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R Wolfe

Publications and source records attributed to R Wolfe.

At least 37 records · Page 2Linked to original sources
PubMed2003

Variability in the measurement of uptime in children: a preliminary study.

OBJECTIVE: To examine variability in 'uptime' (the amount of time spent in the upright position). DESIGN: An observational study. SETTING: The community (i.e., homes and schools in the Melbourne metropolitan area). SUBJECTS: Normal children between 8 and 15 years of age (18 girls and 8 boys). EQUIPMENT: An 'uptimer', a lightweight, battery-operated remote monitor, was used to record uptime. PROCEDURE: Each child in the study wore the uptimer continuously over a 24-hour period, which included a typical day at school, on four separate occasions, one week apart. RESULTS: The variability in repeated measures of uptime in the same child (standard deviation 0.8 hours in 24 hours) was lower than the variability between the children (standard deviation 1.1 hours in 24 hours). We estimate that a single uptime measurement has reliability given by an ICC of 0.65 (95% confidence interval 0.49-0.82), which is calculated by dividing the between-child variability by the total variability (within-child and between-child variability). There were no systematic differences in mean uptime between occasions of measurement. CONCLUSION: As an estimate of the time that a child spends in the upright position, a single 24-hour period of measurement of uptime may vary considerably from one occasion to the next. However, this within-child variability is less than the variability between children. In large-scale field studies a one-off measurement of uptime may be acceptable, but in small rehabilitation studies uptime should be measured on at least three occasions.

Adolescent↗
PubMed2001

Structure and functional connections of presynaptic terminals in the vertebrate retina revealed by activity-dependent dyes and confocal microscopy.

The fluorescent dyes sulforhodamine 101 (SR 101) and FM1-43 were used as activity-dependent dyes (ADDs) to label presynaptic terminals in the retinas of a broad range of animals, including amphibians, mammals, fish, and turtles. The pattern of dye uptake was studied in live retinal preparations by using brightfield, fluorescence, and confocal microscopy. When bath-applied to the retina-eyecup, these dyes were avidly sequestered by the presynaptic terminals of virtually all rods, cones, and bipolar and amacrine cells; ganglion cell dendrites and horizontal cells lacked significant dye accumulation. Other structures stained with these dyes included pigment epithelial cells, cone outer segments, and Müller cell end-feet. Studies of dye uptake in dark- and light-adapted preparations showed significant differences in the dye accumulation pattern in the inner plexiform layer (IPL), suggesting a dynamic, light-modulated control of endocytotic activity. Presynaptic terminals in the IPL could be segregated on the basis of volume: bipolar varicosities in the IPL were typically larger than those of amacrine cells. The combination of retrograde labeling of ganglion cells and presynaptic terminal labeling with ADDs served as the experimental preparation for three-dimensional reconstruction of both structures, based on dual detector, confocal microscopy. Our results demonstrate a new approach for studying synaptic interactions in retinal function. These findings provide new insights into the likely number and position of functional connections from amacrine and bipolar cell terminals onto ganglion cell dendrites.

Adaptation, Ocular↗
PubMed2001

Parental 'affectionless control' in adolescent depressive disorder.

BACKGROUND: Adults with depressive disorder report high rates of sub-optimal maternal care in childhood. Despite the greater salience of relationships with parents earlier in life, associations with parenting style have not yet been systematically studied in adolescent onset disorder. METHODS: A six-wave, 3-year study of adolescent health in 2032 Australian secondary school students provided an opportunity to undertake a two-phase study of early onset depression. Between waves 2 to 6, a self-administered computerised form of the revised Clinical Interview Schedule (CIS-R) was used to generate a first phase diagnosis of ICD-10 depressive episode. Each subject with a CIS-R-defined depressive episode was selected for second phase assessment together with two subjects from the CIS-R non-cases in each school. Second phase assessment included a second diagnostic assessment using the depression and hypomania modules of the Composite International Diagnostic Interview (CIDI) and assessment of paternal and maternal style using the Parental Bonding Instrument. RESULTS: A total of 1947 out of 2032 subjects in the sampling frame (95.8%) participated in the cohort study (phase 1) at least once; 406 (94%) of the 435 selected subjects completed second phase assessment. One hundred and nineteen subjects fulfilled criteria for depressive episode on the CIS-R at one or more waves. Over the 30-month study period, 69 subjects (10 male, 59 female) fulfilled both CIS-R and CIDI definitions of depression at the same wave and were classified as 'definite depressive disorder'. Low maternal and paternal care held independent associations with both definitions of depression, with the effects clearest in those in the lowest quartile of reported care. After adjusting for low parental care, the associations between high parental control and depression were small. CONCLUSIONS: Sub-optimal parenting is associated with depressive disorder in adolescents. Low maternal and paternal care are each associated with a two- to three-fold higher rate of depressive disorder. These findings are consistent with an effect of sub-optimal parenting on the onset rather than course of disorder. Whether sub-optimal parenting is associated with a risk for the onset of depression outside the adolescent years has yet to be clarified.

Adolescent↗
PubMed2001

Improved outcomes from a comprehensive management system for heart failure.

AIMS: Congestive heart failure (CHF) is associated with a high readmission rate after diagnosis. We assessed the ability of a comprehensive management program (CMP) for CHF to reduce readmissions with secondary endpoints of improving quality of life, exercise capacity and targeted drug doses. METHODS AND RESULTS: Patients (pts) with: New York Heart Association Class (NYHA) III or IV CHF; left ventricular ejection fraction <40%; and stable outpatient therapy were assigned to a CMP of cardiology assessment intensive education and referral to a tailored exercise program. Forty-two pts (35 M, 7 F, mean age 54 years, S.D. 12 years) were enrolled. Two pts were transplanted, two died during follow-up and two were lost to follow-up. Hospital admissions were reduced by 87.2%, (mean 1.05, S.D. 0.98, admissions per pt to mean 0.08, S.D. 0.28, admissions per pt at 6-month follow-up; P<0.0001). ACE-inhibitor dose increased by 42% (P<0.0008) and beta-blocker dose increased by 61% (P<0.0001). NYHA Class, 6-min walk and quality of life scores all improved significantly (P<0.0001). CONCLUSION: A CMP improves QOL and exercise capacity as well as substantially reducing hospital admissions in CHF pts. This study validates the benefit of intensive outpatient care of CHF.

Aged↗
PubMed2001

Adverse outcomes of alcohol use in adolescents.

AIMS: To compare the occurrence of behaviours occurring under the influence of alcohol in 16-17-year-olds and determine associated risk factors for the different behaviours. DESIGN/SETTING: Cross-sectional survey administered by laptop computers in secondary schools across the state of Victoria, Australia. MEASUREMENT/FINDINGS: The participation rate was 79%. Seventy per cent of participants drank alcohol; 17% of drinkers reported alcohol-related violence (accidents or injuries) and 15% reported problems relating to sex under the influence of alcohol (having sex and later regretting it or having had unsafe sex) in the previous 12 months. Males were more likely to report alcohol-related violence (20% compared to 14% females). Almost one in 10 young people reported having sex while under the influence of alcohol and later regretting it and 10% reported having had unsafe sex. There were no significant gender differences in the reporting rates of alcohol-related sexual risk taking (prop. cum. OR 1.1, 95% CI 0.68-1.9). For alcohol-related injuries, strong independent associations were found with dose of alcohol consumed (prop. cum. OR 2.3, 95% CI 1.3-4.0), frequency of alcohol consumption (prop. cum. OR 2.7, 95% CI 0.94-7.5), antisocial behaviour (prop. cum. OR 2.4, 95% CI 1.4-4.1) and peer drinking (prop. cum. OR 3.3, 95% CI 1.4-8.1). For alcohol-related sexual risk-taking, psychiatric morbidity (prop. cum. OR 4.1, 95% CI 1.9-9.0) and high frequency of alcohol consumption (prop. cum. OR 2.0, 95% CI 0.87-4.6) had strong independent associations. CONCLUSIONS: Physical injury and high-risk sexual behaviour under the influence of alcohol are common in teenagers. Alcohol-related physical injury appears closely related to patterns of alcohol consumption whereas alcohol-related sexual risk-taking is most closely associated with symptoms of depression and anxiety.

Adolescent↗
PubMed2001

The prevalence of fecal colonization with VRE among residents of long-term-care facilities in Melbourne, Australia.

A point-prevalence survey performed among residents of eight nursing homes in Melbourne, Australia, found a rate of fecal VRE colonization of 3.1% (9/292; 95% confidence interval, 1.1-5.1), all vanB Enterococcusfaecium. This is a higher rate than in the general community (3.1% vs 0.2%). Many residents (16%) had been inpatients in acute-care hospitals in the previous 3 months.

Aged↗
PubMed2001

A case study on the choice, interpretation and checking of multilevel models for longitudinal binary outcomes.

Recent advances in statistical software have led to the rapid diffusion of new methods for modelling longitudinal data. Multilevel (also known as hierarchical or random effects) models for binary outcomes have generally been based on a logistic-normal specification, by analogy with earlier work for normally distributed data. The appropriate application and interpretation of these models remains somewhat unclear, especially when compared with the computationally more straightforward semiparametric or 'marginal' modelling (GEE) approaches. In this paper we pose two interrelated questions. First, what limits should be placed on the interpretation of the coefficients and inferences derived from random-effect models involving binary outcomes? Second, what diagnostic checks are appropriate for evaluating whether such random-effect models provide adequate fits to the data? We address these questions by means of an extended case study using data on adolescent smoking from a large cohort study. Bayesian estimation methods are used to fit a discrete-mixture alternative to the standard logistic-normal model, and posterior predictive checking is used to assess model fit. Surprising parallels in the parameter estimates from the logistic-normal and mixture models are described and used to question the interpretability of the so-called 'subject-specific' regression coefficients from the standard multilevel approach. Posterior predictive checks suggest a serious lack of fit of both multilevel models. The results do not provide final answers to the two questions posed, but we expect that lessons learned from the case study will provide general guidance for further investigation of these important issues.

Journal Article↗
PubMed2001

Respiratory distress syndrome and birth order in premature twins.

OBJECTIVE: To determine the effect of birth order on respiratory distress syndrome (RDS) in the outcome of twins in a large premature population managed in a modern neonatal intensive care unit. METHODS: An historical cohort study design was used to analyse the neonatal outcomes of 301 premature liveborn twin sibling pairs of between 23 and 31 weeks gestation from the Australia and New Zealand Neonatal Network 1995 database. RESULTS: Among the 56 twin sibling pairs who were discordant for RDS, the second twin was affected in 41 cases (odds ratio (OR) 2.7, 95% confidence interval (CI) 1.5 to 5.3). The excess risk of RDS in the second twin increased with gestation and was statistically significant for twins above 29 weeks gestation (OR 4.4, 95% CI 1.6 to 15). CONCLUSIONS: There is a significant increased risk of RDS associated with being the second born of premature twins, which appears to depend on gestation.

Birth Order↗
PubMed2000

Distribution of pulmonary blood flow in the perfluorocarbon-filled lung.

OBJECTIVE: Partial liquid ventilation (PLV) improves gas exchange in animal studies of lung injury. Perfluorocarbons (PFCs) are heavy liquids and are therefore preferentially delivered to the most dependent areas of lung. We hypothesised that improved oxygenation during PLV might be the consequence of a redistribution of pulmonary blood flow away from poorly ventilated, dependent alveoli, leading to improved ventilation/perfusion (V/Q) matching. This study investigated whether partially filling the lung with PFC would result in a redistribution of pulmonary blood flow. DESIGN: Prospective experimental study. SETTING: Hospital research institute laboratory. PARTICIPANTS: Six anaesthetised pigs without lung injury. INTERVENTIONS: Animals were anaesthetised and ventilated (gas tidal volume 12 ml/kg, PEEP 5, FIO2 1.0, rate 16). Whilst the pigs were maintained in the supine position, regional pulmonary blood flow was measured during conventional gas ventilation and repeated during PLV. Flow to regions of lung was determined by injection of radioactive microspheres (Co(57), Sn(113), Sc(46)). Measurements were performed with ventilation held at end-expiratory pressure and, in two PLV animals only, repeated with ventilation held at peak inspiratory pressure. RESULTS: During conventional gas ventilation, blood flow followed a linear distribution with the highest flow to the most dependent lung. In the lung partially filled with PFC a diversion of blood flow away from the most dependent lung was seen (p = 0.007), resulting in a more uniform distribution of flow down the lung (p = 0.006). Linear regression analysis (r2 = 0.75) also confirmed a difference in distribution pattern. On applying an inspiratory hold to the liquid-containing lung, blood flow was redistributed back towards the dependent lung. CONCLUSIONS: Partially filling the lung with PFC results in a redistribution of pulmonary blood flow away from the dependent region of the lung. During PLV a different blood flow distribution may be seen between inspiration and expiration. The clinical significance of these findings has yet to be determined.

Animals↗
PubMed2000

Biomechanical transformation of the gastroc-soleus muscle with botulinum toxin A in children with cerebral palsy.

Objective measures (kinematics and kinetics) were used to study prospectively the effects of botulinum toxin A (BTX/A) on the gastro-soleus muscle in ambulant children with cerebral palsy. In this prospective before and after trial, 15 children with diplegia and 10 children with hemiplegia were studied (mean age 5 years 7 months, range 4 years to 9 years). A range of standardized clinical measures was undertaken but the emphasis for this report is on the three-dimensional gait analysis (3DGA) results. All children showed improvements in sagittal ankle kinematics, as has been previously reported. Two new measures of ankle kinetics were devised: ankle moment quotient (AMQ), and ankle power quotient (APQ). Before intervention, ankle moments were characterized by a 'double bump' ankle moment. A typical abnormal baseline ankle-power curve was triphasic with an initial trough of absorption followed by abnormal mid-stance power generation, instead of the usual A1 pattern, and reduced terminal stance power generation (A2). Three weeks after treatment with BTX/A alone there was a statistically significant improvement of AMQ and APQ; some patients required potentiation of BTX/A with a short period of serial casts. Both groups (BTX/A alone and BTX/A plus casting) continued to show improvement in ankle kinetics from baseline after 12 and 24 weeks. This is the first study to demonstrate improvements in the typical abnormal ankle kinetics which we believe provides evidence of the 'biomechanical transformation of muscle'.

Ankle Joint↗
PubMed2000

Initiation and progression of cannabis use in a population-based Australian adolescent longitudinal study.

AIMS: To examine predictors of cannabis use initiation, continuity and progression to daily use in adolescents. DESIGN: Population-based cohort study over 3 years with 6 waves of data collection. PARTICIPANTS: 2032 students, initially aged 14-15 years, from 44 secondary schools in the state of Victoria, Australia. MEASUREMENTS: Self-report cannabis use was categorized on four levels (none, any, weekly, daily) and summarized as mid-school (waves 2/3) and late-school (waves 4/5/6) use. Background, school environment, mid-school peer use and individual characteristics were assessed. FINDINGS: Peer cannabis use, daily smoking, alcohol use, antisocial behaviour and high rates of school-level cannabis use were associated with mid-school cannabis use and independently predicted late-school uptake. Cannabis use persisted into late-school use in 80% of all mid-school users. Persisting cannabis use from mid- to late-school was more likely in regular users (odds ratio (OR) 3.4), cigarette smokers (OR any smoking: 2.0, daily smoking: 3.3) and those reporting peer use (OR 2.1). Mid-school peer use independently predicted incident late-school daily use in males (OR 6.5) while high-dose alcohol use (OR 6.1) and antisocial behaviour (OR 6.6) predicted incident late-school daily use in females. CONCLUSIONS: Most cannabis use remained occasional during adolescence but escalation to potentially harmful daily use in the late-school period occurred in 12% of early users. Transition was more likely in males, for whom availability and peer use were determinants. In contrast, females with multiple extreme behaviours were more likely to become daily users. Cigarette smoking was an important predictor of both initiation and persisting cannabis use.

Adolescent↗
PubMed2000

Adolescent depressive disorder: a population-based study of ICD-10 symptoms.

OBJECTIVE: Earlier studies have suggested that symptoms of depressive disorder in adolescents may differ from those found in adults. Even so, diagnostic criteria developed in adults have come to be widely applied to younger subjects. This study examines the frequency of ICD-10 symptoms in depressive disorder and their association with severity in a large community sample of adolescents aged 15 to 18 years. METHOD: A six-wave prospective study of adolescent health and emotional wellbeing in 2032 Australian secondary school students provided an opportunity to conduct a two-phase study of adolescent onset depression. A self-administered computerised form of the revised Clinical Interview Schedule (CIS-R) was used as a first phase diagnostic measure. Second phase assessment using the Composite International Diagnostic Interview (CIDI) allowed the delineation of a group fulfilling criteria on both instruments. The ICD-10 symptoms and severity profiles for depression were generated with standard algorithms. RESULTS: 1947 (95.8%) out of 2032 subjects in the designated sample completed phase 1 assessment at least once. Participation rates at phase 2 interviews were 93%. Over the 30-month study period 69 subjects (10 male, 59 female) fulfilled criteria for ICD-10 depressive episodes on both the CIS-R and CIDI. Thirty-one per cent (n = 21) had experienced a severe episode, 46% (n = 32) moderate and 23% (n = 16) mild episodes. Loss of interest and pleasure, decreased energy and fatigue, sleep disturbance, suicidal ideation and diminished concentration most clearly distinguished adolescents with depressive disorder from controls. Self-reproach and guilt, psychomotor agitation and/or retardation and appetite disturbance with weight change showed the clearest increase in frequency with increasing severity of episode. The somatic syndrome was reported by close to one in three of those with a severe depressive episode, but was uncommon in those with mild and moderate episodes. CONCLUSIONS: The ICD-10 diagnostic criteria are applicable to depressive disorder in older adolescents. With the exception of depressed mood, found in one in five non-cases, all other symptoms were common in cases and uncommon in non-cases. Practitioner awareness of symptoms indicating the presence and severity of disorder should enhance early identification and choice of treatment in adolescent depression.

Adolescent↗
PubMed2000

Association between allergy and asthma from childhood to middle adulthood in an Australian cohort study.

A cohort of 378 asthmatic children was studied from 7 to 35 yr of age at 7-yr intervals. On selection for inclusion in the study sample, the children had a wide range of severity of wheezing. At each 7-yr review, asthma severity, the presence of eczema or hay fever, and skin test reactivity to house dust mite or rye grass were recorded by questionnaire or clinical interview. We report on the course of asthma and these atopic conditions over the study period and discuss associations between the two phenomena. The presence of an atopic condition in childhood was found to increase the odds of more severe asthma in later life (odds ratio [OR] = 1.66, 95% confidence interval [CI]: 1.17 to 2.36 in the case of eczema; OR = 1. 39, 95% CI: 1.00 to 1.92 for hay fever; and OR = 2.25, 95% CI: 1.49 to 3.39 for skin test reactivity). Additionally, the odds of eczema and hay fever in later life increased with severity of asthma in childhood. The findings of this study provide substantially new quantitative information on the extent of association between asthma and atopic conditions from childhood into middle adulthood.

Adolescent↗
PubMed2000

Influence of parental gender and self-reported health and illness on parent-reported child health.

BACKGROUND: Although there is clear evidence of the influence of parental factors on child health outcomes, the influence of parental perceptions of their health and illness on the reporting of child health remains primarily unknown. OBJECTIVES: To examine relationships between parents' reporting of their own health and illness with the reporting of their children's health and illness. METHOD: We surveyed parents of a representative population-based sample of children aged 5 to 18 years. One parent of each child completed a written questionnaire including the Child Health Questionnaire, a subjective measure of functional health and well-being, and an assessment of self-reported parental health and illness. Logistic regression models were used to examine relationships between parent and child health and illness. MAIN RESULTS: 5340 parents responded (86% mothers, 14% fathers). After adjusting for confounding effects, parents self-reporting poor health had increased odds of reporting their children with poor health (odds ratio: 7.5), although the effect was modified by parent gender. There were increased odds of mothers with self-reporting poor global health reporting their children with poor global health and illness (odds ratio: 9.0 and 2.5, respectively) that were not observed for fathers. CONCLUSIONS: A mother's self-reported health is strongly associated with her reporting of her child's health; this was not observed for fathers. These results suggest that parental gender should be considered as a mediating factor in the reporting of child health.

Adolescent↗
PubMed2000

Testosterone and muscle protein metabolism.

This presentation discusses recent investigations into testosterone's effects on muscle protein metabolism. Protein synthesis is the principal end point, but protein breakdown and the availability of an amino acid pool are important to the process of net muscle protein synthesis. The effects of other hormones--including growth hormone, oxoandrolone (a synthetically derived testosterone), and androstenedione--on muscle protein synthesis also are discussed. Effects in both normal and elderly men are considered.

Aged↗
PubMed1999

Analysis of binary outcomes in longitudinal studies using weighted estimating equations and discrete-time survival methods: prevalence and incidence of smoking in an adolescent cohort.

Longitudinal studies are increasingly popular in epidemiology. In this tutorial we provide a detailed review of methods used by us in the analysis of a longitudinal (multiwave or panel) study of adolescent health, focusing on smoking behaviour. This example is explored in detail with the principal aim of providing an introduction to the analysis of longitudinal binary data, at a level suited to statisticians familiar with logistic regression and survival analysis but not necessarily experienced in longitudinal analysis or estimating equation methods. We describe recent advances in statistical methodology that can play a practical role in applications and are available with standard software. Our approach emphasizes the importance of stating clear research questions, and for binary outcomes we suggest these are best organized around the key epidemiological concepts of prevalence and incidence. For prevalence questions, we show how unbiased estimating equations and information-sandwich variance estimates may be used to produce a valid and robust analysis, as long as sample size is reasonably large. We also show how the estimating equation approach readily extends to accommodate adjustments for missing data and complex survey design. A detailed discussion of gender-related differences over time in our smoking outcome is used to emphasize the need for great care in separating longitudinal from cross-sectional information. We show how incidence questions may be addressed using a discrete-time version of the proportional hazards regression model. This approach has the advantages of providing estimates of relative risks, being feasible with standard software, and also allowing robust information-sandwich variance estimates.

Adolescent↗