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Special Articles Indian Pediatrics 2003; 40:639-644 |
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Benefits of a Population Register of Children with Cerebral Palsy |
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Correspondence to: Dr. Allan Colver, Reader
in Community Child Health, University of New-castle upon Tyne and
Northumbria Healthcare NHS Trust, Sir James Spence Institute, Royal
Victoria Infirmary, Queen Victoria Road, Newcastle upon Tyne NE 1 4LP,
UK.
Over the last 30 years, many centers have developed population based registers of children with cerebral palsy. Centers wishing to start a register can learn from some of the difficulties encountered by earlier registers: (i) When establishing a register it is important to bring together from the outset epidemiologists and clinicians so that definitions of cerebral palsy are clarified, inclusion and exclusion criteria decided and a simple minimum data set agreed upon. (ii) Data are more useful if the data set is small, accurate and complete rather than large, inaccurate and incomplete. A data set can be enhanced later to answer specific questions but at the outset it is much more important to have complete coverage and identification of where children are. (iii) The aims of a register need to be clearly set out and should not be too ambitious at first. Once the register is established and data are flowing well, additional aims can be introduced. A register being established in Lithuania at the moment is aiming to increase knowledge amongst clinicians about cerebral palsy and also to have data for planning rehabilitation services. (iv) The minimum data set should attempt to include a measure of severity of cerebral palsy(1). This enables trends in severe and less severe cerebral palsy to be monitored; but as importantly it enables application of a threshold severity at which one can be confident that the ascertainment is complete. There will always be very mild cases of cerebral palsy which are not ascertained because parents may not have sought help or because another diagnosis such as dyspraxia has been used. By using a severity measure, different countries can then be compared with each other at a particular severity level. (v) It is important from the outset to disseminate the developments of the register and the use to which the data are being put. Parents should be kept informed as well as clinicians and service planners. (vi) Many of the benefits are not immediate and five to ten years of careful data collection may be needed before full benefits are seen. (vii) Population denominator data must be available such as numbers of births with breakdowns by birth weight, gestational age, twins and sex. (viii) Parents have a right to have information about the register and to have access to anonymised data. Special efforts have to be made to keep parents informed and to involve parents groups in the planning and development of the register. Rate of Cerebral Palsy I am involved with the north of England register, which is a well-defined area of about 8 million people. Figure 1 shows rates of cerebral palsy by year and severity for 1964 to 1993 births(2). Each line of the graph corresponds to a different severity level. Therefore the upper line represents the overall rate of cerebral palsy and shows an increase in rate. From 1979, the year in which neonatal intensive care was introduced in the north of England, the increase is particularly convincing and occurs across the severity spectrum. Between 1964 and 1974 the graph illustrates the point made earlier about a threshold severity. Most of the rates were steady or slightly decreased but at the mildest end there were actually increases in rates. This is suggestive that completeness of ascertainment of very mild cerebral palsy varied considerably during these years.
Fig. 1. Cerebral palsy rate by year of birth and cumulative severity - northeast England 1964-93.
Gestational Age Specific Rates of Cerebral Palsy Although it is customary to look at birth weight specific rates when trying to understand changes in rates(3), birth weight is really a proxy for gestational age. In the north of England, we have been able to calculate gestational age specific rates for cerebral palsy going back to the late 1960s because of a long standing interest in accurate measure-ment of gestational age by obstetricians and pediatricians(4). Figure 2 shows these rates on the y-axis with a logarithmic scale. At lower gestational ages rates of cerebral palsy are almost 100 per 1000 neonatal survivors and around 33 weeks gestation there is a striking fall from rates of ten to four. This is of course the age at which the vasculature around the cerebral ventricles involutes, rendering the risk of intraventricular or parenchymal hemorrhages less likely.
Fig. 2. Cerebral palsy rate by gestational age northeast England 1970-1994. Life Expectancy We have also been able to study in the north of England how long people with cerebral palsy live(5). This is important for planning purposes. In the United Kingdom there is a central register of all citizens registered with the National Health Service. When a person dies the death certificate is linked to this register. Researchers can ask for people with a condition such as cerebral palsy to be "flagged" so that when the person dies, the researchers are automatically notified. In people with the severest cerebral palsy (that is people who would typically be very restricted in walking and have in addition severe learning difficulty or epilepsy or severe hearing and visual problems), 95% live to age 10 years, 75% to 20 years and 60% to thirty years. European Collaboration The register in the north of England is linked to fourteen other registers across Europe. Figure 3 and 4 show rates of cerebral palsy across the eleven centres for which there are complete data on overall trends in rates of cerebral palsy by severity(6,7)
Fig.3. Rates of cerebral palsy per 1000 live births by 11 European centres 1980-1990
Figure 4. Rate of cerebral palsy per 1000 live births across Europe by year and severity Participation Population registers also allow the study of the epidemiology of handicap itself rather than just numbers of cases. The World Health Organization introduced the International Classification of Impairment, Disability and Handicap in 1981, presenting us with a common language(8). This was revised in 2001 in the International Classification of Functioning (ICF)(9) and the word "participation" has now replaced the word "handicap". Participation is defined as involvement in life situations and is a concept which embodies the social model of disability. This means that difficulties, rather than being regarded as residing in the individual, are regarded as resulting from the interaction between an individual and their environment. The concept of participation applies to all people not just the disabled and has positive connotations rather than the negative ones associated with the word handicap. Table I shows the dimensions of participation as defined in the ICF. Table I ICF Definition of Participation.
In the early 1990s Professor Jarvis in Newcastle
developed a measure of participa-tion of children with cerebral palsy
along 6 dimensions (education, social participation, economic
participation, clinical burden, mobility and independence)(10). Using
judgements of a panel of professionals and parents, these dimensions
were then weighted to provide an overall participation score. The data
are collected through a parent-completed questionnaire when a child is
five years old. In Fig 5, the average participation of all the
children with cerebral palsy in a district is shown for the fifteen
districts in the north of England. In any district the case mix is
likely to be different because there may be different proportions of
children with severe cerebral palsy, associated epilepsy, associated
learning difficulties, etc. We, therefore, used a step-wise
logistic regression technique to develop a model which controlled for
types of cerebral palsy and other case-mix variables. In Fig 5
the adjusted meausres are also shown. The amount of variation between
districts is reduced but there are still significant variations between
districts. What is it about the environment in each district that might
account of this? Why is it that a child in district A with a bilateral
spastic cerebral palsy including all four limbs and no mental
retardation participates more than a similar child in district B? The
answer must lie in the differences in the environments in different
districts. Figure 5. Average participation by district in North of England.
A further difference between the 1980 and 2001 WHO classifications is that there is a formal taxonomy of environmental factors which are defined as the physical, social and attitudinal environment in which people live and conduct their lives. Table II shows how these are categorized. This classification has not been "operationalized" but we are in the process of doing this for children. Table II ICF Definition of Environmental Factors.
European Study of the Relationship of the Environment to Participation and Quality of Life We are about to start a 3-year study across Europe to describe and quantify important environment factors. Our hypothesis is that children with cerebral palsy with similar severity of underlying impairment will experience variable outcomes in their participation and quality of life in different countries due to variations in environmental factors in those countries. If we can confirm this hypothesis we will be in a position to make recommendations about the optimal environment for children with cerebral palsy to live in – recommendations which should influence policy and legislation across the European Union.
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