScienceDirect
Research in Developmental Disabilities
The research on the status, rehabilitation, education, vocational development, social integration and support services related to intellectual disability in China Lihui Wu a,*, Zhuoying Qiu b,**, Daniel Wong c, Lucy Wong Hernandez c, Qianlei Zhao a a b c
Yuying Children’s Hospital of Wenzhou Medical College, 109 Xueyuan Road, Wenzhou, Zhejiang 325003, China Research Institute of Rehabilitation Information China Rehabilitation Research Center, 21 North Jiaomen Road, Fengtai District, Beijing 100068, China Department of Rehabilitation Studies, College of Allied Health Sciences, East Carolina University, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 June 2010 Received in revised form 21 July 2010 Accepted 30 July 2010
Intellectual disability (ID) is a prevalent form of non-progressive cognitive impairment. The objectives of this articles are: to analyze the changes of ID in China, including its definition, prevalence, rehabilitation, education, vocational development, social life and support services; to review and to compare the issues of intellectual disability in China with the international literatures and research studies and to provide useful updated information and reference data for scholars and researchers who study intellectual disability. Analyzed the data obtained from two national sample surveys on disability with respect to intellectual disability in China. The estimated prevalence of individuals with intellectual disabilities in China was 7.5% in 2006 nationally which was lower than the previous results obtained in the 1987 national survey. The fourth level of ID showed a downward trend, while the proportion among the population aged 60 and over with ID tended to increase. The 2006 national survey indicated that the prevalence of ID in rural areas was higher than that in urban areas. This finding was consistent with the national survey conducted in 1987. As indicated by the 2006 national survey, 29.4% cases had no known causes for the ID, the proportion tended to decrease as compared with the first survey. However, when compared to the 1987 report, the proportion of senile dementia among older people as indicated by the 2006 report was higher than before. During the past years, the prevention of ID and the quality of life of individuals with ID have improved due to the enactment and implementation of a series of national laws and regulations, however, there is more that needs to be done in the areas of education, vocational development, social integration and support services for individuals with ID in order to improve the quality of life of individuals with ID in China. The findings of this study are consistent with the research findings presented in the international literatures. ID is the conditions that deserve further study and deserve the attention of policy makers and rehabilitation professionals in China. Furthermore, with the ageing of population in China and its impact to the social security system, the in-depth study of ID and its implications has become more pertinent in China in the future. ß 2010 Elsevier LtdElsevier Ltd. All rights reserved.
Keywords: Intellectual disability Definition Prevalence rate
* Corresponding author. Tel.: +86 577 86689882; fax: +86 577 86689882. ** Corresponding author. Tel.: +86 010 67562515. E-mail addresses: [email protected], [email protected] (L. Wu), [email protected] (Z. Qiu). 0891-4222/$ – see front matter ß 2010 Elsevier LtdElsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2010.07.024
L. Wu et al. / Research in Developmental Disabilities 31 (2010) 1216–1222
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1. Introduction Intellectual disability (ID) is a prevalent form of non-progressive cognitive impairment, affecting 2–3% of the population in the industrialized world. Disorders under the category of ID, although narrowly defined by an IQ <70 and by deficits in academic, adaptive and interpersonal skills, are widely diverse in their causes. Intellectual disability is characterized both by a significantly below-average score on a test of mental ability or intelligence and by limitations in the ability to function in areas of daily life, such as communication, self-care, and getting along in social situations and school activities. Intellectual disability is sometimes referred to as a cognitive disability or mental retardation (US CDC, 2005). ID has a prevalence of 1.5% in most western countries, although this rate increases to 4% in most of developing nations (Salvador-Carulla, Rodriguez-Blazquez, & Martorell, 2008). Since the first national disability sample survey in China in 1987, great changes have taken place for disabled people and disability prevalence in terms of disability prevention, geographic distribution, causes of disability, rehabilitation services, education services, vocational development, social integration and social support services. The Second China National Disability Sample Survey was conducted in 2006–2007. The aims of this study are: (1) to conclude the latest estimated prevalence of ID from Documentation of the Second China National Sample Survey on Disability and to compare the findings to the international literatures, (2) to identify the main characteristics of ID in China, and (3) to survey and to study the lives of individuals with ID in China and to provide useful reference data for scholars in disability, rehabilitation education, sociology, and others. 2. Materials and methods 2.1. Participants According to the ‘‘Disability Screening Method of the Second National Sample Survey on Disability’’ (OSSD, 2007), the survey utilized the methods of stratified, multi-phased and cluster probability sampling design, the survey sampled a total of 734 counties (cities or districts) and 2980 towns (townships or communities) from 31 provinces, autonomous regions, and municipalities directly under the Central Government. The number of sampling areas was 5964, with 420 persons averaged in each area. The survey reference time was zero hour, April 1, 2006 and the enumeration period started on April 1 and ended on May 31, 2006. Under the leadership of governments at different levels, 738 survey teams were organized, comprising more than 20,000 enumerators, nearly 6000 doctors of various specialties, more than 730 statisticians and over 50,000 survey assistants. The survey teams visited each of the sampled households to conduct interviews, screens and assessments of disabled people. In this Survey, 2,526,145 persons in 771,797 households were investigated and the sampling ratio was 19.3 per ten thousand. A total of 2,108,410 persons were interviewed, accounting for 834.6 per 1000 of all people being covered. 2.2. Materials and procedures ID was divided into four levels according to diagnosis (IQ scores and adaptive behavior) and covered four aspects: Structure, function, activity and participation, environment and support (Table 1). In this survey, 0–6 years age grouping was screened by DDST (Denver Developmental Screening Test), which has been utilized extensively worldwide (Frankenburg, Dodds, Archer, Shapiro, & Bresnick, 1992). If a participant was suspected of ID by screening tests, a definite diagnosis with the Gesell Developmental Inventory (Knobloch, Stevens, & Malone, 1980) was conducted to validate the result. If the result was indicated in a critical category, then infant-junior high social life scale was used to assist diagnose; 7 years age grouping was screened by disability screening questionnaire. If the screening found that the subject has ID tendency, then adaptive behavior would be evaluated. If two conditions (IQ and adaptive behavior) were both indicated abnormality, the individual was identified as having ID. 2.3. Statistical analysis Group comparisons were conducted using chi-square tests for categorical variables (prevalence or proportion). 3. Results 3.1. The prevalence of ID and the proportion in total disabilities in China The results of the second national survey of disability indicated that there were 10,844 with simply ID (those with ID but do not suffer from other disabilities) and 26,080 with multiple disabilities (those with at least two disabilities). 19,218 individuals (included ID in multiple disabilities, those with ID and other disabilities) diagnosed with ID totally in total surveyed population. With reference to the 2005 year-end statistics on the total population of China released by the National Bureau of Statistics of China, the estimated population with ID (included ID in multiple disabilities) was about 9.88 million. The estimated prevalence of total ID was 0.75% in total national population and 11.9% in total disabilities. The proportion of the four levels that had significant difference between 1987 and 2006 (x2 = 2384.722, P < 0.0001) indicated the fourth level ID was decreased obviously in 2006 (Fig. 1).
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Table 1 The classification of intellectual disability in the second survey (2006). Levels
DQ scores (age 0–6)
IQ scores (age 7)
Adaptive behavior
WHO-DAS scores
I II III IV
25 26–39 40–54 55–75
20 20–34 35–49 50–69
Profound Severe Moderate Mild
116 106–115 96–105 52–95
DQ, developmental quotient; IQ, intelligence quotient; WHO-DAS, The World Health Organization’s Disability Assessment Scale.
[(Fig._1)TD$IG]
Fig. 1. The proportion of four levels of ID. The proportion of ID in the above figure included ID in multiple disability. Four levels had significant difference between two groups respectively by partitions of chi-square method (P < 0.0001).
[(Fig._2)TD$IG]
Fig. 2. The structure analysis of simple ID in total disabilities based on national population. The figure showed seven main disabilities in China. Mental disability was different from ID. Its definition was mental disorder lasted more than one year and daily life and participation were restricted for the disorder of cognition, behavior and emotion in this survey. **P < 0.0001.
The proportion of simple ID in the total disabilities was 6.7% (10,844 in 16,1479), lower than 19.70% (15,233 in 77,345) in 1987 significantly (x2 = 9057.696, P < 0.0001) (Fig. 2). 8374 (43.6%) persons with ID suffered from associated disabilities in total 19,218 intellectual disabled persons, excluded 10,844 simple ID. It was in general accord with foreign research. 3.2. The main function disorders of ID in participation and activity level According to the second survey, only 3.6% persons with ID aged 18 and above had no disturbance of social participation and 3.8% had no disturbance of life activities and 4.8% had no disturbance of getting along with others. The proportions of ‘‘no disturbance and mild disturbance’’ of social participation, life activity and getting along with others were similar by regions, gender. Interestingly, the proportion by ID levels was inconsistent. The proportion of ‘‘no disturbance and mild disturbance’’ in the fourth level was higher than it in the other three levels obviously. (Tables 2–4). 3.3. The distribution of ID in China Age 15–19 had the highest proportion 8.9% in age-specific proportion of ID in the survey. After the peak, the proportion then declined among adolescents about age 20–29, particularly people aged 40 and over. Comparing the two national surveys, we can find that the proportion among aged 0–14 grouping was considerably lower than the proportion of that special age grouping in 1987, while the proportion among the population aged 60 and over tended to increase. The estimates from the two national surveys suggested that there were a consistently higher overall proportion among males as compared with females, particularly among the population aged 20 and under. However, the sex difference was obvious among people aged 40 and under, after that the difference reduced substantially. Compared with 1987, the
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Table 2 The disturbance of social participation in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
4.0 3.4
30.7 27.6
35.2 34.2
18.9 22.5
11.2 12.3
0.8 0.7 1.9 7.3
2.1 5.6 17.8 56.6
9.4 25.1 50.6 28.6
26.3 46.2 24.0 6.2
61.4 22.4 5.7 1.3
2.9 4.3 3.6
27.2 29.7 28.3
35.1 33.6 34.4
22.4 20.9 21.7
12.4 11.5 12.0
Table 3 The disturbance of life activities in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
3.9 3.7
27.3 25.3
28.0 28.0
21.2 23.7
19.6 19.3
0.6 0.4 1.8 8.3
1.2 2.4 13.6 55.5
2.6 15.5 42.7 25.2
14.9 43.7 29.4 8.5
80.7 38.0 12.5 2.5
3.3 4.4 3.8
24.7 27.0 25.7
27.1 29.0 28.0
24.5 21.5 23.1
20.4 18.1 19.4
Table 4 The disturbance of getting along with others in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
5.5 4.6
30.9 28.0
30.4 29.5
20.2 22.6
13.0 15.3
0.4 0.4 2.2 10.6
1.2 4.1 18.1 58.0
5.7 19.8 46.1 23.7
22.0 45.5 25.8 6.7
70.7 30.2 7.8 1.0
4.3 5.4 4.8
28.4 28.9 28.6
29.8 29.5 29.7
22.4 21.7 22.1
15.1 14.5 14.8
prevalence of male with ID in surveyed population dropped from 1.32% to 0.81% in 2006. The prevalence of female with ID dropped from 1.22% to 0.70%. The data of latest national survey on disability showed that the prevalence of ID in rural areas was higher than that in urban areas. It was consistent with the survey in 1987. The result probably reflected the unbalanced distribution of health resources between urban areas and rural areas. With reference to the 2005 year-end statistics on the total population of China released by the National Bureau of Statistics of China, it was estimated that the prevalence of ID (included ID in multiple disabilities) was about 0.40% in urban areas and it was about 1.02% in rural areas based on total national population. 3.4. Etiology of ID in China From Fig. 3 we can know the causes of most ID were unknown, the proportion was 29.5% but it tended to decrease as compared with the first national survey. At the same time, the proportion of ‘‘other’’ has come down. Both proved our understanding of ID was much more comprehensive and profound than before and the directivity of the standard was much
[(Fig._3)TD$IG]
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Fig. 3. The constitution of reasons of ID in China.
[(Fig._4)TD$IG]
Fig. 4. The proportion of ‘‘had received service and support’’ in ID by year-group.
stronger. It was noteworthy that the proportion of senile dementia which as one of mental disabilities was higher than before. It rose from 2.9% in 1987 to 9.7% in 2006. 3.5. The rehabilitation and service of ID in China The data of the first survey indicated 4.3% ID children need medical treatment. According to the second survey, the main rehabilitation form was community and family services, accounting for 72.7% of total ID population in three rehabilitation form. So community and family services play an important role in the rehabilitation of ID. The main rehabilitation content was rehabilitation training and service, accounting for 49.6%. Medical service accounting for 11.5% was higher than before. The data of the first survey indicated 61.6% ID children need special education. At present, there are three major forms of education for them: special-education schools and classes, special classes at ordinary schools which are carried out widely and ordinary classes at ordinary schools. Data from the second survey showed 5.5% individuals accepted ordinary education at ordinary schools, while only 1.5% individuals accepted special classes education at ordinary schools. 3.4% individuals accepted special education at special schools. 4.0% individuals accepted other education in 1490 persons with ID of aged 6– 14 group. 57.0% accepted ordinary education at ordinary schools in the fourth level ID. And we can find that the special education for ID is still unable to meet needs at present. Forty-seven point nine percent (5289 in 11,040) ID complain ‘‘Never receive any service and support’’ in rural area and it was higher than urban area (30.7%, 988 in 3221) (x2 = 300.542, P < 0.0001). 46.7% (2936 in 6291) female ID complain ‘‘Never receive any service and support’’ and it was higher than male (42.0%, 3351 in 7970) (x2 = 30.505, P < 0.0001). It indicated male and person lived in urban area had more chance to receive service and supply. The results also showed child aged 0–9 and adolescent age 10–19 were the groups received least service and support. The proportion was 35.3% and 54.2% respectively (Fig. 4). Most ID persons had not participated in the social insurance, accounting for 66.37%. The main form of social insurance for ID was medical insurance, account 93.99% in all social insurance. 4. Discussion Intellectual disability (ID) has a prevalence of 1.5% in most western countries, although this rate increases to 4% in most of developing nations (Salvador-Carulla et al., 2008). Durkin (2002) noted that the prevalence of ID is 2.4–24.3 per 1000 children. The survey showed the prevalence of ID based on national population was 7.5 per 1000 in China. Compared with the results of intellectual disabled surveys in some other countries, this prevalence is higher than some countries and lower than some countries also. A study by Shea (2006) indicated that based on available population figures and 1% prevalence, there were currently approximately 6 million American and 560 thousand Canadian children under the age of 14 years with MR. The Australian Bureau of Statistics (ABS) disability surveys in 1998 showed estimates of the prevalence of ID based on a consideration of all reported disabling conditions, 2.7% of Australians, reported one or more intellectual disabling conditions.
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For people aged under 65, 2.3% of Australians in that age group, reported an ID based on reported all disabling conditions. Around 1.1% of the Australian population, reported an intellectual main disabling condition (AIHW, 2003). We know the estimates of prevalence of ID are very well differentiated in different countries. It is affected by various factors associated with operational definitions and methods of estimation, The non-methodological factors affecting the estimates include differences in the characteristics of the population surveyed, such as social, economic, cultural, ethnic and regional differences (AIHW, 2003). The definitions of ID may be diversified in different countries. The terms ‘‘intellectual impairment’’, ‘‘ID’’, ‘‘developmental disability’’ and ‘‘mental retardation (MR)’’ ‘‘learning disabilities’’ are in common use (Salvador-Carulla & Bertelli, 2008; Wen, 1997). But MR and learning disabilities are considered outdated whereas ID is gaining increasing acceptance (Salvador-Carulla & Bertelli, 2008). The American Association on Mental Retardation (Luckasson et al., 2002) definition of ID (referred to as mental retardation by the AAMR) states that the disability is characterized by significant limitations in both intellectual functioning and adaptive behavior as expressed in conceptual, social, and practical adaptive skills, with a standard score of 70 (two standard deviations below the mean) usually being accepted as the cut-off for ID (Luckasson et al., 2002). Australia used the International Classification of Functioning, Disability and Health (ICF) on the definition of ID is: IQ score <70 and the state of Physical activities and social participation restrictions and the need for an appropriate level support (Wen, 1997). In the first national survey of disability in China, the definition have adapted the related definitions of The Diagnostic and Statistical Manual of Mental Disorders (DSM-III), while in the second national sample survey on disability, the definition of ID adapted the definition of Australia in the second national survey of disability and it was consistent with ICF conceptual framework of ID. In the meantime, the definition indicated significantly subaverage general intellectual function (intelligence quotient, IQ < 70) with concurrent impairments in adaptive behavior, such disability was caused by disabilities of the structure and function of the nervous system, the result was that the individual activities and participation were restricted, therefore comprehensive, extensive, limited, intermittent support provided by environment was needed. So the definition of the second survey laid more emphasis on the interaction between individuals and environment. A number of significant reports have highlighted the need to improve the consistency of disability definitions and the comparability of disability data collections. ICF as a very extensive and very accurate international tool provides a theoretical framework for describing and measuring the health. We have reasons to believe ICF can solve the issue. On the whole, the findings of this study are consistent with the research findings presented in the international literatures. The estimated prevalence of ID showed downward trend in China compared with the first national survey. There were four possible reasons: First, the difficulties in case identification among children at preschool ages influence on the prevalence of ID in children under age 6. Second, the influence of method of estimation, this survey strictly complied with the universally diagnosis (IQ scores and adaptive behavior) of ID. In the worldwide scale, when criteria of IQ scores and adaptive behavior are used simultaneously, the prevalence will be reduced substantially (Mercer, 1973). Third, Person with mild intellectual handicap was the major proportion of decreasing population. In this survey the prevalence of mind ID dropped by 18.5%. It was in general accord with result of foreign research. The presence of mild ID was more likely a consequence of both polygenetic and social/environmental influence (Holland & Jacobson, 2001). Studies have consistently found that the presence of mild ID was associated with low socioeconomic status, while a relationship between severe ID and socioeconomic status has not consistently been found (Drews, Yeargin-Allsopp, Decoufle, & Murphy, 1995). Fourth, it was relating to dementia. The proportion of dement to the total surveyed population was 0.8 per 1000. Dementia as a mental disability rather than ID in the second survey caused to the proportion of ID dropped by 0.08%. The proportion of the fourth level ID (the most serious type) was decreased by 18.4%, the proportion of age 0–14 was decreased by 22.6% and the proportion of ID in total disabilities was decreased by 13.0% based on national population. It was related to the ID prevention work in China. But the proportion of old population (age 60 and over) with ID and the proportion of ID caused by senile dementia were increased by 8.3% and 6.8% respectively. Aging of the population is prominent in China. In this survey, we paid more attention to the participation, activity level and environmental support of ID, which was neglected in the first survey. The result showed most ID had disturbance of participation and activity. To our surprised, the condition of the fourth level ID seemed to be better than the other three levels. We had no exact explanation at present. The survey indicated that medical service, rehabilitation, education, social and environmental support are still unable to meet the actual requirement. 5. Conclusion ID is certainly a social problem to be reckoned with in China, but, when view as a whole, the prevalence of ID showed downward trend. These results of this major study are consistent with the international literature. The analysis of proportion of ID among the population aged 60+ and the proportion of ID caused by certain disease that the older is liable to suffer from indicated aging of population would be prominent in China. Though a series of measures had been adopted to improve the quality of life of the intellectual disabled people, it is unable to fulfill a need of requirement. And more supply and detailed study of ID would be necessary. Acknowledgements This research project granted by China Ministry of Science and Technology (Project No. 2003DIB1J063 and Project No. 2004DIB5J183), by the Second China National Disability Sample Survey Office (Project 2003-1), by the Zhejiang Provincial
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Commission for population and family planning research program (Project 2007-72) and science and technology plan of Wenzhou science committee (Project No. Y20070076). This work was approved by the State Council. Data of Second China National Sample Survey on Disability extracted from Documentation of the Second China National Sample Survey on Disability. References Australian Institute of Health Welfare (AIHW). (2003). Disability prevalence and trends: Disability series. Canberra: AIHW. Drews, C. D., Yeargin-Allsopp, M., Decoufle, P., & Murphy, C. C. (1995). Variation in the influence of selected sociodemographic risk factors for mental retardation. American Journal of Public Health, 85, 329–334. Durkin, M. (2002). The epidemiology of developmental disabilities in low-income countries. Mental Retardation and Developmental Disabilities Research Reviews, 8, 206–211. Frankenburg, W. K., Dodds, J., Archer, P., Shapiro, H., & Bresnick, B. (1992). The Denver II: A major revision and restandardization of the Denver Developmental Screening Test. Pediatrics, 89, 91–97. Holland, T., & Jacobson, J. (2001). Mental health and intellectual disabilities: Addressing the mental health needs of people with intellectual disabilities. Report by the Mental Health Special Interest Group of IASSID to the WHO, Clifton Park, NY: IASSID. Knobloch, H., Stevens, F., & Malone, A. (1980). Manual of developmental diagnosis. Hagerstown, MD: Harper & Row. Luckasson, R., Borthwick-Duffy, S., Buntinx, W. H. E., Coulter, D. L., Craig, E. M., Reeve, A., et al. (2002). Mental retardation: Definition, classification, and systems of supports (10th ed.). Washington, DC: American Association on Mental Retardation. Mercer, J. (1973). The myth of 3% prevalence. In R. Eyman, C. Meyers, & G. Tarjan (Eds.), Sociobehavioural studies in mental retardation. Washington, DC: American Association on Mental Deficiency. Office of the second China national sample survey on disability (OSSD). (2007). Documentation of the second China national sample survey on disability. Beijing: China Statistics Press. Salvador-Carulla, L., & Bertelli, M. (2008). ‘Mental retardation’ or ‘intellectual disability’: Time for a conceptual change. Psychopathology, 40, 10–16. Salvador-Carulla, L., Rodriguez-Blazquez, C., & Martorell, A. (2008). Intellectual disability: An approach from the health sciences perspective. Salud Publica Mexico, 50(Suppl. 2), s142–s150. Shea, S. E. (2006). Mental retardation in children ages 6 to 16. Seminars in Pediatric Neurology, 13, 262–270. US CDC. (2005). Developmental disabilities. Intellectual disability. Viewed August 2008. Source: National Center on Birth Defects and Developmental Disabilities. Wen, X.Y. (1997). The definition and prevalence of intellectual disability in Australia. Canberra: AIHW.
Contents lists available at ScienceDirect
Research in Developmental Disabilities
The research on the status, rehabilitation, education, vocational development, social integration and support services related to intellectual disability in China Lihui Wu a,*, Zhuoying Qiu b,**, Daniel Wong c, Lucy Wong Hernandez c, Qianlei Zhao a a b c
Yuying Children’s Hospital of Wenzhou Medical College, 109 Xueyuan Road, Wenzhou, Zhejiang 325003, China Research Institute of Rehabilitation Information China Rehabilitation Research Center, 21 North Jiaomen Road, Fengtai District, Beijing 100068, China Department of Rehabilitation Studies, College of Allied Health Sciences, East Carolina University, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 June 2010 Received in revised form 21 July 2010 Accepted 30 July 2010
Intellectual disability (ID) is a prevalent form of non-progressive cognitive impairment. The objectives of this articles are: to analyze the changes of ID in China, including its definition, prevalence, rehabilitation, education, vocational development, social life and support services; to review and to compare the issues of intellectual disability in China with the international literatures and research studies and to provide useful updated information and reference data for scholars and researchers who study intellectual disability. Analyzed the data obtained from two national sample surveys on disability with respect to intellectual disability in China. The estimated prevalence of individuals with intellectual disabilities in China was 7.5% in 2006 nationally which was lower than the previous results obtained in the 1987 national survey. The fourth level of ID showed a downward trend, while the proportion among the population aged 60 and over with ID tended to increase. The 2006 national survey indicated that the prevalence of ID in rural areas was higher than that in urban areas. This finding was consistent with the national survey conducted in 1987. As indicated by the 2006 national survey, 29.4% cases had no known causes for the ID, the proportion tended to decrease as compared with the first survey. However, when compared to the 1987 report, the proportion of senile dementia among older people as indicated by the 2006 report was higher than before. During the past years, the prevention of ID and the quality of life of individuals with ID have improved due to the enactment and implementation of a series of national laws and regulations, however, there is more that needs to be done in the areas of education, vocational development, social integration and support services for individuals with ID in order to improve the quality of life of individuals with ID in China. The findings of this study are consistent with the research findings presented in the international literatures. ID is the conditions that deserve further study and deserve the attention of policy makers and rehabilitation professionals in China. Furthermore, with the ageing of population in China and its impact to the social security system, the in-depth study of ID and its implications has become more pertinent in China in the future. ß 2010 Elsevier LtdElsevier Ltd. All rights reserved.
Keywords: Intellectual disability Definition Prevalence rate
* Corresponding author. Tel.: +86 577 86689882; fax: +86 577 86689882. ** Corresponding author. Tel.: +86 010 67562515. E-mail addresses: [email protected], [email protected] (L. Wu), [email protected] (Z. Qiu). 0891-4222/$ – see front matter ß 2010 Elsevier LtdElsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2010.07.024
L. Wu et al. / Research in Developmental Disabilities 31 (2010) 1216–1222
1217
1. Introduction Intellectual disability (ID) is a prevalent form of non-progressive cognitive impairment, affecting 2–3% of the population in the industrialized world. Disorders under the category of ID, although narrowly defined by an IQ <70 and by deficits in academic, adaptive and interpersonal skills, are widely diverse in their causes. Intellectual disability is characterized both by a significantly below-average score on a test of mental ability or intelligence and by limitations in the ability to function in areas of daily life, such as communication, self-care, and getting along in social situations and school activities. Intellectual disability is sometimes referred to as a cognitive disability or mental retardation (US CDC, 2005). ID has a prevalence of 1.5% in most western countries, although this rate increases to 4% in most of developing nations (Salvador-Carulla, Rodriguez-Blazquez, & Martorell, 2008). Since the first national disability sample survey in China in 1987, great changes have taken place for disabled people and disability prevalence in terms of disability prevention, geographic distribution, causes of disability, rehabilitation services, education services, vocational development, social integration and social support services. The Second China National Disability Sample Survey was conducted in 2006–2007. The aims of this study are: (1) to conclude the latest estimated prevalence of ID from Documentation of the Second China National Sample Survey on Disability and to compare the findings to the international literatures, (2) to identify the main characteristics of ID in China, and (3) to survey and to study the lives of individuals with ID in China and to provide useful reference data for scholars in disability, rehabilitation education, sociology, and others. 2. Materials and methods 2.1. Participants According to the ‘‘Disability Screening Method of the Second National Sample Survey on Disability’’ (OSSD, 2007), the survey utilized the methods of stratified, multi-phased and cluster probability sampling design, the survey sampled a total of 734 counties (cities or districts) and 2980 towns (townships or communities) from 31 provinces, autonomous regions, and municipalities directly under the Central Government. The number of sampling areas was 5964, with 420 persons averaged in each area. The survey reference time was zero hour, April 1, 2006 and the enumeration period started on April 1 and ended on May 31, 2006. Under the leadership of governments at different levels, 738 survey teams were organized, comprising more than 20,000 enumerators, nearly 6000 doctors of various specialties, more than 730 statisticians and over 50,000 survey assistants. The survey teams visited each of the sampled households to conduct interviews, screens and assessments of disabled people. In this Survey, 2,526,145 persons in 771,797 households were investigated and the sampling ratio was 19.3 per ten thousand. A total of 2,108,410 persons were interviewed, accounting for 834.6 per 1000 of all people being covered. 2.2. Materials and procedures ID was divided into four levels according to diagnosis (IQ scores and adaptive behavior) and covered four aspects: Structure, function, activity and participation, environment and support (Table 1). In this survey, 0–6 years age grouping was screened by DDST (Denver Developmental Screening Test), which has been utilized extensively worldwide (Frankenburg, Dodds, Archer, Shapiro, & Bresnick, 1992). If a participant was suspected of ID by screening tests, a definite diagnosis with the Gesell Developmental Inventory (Knobloch, Stevens, & Malone, 1980) was conducted to validate the result. If the result was indicated in a critical category, then infant-junior high social life scale was used to assist diagnose; 7 years age grouping was screened by disability screening questionnaire. If the screening found that the subject has ID tendency, then adaptive behavior would be evaluated. If two conditions (IQ and adaptive behavior) were both indicated abnormality, the individual was identified as having ID. 2.3. Statistical analysis Group comparisons were conducted using chi-square tests for categorical variables (prevalence or proportion). 3. Results 3.1. The prevalence of ID and the proportion in total disabilities in China The results of the second national survey of disability indicated that there were 10,844 with simply ID (those with ID but do not suffer from other disabilities) and 26,080 with multiple disabilities (those with at least two disabilities). 19,218 individuals (included ID in multiple disabilities, those with ID and other disabilities) diagnosed with ID totally in total surveyed population. With reference to the 2005 year-end statistics on the total population of China released by the National Bureau of Statistics of China, the estimated population with ID (included ID in multiple disabilities) was about 9.88 million. The estimated prevalence of total ID was 0.75% in total national population and 11.9% in total disabilities. The proportion of the four levels that had significant difference between 1987 and 2006 (x2 = 2384.722, P < 0.0001) indicated the fourth level ID was decreased obviously in 2006 (Fig. 1).
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Table 1 The classification of intellectual disability in the second survey (2006). Levels
DQ scores (age 0–6)
IQ scores (age 7)
Adaptive behavior
WHO-DAS scores
I II III IV
25 26–39 40–54 55–75
20 20–34 35–49 50–69
Profound Severe Moderate Mild
116 106–115 96–105 52–95
DQ, developmental quotient; IQ, intelligence quotient; WHO-DAS, The World Health Organization’s Disability Assessment Scale.
[(Fig._1)TD$IG]
Fig. 1. The proportion of four levels of ID. The proportion of ID in the above figure included ID in multiple disability. Four levels had significant difference between two groups respectively by partitions of chi-square method (P < 0.0001).
[(Fig._2)TD$IG]
Fig. 2. The structure analysis of simple ID in total disabilities based on national population. The figure showed seven main disabilities in China. Mental disability was different from ID. Its definition was mental disorder lasted more than one year and daily life and participation were restricted for the disorder of cognition, behavior and emotion in this survey. **P < 0.0001.
The proportion of simple ID in the total disabilities was 6.7% (10,844 in 16,1479), lower than 19.70% (15,233 in 77,345) in 1987 significantly (x2 = 9057.696, P < 0.0001) (Fig. 2). 8374 (43.6%) persons with ID suffered from associated disabilities in total 19,218 intellectual disabled persons, excluded 10,844 simple ID. It was in general accord with foreign research. 3.2. The main function disorders of ID in participation and activity level According to the second survey, only 3.6% persons with ID aged 18 and above had no disturbance of social participation and 3.8% had no disturbance of life activities and 4.8% had no disturbance of getting along with others. The proportions of ‘‘no disturbance and mild disturbance’’ of social participation, life activity and getting along with others were similar by regions, gender. Interestingly, the proportion by ID levels was inconsistent. The proportion of ‘‘no disturbance and mild disturbance’’ in the fourth level was higher than it in the other three levels obviously. (Tables 2–4). 3.3. The distribution of ID in China Age 15–19 had the highest proportion 8.9% in age-specific proportion of ID in the survey. After the peak, the proportion then declined among adolescents about age 20–29, particularly people aged 40 and over. Comparing the two national surveys, we can find that the proportion among aged 0–14 grouping was considerably lower than the proportion of that special age grouping in 1987, while the proportion among the population aged 60 and over tended to increase. The estimates from the two national surveys suggested that there were a consistently higher overall proportion among males as compared with females, particularly among the population aged 20 and under. However, the sex difference was obvious among people aged 40 and under, after that the difference reduced substantially. Compared with 1987, the
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Table 2 The disturbance of social participation in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
4.0 3.4
30.7 27.6
35.2 34.2
18.9 22.5
11.2 12.3
0.8 0.7 1.9 7.3
2.1 5.6 17.8 56.6
9.4 25.1 50.6 28.6
26.3 46.2 24.0 6.2
61.4 22.4 5.7 1.3
2.9 4.3 3.6
27.2 29.7 28.3
35.1 33.6 34.4
22.4 20.9 21.7
12.4 11.5 12.0
Table 3 The disturbance of life activities in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
3.9 3.7
27.3 25.3
28.0 28.0
21.2 23.7
19.6 19.3
0.6 0.4 1.8 8.3
1.2 2.4 13.6 55.5
2.6 15.5 42.7 25.2
14.9 43.7 29.4 8.5
80.7 38.0 12.5 2.5
3.3 4.4 3.8
24.7 27.0 25.7
27.1 29.0 28.0
24.5 21.5 23.1
20.4 18.1 19.4
Table 4 The disturbance of getting along with others in ID aged 18 and above by regions, levels, gender in total 7448 persons in 2006. Disturbance Area Urban Rural Levels I II III IV Sex Male Female Total
No (%)
Mild (%)
Moderate (%)
Severe (%)
Profound (%)
5.5 4.6
30.9 28.0
30.4 29.5
20.2 22.6
13.0 15.3
0.4 0.4 2.2 10.6
1.2 4.1 18.1 58.0
5.7 19.8 46.1 23.7
22.0 45.5 25.8 6.7
70.7 30.2 7.8 1.0
4.3 5.4 4.8
28.4 28.9 28.6
29.8 29.5 29.7
22.4 21.7 22.1
15.1 14.5 14.8
prevalence of male with ID in surveyed population dropped from 1.32% to 0.81% in 2006. The prevalence of female with ID dropped from 1.22% to 0.70%. The data of latest national survey on disability showed that the prevalence of ID in rural areas was higher than that in urban areas. It was consistent with the survey in 1987. The result probably reflected the unbalanced distribution of health resources between urban areas and rural areas. With reference to the 2005 year-end statistics on the total population of China released by the National Bureau of Statistics of China, it was estimated that the prevalence of ID (included ID in multiple disabilities) was about 0.40% in urban areas and it was about 1.02% in rural areas based on total national population. 3.4. Etiology of ID in China From Fig. 3 we can know the causes of most ID were unknown, the proportion was 29.5% but it tended to decrease as compared with the first national survey. At the same time, the proportion of ‘‘other’’ has come down. Both proved our understanding of ID was much more comprehensive and profound than before and the directivity of the standard was much
[(Fig._3)TD$IG]
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Fig. 3. The constitution of reasons of ID in China.
[(Fig._4)TD$IG]
Fig. 4. The proportion of ‘‘had received service and support’’ in ID by year-group.
stronger. It was noteworthy that the proportion of senile dementia which as one of mental disabilities was higher than before. It rose from 2.9% in 1987 to 9.7% in 2006. 3.5. The rehabilitation and service of ID in China The data of the first survey indicated 4.3% ID children need medical treatment. According to the second survey, the main rehabilitation form was community and family services, accounting for 72.7% of total ID population in three rehabilitation form. So community and family services play an important role in the rehabilitation of ID. The main rehabilitation content was rehabilitation training and service, accounting for 49.6%. Medical service accounting for 11.5% was higher than before. The data of the first survey indicated 61.6% ID children need special education. At present, there are three major forms of education for them: special-education schools and classes, special classes at ordinary schools which are carried out widely and ordinary classes at ordinary schools. Data from the second survey showed 5.5% individuals accepted ordinary education at ordinary schools, while only 1.5% individuals accepted special classes education at ordinary schools. 3.4% individuals accepted special education at special schools. 4.0% individuals accepted other education in 1490 persons with ID of aged 6– 14 group. 57.0% accepted ordinary education at ordinary schools in the fourth level ID. And we can find that the special education for ID is still unable to meet needs at present. Forty-seven point nine percent (5289 in 11,040) ID complain ‘‘Never receive any service and support’’ in rural area and it was higher than urban area (30.7%, 988 in 3221) (x2 = 300.542, P < 0.0001). 46.7% (2936 in 6291) female ID complain ‘‘Never receive any service and support’’ and it was higher than male (42.0%, 3351 in 7970) (x2 = 30.505, P < 0.0001). It indicated male and person lived in urban area had more chance to receive service and supply. The results also showed child aged 0–9 and adolescent age 10–19 were the groups received least service and support. The proportion was 35.3% and 54.2% respectively (Fig. 4). Most ID persons had not participated in the social insurance, accounting for 66.37%. The main form of social insurance for ID was medical insurance, account 93.99% in all social insurance. 4. Discussion Intellectual disability (ID) has a prevalence of 1.5% in most western countries, although this rate increases to 4% in most of developing nations (Salvador-Carulla et al., 2008). Durkin (2002) noted that the prevalence of ID is 2.4–24.3 per 1000 children. The survey showed the prevalence of ID based on national population was 7.5 per 1000 in China. Compared with the results of intellectual disabled surveys in some other countries, this prevalence is higher than some countries and lower than some countries also. A study by Shea (2006) indicated that based on available population figures and 1% prevalence, there were currently approximately 6 million American and 560 thousand Canadian children under the age of 14 years with MR. The Australian Bureau of Statistics (ABS) disability surveys in 1998 showed estimates of the prevalence of ID based on a consideration of all reported disabling conditions, 2.7% of Australians, reported one or more intellectual disabling conditions.
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For people aged under 65, 2.3% of Australians in that age group, reported an ID based on reported all disabling conditions. Around 1.1% of the Australian population, reported an intellectual main disabling condition (AIHW, 2003). We know the estimates of prevalence of ID are very well differentiated in different countries. It is affected by various factors associated with operational definitions and methods of estimation, The non-methodological factors affecting the estimates include differences in the characteristics of the population surveyed, such as social, economic, cultural, ethnic and regional differences (AIHW, 2003). The definitions of ID may be diversified in different countries. The terms ‘‘intellectual impairment’’, ‘‘ID’’, ‘‘developmental disability’’ and ‘‘mental retardation (MR)’’ ‘‘learning disabilities’’ are in common use (Salvador-Carulla & Bertelli, 2008; Wen, 1997). But MR and learning disabilities are considered outdated whereas ID is gaining increasing acceptance (Salvador-Carulla & Bertelli, 2008). The American Association on Mental Retardation (Luckasson et al., 2002) definition of ID (referred to as mental retardation by the AAMR) states that the disability is characterized by significant limitations in both intellectual functioning and adaptive behavior as expressed in conceptual, social, and practical adaptive skills, with a standard score of 70 (two standard deviations below the mean) usually being accepted as the cut-off for ID (Luckasson et al., 2002). Australia used the International Classification of Functioning, Disability and Health (ICF) on the definition of ID is: IQ score <70 and the state of Physical activities and social participation restrictions and the need for an appropriate level support (Wen, 1997). In the first national survey of disability in China, the definition have adapted the related definitions of The Diagnostic and Statistical Manual of Mental Disorders (DSM-III), while in the second national sample survey on disability, the definition of ID adapted the definition of Australia in the second national survey of disability and it was consistent with ICF conceptual framework of ID. In the meantime, the definition indicated significantly subaverage general intellectual function (intelligence quotient, IQ < 70) with concurrent impairments in adaptive behavior, such disability was caused by disabilities of the structure and function of the nervous system, the result was that the individual activities and participation were restricted, therefore comprehensive, extensive, limited, intermittent support provided by environment was needed. So the definition of the second survey laid more emphasis on the interaction between individuals and environment. A number of significant reports have highlighted the need to improve the consistency of disability definitions and the comparability of disability data collections. ICF as a very extensive and very accurate international tool provides a theoretical framework for describing and measuring the health. We have reasons to believe ICF can solve the issue. On the whole, the findings of this study are consistent with the research findings presented in the international literatures. The estimated prevalence of ID showed downward trend in China compared with the first national survey. There were four possible reasons: First, the difficulties in case identification among children at preschool ages influence on the prevalence of ID in children under age 6. Second, the influence of method of estimation, this survey strictly complied with the universally diagnosis (IQ scores and adaptive behavior) of ID. In the worldwide scale, when criteria of IQ scores and adaptive behavior are used simultaneously, the prevalence will be reduced substantially (Mercer, 1973). Third, Person with mild intellectual handicap was the major proportion of decreasing population. In this survey the prevalence of mind ID dropped by 18.5%. It was in general accord with result of foreign research. The presence of mild ID was more likely a consequence of both polygenetic and social/environmental influence (Holland & Jacobson, 2001). Studies have consistently found that the presence of mild ID was associated with low socioeconomic status, while a relationship between severe ID and socioeconomic status has not consistently been found (Drews, Yeargin-Allsopp, Decoufle, & Murphy, 1995). Fourth, it was relating to dementia. The proportion of dement to the total surveyed population was 0.8 per 1000. Dementia as a mental disability rather than ID in the second survey caused to the proportion of ID dropped by 0.08%. The proportion of the fourth level ID (the most serious type) was decreased by 18.4%, the proportion of age 0–14 was decreased by 22.6% and the proportion of ID in total disabilities was decreased by 13.0% based on national population. It was related to the ID prevention work in China. But the proportion of old population (age 60 and over) with ID and the proportion of ID caused by senile dementia were increased by 8.3% and 6.8% respectively. Aging of the population is prominent in China. In this survey, we paid more attention to the participation, activity level and environmental support of ID, which was neglected in the first survey. The result showed most ID had disturbance of participation and activity. To our surprised, the condition of the fourth level ID seemed to be better than the other three levels. We had no exact explanation at present. The survey indicated that medical service, rehabilitation, education, social and environmental support are still unable to meet the actual requirement. 5. Conclusion ID is certainly a social problem to be reckoned with in China, but, when view as a whole, the prevalence of ID showed downward trend. These results of this major study are consistent with the international literature. The analysis of proportion of ID among the population aged 60+ and the proportion of ID caused by certain disease that the older is liable to suffer from indicated aging of population would be prominent in China. Though a series of measures had been adopted to improve the quality of life of the intellectual disabled people, it is unable to fulfill a need of requirement. And more supply and detailed study of ID would be necessary. Acknowledgements This research project granted by China Ministry of Science and Technology (Project No. 2003DIB1J063 and Project No. 2004DIB5J183), by the Second China National Disability Sample Survey Office (Project 2003-1), by the Zhejiang Provincial
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Commission for population and family planning research program (Project 2007-72) and science and technology plan of Wenzhou science committee (Project No. Y20070076). This work was approved by the State Council. Data of Second China National Sample Survey on Disability extracted from Documentation of the Second China National Sample Survey on Disability. References Australian Institute of Health Welfare (AIHW). (2003). Disability prevalence and trends: Disability series. Canberra: AIHW. Drews, C. D., Yeargin-Allsopp, M., Decoufle, P., & Murphy, C. C. (1995). Variation in the influence of selected sociodemographic risk factors for mental retardation. American Journal of Public Health, 85, 329–334. Durkin, M. (2002). The epidemiology of developmental disabilities in low-income countries. Mental Retardation and Developmental Disabilities Research Reviews, 8, 206–211. Frankenburg, W. K., Dodds, J., Archer, P., Shapiro, H., & Bresnick, B. (1992). The Denver II: A major revision and restandardization of the Denver Developmental Screening Test. Pediatrics, 89, 91–97. Holland, T., & Jacobson, J. (2001). Mental health and intellectual disabilities: Addressing the mental health needs of people with intellectual disabilities. Report by the Mental Health Special Interest Group of IASSID to the WHO, Clifton Park, NY: IASSID. Knobloch, H., Stevens, F., & Malone, A. (1980). Manual of developmental diagnosis. Hagerstown, MD: Harper & Row. Luckasson, R., Borthwick-Duffy, S., Buntinx, W. H. E., Coulter, D. L., Craig, E. M., Reeve, A., et al. (2002). Mental retardation: Definition, classification, and systems of supports (10th ed.). Washington, DC: American Association on Mental Retardation. Mercer, J. (1973). The myth of 3% prevalence. In R. Eyman, C. Meyers, & G. Tarjan (Eds.), Sociobehavioural studies in mental retardation. Washington, DC: American Association on Mental Deficiency. Office of the second China national sample survey on disability (OSSD). (2007). Documentation of the second China national sample survey on disability. Beijing: China Statistics Press. Salvador-Carulla, L., & Bertelli, M. (2008). ‘Mental retardation’ or ‘intellectual disability’: Time for a conceptual change. Psychopathology, 40, 10–16. Salvador-Carulla, L., Rodriguez-Blazquez, C., & Martorell, A. (2008). Intellectual disability: An approach from the health sciences perspective. Salud Publica Mexico, 50(Suppl. 2), s142–s150. Shea, S. E. (2006). Mental retardation in children ages 6 to 16. Seminars in Pediatric Neurology, 13, 262–270. US CDC. (2005). Developmental disabilities. Intellectual disability. Viewed August 2008. Source: National Center on Birth Defects and Developmental Disabilities