the global burden of disease 2004 data estimated that 186 million ( 2.9% ) of the world s 
 population were severely disabled and another 797 million ( 12.4% ) had moderate long - term 
 disability . the average global 
 prevalence of moderate and severe disability in children is 93 million ( 5.1% ) . however , the situation with regard 
 to children with disabilities has often been neglected . the proportion of children among all age groups suffering 
 both moderate and severe disability is higher in low- and middle - income countries than in 
 high - income countries . previous research on childhood disability in low- and middle - income countries focused on 
 intellectual and hearing disabilities , and little is known about other types of 
 disabilities . presence of disability is considered as a key component of quality - of - life 
 evaluation . children with 
 disabilities continue to face discrimination and restricted access to social services up to 
 adulthood . for example , vision problems 
 correctable by glasses accounted for 40 percent of disabled children not attending school in 
 brazil . development of principles and standard scales for disabilities that are sensitive to 
 cultural and resource differences has long been desired . after the united nations 
 international seminar on measurement of disability in 2001 , the washington group on 
 disability statistics ( washington group ) was formed under united nations sponsorship and 
 developed a set of general disability measures that have been used by several countries in 
 censuses and surveys . the questions use the world health organization s international 
 classification of functioning , disability , and health as a conceptual framework and focus on 
 functioning in basic actions . the disability status of the population has been a concern in vietnam due to prolonged 
 periods of war . in 2006 , the 
 washington group disability measures were translated into vietnamese and included in the 
 questionnaire of the vietnam household living standard survey . economic burden had been expressed as a percentage 
 of health - care expenditure relative to household income , with the rationale that a high 
 percentage means that  it is likely to force household members to cut their consumption of 
 other minimum needs , trigger productive asset sales or high levels of debt , and lead to 
 impoverishment  . a study 
 on data from the world health survey in 20022004 in 14 developing countries showed that 
 households with disabilities experienced higher ratios of health - care to total household 
 expenditure than households without disabilities in two - thirds of countries . although the vietnamese 
 government is developing a universal health insurance system , households with members 
 suffering disabilities have to pay extra expenses for examination , treatment , 
 rehabilitation , and other costs related to health - care use . further , the disability statuses of children differ according to the socioeconomic statuses 
 of their families . data from the world health surveys in 14 countries showed that persons 
 with disabilities are significantly worse off in two or more dimensions of economic 
 well - being ( education , employment , assets / living conditions , household expenditures , and 
 household expenditures on health care ) . on the other hand , study of the multiple indicator cluster 
 survey data in 20 countries did not indicate a consistent relationship . pattern of associations differ by 
 countries and type of disabilities ; there are still controversial issues that need to be 
 resolved based on evidence . the objectives of this study were to assess the economic burden of disability in different 
 functional domains among school - aged children in vietnam and to evaluate the association 
 between presence of disability and demographic and household characteristics of children , as 
 well as between economic burden of disability and demographic and household characteristics 
 of children , using a large national representative sample . the vietnam 
 household living standard survey has been conducted nationwide by the general statistics 
 office , ministry of planning and investment , vietnam in 1993 , 1998 and every 2 years since 
 2002 . survey households were chosen using a multistage stratified cluster sampling process 
 in which representative clusters were selected from all 64 provinces in vietnam , and a 
 random sample of households was selected within each cluster . information collected 
 regularly in every survey included basic demographic characteristics , educational 
 attainment , health care use , and employment for all household members ; household income 
 and expenditure ; and housing condition . information was collected through face - to - face 
 interviews with household heads , and key commune officials . the survey employed intensive 
 interviewer training , standardized measurement tools and techniques , and instrument 
 pretesting . the reason for selecting the survey conducted in 2006 was that it was the latest survey 
 that had collected information about disability . the survey was conducted among a total of 
 9,189 households in may and september 2006 . use of the vietnam household living standard survey data for this study was approved by 
 the general statistics office , ministry of planning and investment , vietnam . the data set 
 used in this study was provided by the general statistics office and did not contain 
 personally identifiable information . two types of main outcome variable were presence of difficulties that were result of some 
 physical or mental health problems , and health - care expenditure in the past 12 months . presence of difficulties was assessed according to the standard set of questions 
 recommended by the washington group . the validity of this scale in the surveys in asian 
 and pacific countries confirmed previously . the questions aimed to identify difficulties in six 
 functional domains : vision ( vision difficulties or problems ) , hearing ( hearing limitation 
 or problems ) , remembering or concentrating ( problems with remembering or thinking that 
 contribute to difficulty in doing daily activities ) , mobility ( limitation or problems 
 getting around on foot ) , self - care ( problems with taking care of yourself independently ) , 
 and communication ( problems with talking , listening , or understanding speech such that it 
 contributes to difficulty in doing daily activities ) . furthermore , the response categories 
 captured the degree or severity of the difficulty ; the response options were no , at least 
 some difficulty , at least a lot of difficulty , and unable to do it at all . in this study , 
 we dichotomized the response into no and yes ( at least some difficulty or more ) . information regarding expenses related to use of medical services was collected for each 
 household member who had used health - care services in the past 12 months . the expenses 
 included out - of - pocket payment for medical service , treatment , and other related costs , 
 such as bonuses for medical staff , and transportation fees . the unit of measurement was 
 1000 vietnamese dong ( vnd ) ( equivalent to 0.063 - 0.066 united states dollars during the 
 survey periods ) . we did not include payment for non - prescribed medicine , medical tools , 
 health insurance , and aid , because information about them was not collected at the 
 individual level . independent variables included sex , age , area ( urban , and rural ) , household income in the 
 past 12 months , educational attainment , and occupation of household head . age was 
 categorized into three groups : 610 , 1114 , and 1517 years , each corresponding to modal 
 age for a primary school , a lower secondary school , and an upper secondary school , 
 respectively . household income was calculated as total household revenue minus total 
 expenditure for the revenue - generating activities and divided into quintiles . we analyzed all 
 children ( n=9,882 ) between 6 and 17 years of age in survey households . the analysis did 
 not account for the intra - household correlation because a small proportion of households 
 ( 7.6% ) had more than one child with disabilities . the data set included the household 
 sampling weight for each household , which had been calculated as the inverse of its 
 household selection probability . we used the weight to take into account the multistage 
 sampling design for all analyses . the prevalence of difficulty in six functional domains was calculated by sex , age , area , 
 household income , educational attainment , and occupation of household head . the difference 
 in prevalence by these characteristics was assessed with a logistic regression 
 analysis . the multivariable logistic regression analysis required ten cases per independent 
 indicator variable in the model . in the subsequent analysis , a combined variable for 
 difficulty in hearing , remembering or concentrating , mobility , self - care , or communication 
 was used instead of using separate variables for difficulty in each domain . the frequency 
 of having difficulty in vision was high enough for a multivariable analysis , and this 
 domain was not combined . the per capita household income was calculated by dividing household income by the number 
 of household members . then the ratio of the mean health - care expenditure to the mean per 
 capita household income in the past 12 months was computed for each difficulty status . to 
 compare the ratio by difficulty status , a dichotomous variable to indicate whether the 
 ratio was greater than 0.05 or not was created and used as a dependent variable in the 
 logistic regression models . the choice of 0.05 was based on the lower threshold value for 
 catastrophic impact of health - care expenditure share used by van doorslaer . the ratio of the mean health - care expenditure to the mean per capita household income was 
 also compared by characteristics of subjects among all children , among children with 
 difficulty in vision , and among children with difficulty in hearing , remembering or 
 concentrating , mobility , self - care , or communication . the odds ratio was adjusted for sex , 
 age , area , household income in the past 12 months , educational attainment , and occupation 
 of household head . the vietnam 
 household living standard survey has been conducted nationwide by the general statistics 
 office , ministry of planning and investment , vietnam in 1993 , 1998 and every 2 years since 
 2002 . survey households were chosen using a multistage stratified cluster sampling process 
 in which representative clusters were selected from all 64 provinces in vietnam , and a 
 random sample of households was selected within each cluster . information collected 
 regularly in every survey included basic demographic characteristics , educational 
 attainment , health care use , and employment for all household members ; household income 
 and expenditure ; and housing condition . information was collected through face - to - face 
 interviews with household heads , and key commune officials . the survey employed intensive 
 interviewer training , standardized measurement tools and techniques , and instrument 
 pretesting . the reason for selecting the survey conducted in 2006 was that it was the latest survey 
 that had collected information about disability . the survey was conducted among a total of 
 9,189 households in may and september 2006 . use of the vietnam household living standard survey data for this study was approved by 
 the general statistics office , ministry of planning and investment , vietnam . the data set 
 used in this study was provided by the general statistics office and did not contain 
 personally identifiable information . two types of main outcome variable were presence of difficulties that were result of some 
 physical or mental health problems , and health - care expenditure in the past 12 months . presence of difficulties was assessed according to the standard set of questions 
 recommended by the washington group . the validity of this scale in the surveys in asian 
 and pacific countries confirmed previously . the questions aimed to identify difficulties in six 
 functional domains : vision ( vision difficulties or problems ) , hearing ( hearing limitation 
 or problems ) , remembering or concentrating ( problems with remembering or thinking that 
 contribute to difficulty in doing daily activities ) , mobility ( limitation or problems 
 getting around on foot ) , self - care ( problems with taking care of yourself independently ) , 
 and communication ( problems with talking , listening , or understanding speech such that it 
 contributes to difficulty in doing daily activities ) . furthermore , the response categories 
 captured the degree or severity of the difficulty ; the response options were no , at least 
 some difficulty , at least a lot of difficulty , and unable to do it at all . in this study , 
 we dichotomized the response into no and yes ( at least some difficulty or more ) . information regarding expenses related to use of medical services was collected for each 
 household member who had used health - care services in the past 12 months . the expenses 
 included out - of - pocket payment for medical service , treatment , and other related costs , 
 such as bonuses for medical staff , and transportation fees . the unit of measurement was 
 1000 vietnamese dong ( vnd ) ( equivalent to 0.063 - 0.066 united states dollars during the 
 survey periods ) . we did not include payment for non - prescribed medicine , medical tools , 
 health insurance , and aid , because information about them was not collected at the 
 individual level . independent variables included sex , age , area ( urban , and rural ) , household income in the 
 past 12 months , educational attainment , and occupation of household head . age was 
 categorized into three groups : 610 , 1114 , and 1517 years , each corresponding to modal 
 age for a primary school , a lower secondary school , and an upper secondary school , 
 respectively . household income was calculated as total household revenue minus total 
 expenditure for the revenue - generating activities and divided into quintiles . we analyzed all 
 children ( n=9,882 ) between 6 and 17 years of age in survey households . the analysis did 
 not account for the intra - household correlation because a small proportion of households 
 ( 7.6% ) had more than one child with disabilities . the data set included the household 
 sampling weight for each household , which had been calculated as the inverse of its 
 household selection probability . we used the weight to take into account the multistage 
 sampling design for all analyses . the prevalence of difficulty in six functional domains was calculated by sex , age , area , 
 household income , educational attainment , and occupation of household head . the difference 
 in prevalence by these characteristics was assessed with a logistic regression 
 analysis . the multivariable logistic regression analysis required ten cases per independent 
 indicator variable in the model . in the subsequent analysis , a combined variable for 
 difficulty in hearing , remembering or concentrating , mobility , self - care , or communication the frequency 
 of having difficulty in vision was high enough for a multivariable analysis , and this 
 domain was not combined . the per capita household income was calculated by dividing household income by the number 
 of household members . then the ratio of the mean health - care expenditure to the mean per 
 capita household income in the past 12 months was computed for each difficulty status . to 
 compare the ratio by difficulty status , a dichotomous variable to indicate whether the 
 ratio was greater than 0.05 or not was created and used as a dependent variable in the 
 logistic regression models . the choice of 0.05 was based on the lower threshold value for 
 catastrophic impact of health - care expenditure share used by van doorslaer . the ratio of the mean health - care expenditure to the mean per capita household income was 
 also compared by characteristics of subjects among all children , among children with 
 difficulty in vision , and among children with difficulty in hearing , remembering or 
 concentrating , mobility , self - care , or communication . the odds ratio was adjusted for sex , 
 age , area , household income in the past 12 months , educational attainment , and occupation 
 of household head . among 9,882 children , 397 ( 4.0% ) children had at least one type of disability . table 1table 1prevalence of difficulty in six functional domains by demographic and household 
 characteristics of childrennfunctional domainsvisionhearing , remembering or concentrating , 
 mobility , self - care , or communicationtotalhearingrememberingor concentratingmobilityself - carecommunicationoverall9882186(1.9%)223(2.3%)49(0.5%)98(1.0%)58(0.6%)82(0.8%)93(0.9%)sexboy503271(1.4%)119(2.4%)27(0.5%)53(1.1%)29(0.6%)51(1.0%)52(1.0%)girl4850114(2.4%)104(2.1%)22(0.5%)45(0.9%)29(0.6%)31(0.6%)41(0.8%)p=0.002p=0.459p=0.614p=0.539p=0.849p=0.047p=0.328age6 - 10313233(1.1%)89(2.8%)16(0.5%)33(1.1%)12(0.4%)44(1.4%)31(1.0%)11 - 14364181(2.2%)63(1.7%)17(0.5%)32(0.9%)19(0.5%)19(0.5%)30(0.8%)15 - 17310972(2.3%)71(2.3%)16(0.5%)33(1.1%)27(0.9%)20(0.6%)31(1.0%)trendp<0.001trendp=0.197trendp=0.909trendp=0.979trendp=0.017trendp=0.003trendp=0.971areaurban2198104(4.7%)39(1.8%)8(0.4%)14(0.6%)12(0.6%)21(1.0%)13(0.6%)rural768482(1.1%)184(2.4%)41(0.5%)84(1.1%)46(0.6%)61(0.8%)80(1.0%)p<0.001p=0.090p=0.271p=0.066p=0.814p=0.484p=0.044household income1st quintile ( lowest)254218(0.7%)82(3.2%)20(0.8%)35(1.4%)18(0.7%)26(1.0%)37(1.5%)2nd quintile234128(1.2%)60(2.6%)15(0.6%)30(1.3%)19(0.8%)19(0.8%)26(1.1%)3rd quintile194832(1.7%)35(1.8%)8(0.4%)17(0.9%)5(0.2%)12(0.6%)15(0.8%)4th quintile157542(2.7%)21(1.4%)4(0.3%)11(0.7%)5(0.3%)11(0.7%)7(0.4%)5th quintile ( highest)147465(4.4%)24(1.6%)2(0.1%)5(0.3%)12(0.8%)13(0.9%)9(0.6%)trendp<0.001trendp<0.001trendvp<0.001trendp<0.001trendp=0.545trendp=0.503trendp=0.001educational attainment of household 
 headprimary school graduate or none277938(1.4%)49(1.8%)16(0.6%)20(0.7%)10(0.4%)19(0.7%)16(0.6%)lower secondary school graduate312265(2.1%)79(2.5%)22(0.7%)43(1.4%)22(0.7%)24(0.8%)39(1.3%)upper secondary school graduate121944(3.6%)19(1.5%)2(0.2%)6(0.5%)7(0.6%)11(0.9%)2(0.2%)junior college degree , bachelor s degree , or 
 higher276139(1.4%)76(2.8%)9(0.3%)29(1.0%)20(0.7%)28(1.0%)36(1.3%)trendp=0.523trendp=0.064trendp=0.054trendp=0.789trendp=0.151trendp=0.116trendp=0.079occupation of household headleaders , professionals , or staffs in any 
 fields72535(4.8%)11(1.6%)2(0.3%)3(0.4%)7(1.0%)8(1.1%)3(0.4%)skilled workers in personal services and sales24510(3.9%)5(2.0%)2(0.8%)3(1.2%)002(0.8%)skilled workers in agriculture and fisheries4065(1.2%)8(2.0%)2(0.5%)5(1.2%)0(0.1%)2(0.4%)4(1.0%)skilled handicraftsman and other skilled manual 
 workers109238(3.5%)18(1.6%)3(0.3%)10(0.9%)5(0.5%)6(0.5%)5(0.5%)assemblers and machine operators2695(1.9%)3(1.0%)2(0.7%)2(0.7%)1(0.4%)1(0.4%)1(0.4%)unskilled workers636076(1.2%)157(2.5%)35(0.6%)64(1.0%)43(0.7%)57(0.9%)66(1.0%)armed forces1801(4.4%)01(4.4%)1(4.4%)1(4.4%)1(4.4%)not working76718(2.3%)20(2.6%)3(0.4%)10(1.3%)1(0.2%)7(1.0%)10(1.3%)p<0.001p=0.402p=0.719p=0.582p=0.104p=0.442p=0.226data for per capita household income and educational attainment of the household head 
 were missing in 2 cases and 1 case , respectively . shows the prevalence of difficulty in six functional domains marginally and by 
 demographic and household characteristics of the 9,882 children . the overall prevalence of 
 difficulty were 1.9% for vision , 0.5% for hearing , 1.0% for remembering or concentrating , 
 0.6% for mobility , 0.8% for self - care , and 0.9% for communication . data for per capita household income and educational attainment of the household head 
 were missing in 2 cases and 1 case , respectively . table 2table 2relation between having difficulties and demographic and household 
 characteristics of childrendifficulties in visiondifficulties in hearing , remembering or 
 concentrating , mobility , self - care or communicationor(95%ci)or(95%ci)sexboyreferencereferencegirl1.70(1.23 , 2.37)p=0.0020.91(0.69 , 1.20)p=0.513age610referencereference11142.10(1.35 , 3.27)p=0.0010.61(0.43 , 0.86)p=0.00415172.09(1.34 , 3.28)p=0.0010.84(0.60 , 1.18)p=0.319trend p=0.001trend p=0.300areaurbanreferencereferencerural0.34(0.23 , 0.50)p<0.0011.04(0.69 , 1.56)p=0.842household income1st quintile ( lowest)referencereference2nd quintile1.35(0.73 , 2.49)p=0.3330.83(0.58 , 1.19)p=0.3013rd quintile1.50(0.82 , 2.73)p=0.1840.60(0.39 , 0.92)p=0.0204th quintile1.93(1.05 , 3.55)p=0.0340.46(0.27 , 0.77)p=0.0045th quintile ( highest)2.54(1.39 , 4.66)p=0.0030.55(0.32 , 0.94)p=0.029trend p=0.001trend p=0.002educational attainment of household 
 headprimary school graduate or nonereferencereferencelower secondary school graduate1.25(0.81 , 1.93)p=0.3191.57(1.08 , 2.27)p=0.017upper secondary school graduate1.30(0.77 , 2.17)p=0.3271.08(0.59 , 1.98)p=0.804junior college degree , bachelor s degree , or 
 higher0.82(0.49 , 1.35)p=0.4261.47(1.02 , 2.11)p=0.040trend p=0.380trend p=0.124occupation of household headleaders , professionals , or staffs in any 
 fieldsreferencereferenceskilled workers in personal services and sales0.87(0.38 , 1.96)p=0.7311.17(0.39 , 3.53)p=0.782skilled workers in agriculture and fisheries0.43(0.16 , 1.21)p=0.1111.09(0.43 , 2.76)p=0.858skilled handicraftsman and other skilled manual 
 workers1.00(0.59 , 1.70)p=0.9990.88(0.39 , 1.97)p=0.757assemblers and machine operators0.36(0.13 , 0.98)p=0.0450.63(0.17 , 2.35)p=0.490unskilled workers0.48(0.29 , 0.80)p=0.0041.19(0.62 , 2.30)p=0.606armed forces3.27(0.38 , 27.94)p=0.279not working0.67(0.33 , 1.36)p=0.2631.32(0.59 , 2.95)p=0.492the odds ratios were adjusted for all other characteristics . shows the adjusted odds ratios of difficulties in vision as well as those in 
 hearing , remembering or concentrating , mobility , self - care , or communication for each 
 characteristics of subjects . difficulties in vision were more prevalent among girls than 
 boys , among children who were 1117 years of age than those who were 610 years of age , and 
 in urban areas than rural areas . with regard to the association between difficulty and 
 household income , the direction of association differed between difficulty in vision and 
 difficulty in the other domains : household income of a child with difficulty in vision was 
 higher than that of a child without difficulty in vision , whereas household income of a 
 child with difficulty in domains other than vision was lower than that of a child without 
 difficulty in domains other than vision . the odds ratios were adjusted for all other characteristics . with regard to all subjects , the average per capita household income was 7441.2 thousand 
 vietnamese dong , or 469491 united states dollars ; per capita total household expenditure 
 was 5350.6 thousand dong , or 337353 dollars ; and health - care expenditure was 95.0 thousand 
 dong , or 6 dollars . table 3table 3per capita household income and health - care expenditure in the past 12 
 monthsper capitahousehold income(1000 vnd ) 
 [ a]health - careexpenditure(1000 vnd ) 
 [ b][b]/[a][b]/[a]>0.05mean(sd)mean(sd)share of inpatientcare expenditure%or(95%ci)overall7441.2(9043.1)95.0(887.9)54.9%0.01284.6%children with difficulties in specific 
 domainsvisionno7382.2(9052.6)81.3(709.5)53.4%0.01104.4%referenceyes10521.5(7969.7)807.4(3901.1)62.9%0.076714.6%4.78(2.95 , 7.73)p<0.001p<0.001p<0.001hearing , remembering or concentrating , 
 mobility , self - care , or communicationno7467.9(9059.6)83.3(792.7)50.2%0.01124.4%referenceyes6284.0(8234.2)601.0(2735.9)83.1%0.095613.3%3.13(2.04 , 4.80)p<0.001p<0.001p<0.001hearingno7454.2(9061.6)94.8(888.4)54.9%0.01274.6%referenceyes4827.1(2777.5)133.6(783.7)54.2%0.02776.8%1.33(0.49 , 3.62)p=0.578p<0.001p<0.001remembering or concentratingno7461.8(9073.7)91.6(845.4)53.6%0.01234.5%referenceyes5391.7(4743.5)430.1(2845.4)82.3%0.079814.3%3.22(1.78 , 5.81)p<0.001p<0.001p<0.001mobilityno7441.8(9055.9)85.7(810)51.2%0.01154.5%referenceyes7341.7(6615.2)1656.5(4567.1)87.0%0.225624.8%7.49(3.90 , 14.38)p<0.001p<0.001p<0.001self - careno7438.1(9014.6)86.7(807.7)51.3%0.01174.5%referenceyes7809.8(12029.1)1079.7(4023.4)89.7%0.138216.2%3.99(2.06 , 7.74)p<0.001p<0.001p<0.001communicationno7460.0(9069.7)89.7(825.3)52.8%0.01204.5%referenceyes5456.8(5231.6)649.4(3447.4)84.8%0.119014.9%3.46(1.91 , 6.28)p<0.001p<0.001p<0.001p - values compairing per capita household income or healthcare expenditure by 
 difficulty status were obtained with mann - whitney u tests . the odds ratios compared 
 the odds of [ b]/[a]>0.05 between children with a specific disability and those 
 without . the odds ratios were adjusted for sex , age , area , household income , and 
 educational attainment and occupation of household head . compares the ratio of health - care expenditure to per capita household income 
 between children with a specific disability and those without . the proportion of children with a ratio greater than 0.05 was 4.6% and was higher among 
 children with difficulty in vision , remembering or concentrating , mobility , self - care , and 
 communication than those without these respective difficulties . among children with 
 difficulty in vision , both household income and health - care expenditure were higher among 
 children without difficulty in vision , respectively . on the other hand , among children with 
 difficulty in hearing , remembering or concentrating , mobility , self - care , or communication , 
 household income was lower and health - care expenditure was higher than among children 
 without difficulty , respectively . p - values compairing per capita household income or healthcare expenditure by 
 difficulty status were obtained with mann - whitney u tests . the odds ratios compared 
 the odds of [ b]/[a]>0.05 between children with a specific disability and those 
 without . the odds ratios were adjusted for sex , age , area , household income , and 
 educational attainment and occupation of household head . table 4table 4ratio of health - care expenditure to per capita household income among all 
 children who were 617 years of ageper capita householdincome [ a](1000 
 vnd)health - careexpenditure [ b](1000 
 vnd)[b]/[a][b]/[a]>0.05mean(sd)mean(sd)%or(95%ci)overall7441.2(9043.1)95.0(887.8)0.01284.6%areaurban12349.6(13779.1)126.6(945.6)0.01034.0%referencerural6036.5(6480.7)86.0(870.4)0.01424.8%0.91(0.69 , 1.22)p=0.535household income1st quintile ( lowest)2607.1(642.9)44.8(448.6)0.01725.3%reference2nd quintile4324.0(465.6)91.3(746.9)0.02116.0%1.13(0.87 , 1.45)p=0.3643rd quintile6215.7(642.9)130.5(1500.5)0.02104.6%0.82(0.61 , 1.10)p=0.1914th quintile9090.6(1068.7)96.1(685)0.01063.0%0.52(0.36 , 0.75)p=0.0015th quintile ( highest)20582.2(17665.2)139.3(754)0.00683.0%0.53(0.36 , 0.80)p=0.002trend p<0.001educational attainment of household 
 headprimary school graduate or none6528.2(6541.5)84.6(681.4)0.01304.9%referencelower secondary school graduate7223.7(6977.3)107.5(1138.1)0.01494.8%1.03(0.80 , 1.33)p=0.793upper secondary school graduate11528.2(14240.1)136.2(1135.5)0.01184.5%1.13(0.79 , 1.63)p=0.497junior college degree , bachelor s degree , or 
 higher6800.9(9819.9)73.2(564.8)0.01084.2%0.86(0.66 , 1.13)p=0.279trend p=0.319occupation of household headleaders , professionals , or staffs in any 
 fields14587.6(19354.9)120.7(693.7)0.00832.9%referenceskilled workers in personal services and sales12555.6(18497.1)142.9(929.3)0.01144.5%1.35(0.61 , 2.99)p=0.459skilled workers in agriculture and fisheries8658.4(11815.4)99.3(548.3)0.01155.8%1.76(0.91 , 3.41)p=0.092skilled handicraftsman and other skilled manual 
 workers7300.0(5111.7)114.2(801.1)0.01565.2%1.45(0.82 , 2.56)p=0.205assemblers and machine operators11464.5(9493.2)84.7(662.9)0.00743.9%1.25(0.53 , 2.97)p=0.612unskilled workers6082.9(5630.6)92.5(992.7)0.01524.7%1.25(0.75 , 2.10)p=0.389armed forces14426.3(5345.6)40.6(82.1)0.00280.0%not working8288.8(10242.1)51.9(157.5)0.00634.7%1.40(0.76 , 2.58)p=0.280the odds ratios were adjusted for sex , age , and all other characteristics . compares the ratio of health - care expenditure to per capita household income 
 among all children who were 617 years of age by their characteristics . the proportion of 
 children with a ratio being greater than 0.05 was higher among children from the poorer 
 households . table 5table 5ratio of health - care expenditure to per capita household income among children 
 with difficulty in visionper capita householdincome [ a](1000 
 vnd)health - careexpenditure [ b](1000 
 vnd)[b]/[a][b]/[a]>0.05mean(sd)mean(sd)%or(95%ci)overall10521.5(7969.7)807.4(3901.1)0.076714.6%-areaurban13450.2(9074.0)308.2(1432.3)0.02298.0%referencerural6811.5(3937.7)1439.8(5603.3)0.211423.1%5.19(1.53 , 17.60)p=0.008household income1st quintile ( lowest)2941.3(498.8)296.4(1044.2)0.100816.6%reference2nd quintile4319.3(477.3)191.0(365.9)0.044223.3%2.29(0.41 , 12.59)p=0.3423rd quintile6293.8(694.8)1665.8(7964.4)0.264710.7%0.83(0.11 , 6.03)p=0.8534th quintile8979.4(900.8)705.1(2693.2)0.07859.4%0.87(0.15 , 5.21)p=0.8805th quintile ( highest)18369.0(8705.7)853.5(2665.9)0.046515.6%3.24(0.61 , 17.27)p=0.168trend p=0.383educational attainment of household 
 headprimary school graduate9437.2(9528.8)586.8(2222.6)0.062217.4%referencelower secondary school graduate8397.7(4406.0)1601.3(6128.6)0.190720.0%1.31(0.47 , 3.64)p=0.611upper secondary school graduate14054.0(10112.1)197.9(343.0)0.01419.9%0.81(0.16 , 4.07)p=0.796junior college degree , bachelor s degree , or 
 higher11153.5(7011.5)392.1(2088.0)0.03528.4%0.51(0.11 , 2.37)p=0.386trend p=0.303occupation of household headleaders , professionals , or staffs in any 
 fields13808.2(5597.7)524.8(1932.6)0.03808.6%referenceskilled workers in personal services and sales12739.0(7626.8)1212.3(4290.6)0.09527.9%0.68(0.04 , 12.59)p=0.798skilled workers in agriculture and fisheries7388.3(1640.2)1292.3(2707.2)0.174920.2%2.80(0.14 , 54.00)p=0.496skilled handicraftsman and other skilled manual 
 workers7424.0(4390.7)1068.1(3417.2)0.143917.1%1.08(0.17 , 6.79)p=0.935assemblers and machine operators10534.1(3370.4)630.5(860.6)0.059941.9%9.18(0.95 , 88.46)p=0.055unskilled workers9511.7(8433.8)876.3(5236.1)0.092116.8%1.15(0.21 , 6.20)p=0.871not working14710.4(13221.9)205.4(290.6)0.01406.2%0.52(0.04 , 7.47)p=0.628the odds ratios were adjusted for sex , age , and all other characteristics . compares the ratio of health - care expenditure to per capita household income 
 among children with difficulties in vision by their characteristics . in rural areas , 
 household income was lower and health - care expenditure was higher compared with urban areas , 
 among children with a difficulty in vision . the proportion of children with a ratio greater 
 than 0.05 was higher in rural areas than urban areas . table 6table 6ratio of health - care expenditure to per capita household income among children 
 with difficulty in hearing , remembering or concentrating , mobility , self - care , or 
 communicationper capita householdincome [ a](1000 
 vnd)health - careexpenditure [ b](1000 
 vnd)[b]/[a][b]/[a]>0.05mean(sd)mean(sd)%or(95%ci)overall6284.0(8234.2)601.0(2735.9)0.09613.3%areaurban12824.1(16921.9)282.8(675.7)0.02215.4%referencerural4907.6(3477.6)668.0(2991.4)0.13612.9%1.34 ( 0.29 , 6.26)p=0.710household income1st quintile ( lowest)2618.1(632.8)349.0(2097.2)0.13311.9%reference2nd quintile4322.5(506.4)749.1(2560.5)0.17317.0%1.05 ( 0.32 , 3.43)p=0.9293rd quintile6222.9(687.4)937.6(4695.9)0.15111.1%0.15 ( 0.03 , 0.86)p=0.0334th quintile9108.4(1140.7)61.4(85.8)0.0070.0%-5th quintile ( highest)21188.9(18713.3)1074.0(2424)0.05124.0%0.59 ( 0.15 , 2.23)p=0.432trend p=0.033educational attainment of household 
 headprimary school graduate4801.7(3129.5)319.8(1365.7)0.06710.1%referencelower secondary school graduate5816.4(4466.5)861.3(3858.1)0.14814.2%1.40 ( 0.33 , 5.85)p=0.648upper secondary school graduate11232.7(22455)1471.4(3432.9)0.13138.4%12.30 ( 2.29 , 66.07)p=0.003junior college degree , bachelor s degree , or 
 higher6515.3(6914.2)298.1(1508.6)0.0468.4%0.70 ( 0.13 , 3.68)p=0.673trend p=0.972occupation of household headleaders , professionals , or staffs in all 
 fields24946.8(26821.6)1751.4(3303.5)0.07028.6%referenceskilled workers in personal services and sales5541.4(1866.3)92.3(143.1)0.01725.7%1.40 ( 0.04 , 43.55)p=0.848skilled workers in agriculture and fisheries6949.9(4327.8)1062.1(2487.6)0.15335.9%0.92 ( 0.10 , 8.60)p=0.944skilled handicraftsman and other skilled manual 
 workers6118.2(3232.9)264.8(378.6)0.04329.3%0.42 ( 0.05 , 3.73)p=0.439assemblers and machine operators8885.6(5298.1)969.6(932.7)0.10972.2%-unskilled workers4917.6(4013.0)611.4(3070.9)0.1247.6%0.09 ( 0.01 , 0.65)p=0.017armed forces10092.00.0 - 0.0%-not working5985.4(4888.2)79.9(121.6)0.01315.5%0.35 ( 0.02 , 5.65)p=0.462the odds ratios were adjusted for sex , age , and all other characteristics . compares the ratio of health - care expenditure to per capita household income 
 among children with difficulties in hearing , remembering or concentrating , mobility , 
 self - care , or communication by their characteristics . the proportion of children with a 
 ratio greater than 0.05 was higher among children from the poorer households . the goodness - of - fit of the multivariable logistic regression model was higher for analysis 
 in children with difficulties than in all children : the pseudo r of the 
 multivariable logistic regression model was 0.013 among all children , 0.163 among children 
 with difficulty in vision , and 0.231 among children with difficulty in hearing , remembering 
 or concentrating , mobility , self - care , or communication . we used a large national representative sample to present the economic burden of 
 disabilities by different functional domains among school - aged children and its association 
 with demographic and household characteristics of children in vietnam . the ratio of health - care 
 expenditure to per capita household income was higher among children who had a difficulty in 
 vision , remembering or concentrating , mobility , self - care , or communication compared with 
 those who did not have the respective difficulty . there was a relation between household 
 income and the presence of difficulty in vision , as well as between household income and the 
 presence of difficulty in hearing , remembering or concentrating , mobility , self - care , or 
 communication : difficulty in vision was more prevalent in richer households ; on the other 
 hand , difficulty in hearing , remembering or concentrating , mobility , self - care , or 
 communication was more prevalent in poorer households . in the vietnam household living standard survey 2006 , the estimated prevalence of difficulty in 
 vietnamese children ranged from 0.5% for hearing to 1.9% for vision . the prevalence of 
 disability among children in low- and middle - income countries has varied across studies . for 
 example , the prevalence of visual impairment varied between 0.1% and 12.5% ; the prevalence 
 of hearing impairment between 0.4% and 19.7% ; and the prevalence of intellectual disability 
 between 0.09% and 18.3% . the 
 prevalence of difficulty estimated in this study was within the range of previous reports in 
 low- and middle - income countries . households with children with a disability spent more on health care than households 
 without such children . regarding difficulty in vision , the increase in the economic burden 
 of health care among children with disability was caused by substantially higher health - care 
 expenditure . the higher household income among children with difficulty in vision than 
 children without this difficulty diluted the influence of the increase in the health - care 
 expenditure for difficulty in vision . the share of inpatient care expenditure relative to 
 total health - care expenditure among children with difficulty in vision was not as high as 
 that among children with disabilities in other domains . this low share of inpatient care is 
 consistent with the fact that among the pediatric population in the uk , the proportion of 
 children who received hospital eye services and required hospital admission was low ( less 
 than 10% ) and with the fact that the total cost of ophthalmic surgery and inpatient eye 
 services was less than that of ophthalmology outpatient eye services . regarding difficulties in other domains , the difference in the ratio was caused by both 
 relatively lower income and substantially higher health - care expenditure among children with 
 a disability than those without the respective disability . households with children with 
 difficulty in hearing , remembering or concentrating , mobility , self - care , or communication 
 tended to be poorer than those without children with difficulties . with the exception of 
 difficulty in hearing , there were systematic differences in the mechanisms of high economic burden of 
 disability between difficulty in vision and difficulty in other domains . in our analysis among children 617 years of age , a higher prevalence of disability was 
 observed in the poorer households with regard to disability in hearing , remembering or 
 concentrating , mobility , self - care , and communication . with regard to difficulty in vision , 
 on the other hand , the prevalence was higher among those better off . in studies among adult 
 populations , it has been 
 reported that a larger percentage of children among those who are less wealthy were screened 
 positive with the disability questions , but the association was not consistent . the possible reason for the reverse 
 trend with regard to difficulty in vision observed in this study is longer study hours among 
 children from better off households than those from worse off households . in vietnam , 
 besides engaging in the standard school curriculum , children are enrolled in many kinds of 
 academic tutorials to improve their knowledge and skills . these extra classes have 
 proliferated , since teachers often organize home - based classes to supplement their income 
 . extra classes mean an 
 increased workload for the participating students compared with those not participating . the 
 location can be at school , a teacher s house , or a student s house . lengthy exposure to such 
 factors as inadequate indoor illumination in the reading environment or a chair or table 
 unsuitably large for a child s body size are reported to adversely impact a student s visual 
 acuity . in addition to known risk factors 
 of visual difficulties , such as retinopathy of prematurity and family history of high 
 refractive error , these 
 environmental conditions and lifestyles are now suggested as modifiable causes . the increase 
 in the working hours of children under uncontrolled conditions is considered as a potential 
 concern for child visual development . the authors hypothesized that the different impact of health - care expenditure by 
 demographic and household characteristics of subjects was captured by the fitness of the 
 regression model to the observed data . the model , which included socioeconomic factors , 
 namely household income , educational attainment , and occupation of the household head , 
 explained the variation in the ratio of health - care expenditure to the per capital household 
 income better in the analysis including only children with a disability than in the analysis 
 including all children . this finding was interpreted as indicating that the association 
 between socioeconomic status and household burden was stronger ; in other words , the impacts 
 of differences in socioeconomic status on the household burden of health - care expenditure 
 were higher for children who had disabilities than for those who did not . socioeconomically 
 disadvantaged children not only suffered from higher risk of disability but also experienced 
 heavier disadvantage from their socioeconomic status when they had a disability compared 
 with those who were well off . more attention should be paid to reducing the disadvantage 
 caused by poor socioeconomic conditions when households have children with disabilities . the 
 results of the present study will be useful for the design of equitable health systems in 
 vietnam . this study used a nationwide household sample that was representative for the whole 
 country , that is , the 8 regions , urban / rural areas and 64 provinces in vietnam . the sample 
 size was large , allowing us to reliably estimate the prevalence of difficulties and to 
 conduct multivariable analyses . the information was self - reported , and there is a potential 
 for information bias ; however , the magnitude of the bias is considered to be low because of 
 several reasons : the survey employed high - quality interviewer training and standardized data 
 collection procedures across geographic regions ; the response rates were high , and there 
 were only a small amount of missing data ; and validated measurement scale for disability was 
 used , and the calculated prevalence of disability was within the range from studies in other 
 countries . income was measured as a sum of all reported revenue and costs for all types of 
 activities . health - care expenditure was collected for each member of family and asked 
 separately for inpatient and outpatients care . the survey was cross - sectional and suitable for estimating prevalence and national average 
 income and expenditure . however , no temporal relation was definitively confirmed because of 
 the possibility of reverse causation . to ascertain if poor socioeconomic status causes 
 difficulty or difficulty leads to poor socioeconomic status or both , further studies are 
 necessary . if 
 the poor families had difficulty in accessing health care and did not receive all the needed 
 care , their health - care expenditure would tended to be lower than needed , leading to 
 underestimation of the potentially higher burden of disability among the poor households . data included siblings living in the same household , and underestimation of standard errors 
 was possible , because the analyses did not take the intraclass correlation into account . the 
 magnitude of the bias , however , is considered to be small because there was only one child 
 with a disability in most of the households . health - care needs of children with a disability pose a higher burden on households with 
 lower financial resources . visual disability was more prevalent among children from richer 
 households , whereas other disabilities were more prevalent among children from poorer 
 households .
objective : the aim of this study was to assess the economic burden of 
 disability of school - aged children and to evaluate the association between disabilities 
 and household socioeconomic status , as well as the economic burden of disability and 
 household socioeconomic status in vietnam.materials and methods : nationally representative data for 9,882 children 
 aged 6 to 17 years from the vietnam household living standard survey 2006 were used . 
 disabilities were measured in six basic functional domains , including vision , hearing , 
 remembering or concentrating , mobility , self - care , and communication . 
 we evaluated the 
 association between area , household income , educational attainment , or occupation of 
 household head , and each difficulty . 
 the ratio of health - care expenditure to per capita 
 household income was compared by presence of a disability as well as household 
 socioeconomic status.results : the prevalence of difficulty was 1.9% for vision and 2.3% for at 
 least one of the other five domains . 
 difficulty in vision was more prevalent in the richer 
 households ( p=0.001 ) , whereas difficulty in the other five domains was more prevalent in 
 the poorer households ( p=0.002 ) . 
 the ratio of health - care expenditure to per capita 
 household income was greater than 0.05 in 4.6% of children . the adjusted odds ratio of 
 children with difficulty in vision having a health - care expenditure share greater than 
 0.05 compared with children without difficulty was 4.78 ( 95% ci : 2.95 , 7.73 ; p<0.001 ) , 
 and that for difficulty in the other five domains was 3.13 ( 95% ci : 2.04 , 4.80 ; 
 p<0.001 ) . among children with difficulty in at least one of the five domains other than 
 vision , the proportion of children with a health - care expenditure share greater than 0.05 
 was higher among children from the poorer households ( p=0.033).conclusions : children with a disability spent more on health care relative 
 to their income than those without . 
 visual disability was more prevalent among children 
 from the richer households , whereas other disabilities were more prevalent among children 
 from the poorer households .