Prevalence and features of ICF-disability in Spain as captured by the 2008 National Disability Survey
© Maierhofer et al; licensee BioMed Central Ltd. 2011
Received: 9 June 2011
Accepted: 28 November 2011
Published: 28 November 2011
Since 1986, the study of disability in Spain has been mainly addressed by National Disability Surveys (NDSs). While international attempts to frame NDS designs within the International Classification of Functioning, Disability and Health (ICF) have progressed, in general, the ICF has hardly been used in either the NDS or epidemiological studies. This study sought to identify ICF Activity- and Participation-related content in the most recent Spanish NDS, the 2008 Survey on Disabilities, Independence and Dependency Situations (Encuesta sobre discapacidades, autonomía personal y situaciones de Dependencia - EDAD 2008), and estimate the prevalence of such ICF-framed disability.
EDAD 2008 methods and questions were perused. Of the 51 EDAD items analysed, 29 were backcoded to specific d2-d7 domains of the ICF Checklist and, by rating the recorded difficulty to perform specific tasks with or without help, these were then taken as performance and capacity respectively. A global ICF score was also derived, albeit lacking data for d1, "Learning and applying knowledge", d8, "Major Life Areas" and d9, "Community, Social and Civic Life". Data were grouped by sex, age, residence and initial positive screening, and prevalence figures were calculated by disability level both for the general population, using the originally designed weights, and for the population that had screened positive to disability. Data for institutionalised persons were processed separately.
Crude prevalence of ICF severe/complete and moderate disability among the community-dwelling population aged ≥6 years was 0.9%-2.2% respectively, and that of severe/complete disability among persons living in sheltered accommodation was 0.3%.
Prevalence of severe/complete disability was: higher in women than in men, 0.8% vs. 0.4%; increased with age; and was particularly high in domains such as "Domestic Life", 3.4%, "Mobility", 1.8%, and "Self-care", 1.9%, in which prevalence decreased when measured by reference to performance. Moreover, global scores indicated that severe/complete disability in these same domains was frequent among the moderately disabled group.
The EDAD 2008 affords an insufficient data set to be ICF-framed when it comes to the Activity and Participation domains. Notwithstanding their unknown validity, ratings for available ICF domains may, however, be suitable for consideration under the ADL model of functional dependency, suggesting that there are approximately 500,000 persons suffering from severe/complete disability and 1,000,000 suffering from moderate disability, with half the latter being severely disabled in domains capable of benefiting from technical or personal aid. Application of EDAD data to the planning of services for regions and other subpopulations means that need for personal help must be assessed, unmet needs ascertained, and knowledge of social participation and support, particularly for the mentally ill, improved. International, WHO-supported co-operation in ICF planning and use of NDSs in Spain and other countries is needed.
KeywordsADL Disability Epidemiology ICF Prevalence Survey WHO
The World Health Organization (WHO) approved the International Classification of Functioning, Disability and Health (ICF) in 2001 as a framework and classification for understanding the impact of health conditions on functioning and disability . The ICF conceptual framework encompasses different components, such as body functions, body structures, activities and participation, with some personal and environmental factors being included among the causes of disability . The ICF enables individuals' functioning and disability to be comprehensively described and categorised in a way that is systematic, standardised and readily understandable by all health professionals and social workers involved in the care and support of patients . The ICF is increasingly used in different sectors, including health, social affairs, labour and education [3, 4].
Conceivably, the most powerful and regularly used tools for describing how disability affects citizens and supporting social policies are National Disability Surveys (NDSs). Early efforts by the Disability Tabulations (DISTAB) group, including rigorous selection of questions from five NDSs and backcoding these to the ICF, suggested that cross-country comparisons would be restricted to comparable backcoded questions, and that the best basis for international comparability would thus be for questions' focus and format to be structured to the ICF during the surveys' development phase . Mulhorn and Threats, using the ICF, described several-fold variations in age- and sex-specific prevalence of speech and hearing limitations across five countries included in the DISTAB study, and revealed difficulties in comparing figures based on measures of differing sensitivity . Recently, international action to understand disability in populations was led by the Washington City Group (a working group of the United Nations) . Using the ICF to develop the Irish National Disability Survey resulted in a broader range of disabilities encompassed and the incorporation of policy-relevant environmental factors, and prompted a discussion on ethics .
While it would seem that the ICF capacity and performance qualifiers are considered useful by rehabilitation and social workers , the use of capacity and performance prevalence data for assessing or developing social services and policies appears to have been less explored. Stineman et al, after confirmatory factor analysis of a large US population, proposed that a standard set of ICF core chapters -mobility, self-care and domestic life- could help link and co-ordinate care across general practitioners, rehabilitation professionals and social services, as well as the acute and long-term care sectors . In Spain, a personal disability index has been proposed, based on unselected disabilities registered in the 1999 NDS and taking into account the severity and number of hours of personal help received per week .
The type of disability data collected among the Spanish population has changed over the years. National and certain regional health surveys contain specific information on impairments, limitations and restrictions assessed using patient-reported outcomes, such as the EQ-5, as well as time received from caregivers . The large-scale, nation-wide household surveys conducted by trained interviewers in 1986 and 1999 (http://www.ine.es/) were developed using the framework of the International Classification of Impairments, Disabilities and Handicaps (ICIDH). The most recent of these was the 2008 Survey on Disabilities, Independence and Dependency Situations (Encuesta sobre discapacidades, autonomía personal y situaciones de Dependencia - EDAD 2008) [13–15], which partly incorporated the ICF's understanding of disability and some of its concepts.
Accordingly, this study sought: (a) to explore the potential of EDAD 2008 data for an ICF-based interpretation, detect any ICF-biased aspects and implement a specific application of the EDAD 2008 after ICF re-structuring; (b) to quantify prevalence of disability for selected ICF domains and for an individual ICF global score; and, (c) to describe severity patterns among the disabled population.
The EDAD 2008
Study population and sampling methodology
The study population covered by the EDAD 2008 [16, 17] consisted of two residence-based population samples, one community-dwelling and the other institutionalised. For the community-dwelling sample, a two-step, stratified, random sample was used to provide a representative sample for each province: firstly, a sample of census sections was drawn, and a sample of family dwellings was then randomly drawn within each section. Thereafter, all households within the dwelling were group screened, with one member of each household being interviewed as the main informant [16, 17]. A total of 258,187 persons living in 91,290 households were thus screened for disability.
In the case of institutions, a sample of Spanish residential centres and hospitals, representative of the country's Autonomous Regions, was drawn [16, 17]. The centres had been classified into two different types, namely: (a) home or residential centres; and (b) psychiatric or geriatric hospitals or centres for disabled persons. At each centre, a random sample of inhabitants was drawn, yielding a sample of 10,567 institutionalised persons.
Individually tailored data-collection
For screening purposes, a catalogue of 44 questions about possible "disabilities" read verbatim, was presented to the main informant of each household. It addressed the following eight domains: vision; audition; communication; learning and application of knowledge and performance of tasks; mobility; self-care; domestic life; interaction and interpersonal relationships [16–19]. Persons for whom at least one of these questions was answered in the positive were then examined in depth, using a detailed disability questionnaire, covering the above-mentioned eight domains, medical conditions, diagnoses, professional life, education, discrimination, social contacts, accessibility and main caregivers. For some items, the level of difficulty experienced in a given item was measured against two different backgrounds, namely, the difficulty encountered when performing without aid and that encountered when performing with technical or personal aid [18, 19]. In addition, the technical or "de facto" personal help received was recorded. For subjects aged under 6 years, an adapted version of the questionnaire was used [18, 19]. To evaluate the disabilities of children aged < 6 years, an informant was given a list of possible limitations and asked to select those that were present. All institutionalised persons allocated to the sample were interviewed with an adapted version of the detailed questionnaire used for the household-based disability study.
Database structure and records on study
The National Institute of Statistics (Instituto Nacional de Estadística - INE) provided us with individual EDAD 2008 records. Following the survey format, the data were organised into four data sets, i.e., one covering all persons screened in households (denoted as household data set), one covering persons who screened positive and answered the detailed questionnaire about their disabilities (disability data set), one covering positively screened children (data limitations), and lastly, one covering all institutionalised persons (data centres). To cover specific issues of relevance, we used data from the above-mentioned four data sets, selecting the most appropriate for any given purpose.
ICF framing of EDAD 2008data
ICF-EDAD 2008 cross-walking; ICF backcoding of selected EDAD 2008 variables
EDAD 2008 items of potential interest and those finally selected for ICF backcoding*.
ICF Checklist variables
EDAD 2008variables considered (regardless of selection)
EDAD 2008 item used
Short list of activity and participation domains
Content of EDAD 2008 variables
d1. Learning and applying knowledge
to hold a gaze or pay attention when listening
to hold a gaze or pay attention when listening
d140 Learning to read
to learn to perform simple tasks
d145 Learning to write
to learn to perform simple tasks
d150 Learning to calculate
to learn to perform simple tasks
d175 Solving problems
d2. General tasks and demands
d210 Undertaking a single task
to perform simple tasks
d220 Undertaking multiple tasks
to perform complex tasks
d310 Communicating with -- receiving -- spoken messages
to understand the meaning of what other persons say
d315 Communicating with -- receiving -- non-verbal messages
to understand and express yourself via gestures, symbols, illustrations or sounds
to speak intelligibly or utter coherent phrases
d335 Producing non-verbal messages
to hold a dialogue and exchange ideas with one or more persons
d430 Lifting and carrying objects
to lift or carry objects
d440 Fine hand use
to lift or carry small objects
to walk and move inside the home
to walk and move around the home
d465 Moving around using equipment
d470 Using transportation
to get around via passenger transport
to drive vehicles
d510 Washing oneself
to wash or dry different body parts
d520 Caring for body parts
to perform basic grooming
to carry out activities related to urination
to carry out activities related to defecation
to carry out activities related to menstrual care (only for women)
to dress or undress
to eat and drink
to eat and drink
d570 Looking after one's health
to follow medical prescriptions
to avoid dangerous situations
d6. Domestic life
d620 Acquisition of goods and services
to do shopping
d630 Preparation of meals
to prepare meals
d640 Doing housework
to carry out housework
d660 Assisting others
d7. Interpersonal interactions and relationships
d710 Basic interpersonal interactions
to show other persons affection, respect or transmit feelings
d720 Complex interpersonal interactions
d730 Relating with strangers
to relate to strangers
d740 Formal relationships
to initiate and maintain relations with subordinates, peers or superiors
d750 Informal social relationships
to initiate and maintain relations with friends, neighbours, acquaintances or colleagues
d760 Family relationships
to initiate and maintain family relations
d770 Intimate relationships
to initiate and maintain intimate or sexual relations
d8. Major life areas
d810 Informal education
d820 School education
d830 Higher education
Level of studies completed
In relation to your finished studies, what is your diploma degree or graduate degree?
In the last five years, have you done any vocational training course?
In relation to education and school integration, what was your situation last week?
d850 Remunerative employment
Due to the onset or worsening of your disability, have you had to amend your relationship with economic activity or your occupation?
Relation with economic activity in the past week.
Have you worked at some point as an employee or freelance worker?
Why did you stop working?
d860 Basic economic transactions
d870 Economic self-sufficiency
What is the monthly amount of the total income for this household?
d9. Community, social and civic life
d910 Community Life
In the last 12 months, have you felt discriminated against on the basis of your disability in any of the following situations? In social participation
In the last 12 months, have you felt discriminated against on the basis of your disability in any of the following situations? In social relations
Have you had any opportunities in the last 12 months? Relating with friends or persons who are close
d920 Recreation and leisure
What activities do you spend most of your spare time on, and which would you like to carry out for enjoyment or recreation that you do not already, due to your disability? Please select the three main activities in both columns.
d930 Religion and spirituality
d940 Human rights
d950 Political life and citizenship
In the last 12 months, have you felt discriminated against on the basis of your disability in any of the following situations? - Public Administration
In accordance with a recognised, optional interpretation of capacity and performance as relating to difficulties in the absence or presence of technical and personal help, we took advantage of the above information on difficulty encountered with and without technical or personal aid to derive firstly a measure of capacity and thence a measure of performance from the EDAD 2008, both recorded in each individual ICF-framed incomplete Checklist record. In practice, measurements were taken in such a way that, if the answer about receiving any type of aid (technical, personal or both) was positive, the level of performance was assessed. To sum up, in the case of selected variables (see Table 1), two ICF disability indices were obtained, one for capacity and the other for performance, using the same ICF score conversion procedure explained below. Domains for which there were no questions on aid (d1, "Learning and applying knowledge", d7 "Interpersonal interactions and relationships", and, in part, d3 "Communication", see Table 1) were excluded from this method of deriving performance. For items from other domains where there was confirmation that no aid had been received, information on capacity was used to impute the value of performance, assuming that capacity equalled performance in such cases. In the EDAD 2008, we were unable to identify collected data on barriers, whether physical or social, and facilitators (other than the above-mentioned "help") linked to disability items.
Calculation of a tentative ICF checklist-oriented individual score
ICF categories: (a) as originally denoted and described in words, numerals, percentages and mid-point scores for each categorical percentage-span; and (b) as backcoded in this study.
ICF (in words)
ICF (in categories)
ICF (in percentage terms)
EDAD 2008 categories
No or mild difficulty
Score intervals were then selected as values corresponding to ordinal ICF qualifiers. Qualifiers for ICF items resulting from EDAD 2008 data were obtained by combining the scores for the selected EDAD 2008 variables, as indicated in Table 1, where "Learning and applying knowledge" (d1), "Major life areas" (d7) and "Community, social and civic life" (d9) were excluded, both for the remaining specific domains and for the global score which lacked data from the excluded domains. In practice, the effect of such exclusion on the method is to render global scores rather insensitive to restrictions in social participation. Moreover, the fact that disability data were obtained after screening positive for at least one of 44 disability items, means that the value 1 for no/mild difficulty described in Table 2 and denoted as N, most frequently corresponded to "mild" difficulty, i.e., mild disability, and for our purposes will therefore be referred to as the "mild disability group". Screened negative status was denoted as SN.
Different age groupings (1, 2 and 3) used in the sample of institutionalised persons, and the grouping used in this study to merge the information on age
In view of the fact that (a) sample probability was different for community-dwelling and institutionalised persons, with the former being tailored to provinces and the latter to Autonomous Regions, and that (b) result interpretability in terms of representativeness vis-à-vis the Spanish resident population was required, EDAD 2008 weighting was systematically applied to the numerators and denominators of the above-mentioned prevalence. After weighting, the subsamples were found to be accurately representative of the resident Spanish population. Our estimate of 45,031,810 community-dwelling and 290,506 institutionalised persons fitted well with the data reported on the survey web page . Comparison with the National Institute of Statistics' data on the general population at 1 January 2008  for each Autonomous Region yielded numbers 1%-3% higher than the numbers obtained by us from the EDAD 2008 data, except for a 5% difference in the case of Melilla and Ceuta, two relatively small cities located in Northern Africa.
Descriptive statistics for items in single disability domains
Percentages for ICF-Categories (No/mild difficulty, N; moderate difficulty, M; severe difficulty, S; complete difficulty, C) and subscores for each of the seven domains, as well as missing values (MV) in percentages.
General tasks and demands
Undertaking a single task
Undertaking multiple tasks
Communicating with -- receiving -- spoken messages
Communicating with -- receiving -- non-verbal messages
Lifting and carrying objects
Fine hand use
Caring for body parts
Looking after one's health
Acquisition of goods and services
Preparation of meals
Interpersonal inter-actions and relationships
Basic interpersonal interactions
Relating with strangers
Informal social relationships
Prevalence of disability by ICF capacity index
Assuming that all persons living in centres screened positive, prevalence of disability as seen from positive screening nation-wide (all levels included) was: 9.6% among persons aged ≥6 years; 2.2% among persons aged 0-5 years; 9% among community-dwelling persons aged ≥6 years; and 0.7% for institutionalised persons among the over-all population aged ≥6 years. Prevalence of severe or complete disability as defined by ICF qualifiers 3 and 4 from capacity scores for all persons aged ≥6 years was 1.2%, with 0.9% corresponding to those living in the community and 0.3% to institutionalised persons using the same population denominator. In other words, approximately one out of four severely/completely disabled persons was institutionalised.
Capacity and performance patterns: ICF index by specific domain within single group by total ICF score
The EDAD 2008 is not only the most important database on disability among the Spanish population, but is arguably also one of the most complete, periodic, national population approaches to studying disability worldwide. The EDAD 2008 incorporated important contributions, such as data for institutionalised persons. Major differences between the EDAD 2008 and previous disability surveys in Spain pertain to the former's additional, newly designated target of providing information on functional dependency in order to support planning and funding of the Spanish dependency system. As a first step, this study sought to link the EDAD 2008 to an analysis of functional dependency, by ICF Checklist backcoding and score rescaling of EDAD 2008 items restricted to the Activity and Participation domains. An important limitation of this exercise is asymmetry, in that it suffers from a lack of crosswalking between EDAD 2008 variables and Body Structures and Functions, as well as a neglect of aspects potentially related to ICF contextual factors in general and to Environmental Factors in particular.
Results show that, in practice, ICF domains such as "Learning and applying knowledge", "Major life areas" and "Community, social and civic life" were disregarded, and others, such as "General tasks and demands", were not appropriately covered by posing just a couple of questions. The frequent NDS bias towards activity-level data, described above in the case of United Nations efforts , permeates the EDAD 2008. Hence, ICF domain restriction, score rescaling and exclusion of institutionalised persons in age-specific counts may seriously limit the interpretability and international comparability of prevalence figures in respect of both capacity and performance, whether for single ICF domains or individual total ICF score indices. In addition, much remains to be improved to ensure a homogeneous and complete data-contribution from institutionalised persons in the country's different Autonomous Regions (Comunidades Autónomas), which currently constitute the main EDAD 2008 stakeholders in terms of health and social services.
Once the most relevant limitations have thus been defined, our results can be said to afford a structured, albeit non-validated, view of the prevalence of ICF disability in Spain in 2008, with approximately 12/1000 severely/completely disabled and 24/1000 moderately disabled persons, and the latter registering relatively high proportions of severe/complete disability in the following subscores: "Self-care", 1/3; "Mobility", 3/10; and "Domestic life", 8/10. These proportions were considerably reduced, though not eliminated, by personal or technical aid.
Interpretation and analysis of results may be better suited to comparisons with other ICF measurements in populations. In a Turkish study on the elderly population, Donmetz et al in 2005  reported median scores for persons found to give at least one positive answer in the WHODAS-2. The fact that we cannot compare our results from ICF prevalence measurements of similar ICF categories obtained from total scores or for specific domains illustrates the implications of application or neglect of epidemiological principles and of descriptive and analytical purposes in population research.
Reported age-specific prevalence of ICF moderate disability among the very old in Spain  is remarkably similar to figures cited here for community-dwelling residents, e.g., 10.61% for men and 16.47% for women in the 80-84 age group compared to the corresponding values of 10.2% for men and 16.9% for women shown in Figure 1. Despite the fact that the sample in Virués et al's study was certainly not geographically representative of the Spanish population, the similarities are nonetheless striking, suggesting that the external validity of the risk factors of ICF severe/complete disability identified by this study for the Spanish population is high [Virués Ortega J et al. Medical, Environmental and Personal Factors of Disability in the Elderly People in Spain: A Screening Survey based on the International Classification of Functioning (Gaceta Sanitaria 2011, in press)].
Assuming that our figures are accurate, the numbers obtained by us for the severe or complete disability levels would allow the numbers of severely/extremely disabled persons in Spain to be estimated for the first time. These figures, namely, 135,506 men and 245,331 women, constitute figures that are remarkably lower and easier to interpret than those reported in 1999 for persons with, say, several disabilities  but may not be comparable. Prevalence of severe disability among 85-89 year-old community-dwelling residents in Gloucester UK, measured by a postal survey using a validated independence scale, was 13.4% for men and 20.9% for women, approximately double that found for severe/complete capacity in our study . Similar differences were seen in other sex- and age-groups. It is possible that, despite limited comparability, our figures constitute undercounts, an effect reinforced by the impact of assigning 1 to items where data were missing, something that particularly affected men in "Domestic life" and women in outdoor "Mobility".
Thanks to the large sample size, the value our results is almost unique when it comes to describing disability patterns by ICF domain. The higher prevalence registered for women and for "Domestic Life", "Mobility" and "Self-care" replicate similar patterns observed for extremely aged Spanish ; and for elderly Turkish subjects, with mean scores when disabled of 50.5, 40.6 and 34.2 respectively, and a total WHODAS-2 score of 23.0 .
The fact that the above-mentioned domains with higher prevalence correspond to domains in which prevalence of disability decreases when measured by performance, i.e., with personal or technical aid, fits expected changes expected from the ICF framework. The considerable modification of patterns in the moderately disabled group might indicate that such groups constitute a target for provision of services, in cases where severe/extreme disability can be reduced by personal or technical aid. The large size of this group renders it even more relevant for policy-making and points to a large population segment of the Spanish population which, in addition to the approximately 500,000 severely/completely disabled, encompasses more than 50% of the 1,000,000 persons with ICF moderate disability who could potentially benefit from personal aid if available. Since the EDAD 2008 furnishes data on time devoted by caregivers and an assessment of the shortfall, Figure 4 may provide some clues for estimating the need -both met and unmet- for help from other persons, and for building an index of such help in terms of work time, e.g., hours/week. Unfortunately, the lack of availability of data for domains such as social participation, limits the usefulness of the EDAD 2008 when it comes to estimating the need for help to improve social participation in, e.g., work, leisure or economy. This domain may be particularly relevant for persons affected by non-somatic ailments, such as psychiatric patients whose disability may have been underrepresented in the EDAD 2008 due to formulation, inasmuch as it documents occupational status but not the barriers encountered in overcoming restricted access to work. In brief, it would appear that, taking ICF categories as the point of departure, the EDAD 2008 may provide a basis for estimating the prevalence of need for personal help, with it being more difficult to address the need for social support required to improve social participation in, e.g., work, leisure or economy.
Focusing prevalence on disease status, the required epidemiological dimension of services research is well recognised. Nevertheless, an ICF-based approach to the design of National Disability Surveys might be difficult to reconcile with usability of an ICF "which does not classify people" despite "ICF classifies health-related states" (quotation marked fragments obtained from ICF ref 1, page 8). Our results may point towards a role for an epidemiological approach which reinforces the concept of functional dependence, by minimising the visualisation of severe mental disorders with sparse limitations of basic ADL and their need of social support. A description of the differences between functional dependency and disability, and the particularities of the Spanish approach to dependency in the context of the ICF has recently been published . The need for bridging and knowledge transfer in the field of disabilities and ageing, possibly related to certain content discrepancies between the ICF and EDAD 2008, has been highlighted . It is not known whether differences between the ICF and EDAD 2008 evidenced in Table 1 and the limitations of our approach rely on the lack of bridging between the Spanish group who drew up the survey and the existing international ICF-WHO groups (e.g., ICF/FDRG, ICF Spanish Network on Disabilities, and the above-mentioned experiences of the Washington City Group and Ireland) or on deeper ICF constraints discussed by Salvador-Carulla and others .
To sum up, the Spanish EDAD 2008 represents a powerful initiative and considerable limitations in terms of applying the ICF to questionnaire design and epidemiological analysis of disability. However, the EDAD 2008 can be said to be a useful tool for describing the prevalence of disability and, potentially, for estimating functional dependence for planning aid and services, taking social and geographical differences into account. Approximately 500,000 to 1,000,000 persons present with ICF levels of severe/complete and moderate disability, respectively. In terms of magnitude, such figures fit reported age-specific prevalence data for disability levels obtained from the WHODAS-2 for the very old in Spain, and match the higher difficulty pattern in mobility, domestic life and self-care domains.
This study was partially supported by the Consortium for Biomedical Research in Neurodegenerative Diseases (Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas - CIBERNED), Spanish Health Research Fund (Fondo de Investigaciones Sanitarias) project PI06/1098 and Farasdués Foundation.
The authors would like to acknowledge the support received from Alarcos Cieza and Cornelia Oberhauser, at the Institute for Health & Rehabilitation Sciences, Biopsychosocial Health Research Unit, Ludwig-Maximilians University, Munich, Germany, for having inspired this manuscript, based on their initial analyses of the Spanish 1999 and 2008 surveys, which were presented at the conference, "Aplicación en España de la Clasificación Internacional del Funcionamiento, la Discapacidad y la Salud (CIF): Presente y Futuro" on May 30, 2010 in Madrid. Thanks must also go to Michael Benedict for his help with the review and revision of the English-language version of the manuscript.
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