This thesis investigated the relationship between sleep disturbance and neuropsychological functioning in healthy, typically developing children and children with cystic fibrosis (CF). Three research questions were examined in this thesis. The first examined whether sleep disturbance is associated with specific deficits in executive functions or an overall deficit in executive functioning. The second research question examined the relationship between sleep disturbance and behaviour problems. A final research question examined whether sleep disturbance, in the absence of hypoxia, affects executive functioning in a comparable way to sleep disturbance associated with hypoxia. The first study demonstrated that global executive function (GEF) was significantly lower in healthy children with higher sleep disturbance. Sleep disturbance was not associated with individual performance on executive function tasks. The second study also examined sleep and executive function in healthy children using a revised battery of neuropsychological tests. Compared to children with low sleep disturbance, children with high sleep disturbance had significantly lower GEF and lower processing speed. Both sleep quantity and sleep quality predicted GEF however sleep quantity explained an additional unique proportion of the variance. The third study examined sleep in children with cystic fibrosis. When dichotomized into high and low sleep disturbed groups, neither GEF nor processing speed was significantly different between the two groups. The sleep and neuropsychological functioning of children with CF was compared to the healthy, typically developing children from Study 3. There were no significant differences between children with CF and healthy controls on any sleep measures or executive function performance. Nine children with CF underwent one night of polysomnography. A further aim of Study 3 was to examine whether neuropsychological deficits were greater if in the presence of both high sleep disturbance and nocturnal hypoxia. Executive function deficits were worse in children with nocturnal hypoxia, irrespective of whether they had high or low sleep disturbance. In contrast, processing speed deficits were more evident in children with high sleep disturbance, irrespective of whether they had nocturnal hypoxia. A consistent finding throughout this thesis was that children with higher conduct problems have increased sleep disturbance (measured using parent report and actigraphy). These findings have implications for children’s development; future research examining the effects of sleep disturbance on executive function should consider whether these effects are irreversible.

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A detailed review of the literature revealed that children report mixed views towards ADHD and medication. They are also reported to experience a lack of control over their symptoms and in turn, report a reliance on medication to control behaviours. Research into children’s sense of self is conflicting, where studies reveal poor self-image, but other work confirms an inflated sense of self. In addition, differences between adult and child perceptions of ADHD exist, and are explained by the Attribution Bias Context (ABC) model which describes the nature of informant discrepancies. Gaining a greater understanding of children’s perceptions of ADHD is important in identifying and implementing effective interventions for children and their families. This qualitative study explored 5 children’s perceptions of ADHD through interview and drawing. Children’s teachers were also interviewed in order to explore discrepancies. Analysis of the data revealed a grounded theory of internalisation of the ADHD label for children, and difference for teachers. Children were found to experience ADHD emotionally, in on/off conditions, as a medical disorder, with external locus of control and as part of their self/identity. Medication was felt to control their behaviour. Teachers described children’s ADHD using a medical discourse and strengths were identified as attributes which are present in the absence of ADHD symptoms. Results are discussed in terms of similarities and differences between adult and child perspectives, and only some of the data supports the predictions of the ABC model. Implications of the findings are discussed in terms of academic and applied settings, and future research directions are considered with particular reference to exploration of the process of internalisation of the ADHD label.

This thesis used a multi-methods approach to explore children’s out-of-school physical activity (PA). Study 1 found that children living in the most deprived neighbourhoods represent an important target group for future PA and health interventions. Further, the study also revealed that self-reported PA was positively associated with independent mobility. Study 2 confirmed that the weekend was a period of low moderate-to-vigorous PA (MVPA), and revealed that raw PA levels derived from the wrist-worn GENEActiv are not comparable with hip-worn ActiGraph. Agreement between the devices differed according to PA intensity and time of day, with the greatest difference occurring in light PA (LPA) during school hours. Using children’s recounted perceptions and experiences of out-of-school PA, study 3 demonstrated how an inclusive, interactive and child-centred methodology (i.e., write, draw show and tell; WDST) may be advantageous when compared to traditional singular qualitative methods. In study 4 parental safety concerns were reported to be the most consistent barrier to children’s out-of-school PA. The family case studies demonstrated how family perceptions and constraints can influence children’s out-of-school PA levels and activity mode (i.e., active school travel, outdoor play and organised sport). Such constraints include factors such as, school proximity, neighbourhood perceptions and family context. Study 5 revealed substantial intra-individual variability in children’s weekend MVPA. PA diary data revealed that children's weekend PA was mostly unstructured in nature and undertaken with friends, whereas a greater proportion of parents’ weekend PA was undertaken alone in structured settings. Family case studies demonstrated that in the selected cases MVPA levels and variability across weekends were contingent on mode of PA participation. This thesis contributes evidence to inform future out-of-school PA interventions. The research has demonstrated that children’s out-of-school PA is influenced by a complex interaction of individual, social and environmental factors. Specific highlights include the family and neighbourhood environment. The weekend is associated with low PA and as such represents an important time period to promote PA in children. Future weekend PA interventions should target specific modes of activity, as the facilitators and barriers to these activities vary considerably. Moreover, in future, research and practice should focus on ways in which to modify neighbourhood attributes to support children’s out-of-school active living.

Childhood onset growth hormone deficiency (CO-GHD) may contribute to low bone mass and alterations to body composition. This thesis consists of a series of studies utilising dual-energy X-ray absorptiometry (DXA), peripheral quantitative computerized tomography (pQCT) and biochemical assessment of bone health and body composition of CO-GHD. In addition, metabolic profiles, glucose metabolism as well as quality of life have been studied in these subjects. Furthermore, an interventional study of weight bearing exercise (WBE) was performed to explore its role in influencing the bone health of children and adolescents with CO-GHD. Chapter 1, relevant literature reviews explore: bone structure, growth, development and strength; GH/IGF-1 system and its actions; CO-GHD and its impacts during childhood and transition; and WBE and its mechanism and impacts on bone health. Chapter 2 presents the rationale and specific aims of this thesis. Chapter 3, a retrospective multicentre review of management of young adults with CO-GHD in four paediatric centres in Scotland during transition. Medical records of 130 eligible CO-GHD adolescents (78 males), who attained final height between 2005-2013 were reviewed. Of the 130, 74/130(57%) had GH axis re-evaluation by stimulation tests /IGF-1 measurements. Of those, 61/74(82%) remained GHD with 51/74(69%) restarting adult rhGH. Predictors of persistent GHD included an organic hypothalamic-pituitary disorder and multiple pituitary hormone deficiencies (MPHD). Despite clinical guidelines, there was significant variation in the management of CO-GHD in young adulthood across Scotland. Chapter 4, a cross-sectional control study of bone DXA measurements in (n=21) subjects with CO-GHD treated with rhGH and had attained final height from 2005 to 2013 in a single tertiary paediatric centre compared to (n= 21) heights/age matched healthy controls. By applying different models of DXA adjustment, our analysis revealed lower TB-BMC for bone area in males with CO-GHD and lower LS-BMAD SDS in females with CO-GHD compared to matched controls. In addition, subjects with CO-GHD had lower LM for height and higher FM for height compared to controls, and this was more pronounced in males than females (p=0.04). The time of onset and aetiology of CO-GHD have a larger influence on accrual of bone mass in these patients. These findings indicate that adolescents with CO-GHD have a low bone mass, despite prior long term rhGH replacement therapy. In chapter 5, we investigated bone health of subjects with CO-GHD at time of initial evaluation and retesting at final height. A total of 25 children (first time assessment group) undergoing GH stimulation tests for investigation of short stature (naive GHD-15, normal-10), and 11adolescents with CO-GHD (retesting group) undergoing biochemical re-evaluation at final height after withdrawal of rhGH therapy (persistent GHD-7, GH-sufficient-4) were recruited from Royal Hospital for Children between 2012-2013. By using further bone health assessment methods in addition to DXA (including p.QCT, mechanography, bone profiles and biomarkers), the bone density and body composition did not differ when we compared GHD to matched height but normal GH at initial evaluation and retesting. However, naive GHD had lower muscle force as assessed by mechanography compared to the normal. In addition, bone resorption biomarker CTX was significantly higher in naive GHD vs. normal and that was significantly correlated to PTH levels in both first time assessment and retesting groups. Our results suggest that muscle force and serum PTH may be important determinants of bone health in subjects with CO-GHD. Chapter 6 investigates lipids, adipokines (leptin- adiponectin- resistin) and glucose homeostasis and their relationship with bone and body composition in children and adolescents with CO-GHD at times of initial evaluation and retesting at final height (same population as chapter 5). Lipid profiles, adipokines and glucose homeostasis were not different between those with GHD and those who had normal GH levels across the groups of first time assessment and retesting. In the retesting group, those who were older at the time of diagnosis of CO-GHD with a shorter duration of rhGH therapy were more likely to have higher cholesterol(r=0.9, p<0.001), leptin (r=0.8, p<0.001), and lower osteoclacin (r=-0.7, p=0.01) at final height. Leptin levels correlated positively with osteocalcin at diagnosis (r=0.51, p=0.01) but inversely at retesting (r=-0.91, p<0.01). The conclusion was that the timing and duration of childhood rhGH therapy might influence adiposity parameters and bone metabolism in subjects with CO-GHD. In chapter 7 the study participants of chapter 5 were asked to complete either Short Form-36 (SF-36) or Adult Growth Hormone Deficiency Assessment (AGHDA) quality of life (QoL) questionnaires at the time of assessment of their GH axis. Our analysis showed that the overall QoL was not altered in children with naive GHD with a total score of SF-36 [93 (77, 96) naive GHD vs. 90 (84, 93) normal, P=0.56] (higher scores reflect better QoL). However, naive GHD had less energy and vitality scores compared with normal (75 (65, 100) vs. 95 (65,100) respectively, p=0.04), when the normal scored lower in the subscale of emotional well-being compared to those with naive GHD (78 (55, 84) vs. 90 (68, 96) respectively, p<0.001). In the retesting group, those with persistent GHD scored better in the AGHDA than GH sufficient (6 points (2, 8) vs. 9 points (7, 17) respectively, though not significant (p= 0.10) (higher scores reflect poorer QoL). Unexpectedly, subscale analysis showed that GH-sufficient subjects significantly lacked energy and complained of tiredness compared to those who were confirmed to have persistent GHD (5 points (3, 6) vs. 1 point (0, 1) respectively, p= 0.03). Further studies to validate QoL specific instruments in this population are needed with greater insight to elucidate factors that modify the relationship between GH status and QoL in children and adolescents. Chapter 8 was a prospective intervention, randomised controlled study of 14 subjects among the first time assessment group (GHD-10, normal-4) and five subjects with CO-GHD among retesting group (persistent GHD-4, GH-sufficent-1). Subjects were randomised into either an exercise intervention group (EX) (25 jumps off 25 cm platform step/three days/week for six months) or a control, in addition to rhGH being prescribed. The results of this study were limited by the small sample size and poor compliance. Therefore, there were insufficient data to recommend the use of weight bearing exercise in the absence of rhGH in children and adolescents with CO-GHD. Further studies with adequate sample size that can more rigorously exam the optimal exercise interventions are needed. Chapter 9 discusses the main findings of each chapter in this thesis and outlines potential limitations of the thesis methodology, and some important and interesting areas for future research in children and adolescents with CO-GHD.

Childhood obesity is becoming increasingly prevalent in the UK and globally. Over the last 10 years, there has been a rise in prevalence of risk factors for health and a decline in physical activity. Obesity is major health risk factor for a number of other chronic diseases, some of which are prevalent in children. Regular physical activity is associated with reduced adiposity, healthier metabolic status lower risk factors of diabetes and CHD and enhanced bone mineral accrual and protection against osteoporosis. Recent literature suggests that children may not be meeting the recommended daily guideline for physical activity of 60 min per day (Riddoch et al., 2007), while others suggest this guideline is insufficient to protect against risk factors in children. Assessment of programmes promoting physical activity, with robust health related outcome measures are therefore warranted Initially, sixty-one children were recruited for a 9-week exploratory trial. The trial assessed the effect of a structured high impact exercise (STEX) and a lifestyle intervention (PASS). Changes in dual-energy X-ray absorptiometry (DXA) derived body composition and bone mineral were compared to age matched controls (CaNT). The STEX intervention resulted in an additional mean increase in total body BMC of 63.3 g (P= 0.019) and an additional increase of 0.011 g.cm-2 (P= 0.018) for BMD over changes observed in controls. Neither intervention stimulated significant increases in BMC or BMD at the femoral neck or lumbar spine (P > 0.05) compared with the controls. No significant changes were found in fat mass index (P > 0.05), lean mass index (P > 0.05) or percent body fat (p = 0.09) in any groups. Structured impact exercise promoted significant and clinically relevant increases in bone measures, without significant changes to body composition. The exploratory finding therefore supported the need for a larger, definitive randomised trial to confirm the results. Following this, a large cohort of Liverpool school children (n=152) was recruited for cross-sectional analysis. Measures included 3-day physical activity using a uniaxial accelerometer, maturity status, cardia-respiratory fitness and skin-fold measurements in addition to body composition, bone mineral content and density. Analysis of variance was used to uncover any sex differences, partial correlation analysis was performed to investigate relationships between health-related variables and physical activity, with maturity offset as the controlling variable. Regression analysis was performed to find the best predictor of BMC and BMD (primary outcome variable), using LM, FM, Mass, and maturity offset as predictor variables. The results showed that children participated in the recommended amount of activity. However, body fat measures indicated that the children fell between the 85th-95% percentile for overweight. Further more BMD status of both sexes also fell below reference values. The dose-response relationship was highlighted as children who participated in < 60 mln.oay" recommendation were less physically fit (P=0.001) and fatter (P < 0.001) than children achieving this guideline. Children participating in over >90 min.day" had significantly lower percent body fat (P=0.005) and fat mass (P=0.04) than children who participated in < 60 min.day" and significantly lower percent body fat (P=0.02)than all children who participated in < 90 min.day". The findings highlight the importance of the high volume ( > 90 rnin.day") and high-intensity physical activity (over 10 min.day") as a precursor to low body fat and high bone mineral in children. The one hundred and fifty-two children from the baseline cohort were allocated to 1 of 4 groups over a 12 month period. Three groups received a different physical activity intervention; a high-intensity programme ('HIPA'), a skill development programme ('FMS') or a lifestyle-based programme ('PASS'). The 'HIPA' and 'FMS' groups participated in an after-school club (2x60 min.week"), the 'PASS' group attended weekly classroom sessions (1 x week) delivered by a lifestyle coach during the school day. The control group ('CaNT') received health information. All baseline measures were repeated at 9 and 12 months (during and after) intervention. All interventions minimised fat mass accumulation, with the 'HIPA' intervention being most effective (P=0.03), implying that the high-intensity nature of the activity sessions was more effective at minimising body fat accumulation. The greatest magnitude of change in femoral neck BMC (P < 0.001) and BMD (P < 0.001) and cardiorespiratory fitness (P=0.023) was also reported by the 'HIPA' group which is likely to be attributable to the intensity of the weight-bearing activities included in the 'HIPA' programme. The findings suggested that the 'HIPA' intervention was most beneficial for health outcomes, but all interventions had significant effect on increasing time spent in physical activity. The studies within this thesis have provided a unique insight in to the current bone health status, body composition and physical activity of 9-11 year old Liverpool school children. Further data were also generated on the effect of different physical activity interventions on bone health, body composition and physical activity. The findings from this thesis conclude that a proportion of 9- 11 year old children were overweight despite meeting physical activity recommendations of 60 min.day". The high-intensity physical activity intervention had the most beneficial impact on bone health, body composition and cardio-respiratory fitness when compared to the controls. The quantity of physical activity and the time spent in high intensity activity warrants further investigation to quantify an optimal dose.

Low childhood physical activity levels, and high paediatric overweight and obesity levels, carry a considerable burden to health including cardiometabolic disease, low fitness, and reduced psychosocial well-being. Numerous school- based physical activity interventions have been conducted with varied success. This thesis therefore aimed to develop and investigate the effectiveness of the Children's Health, Activity and Nutrition: Get Educated! (CHANGE!) project, which was a school-based curriculum intervention to promote healthy lifestyles using an educational focus on physical activity and healthy eating. The purpose of the formative study (Study 1) was to elicit subjective views of children, their parents, and teachers about physical activity to inform the design of the CHANGE! intervention programme. Analyses revealed that families have a powerful and important role in promoting health-enhancing behaviours. Involvement of parents and the whole family is a strategy that could be significant to ~ncrease children's physical activity levels. There is large variation in the cut-points used to define moderate physical activity (MPA), vigorous physical activity (VPA) and sedentary time, which impacts on accurate estimation of physical activity levels. The purpose of Study 2 was to test a field-based protocol using intermittent activities representative of children's physical activity behaviours, to generate behaviourally valid, population-specific cut-points for sedentary behaviour, MPA and VPA. These cut-points were subsequently applied to CHANGE! to investigate changes in physical activity (Study 3). The CHANGE! intervention resulted in positive changes to body size and VPA outcomes after follow-up. The effects were strongest among those sociodemographic groups at greatest risk of poor health status. Further work is required to test the sustained effectiveness of this approach in the medium and long-term. Further, the development of an inexpensive and replicable field- based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.

A mother's practice of feeding the family is viewed as risk behaviour in published health literature where the dominant research interest lies in its pathogenic potential in the aetiology of Child Obesity. Mothers’ 'participative knowledge' of their practice, which is their lived experience as known and given meaning by them, is absent from this literature. The aim of the thesis is to address this gap in knowledge and reflect upon its significance for health promotion. The exploration of mothers’ family feeding practices was conducted by means of a Co-operative Inquiry (Heron, 1996) which I adapted as a community participatory research study with a core group of 13 volunteer mothers. This community of mothers from a former mining community in the NW of England became in time my co-researchers in the investigation of what feeding the family entailed and meant for them. There are two phases of the inquiry. In Phase 1, methods were developed to enable mothers to collect data and to engage in reflection and dialogue so as to describe and explain their practice. In Phase 2, the Inquiry process was directed towards empowering mothers to engage in transformative experiential learning. Findings at the end of Phase 1 highlighted that the mothers’ routine practices often exposed their children to risk factors linked to childhood obesity. It also identified that their reality and lived experience systematically exposed mothers to social injustice that had the potential to undermine their health. At the end of Phase 2 however, new insights into the potential meaning of their practice, led the mothers to make changes in family feeding; and to transform an alienating environment into an empowering experience of true community. The author reflects and discusses the inquiry and its findings by drawing upon theories of knowledge, practice and health; and empirical evidence of risk factors in health inequalities. This study extends the body of knowledge about family feeding with insights into the participative reality of mothers’ practice. The Author recommends health research should embrace new theoretical frameworks for inquiry with mothers to develop a more socially just knowledge of their practice that can empower both mothers and community.

Smoking is the greatest avoidable cause of premature death in Britain today, particularly among the poorest people in society. Most smokers take up the habit during childhood, and the age at which children begin to smoke is falling over time. Although patterns of regular smoking are often established during the teenage years, rates of experimentation with cigarettes peak during preadolescence. Despite this, in the UK there has been little longitudinal research into the process of smoking uptake during preadolescence, and this research fills that significant gap. The Liverpool Longitudinal Study of Smoking (LLSS) is a unique longitudinal study that has tracked a cohort of approximately 250 children during their early years at primary school. This thesis continues and develops the LLSS by exploring the cohort's experiences of smoking during preadolescence in order to understand how children's early smoking careers develop between the ages of 9 and 11. Baseline quantitative and qualitative data collected at age 9 (in 1999) were compared with data collected at age 10 (in 2000) and at age 11 (in 2001) in order to identify key elements of change. These data were analysed longitudinally using a multiple case study approach that identified the individual trajectories of five children during preadolescence. A cross-case comparative method was then used to identify and explain the relationship between views, intentions and behaviour, and how these were shaped by the social context in which the children lived. The themes that emerged from the case studies were then explored and developed in the context of data generated by the whole cohort. Statistical analysis revealed that smoking by best friends, fathers and brothers, together with knowing someone with a smoking-related disease, at age 9 predicted smoking by age 11. The discourses that the children used to talk about smoking uptake emphasised the role of parents at age 9, but by age 11 the cohort suggested that friends were the key influence on smoking onset. Each year, anxiety about being bullied into smoking by older children also emerged as a key concern for this age group. In addition, the analysis revealed that preadolescents appropriate adult discourses around the use of smoking as a coping strategy. The use of these discourses was patterned by socioeconomic status. Children who lived in deprived areas suggested that both adults and children might smoke to counter stress and to relieve boredom. However, some of the girls living in relatively affluent areas perceived that adults smoke to control their weight. The study also considered the implications of these discourses for differential rates of smoking uptake at primary school. A key finding of this phase of the LLSS is that preadolescents construct smoking as an adult behaviour, and therefore some children smoke in order to negotiate status in anticipation of the transition to adolescence and as a strategy of resistance to the exercise of adult power. The reduction of rates of smoking among children and young people is central to the government's tobacco control strategy, and this research has significant implications for the development of both interventions and policy.

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