The relationship between quality of life and functioning for children with cerebral palsy A Shelly BSc (Hons), School of Health and Social Development; E Davis* PhD; E Waters DPhil, McCaughey Centre, VicHealth Centre for the Promotion of Mental Health and Community Wellbeing, School of Population Health, University of Melbourne, Melbourne; A Mackinnon PhD, Centre for Mental Health Research, Australian National University, Canberra; D Reddihough MD BSc FRACP FAFRM, Department of Developmental Medicine, Royal Children’s Hospital, Melbourne; R Boyd PhD MSc (PT) PGrad (Biomechanics), Queensland Cerebral Palsy and Rehabilitation Research Centre, Faculty of Medicine, University of Queensland, Brisbane; S Reid MClinEpi, Murdoch Childrens Research Institute; H K Graham MD FRCS (Ed) FRACS, Department of Orthopaedics, Royal Children’s Hospital, Melbourne, Australia. *Correspondence to second author at McCaughey Centre, VicHealth Centre for the Promotion of Mental Health and Community Wellbeing, School of Population Health, University of Melbourne Level 5, 207 Bouverie St, Carlton, Victoria, Australia 3053. E-mail:
[email protected] DOI: 10.1111/j.1469-8749.2008.02031.x Published online 21st January 2008 Given that quality of life (QOL) is commonly confused with functioning, the aim of this study was to examine the association between functioning and QOL domains for children with cerebral palsy (CP). Two hundred and five parents of children aged 4 to 12 years with CP and 53 children aged 9 to 12 years with CP, completed the Cerebral Palsy Quality of Life Questionnaire for Children. Children were distributed reasonably evenly between sex (male, 54.6%) and Gross Motor Function Classification System levels (I 17.8%, II 28.3%, III 14.1%, IV 11.2%, and V 27.3%). For parent proxy-report, all domains of QOL were significantly associated with functioning level except access to services. For child self-report, feelings about functioning, participation and physical health, and pain and feelings about disability, were significantly associated with functioning level. Physical type domains of QOL accounted for more of the variance in functioning than psychosocial type domains. Children with CP have the potential to report a high psychosocial QOL score even if they have poor functioning.
Cerebral palsy (CP), defined as a ‘group of permanent disorders of the development of movement and posture’ is the leading cause of physical disability in children.1 Increasingly, quality of life (QOL) is included as an outcome variable to evaluate the effectiveness of interventions for children with CP. QOL is a multidimensional construct, defined as ‘an overall assessment of wellbeing across various domains’.2 Healthrelated QOL is considered to be a subdomain of the more global construct of QOL.3 However, a review of QOL definitions for children demonstrated that many definitions equate QOL with functioning or are based very heavily on functioning.4 For example, QOL is ‘multidimensional, including aspects such as physical function, psychological state, social interaction, and somatic sensation or cognitive, social, physical, and emotional functioning’4,5 and QOL is ‘the child’s perception and evaluation of performance in relevant life areas and its feeling related to problems in functioning’.6 The link between QOL and functioning is particularly evident in QOL questionnaires for children.4 Many QOL questionnaires for children assess the activities the child can do rather then assessing their overall well-being. For example, the Pediatric Quality Of Life Inventory–CP Module (PedsQL) assesses whether a child has difficulty moving their legs and difficulty using scissors.7 Furthermore, the Child Health Questionnaire (CHQ) measures physical functioning by assessing a child’s limitations in terms of activities such as running, bending, and lifting.8 Differing theories and professional perspectives of QOL may result in a variety of conceptualizations, however, the equating of QOL with functioning requires consideration. If it is argued or implied that QOL can be defined or measured as ‘functioning’, the underlying assumption is that children with poorer functioning have poorer QOL. Although this may be the case for some children, it is misguided to suggest that all children with poor functioning have poor QOL. A few studies of children with CP have examined the relationship between functioning and QOL. These studies have demonstrated that although functioning is correlated with the physical domains of QOL, there is a non-significant or weak relationship between functioning and the psychosocial domains of QOL.9–11 For example, Pirpiris et al.9 demonstrated that functioning (Gross Motor Function Classification System [GMFCS]), although correlated with the Paediatric Outcomes Data Collection Instruments (PODCI) transfers and mobility scale (r=–0.64) and sports and physical function scale (r=–0.52), was not correlated with the PODCI Happiness scale (r=0.09). This study also found that GMFCS levels were not correlated with any domains of the PedsQL (r=–0.18 to 0.16). Furthermore, Vargus-Adams10 demonstrated that functioning (GMFCS) was correlated with the physical summary score of the CHQ (r=–0.42) but not the psychosocial summary score (r=0.09). Additionally, a study by Wake et al.11 found that children with mild impairment (n=80) had as low or lower psychosocial health (mean 41.9 [SD 11.5]; as measured by the CHQ) than children with severe CP (mean 45.1 [SD 12.7]), arguing that the relationship was not linear. Although these studies demonstrate that functioning is correlated with the physical domains of QOL, and there is only a weak or non-significant relationship between functioning and the psychosocial domains of QOL, these correlations, although weak, may be inflated given that many of the items in the ‘QOL’ questionnaires (PODCI, PedsQL, and CHQ)
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measure a child’s difficulties or limitations, i.e. difficulty completing daily living tasks, and focus on what a child can or cannot do, i.e. functioning. It remains unknown whether a relationship would exist when QOL is not conceptualized as what a child can do, i.e. functioning, but rather how a child feels about their life, i.e. well-being. Therefore, this study sought to examine the strength of the association between functioning and QOL domains using a recently developed and validated condition-specific QOL questionnaire for children with CP that focuses on the measurement of well-being rather than functioning. Following previous studies, it was hypothesized that domains focused on physical well-being (feelings about functioning, participation, and physical health) would be more strongly associated with functioning than domains that focus on psychosocial well-being (social well-being and acceptance and emotional well-being). Method PARTICIPANTS
Families were eligible to participate in this study if they had a child with CP aged 4 to 12 years. Eligible families were identified through the Victoria Cerebral Palsy Register, maintained as a population patient register at the Royal Children’s Hospital, Melbourne, Australia (n=695).12 Of the 695 families on the register, 224 families were not invited to participate in this study for various reasons, e.g. not contactable due to a change of address or had not visited their paediatrician for several Table I: Demographic characteristics (n=205) Demographics Child Age Sex, n (%) Male Female Child GMFCS levels, n (%) Level I Level II Level III Level IV Level V Primary caregiver Age Sex, n (%) Male Female Mother’s education, n (%) Completed primary school Completed high school TAFE/trade certification University/CAE Father’s education, n (%) Some primary school Completed high school TAFE/trade certification University/CAE
Frequency (%) or mean
Mean 8y 4mo (range 4–12y) 112 (54.6) 93 (45.4) 36 (17.8) 58 (28.3) 29 (14.1) 23 (11.2) 56 (27.3)
Mean 40y 2mo (range 25–69y) 19 (9.3) 186 (90.7) 3 (1.5) 75 (36.7) 45 (22.1) 59 (28.9) 1 (0.05) 80 (39.1) 60 (29.3) 47 (22.9)
Percentages may not add to 100% due to missing data (Gross Motor Function ClassificationSystem [GMFCS] levels, mother’s education, father’s education). TAFE, Technical and Further Education; CAE, Centre for Adult Education.
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years. Of the 471 families that were invited to participate in the study by paediatricians, 225 consented to be involved. The questionnaire was completed by 205 primary caregivers and by 53 children with CP aged 9 to 12 years. Primary caregivers were identified as the person who knew the most about the child. It was not possible to compare the characteristics of respondents with non-respondents as it was not possible to contact nonrespondents on ethical grounds. MEASURES
Parents completed the Cerebral Palsy Quality of Life Questionnaire for Children (CP QOL-Child; parent-proxy version) and questions on functioning (GMFCS level), as well as additional questions regarding demographics. Children completed the CP QOL-Child (child self-report version) for children aged 9 to 12 years. Quality of Life The CP QOL-Child measures the QOL of children with CP. It is a measure of QOL as its development was based on qualitative interviews with children with CP and their parents. These interviews focused on what the child needed to be happy and have a good QOL.5 The parent-proxy version assesses seven domains of QOL including social well-being and acceptance, feelings about functioning, participation and physical health, emotional well-being, access to services, pain and feeling about disability, and family health. The child self-report version assesses all of the above domains except access to services and family health. The primary caregiverproxy form (parents of children aged 4–12y) comprises 66 items and the child self-report form (9–12y) comprises 52 items (administration time 15–20min). Almost all of the items have the following item stem: ‘How do you think your child feels about... ?’ with a nine-point rating scale, where 1=very unhappy, 3=unhappy, 5=neither happy nor unhappy, 7=happy, and 9=very happy. The few items where this stem or rating scale is not appropriate, such as pain, have the following stem and rating scale: ‘How does your child feel about the amount of pain that they have?’, where 1=not upset at all to 9=very upset. The CP QOL-Child is designed to provide several domain scores and items are, therefore, aggregated and averaged. Domain scores range from 0–100. The parent-proxy version of this questionnaire is psychometrically sound while early results of the child self-report version suggest that it has good psychometric properties.13 For parent-proxy, the 2-week test–retest reliability ranged from r=0.76 to 0.89 and internal consistency ranged from 0.74 to0.92.13 The questionnaire was also moderately correlated with the CHQ8 and KIDSCREEN,14 supporting the validity of the CP QOL-Child parent-proxy version.13 Functioning Functioning was measured by the parent-reported measure of the GMFCS.15 The GMFCS varies from Level I (e.g. walking independently) through to Level V (e.g. unable to sit alone).15 The intraclass correlations between parent reported GMFCS and clinician reported GMFCS have been shown to be high (0.93).15 Procedure The primary caregiver was invited to participate by their child’s paediatrician (by telephone or letter). Lack of English did not
constitute a reason for non-contact, as interpreters were available although not required. The researchers telephoned the primary caregiver and if they consented, questionnaires were mailed and completed by the latter. If the child was aged 9 to 12 years, the researchers also asked parents whether the child could complete the self-report version. Children aged 9 to 12 years who could not complete the questionnaire due to intellectual impairment or inability to communicate were excluded. Ethics approval was obtained from the Royal Children’s Hospital (EHRC 22055A) and from Deakin University (EC 9-2005). Researchers obtained written parental informed consent and written or verbal child informed consent from all participants. STATISTICAL ANALYSES Ordinal logistic regression was used to examine the strength of the relationship between functioning and QOL domains. Ordinal logistic regression was required as it allows for the prediction of a discrete outcome, in this case functioning (GMFCS), from a set of continuous variables, in this case QOL domains. All analyses used a significance level of p
