Obstacles in large-scale epidemiological assessment of sensory impairments in a Dutch population with intellectual disabilities

Opt-In and Opt-Out Consent Procedures for the Reuse of Routinely Recorded Health Data in Scientific Research and Their Consequences for Consent Rate and Consent Bias: Systematic Review

BACKGROUND

Scientific researchers who wish to reuse health data pertaining to individuals can obtain consent through an opt-in procedure or opt-out procedure. The choice of procedure may have consequences for the consent rate and representativeness of the study sample and the quality of the research, but these consequences are not well known.

OBJECTIVE

This review aimed to provide insight into the consequences for the consent rate and consent bias of the study sample of opt-in procedures versus opt-out procedures for the reuse of routinely recorded health data for scientific research purposes.

METHODS

A systematic review was performed based on searches in PubMed, Embase, CINAHL, PsycINFO, Web of Science Core Collection, and the Cochrane Library. Two reviewers independently included studies based on predefined eligibility criteria and assessed whether the statistical methods used in the reviewed literature were appropriate for describing the differences between consenters and nonconsenters. Statistical pooling was conducted, and a description of the results was provided.

RESULTS

A total of 15 studies were included in this meta-analysis. Of the 15 studies, 13 (87%) implemented an opt-in procedure, 1 (7%) implemented an opt-out procedure, and 1 (7%) implemented both the procedures. The average weighted consent rate was 84% (60,800/72,418 among the studies that used an opt-in procedure and 96.8% (2384/2463) in the single study that used an opt-out procedure. In the single study that described both procedures, the consent rate was 21% in the opt-in group and 95.6% in the opt-out group. Opt-in procedures resulted in more consent bias compared with opt-out procedures. In studies with an opt-in procedure, consenting individuals were more likely to be males, had a higher level of education, higher income, and higher socioeconomic status.

CONCLUSIONS

Consent rates are generally lower when using an opt-in procedure compared with using an opt-out procedure. Furthermore, in studies with an opt-in procedure, participants are less representative of the study population. However, both the study populations and the way in which opt-in or opt-out procedures were organized varied widely between the studies, which makes it difficult to draw general conclusions regarding the desired balance between patient control over data and learning from health data. The reuse of routinely recorded health data for scientific research purposes may be hampered by administrative burdens and the risk of bias.

Outcome of 10 years of ear and hearing screening in people with intellectual disability in Europe: A multicentre study

BACKGROUND

Undetected ear and hearing problems negatively impact the quality of life of people with intellectual disability.

METHODS

This multicentre retrospective study describes the outcome of 10 years of ear and hearing screening in athletes with intellectual disability in seven European countries. The screening was conducted by a trained team using a strictly standardised protocol.

RESULTS

Of 15,363 screened athletes with intellectual disability, more than half (58.7%) needed referral for ear and/or hearing problems, ranging from 51.7% (<20 years old) to 81.4% (≥60 years old). The most commonly detected conditions were excessive/impacted earwax (40.3%), middle ear problems (30.1%) and hearing loss (27.0%), with significant differences between age groups and countries.

DISCUSSION

This study demonstrates an increased risk of ear and hearing problems in people with intellectual disability as compared to the general population. Considering the unawareness and impact of these problems, it is highly recommended to organise systematic screening. Follow-up for diagnostic elaboration, therapeutic management and long-term guidance should be provided.

Behavioural activation versus guided self-help for depression in adults with learning disabilities: the BeatIt RCT

BACKGROUND

Depression is the most prevalent mental health problem among people with learning disabilities.

OBJECTIVE

The trial investigated the clinical effectiveness and cost-effectiveness of behavioural activation for depression experienced by people with mild to moderate learning disabilities. The intervention was compared with a guided self-help intervention.

DESIGN

A multicentre, single-blind, randomised controlled trial, with follow-up at 4, 8 and 12 months post randomisation. There was a nested qualitative study.

SETTING

Participants were recruited from community learning disability teams and services and from Improving Access to Psychological Therapies services in Scotland, England and Wales.

PARTICIPANTS

Participants were aged ≥ 18 years, with clinically significant depression, assessed using the Diagnostic Criteria for Psychiatric Disorders for use with Adults with Learning Disabilities. Participants had to be able to give informed consent and a supporter could accompany them to therapy.

INTERVENTIONS

BeatIt was a manualised behavioural activation intervention, adapted for people with learning disabilities and depression. StepUp was an adapted guided self-help intervention.

MAIN OUTCOME MEASURES

The primary outcome measure was the Glasgow Depression Scale for people with a Learning Disability (GDS-LD). Secondary outcomes included carer ratings of depressive symptoms and aggressiveness, self-reporting of anxiety symptoms, social support, activity and adaptive behaviour, relationships, quality of life (QoL) and life events, and resource and medication use.

RESULTS

There were 161 participants randomised (BeatIt, n = 84; StepUp, n = 77). Participant retention was strong, with 141 completing the trial. Most completed therapy (BeatIt: 86%; StepUp: 82%). At baseline, 63% of BeatIt participants and 66% of StepUp participants were prescribed antidepressants. There was no statistically significant difference in GDS-LD scores between the StepUp (12.94 points) and BeatIt (11.91 points) groups at the 12-month primary outcome point. However, both groups improved during the trial. Other psychological and QoL outcomes followed a similar pattern. There were no treatment group differences, but there was improvement in both groups. There was no economic evidence suggesting that BeatIt may be more cost-effective than StepUp. However, treatment costs for both groups were approximately only 4-6.5% of the total support costs. Results of the qualitative research with participants, supporters and therapists were in concert with the quantitative findings. Both treatments were perceived as active interventions and were valued in terms of their structure, content and perceived impact.

LIMITATIONS

A significant limitation was the absence of a treatment-as-usual (TAU) comparison.

CONCLUSIONS

Primary and secondary outcomes, economic data and qualitative results all clearly demonstrate that there was no evidence for BeatIt being more effective than StepUp.

FUTURE WORK

Comparisons against TAU are required to determine whether or not these interventions had any effect.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN09753005.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 53. See the NIHR Journals Library website for further project information.

Self-reported measures in health research for people with intellectual disabilities: an inclusive pilot study on suitability and reliability

BACKGROUND

The lack of suitable and reliable scales to measure self-reported health and health behaviour among people with intellectual disabilities (ID) is an important methodological challenge in health research. This study, which was undertaken together with co-researchers with ID, explores possibilities for self-reported health scales by adjusting, testing, and reflecting on three self-reported health scales.

METHODS

In an inclusive process, the researchers and co-researchers with ID adjusted the SBQ (sedentary behaviour), SQUASH (physical activity), and SRH (self-reported health) scales, after which a test-retest study among adults with ID was performed. Test outcomes were analysed on suitability and test-retest reliability, and discussed with the co-researchers with ID to reflect on outcomes and to make further recommendations.

RESULTS

Main adjustments made to the scales included: use easy words, short sentences, and easy answer formats. Suitability (N = 40) and test-retest reliability (N = 15) was higher for the adjusted SQUASH (SQUASH-ID), in which less precise time-based judgements are sought, than in the adjusted SBQ (SBQ-ID). Suitability and test-retest reliability were fair to moderate for the SRH-ID and CHS-ID. The main outcome from the reflection was the recommendation to use SQUASH-ID answer options, in which less precise time-based judgements were sought, in the SBQ-ID as well.

CONCLUSIONS

This study served as a pilot of an inclusive process in which people with ID collaborated in adjusting, testing, and reflecting on self-reported health scales. Although the adjusted self-reported measurements may be reliable and suitable to the target group, the adjustments needed may impair measurement precision. This study's results contribute to informed decision making on the adaptation and use of self-reported health scales for people with ID.

Parent ratings of ability to consent for clinical trials in fragile X syndrome

Advances in understanding neurobiology and intellectual disabilities have led to clinical trials testing new medications. This study assessed parents' perceptions of the ability of their son or daughter with fragile X syndrome (FXS), an inherited form of intellectual disability, to participate in the consent process for clinical trials. Four hundred twenty-two families participated in a survey that included six items assessing various aspects of the ability to provide consent. A rank ordering of decisional tasks was found. The easiest task was to understand that the medication was different from his or her medical treatment; the most difficult was the ability to understand and weigh the potential benefits and risks of study participation. Factor analysis suggested that despite the range in difficulty, the six items were best summarized by a single decisional ability score. Parents of 29% of males reported that their son was not at all capable of participating, but the remainder exhibited a range of decisional skills. Factors associated with this variability include age and parents' willingness to enroll their child in clinical trials. We conclude that many individuals with FXS appear to be able to participate at some level in the consent or assent process, but will likely need individualized support to maximize effective participation.

A test protocol for assessing the hearing status of students with special needs

OBJECTIVES

Individuals with disabilities are often reported to have a high prevalence of undetected hearing disorders/loss, but there is no standardized hearing test protocol for this population. The purposes of this study were (1) to examine the hearing status of students with special needs in Taiwan, and (2) to investigate the use of an on-site hearing test protocol that would adequately detect hearing problems in this population and reduce unnecessary referrals for off-site follow-up services.

METHODS

A total of 238 students enrolled in two schools for special education and one habilitation center participated in the study. Most students had intellectual disabilities and some also had additional syndromes or disorders. A hearing screening protocol including otoscopy, tympanometry, and distortion product otoacoustic emissions was administered to examine students' outer, middle, and inner ear functions, respectively. Pure tone tests were then administered as an on-site follow-up for those who failed or could not be tested using the screening protocol.

RESULTS

Only 32.4% of students passed. When administered alone, the referral rate of otoscopy, tympanometry, and otoacoustic emissions were 38.7%, 46.0%, and 48.5%, respectively. The integration of these subtests revealed 52.1% of students needed follow-up services, 11.8% could not be tested, 2.5% had documented hearing loss, and 1.3% needed to be monitored because of negative middle ear pressure. The inclusion of pure tone audiometry increased the passing rate by 9.9% and provided information on hearing sensitivity for an additional 8.6% of students.

CONCLUSION

Hearing assessments and regular hearing screening should be provided as an integral part of health care services for individuals with special needs because of high occurrences of excessive cerumen, middle ear dysfunction, and sensorineural hearing loss. The training of care-givers and teachers of students with special needs is encouraged so that they can help identify hearing problems and reduce the negative impact of hearing disorders and hearing loss. The screening protocol needs to include subtests that examine the status of different parts of their auditory system. The addition of pure tone audiometry as an on-site follow-up tool reduced the rate of off-site referrals and provided more information on hearing sensitivity.

Participant experience of invasive research in adults with intellectual disability

Clinical research is a necessity if effective and safe treatments are to be developed. However, this may well include the need for research that is best described as 'invasive' in that it may be associated with some discomfort or inconvenience. Limitations in the undertaking of invasive research involving people with intellectual disabilities (ID) are perhaps related to anxieties within the academic community and among ethics committees; however, the consequence of this neglect is that innovative treatments specific to people with ID may not be developed. Such concerns are likely to continue while there is limited published knowledge regarding the actual experiences of people with ID who have participated in invasive clinical research. As part of a pilot study trialling the novel use of a surgically inserted device to curb overeating in people with Prader-Willi syndrome (PWS) we have investigated the experience of research through semistructured qualitative interviews involving three participants and their carers. Thematic analysis revealed that the adults with PWS and their family carers rated their participation positively, seeing it as a rewarding and enriching experience. This brief report discusses findings from our interview data in order to highlight strategies which may ensure that research is acceptable to participants, meets the necessary ethical standards and is able to achieve the aims set out by the researchers. To our knowledge, this is the first study to record experiences directly from people with PWS and their carers regarding their involvement in invasive clinical research.

Recruitment to intellectual disability research: a qualitative study

BACKGROUND

Difficulties in the recruitment of adults with intellectual disability (ID) to research studies are well described but little studied. The aim of this study was to investigate the difficulties in recruiting to a specific research project, in order to inform future recruitment to ID research.

METHODS

Individual semi-structured interviews were held between September 2009 and May 2010 with people who had been involved as intermediaries in recruitment to the research project. These were transcribed verbatim and were independently analysed by two researchers using the Framework approach, who then agreed upon the key emerging themes.

RESULTS

Ten interviews were analysed. A number of themes arose, including participant factors (interview anxiety, difficulties in understanding the concept of research, worry about negative feedback), the importance of the researcher (using a personal approach, meeting potential participants prior to recruitment) and motivators [enjoyment of the research interview (participant), obtaining a medical assessment (carer)]. The themes were then used to generate strategies to improve recruitment to ID research: these include the research team applying a more personal approach, developing the recruitment process to allow for multiple meetings with potential participants, and considering motivators for both participants and carers.

CONCLUSIONS

This study has used the experiences of intermediaries to identify strategies for improving recruitment to future ID research. This has implications in terms of both time and money. However, successful recruitment is essential to ID research, and we hope that the study will be used by ID researchers to review and improve their recruitment processes.

Social exclusion and people with intellectual disabilities: a rural-urban comparison

BACKGROUND

Research suggests that social exclusion is a problem both for people with intellectual disabilities (ID) and for people living in rural areas. This may give rise to a double disadvantage for people with ID living in rural areas. Conversely, aspects of rural life such as community spirit and social support may protect against social exclusion in this population. This study was designed to compare a number of measures of social exclusion in adults with ID living in rural and urban areas, with the aim of identifying whether a double disadvantage exists.

METHOD

Adults with ID were recruited from a rural and an urban area in Scotland. Participants participated in a face-to-face interview and their medical notes were accessed. Social exclusion was investigated using a number of measures comprising: daytime opportunities and physical access to community facilities (using part of the British Institute of Learning Disabilities questionnaire), recent contact with others and the quality of personal relationships (using a modified Interview Measure of Social Relationships questionnaire) and area deprivation by postcode (using the Scottish Index of Multiple Deprivation). The data were analysed using a series of binary logistic regression models that adjusted for variables including age, gender, level of ID, mental illhealth and common physical co-morbidities.

RESULTS

A representative sample of adults with ID from rural (n = 39) and urban (n = 633) areas participated. Participants from rural areas were significantly more likely to have any regular daytime opportunity [odds ratio (OR) = 10.8, 95% CI = 2.3-51.5] including employment (OR = 22.1, 95% CI = 5.7-85.5) and attending resource centres (OR = 6.7, 95% CI = 2.6-17.2) than were participants from urban areas. They were also more likely to have been on holiday (OR = 17.8, 95% CI = 4.9-60.1); however, were less likely to use community facilities on a regular basis. Participants from urban and rural areas had a similar number of contacts with other people in a wide range of situations, but the quality of relationships may have been less close in rural areas. Finally, participants lived in significantly less deprived areas when in rural compared with urban areas (Mann-Whitney U = 7826, Z = -3.675, P ≤ 0.001).

CONCLUSIONS

These results suggest that adults with ID living in rural areas have better opportunities and live in less deprived areas than adults with ID living in urban areas. However, they may not hold such positive or close relationships, and this may be important when considering the subjective experience of social exclusion.

Healthcare and guidelines: a population-based survey of recorded medical problems and health surveillance for people with Down syndrome

BACKGROUND

Medical problems are described in a population of persons with Down syndrome. Health surveillance is compared to the recommendations of national guidelines.

METHOD

Case records from the specialised and primary healthcare and disability services were analysed.

RESULTS

A wide spectrum of age-specific medical and surgical problems was described. Congenital heart defects and middle ear infections were mostly experienced by younger people, while thyroid disease, epilepsy, and Alzheimer's disease were frequent among older people. Psychiatric disorders and behavioural problems were frequent in all age groups.

CONCLUSIONS

Health surveillance remained insufficient, despite the guidelines available. A joint effort by healthcare and disability service providers is required to ensure that the medical needs of people with Down syndrome are adequately met across their entire lifespan. An active provision of healthcare and monitoring for this vulnerable group is needed.

Recruitment and consent of women with intellectual disabilities in a randomised control trial of a health promotion intervention

BACKGROUND

The need for evidence-based health promotion interventions for women with intellectual and developmental disabilities is critical. However, significant barriers impede them from participating in research, including those related to recruitment and obtaining informed consent.

METHODS

This study describes a procedure for the recruitment and consent of women with intellectual disabilities into a community-based, multi-site randomised controlled trial.

RESULTS

Of 269 women who participated in information sessions, 203 (75%) enrolled in the study. While women with and without legal guardians consented at the same approximate rates (83% and 85%, respectively), those with legal guardians enrolled at significantly lower rates (61%) because of lower rates (74%) of guardian consent.

CONCLUSIONS

It is possible to recruit community-dwelling women with intellectual disabilities into randomised controlled trials at relatively high participation rates. Recruiting women who have guardians poses additional challenges for researchers.

Study healthy ageing and intellectual disabilities: recruitment and design

Problems encountered in epidemiologic health research in older adults with intellectual disabilities (ID) are how to recruit a large-scale sample of participants and how to measure a range of health variables in such a group. This cross-sectional study into healthy ageing started with founding a consort of three large care providers with a total client population of 2322 clients of 50 years and over, and two academic institutes. This consort made formal agreements about a research infrastructure and research themes: (1) physical activity and fitness, (2) nutrition and nutritional state, and (3) mood and anxiety. Subsequently, preparation was started by carefully reviewing and selecting instruments to measure a wide set of health variables to answer the research questions. Specific demands of these instruments were that they could be executed efficiently and accurately on-site in a large sample of participants and that the burden of these measurements for participants as well as their caregivers was as minimal as possible. Then, preparation was continued by designing and executing a thorough communication plan for clients, legal representatives and staff of the care providers, preceding the informed consent procedure. In this plan, which had a top-down structure, specific attention was given to personally informing and motivating of key stakeholders: the professional care givers. This preparation led to a recruitment of 1050 participants (45.2%) and to high participation rates in key parts of the assessment. A detailed description is provided about the recruitment and organization and the selected instruments.

Visual local and global processing in low-functioning deaf individuals with and without autism spectrum disorder

BACKGROUND

The ComFor study has indicated that individuals with intellectual disability (ID) and autism spectrum disorder (ASD) show enhanced visual local processing compared with individuals with ID only. Items of the ComFor with meaningless materials provided the best discrimination between the two samples. These results can be explained by the weak central coherence account. The main focus of the present study is to examine whether enhanced visual perception is also present in low-functioning deaf individuals with and without ASD compared with individuals with ID, and to evaluate the underlying cognitive style in deaf and hearing individuals with ASD.

METHOD

Different sorting tasks (selected from the ComFor) were administered from four subsamples: (1) individuals with ID (n = 68); (2) individuals with ID and ASD (n = 72); (3) individuals with ID and deafness (n = 22); and (4) individuals with ID, ASD and deafness (n = 15). Differences in performance on sorting tasks with meaningful and meaningless materials between the four subgroups were analysed. Age and level of functioning were taken into account.

RESULTS

Analyses of covariance revealed that results of deaf individuals with ID and ASD are in line with the results of hearing individuals with ID and ASD. Both groups showed enhanced visual perception, especially on meaningless sorting tasks, when compared with hearing individuals with ID, but not compared with deaf individuals with ID.

CONCLUSIONS

In ASD either with or without deafness, enhanced visual perception for meaningless information can be understood within the framework of the central coherence theory, whereas in deafness, enhancement in visual perception might be due to a more generally enhanced visual perception as a result of auditory deprivation.

Sampling and ethical issues in a multicenter study on health of people with intellectual disabilities

OBJECTIVES

To study health inequalities in persons with intellectual disabilities, representative and unbiased samples are needed. Little is known about sample recruitment in this vulnerable group. This study aimed to determine differences in ethical procedures and sample recruitment in a multicenter research on health of persons with intellectual disabilities. Study questions regarded the practical sampling procedure, how ethical consent was obtained in each country, and which person gave informed consent for each study participant.

STUDY DESIGN AND SETTING

Exploratory, as part of a multicenter study, in 14 European countries. After developing identical guidelines for all countries, partners collected data on health indicators by orally interviewing 1,269 persons with intellectual disabilities. Subsequently, semistructured interviews were carried out with partners and researchers.

RESULTS

Identification of sufficient study participants proved feasible. Sampling frames differed from nationally estimated proportions of persons with intellectual disabilities living with families or in residential settings. Sometimes, people with intellectual disabilities were hard to trace. Consent procedures and legal representation varied broadly. Nonresponse data proved unavailable.

CONCLUSION

To build representative unbiased samples of vulnerable groups with limited academic capacities, international consensus on respectful consent procedures and tailored patient information is necessary.

Participation in intellectual disability research: a review of 20 years of studies

BACKGROUND

Researchers have noted difficulties in attracting adequate numbers of participants with intellectual disabilities (ID) to their studies.

METHODS

This study was a review of participation by adults with ID in research conducted in South Eastern Ontario over a 20-year period (1987-2006). Original research studies were identified by local investigators and then reviewed for inclusion and exclusion criteria. The report of each study was then reviewed by three reviewers and key information was extracted. The extent of study participation was calculated using three methods and compared along with key design characteristics.

RESULTS

Nine studies met all inclusion/exclusion criteria and provided sufficient data to calculate participation. Among the studies there was a variety of purposes, research designs and recruitment strategies. Using the participant/approached calculation, participation varied between 41.8% and 100%. Higher participation was observed in studies where investigators had direct access to participants, the data collection was non-invasive and consent was required from substitute decision-makers only. There was no clear trend of increasing or decreasing participation over time.

CONCLUSIONS

Researchers seeking the participation of adults with ID in their studies must incorporate factors influencing participation into study designs to ensure robust results and effective use of research resources.

Visual dysfunctions and ocular disorders in children with developmental delay. I. prevalence, diagnoses and aetiology of visual impairment

PURPOSE

To describe the prevalence, diagnoses and aetiologies of visual impairment in children with developmental delay (DD) in a Danish county with a population of 618 000 citizens.

METHODS

We carried out a cross-sectional study in Copenhagen County of children aged 4-15 years with profound to borderline DD (IQ <or= 80). Children were located through school psychologists or paediatric clinics. The number of children with DD was estimated using the capture-recapture method.

RESULTS

A total of 1126 children fulfilled the inclusion criteria, corresponding to 97.7% of the estimated number of children with DD in the county. Ophthalmological examinations were performed in 923 children. The prevalence of visual impairment was 10.5% in the study group and 22.4% in those with an IQ <or= 50. The diagnoses were predominantly cerebral visual impairment, optic atrophy, retinal dystrophies and congenital nystagmus. The aetiology of visual impairment was prenatal in 54 children, perinatal in 29 children and postnatal in seven children.

CONCLUSIONS

Visual impairment is highly increased in children with DD and is correlated to low IQ.

Prevalence of visual impairment in adults with intellectual disabilities in the Netherlands: cross-sectional study

PURPOSE

To obtain the first representative and valid population-based prevalence figures on visual impairment and blindness in adults with intellectual disabilities (ID) and to identify risk groups.

METHODS

STUDY DESIGN

Cross-sectional survey. An age-Down's syndrome-stratified random sample of 1,598 persons from a base population of 9,012 adult users of ID services with mild to profound intellectual disabilities was screened. Participants underwent protocollised on-site screening of visual functions. Results were related to degree of ID, occurrence of Down's syndrome (DS) and age.

MAIN OUTCOME MEASURE

Prevalences of visual impairment and blindness in the study population and in subgroups and weighted prevalences in the total Dutch population using ID services.

RESULTS

Prevalences of visual impairment ranged from 2.2% (95% confidence interval (CI), 0.5-6.4) in young adults with mild ID and no Down's syndrome to 66.7% (95% CI, 41.0-86.7) in older adults with profound ID and Down's syndrome; prevalences of blindness ranged from 0.7% (95% CI, 0.1-4.1) to 38.9% (95% CI, 28.1-50.3). Weighted prevalences of visual impairment and blindness in the total Dutch population of adult users of intellectual disability services are 13.8% (95% CI, 9.3-18.4) and 5.0% (95% CI, 3.8-6.2), respectively. Prior to this study, visual impairment or blindness had remained undiagnosed in 106/261 (40.6%) persons.

CONCLUSIONS

As compared to published figures for the general Dutch population aged 55 years and over (visual impairment 1.4%, blindness 0.5%), prevalences of visual impairment and blindness are higher in all subgroups with intellectual disabilities, including the young and mildly handicapped group. The diagnosis is too often missed. All persons with severe or profound intellectual disabilities, and all older adults with Down's syndrome, should be considered visually impaired until proved otherwise.

A population-based nested case control study on recurrent pneumonias in children with severe generalized cerebral palsy: ethical considerations of the design and representativeness of the study sample

Background

In children with severe generalized cerebral palsy, pneumonias are a major health issue. Malnutrition, dysphagia, gastro-oesophageal reflux, impaired respiratory function and constipation are hypothesized risk factors. Still, no data are available on the relative contribution of these possible risk factors in the described population. This paper describes the initiation of a study in 194 children with severe generalized cerebral palsy, on the prevalence and on the impact of these hypothesized risk factors of recurrent pneumonias.

Methods/Design

A nested case-control design with 18 months follow-up was chosen. Dysphagia, respiratory function and constipation will be assessed at baseline, malnutrition and gastro-oesophageal reflux at the end of the follow-up. The study population consists of a representative population sample of children with severe generalized cerebral palsy. Inclusion was done through care-centres in a predefined geographical area and not through hospitals. All measurements will be done on-site which sets high demands on all measurements. If these demands were not met in "gold standard" methods, other methods were chosen. Although the inclusion period was prolonged, the desired sample size of 300 children was not met. With a consent rate of 33%, nearly 10% of all eligible children in the Netherlands are included (n = 194). The study population is subtly different from the non-participants with regard to severity of dysphagia and prevalence rates of pneumonias and gastro-oesophageal reflux.

Discussion

Ethical issues complicated the study design. Assessment of malnutrition and gastro-oesophageal reflux at baseline was considered unethical, since these conditions can be easily treated. Therefore, we postponed these diagnostics until the end of the follow-up. In order to include a representative sample, all eligible children in a predefined geographical area had to be contacted. To increase the consent rate, on-site measurements are of first choice, but timely inclusion is jeopardised. The initiation of this first study among children with severe neurological impairment led to specific, unexpected problems. Despite small differences between participants and non-participating children, our sample is as representative as can be expected from any population-based study and will provide important, new information to bring us further towards effective interventions to prevent pneumonias in this population.