A longitudinal study of the family physical activity environment and physical activity among youth

Purpose. Although the family environment is a potentially important influence on children's physical activity (PA), prospective data investigating these associations are lacking. This study aimed to examine the longitudinal relationship between the family environment and PA among youth.

Design. A 5-year prospective cohort study.

Setting. Nineteen randomly selected public schools in Melbourne, Australia.

Subjects. Families of 5- to 6-year-old (n  =  190) and 10- to 12-year-old (n  =  350) children.

Measures. In 2001, parents reported their participation in PA, family-based PA, and support and reinforcement for their child's PA. In 2001, 2004, and 2006, moderate to vigorous intensity PA (MVPA) was assessed among youth using accelerometers. Weekend and “critical window” (after school until 6:00 p.m.) MVPA were examined because we hypothesized that the family environment would most likely influence these behaviors.

Analysis. Generalized estimating equations predicted average change in MVPA over 5 years from baseline family environment factors.

Results. Maternal role modeling was positively associated with boys' critical window and weekend (younger boys) MVPA. Paternal reinforcement of PA was positively associated with critical window and weekend MVPA among all boys, and paternal direct support was positively associated with weekend MVPA (older boys). Among girls, maternal coparticipation in PA predicted critical window MVPA, and sibling coparticipation in PA was directly associated with weekend MVPA (younger girls).

Conclusions. Longitudinal relationships, although weak in magnitude, were observed between the family environment and MVPA among youth. Interventions promoting maternal role modeling, paternal reinforcement of and support for PA, and maternal and sibling coparticipation in PA with youth are warranted.

Mediators of longitudinal associations between television viewing and eating behaviours in adolescents

Background: Television viewing has been associated with poor eating behaviours in adolescents. Changing unhealthy eating behaviours is most likely to be achieved by identifying and targeting factors shown to mediate the association between these behaviours. However, little is known about the mediators of the associations between television viewing and eating behaviours. The aim of this study was to examine mediators of the longitudinal associations between television viewing (TV) and eating behaviours among Australian adolescents.
Method: Eating behaviours were assessed using a web-based survey completed by a community-based sample of 1729 adolescents from years 7 and 9 of secondary schools in Victoria, Australia, at baseline (2004-2005) and two years later. TV viewing and the potential mediators (snacking while watching TV and perceived value of TV viewing) were assessed via the web-based survey at baseline.
Results: Adolescents who watched more than two hours of TV/day had higher intakes of energy-dense snacks and beverages, and lower intakes of fruit two years later. Furthermore, the associations between TV viewing and consumption of energy-dense snacks, energy-dense drinks and fruit were mediated by snacking while watching TV. Perceived value of TV viewing mediated the association between TV viewing and consumption of energy-dense snacks, beverages and fruit.
Conclusion: Snacking while watching TV and perceived value of TV viewing mediated the longitudinal association between TV viewing and eating behaviours among adolescents. The efficacy of methods to reduce TV viewing, change snacking habits while watching TV, and address the values that adolescents place on TV viewing should be examined in an effort to promote healthy eating among adolescents.

The central nucleus of the amygdala ; a conduit for modulation of HPA axis responses to an immune challenge?

Physical stressors such as infection, inflammation and tissue injury elicit activation of the hypofhalamic-pituitary-adrenal (HPA) axis. This response has significant implications for both immune and central nervous system function. Investigations in rats into the neural substrates responsible for HPA axis activation to an immune challenge have predominantly utilized an experimental paradigm involving the acute administration of the pro-inflammatory cytokine interleukin-1 β (IL-1β). It is well recognized that medial parvocellular corticotrophin-releasing factor cells of the paraventricular nucleus (mPVN CRF) are critical in generating HPA axis responses to an immune challenge but little is known about how peripheral immune signals can activate and/or modulate the mPVN CRF cells. Studies that have examined the afferent control of the mPVN CRF cell response to systemic IL-1β have centred largely on the inputs from brainstem catecholamine cells. However, other regulatory neuronal populations also merit attention and one such region is a component of the limbic system, the central nucleus of the amygdala (CeA). A large number of CeA cells are recruited following systemic IL-lβ administration and there is a significant body of work indicating that the CeA can influence HPA axis function. However, the contribution of the CeA to HPA axis responses to an immune challenge is only just beginning to be addressed. This review examines three aspects of HPA axis control by systemic IL-lβ; (i) whether the CeA has a role in generating HPA axis responses to systemic IL-1 β, (ii) the identity of the neural connections between the CeA and mPVN CRF cells that might be important to HPA axis responses and (iii) the mechanisms by which systemic IL-lβ triggers the recruitment of CeA cells.

Differential involvement of rat medial prefrontal cortex dopamine receptors in modulation of hypothalamic- pituitary-adrenal axis responses to different stressors

Recent investigations have implicated the medial prefrontal cortex (mPFC) in modulation of subcortical pathways that contribute to the generation of behavioural, autonomic and endocrine responses to stress. However, little is known of the mechanisms involved. One of the key neurotransmitters involved in mPFC function is dopamine, and we therefore aimed, in this investigation, to examine the role of mPFC dopamine in response to stress in Wistar rats. In this regard, we infused dopamine antagonists SCH23390 or sulpiride into the mPFC via retrodialysis. We then examined changes in numbers of cells expressing the c-fos immediate-early gene protein product, Fos, in subcortical neuronal populations associated with regulation of hypothalamic-pituitary-adrenal (HPA) axis stress responses in response to either of two stressors; systemic injection of interleukin-1β, or air puff. The D1 antagonist, SCH23390, and the D2 antagonist, sulpiride, both attenuated expression of Fos in the medial parvocellular hypothalamic paraventricular nucleus (mpPVN) corticotropin-releasing factor cells at the apex of the HPA axis, as well as in most extra-hypothalamic brain regions examined in response to interleukin-1β. By contrast, SCH23390 failed to affect Fos expression in response to air puff in any brain region examined, while sulpiride resulted in an attenuation of the air puff-induced response in only the mpPVN and the bed nucleus of the stria terminalis. These results indicate that the mPFC differentially processes the response to different stressors and that the two types of dopamine receptor may have different roles.

Dorsal and ventral medullary catecholamine cell groups contribute differentially to systemic interleukin-1beta-induced hypothalamic pituitary adrenal axis responses

Medial parvocellular paraventricular corticotropin-releasing hormone (mPVN CRH) cells are critical in generating hypothalamic-pituitary-adrenal (HPA) axis responses to systemic interleukin-1beta (IL-1beta). However, although it is understood that catecholamine inputs are important in initiating mPVN CRH cell responses to IL-1beta, the contributions of distinct brainstem catecholamine cell groups are not known. We examined the role of nucleus tractus solitarius (NTS) and ventrolateral medulla (VLM) catecholamine cells in the activation of mPVN CRH, hypothalamic oxytocin (OT) and central amygdala cells in response to IL-1beta (1 microg/kg, i.a.). Immunolabelling for the expression of c-fos was used as a marker of neuronal activation in combination with appropriate cytoplasmic phenotypic markers. First we confirmed that PVN 6-hydroxydopamine lesions, which selectively depleted catecholaminergic terminals, significantly reduced IL-1beta-induced mPVN CRH cell activation. The contribution of VLM (A1/C1 cells) versus NTS (A2 cells) catecholamine cells to mPVN CRH cell responses was then examined by placing ibotenic acid lesions in either the VLM or NTS. The precise positioning of these lesions was guided by prior retrograde tracing studies in which we mapped the location of IL-1beta-activated VLM and NTS cells that project to the mPVN. Both VLM and NTS lesions reduced the mPVN CRH and OT cell responses to IL-1beta. Unlike VLM lesions, NTS lesions also suppressed the recruitment of central amygdala neurons. These studies provide novel evidence that both the NTS and VLM catecholamine cells have important, but differential, contributions to the generation of IL-1beta-induced HPA axis responses.

Medial prefrontal cortex suppression of the hypothalamic–pituitary–adrenal axis response to a physical stressor, systemic delivery of interleukin-1β

Previous studies have shown that the medial prefrontal cortex can suppress the hypothalamic–pituitary–adrenal axis response to stress. However, this effect appears to vary with the type of stressor. Furthermore, the absence of direct projections between the medial prefrontal cortex and corticotropin-releasing factor cells at the apex of the hypothalamic–pituitary–adrenal axis suggest that other brain regions must act as a relay when this inhibitory mechanism is activated. In the present study, we first established that electrolytic lesions involving the prelimbic and infralimbic medial prefrontal cortex increased plasma adrenocorticotropic hormone levels seen in response to a physical stressor, the systemic delivery of interleukin-1β. However, medial prefrontal cortex lesions did not alter plasma adrenocorticotropic hormone levels seen in response to a psychological stressor, noise. To identify brain regions that might mediate the effect of medial prefrontal cortex lesions on hypothalamic–pituitary–adrenal axis responses to systemic interleukin-1β, we next mapped the effects of similar lesions on interleukin-1β-induced Fos expression in regions previously shown to regulate the hypothalamic–pituitary–adrenal axis response to this stressor. It was found that medial prefrontal cortex lesions reduced the number of Fos-positive cells in the ventral aspect of the bed nucleus of the stria terminalis. However, the final experiment, which involved combining retrograde tracing with Fos immunolabelling, revealed that bed nucleus of the stria terminalis-projecting medial prefrontal cortex neurons were largely separate from medial prefrontal cortex neurons recruited by systemic interleukin-1β, an outcome that is difficult to reconcile with a simple medial prefrontal cortex–bed nucleus of the stria terminalis–corticotropin-releasing factor cell control circuit.

Systemic apomorphine alters HPA axis responses to interleukin-1β adminstration but not sound stress

Apomorphine is a dopamine receptor agonist that was recently licensed for the treatment of erectile dysfunction. However, although sexual activity can be stressful, there has been little investigation into whether treatments for erectile dysfunction affect stress responses. We have examined whether a single dose of apomorphine, sufficient to produce penile erections (50 μg/kg, i.a.), can alter basal or stress-induced plasma ACTH levels, or activity of central pathways thought to control the hypothalamic-pituitary-adrenal axis in rats. An immune challenge (interleukin-1β, 1 μg/kg, i.a.) was used as a physical stressor while sound stress (100 dB white noise, 30 min) was used as a psychological stressor. Intravascular administration of apomorphine had no effect on basal ACTH levels but did substantially increase the number of Fos-positive amygdala and nucleus tractus solitarius catecholamine cells. Administration of apomorphine prior to immune challenge augmented the normal ACTH response to this stressor at 90 min and there was a corresponding increase in the number of Fos-positive paraventricular nucleus corticotropin-releasing factor cells, paraventricular nucleus oxytocin cells and nucleus tractus solitarius catecholamine cells. However, apomorphine treatment did not alter ACTH or Fos responses to sound stress. These data suggest that erection-inducing levels of apomorphine interfere with hypothalamic-pituitary-adrenal axis inhibitory feedback mechanisms in response to a physical stressor, but have no effect on the response to a psychological stressor. Consequently, it is likely that apomorphine acts on a hypothalamic-pituitary-adrenal axis control pathway that is unique to physical stressors. A candidate for this site of action is the nucleus tractus solitarius catecholamine cell population and, in particular, A2 noradrenergic neurons.

A longitudinal evaluation of a project-based learning initiative in an engineering undergraduate programme

Project-based learning (PBL) is a well-known student-centred methodology for engineering design education. The methodology claims to offer a number of educational benefits. This paper evaluates the student perceptions of the initial and second offering of a first-year design unit at Griffith University in Australia. It builds on an earlier evaluation conducted after the initial offering of the unit. It considers the implementation of the recommended changes. Evaluations of the two offerings reveal that students (in both the initial and second offering) generally enjoyed the experience, but that the second offering was found to be a significantly more enjoyable learning experience. Students in the second offering also reported a significantly better understanding of what they needed to do for the design projects and where to find the requisite information. The oral presentation aspect of the initial and second offerings received the lowest satisfaction rating. The inclusion (and delivery) of the computer-aided drawing component of the unit is seen as a positive aspect by some students, but many others comment on it negatively. The best aspects of the PBL unit and those aspects needing further improvement were similar to the findings of other investigations documented in the literature.

A 32 year longitudinal study of child and adolescent pathways to well-being in adulthood

The purpose of the study was to investigate the relative importance of child and adolescent social and academic pathways to well-being in adulthood (32-years) indicated by a sense of meaning, social engagement, positive coping and prosocial values. Data were drawn from a 15 wave (32-year) longitudinal study of the health and development of around 1000 New Zealanders (Dunedin Multidisciplinary Health and Development Study, New Zealand). Moderate continuity in social connectedness (0.38) and high continuity in academic ability (0.90) was observed across childhood and adolescence. Adolescent social connectedness was a better predictor of adult well-being than academic achievement (0.62 vs. 0.12). There was evidence of an indirect pathway from adolescent academic achievement to adult well-being through social connectedness (0.29). Indicators of well-being in adulthood appear to be better explained by social connection rather than academic competencies pathways. Implications for promoting longer term well-being during the school years are discussed.

A bi-directional relationship between obesity and health-related quality of life : evidence from the longitudinal AusDiab study

Objective: To assess the prospective relationship between obesity and health-related quality of life, including a novel assessment of the impact of health-related quality of life on weight gain.

Design and setting: Longitudinal, national, population-based Australian Diabetes, Obesity and Lifestyle (AusDiab) study, with surveys conducted in 1999/2000 and 2004/2005.

Participants: A total of 5985 men and women aged 25 years at study entry.

Main outcome measure(s): At both time points, height, weight and waist circumference were measured and self-report data on health-related quality of life from the SF-36 questionnaire were obtained. Cross-sectional and bi-directional, prospective associations between obesity categories and health-related quality of life were assessed.

Results: Higher body mass index (BMI) at baseline was associated with deterioration in health-related quality of life over 5 years for seven of the eight health-related quality of life domains in women (all P0.01, with the exception of mental health, P>0.05), and six out of eight in men (all P<0.05, with the exception of role-emotional, P=0.055, and mental health, P>0.05). Each of the quality-of-life domains related to mental health as well as the mental component summary were inversely associated with BMI change (all P<0.0001 for women and P0.01 for men), with the exception of vitality, which was significant in women only (P=0.008). For the physical domains, change in BMI was inversely associated with baseline general health in women only (P=0.023).

Conclusions: Obesity was associated with a deterioration in health-related quality of life (including both physical and mental health domains) in this cohort of Australian adults followed over 5 years. Health-related quality of life was also a predictor of weight gain over 5 years, indicating a bi-directional association between obesity and health-related quality of life. The identification of those with poor health-related quality of life may be important in assessing the risk of future weight gain, and a focus on health-related quality of life may be beneficial in weight management strategies.

Self-reported medication side effects in an older cohort living independently in the community - the Melbourne Longitudinal Study on Health Ageing (MELSHA) : cross-sectional analysis of prevalence and risk factors

Background Medication side effects are an important cause of morbidity, mortality and costs in older people. The aim of our study was to examine prevalence and risk factors for self-reported medication side effects in an older cohort living independently in the community.

Methods The Melbourne Longitudinal Study on Healthy Ageing (MELSHA), collected information on those aged 65 years or older living independently in the community and commenced in 1994. Data on medication side effects was collected from the baseline cohort (n = 1000) in face-to-face baseline interviews in 1994 and analysed as cross-sectional data. Risk factors examined were: socio-demographics, health status and medical conditions; medication use and health service factors. Analysis included univariate logistic regression to estimate unadjusted risk and multivariate logistic regression analysis to assess confounding and estimate adjusted risk.

Results Self-reported medication side effects were reported by approximately 6.7% (67/1000) of the entire baseline MELSHA cohort, and by 8.5% (65/761) of those on medication. Identified risk factors were increased education level, co-morbidities and health service factors including recency of visiting the pharmacist, attending younger doctors, and their doctor's awareness of their medications. The greatest increase in risk for medication side effects was associated with liver problems and their doctor's awareness of their medications. Aging and gender were not risk factors.

Conclusion Prevalence of self-reported medication side effects was comparable with that reported in adults attending General Practices in a primary care setting in Australia. The prevalence and identified risk factors provide further insight and opportunity to develop strategies to address the problem of medication side effects in older people living independently in the community setting.

Glaucomatous visual field progression with frequency-doubling technology and standard automated perimetry in a longitudinal prospective study

PURPOSE. To compare frequency-doubling technology (FDT) perimetry with standard automated perimetry (SAP) for detecting glaucomatous visual field progression in a longitudinal prospective study.

METHODS. One eye of patients with open-angle glaucoma was tested every 6 months with both FDT and SAP. A minimum of 6 examinations with each perimetric technique was required for inclusion. Visual field progression was determined by two methods: glaucoma change probability (GCP) analysis and linear regression analysis (LRA). For GCP, several criteria for progression were used. The number of locations required to classify progression with FDT compared with SAP, respectively, was 1:2 (least conservative), 1:3, 2:3, 2:4, 2:6, 2:7, 3:6, 3:7, and 3:10 (most conservative). The number of consecutive examinations required to confirm progression was 2-of-3, 2-of-2, and 3-of-3. For LRA, the progression criterion was any significant decline in mean threshold sensitivity over time in each of the following three visual field subdivisions: (1) all test locations, (2) locations in the central 10° and the superior and inferior hemifields, and (3) locations in each quadrant. Using these criteria, the proportion of patients classified as showing progression with each perimetric technique was calculated and, in the case of progression with both, the differences in time to progression were determined.

RESULTS. Sixty-five patients were followed for a median of 3.5 years (median number of examinations, 9). For the least conservative GCP criterion, 32 (49%) patients were found to have progressing visual fields with FDT and 32 (49%) patients with SAP. Only 16 (25%) patients showed progression with both methods, and in most of those patients, FDT identified progression before SAP (median, 12 months earlier). The majority of GCP progression criteria (15/27), classified more patients as showing progression with FDT than with SAP. Contrary to this, more patients showed progression with SAP than FDT, when analysed with LRA; e.g., using quadrant LRA 20 (31%) patients showed progression with FDT, 23 (35%) with SAP, and only 10 (15%) with both.

CONCLUSIONS. FDT perimetry detected glaucomatous visual field progression. However, the proportion of patients who showed progression with both FDT and SAP was small, possibly indicating that the two techniques identify different subgroups of patients. Using GCP, more patients showed progression with FDT than with SAP, yet the opposite occurred using LRA. As there is no independent qualifier of progression, FDT and SAP progression rates vary depending on the method of analysis and the criterion used.