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Search Results: 1 - 10 of 302257 matches for " Philip J Schluter "
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A multivariate hierarchical Bayesian approach to measuring agreement in repeated measurement method comparison studies
Philip J Schluter
BMC Medical Research Methodology , 2009, DOI: 10.1186/1471-2288-9-6
Abstract: Adopting the Bland-Altman framework, but using Bayesian methods, we present this statistical machinery. Two multivariate hierarchical Bayesian models are advocated, one which assumes that the underlying values for subjects remain static (exchangeable replicates) and one which assumes that the underlying values can change between repeated measurements (non-exchangeable replicates).We illustrate the salient advantages of these models using two separate datasets that have been previously analysed and presented; (i) assuming static underlying values analysed using both multivariate hierarchical Bayesian models, and (ii) assuming each subject's underlying value is continually changing quantity and analysed using the non-exchangeable replicate multivariate hierarchical Bayesian model.These easily implemented models allow for full parameter uncertainty, simultaneous method comparison, handle unbalanced or missing data, and provide estimates and credible regions for all the parameters of interest. Computer code for the analyses in also presented, provided in the freely available and currently cost free software package WinBUGS.Accurate measurement of the variable of interest is fundamentally important in any health research or practice setting. However, it is widely recognised that measurements simultaneously made on the same subject or specimen by different instruments, methods or observers invariably yield different empirical values. As such, evaluation of measurement quality is a central issue in deciding the utility of any instrument, method or observer [1]. Measurement validity and reproducibility are essential elements in determining this quality. Validity is the degree to which a measurement measures what it purports to measure and reproducibility is the degree to which a measurement provides the same result each time it is performed on a given subject or specimen [2]. Reproducibility is invariably assessed using agreement analysis of within (intra) and between (inte
Body size, physical activity, and exposure to television in preschoolers  [PDF]
Melody Oliver, Philip J. Schluter, Grant M. Schofield
Open Journal of Preventive Medicine (OJPM) , 2012, DOI: 10.4236/ojpm.2012.23052
Abstract: Objective: To investigate relationships between preschool-aged children’s body size and physiccal activity, exposure to television (TV), and parental body size. Design and subjects: Cross-sectional study of 80 children (age: 2 - 5 y, 29% overweight or obese), 73 mothers (37% overweight or obese), and 22 fathers (72% overweight or obese), residing in Auckland, New Zealand, between October 2006 and July 2007. Measurements: Body size was determined using waist circumference and body mass index (BMI). Child exposure to TV was assessed by questionnaire (number of household TV sets, presence of TV in the child’s bedroom, mean TV/ movie watching hours on weekdays and weekend days), and physical activity by 7 days of accelerometry. Results: Compared with children of normal weight/underweight mothers (classified by BMI status), the age-adjusted odds of a child being overweight/obese if their mother was over-weight/obese/otherwise was 2.46 (95% CI 1.11, 5.48, P = 0.03). No other associates of child body size were identified. Conclusion: Contributors to overweight and obesity in preschool aged children are complex and likely to exist in multiple facets of young children’s lives. More detailed measurement of TV watching and other sedentary behaviours is needed. An ecological approach to identifying risk factors for increased body size in preschoolers is required.
Coastal Accessibility and Availability for Physical Activity: A Cross-Sectional Assessment in New Zealand Adults  [PDF]
Nick Garrett, Melody Smith, Philip J. Schluter, Barbara Bollard-Breen
Open Journal of Preventive Medicine (OJPM) , 2016, DOI: 10.4236/ojpm.2016.612025
Abstract: Background: This study aimed to examine cross-sectional relationships between objective measures of the built environment (neighborhood walkability and access to and availability of public open spaces including the coast) with self-reported physical activity in adults residing in Auckland, New Zealand. Methods: A telephone survey captured self-reported physical activity and socio-demographic information from adult residents from randomly selected households. Robust approaches were employed to deriving and “ground-truthing” objective built environment measures around individual addresses. Multivariable binary logistic regression models were used to examine the associations between environmental factors and being classified as accumulating sufficient physical activity or otherwise. Results: A total of 1986 participants agreed to participate. Compared with those with no coastal access points within an 800 m street network buffer of their residence, those with 1 - 2 access points were 1.45 times more likely to be classified as sufficiently active (95% CI 1.08, 1.94, p = 0.05). Compared with individuals with no coastal settings within their neighborhood buffer, those with at least two coastal settings in their neighborhood were significantly more likely to be sufficiently active (p = 0.03). Conclusion: Access to, and availability of, coastal places were important associates of accumulating sufficient activity for health in this population.
Acculturation of Pacific mothers in New Zealand over time: findings from the Pacific Islands Families study
Philip J Schluter, El-Shadan Tautolo, Janis Paterson
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-307
Abstract: Pacific mothers of a cohort of Pacific infants born at a large tertiary hospital in South Auckland in 2000 were interviewed at 6-weeks, 4-years and 6-years postpartum. At each measurement wave a home interview lasting approximately 90 minutes was conducted with each mother. Adapting the General Ethnicity Questionnaire, two scales of acculturation were elicited: one measuring New Zealand cultural orientation (NZAccult) and one measuring Pacific Islands cultural orientation (PIAccult). Acculturation scores were standardised and analysed using random intercept polynomial and piecewise mixed-effects regression models, accounting for the longitudinal nature of the repeated measured data. Mothers who immigrated to New Zealand and those who lived their lives in New Zealand were investigated separately.Overall, 1276 Pacific mothers provided 3104 NZAccult and 3107 PIAccult responses over the three measurement waves. Important and significant differences were observed in both bi-directional acculturation measures between the two maternal groups studied. New Zealand cultural orientation increased, on average, linearly with years lived in New Zealand both for immigrant mothers (0.013 per year, 95% CI: 0.012, 0.014), after adjusting for maternal age, and for mothers who lived their lives in New Zealand (0.008 per year, 95% CI: 0.06, 0.010). Immigrant mothers maintained their Pacific cultural orientation for, on average, 12 years before it began to linearly decrease with each year lived in New Zealand thereafter (-0.009 per year, 95% CI: -0.010, -0.008), after adjusting for maternal age. Mothers who lived their lives in New Zealand had a Pacific orientation that was, on average, unchanged regardless of the number of years lived in New Zealand. Significant ethnic and socio-demographic variations were noted.Understanding the patterns and trajectories of acculturation over time, and its key determinants, is necessary for the development of appropriate targeted health policy and care
Cyanobacterial lipopolysaccharides and human health – a review
Ian Stewart, Philip J Schluter, Glen R Shaw
Environmental Health , 2006, DOI: 10.1186/1476-069x-5-7
Abstract: We systematically reviewed the literature on cyanobacterial LPS, and also examined the much lager body of literature relating to heterotrophic bacterial LPS and the atypical lipid A structures of some photosynthetic bacteria. While the literature on the biological activity of heterotrophic bacterial LPS is overwhelmingly large and therefore difficult to review for the purposes of exclusion, we were unable to find a convincing body of evidence to suggest that heterotrophic bacterial LPS, in the absence of other virulence factors, is responsible for acute gastrointestinal, dermatological or allergic reactions via natural exposure routes in humans.There is a danger that initial speculation about cyanobacterial LPS may evolve into orthodoxy without basis in research findings. No cyanobacterial lipid A structures have been described and published to date, so a recommendation is made that cyanobacteriologists should not continue to attribute such a diverse range of clinical symptoms to cyanobacterial LPS without research confirmation.Cyanobacterial LPS is attributed with a range of pathological effects in humans, from gastro-intestinal illness, cutaneous signs and symptoms, allergy, respiratory disease, headache and fever. This review will present the studies of cyanobacterial LPS, and will attempt to place the knowledge of these products within the broader understanding of LPS from Gram-negative heterotrophic bacteria. The paper will present an overview of the mechanisms of toxicity of Gram-negative bacterial LPS, discussing the history of its discovery and the present perception of its pathogenicity.Table 1 lists some of the signs and symptoms reportedly associated with exposure to cyanobacterial LPS, and references that imply particular symptoms or symptom groups are explained by such exposures. Table 1 does not present an exhaustive list of citations implicating cyanobacterial LPS with human illness. Many such references are found in review articles, and the table doe
Recreational and occupational field exposure to freshwater cyanobacteria – a review of anecdotal and case reports, epidemiological studies and the challenges for epidemiologic assessment
Ian Stewart, Penelope M Webb, Philip J Schluter, Glen R Shaw
Environmental Health , 2006, DOI: 10.1186/1476-069x-5-6
Abstract: We systematically reviewed the literature on recreational exposure to freshwater cyanobacteria. Epidemiological data are limited, with six studies conducted since 1990. Statistically significant increases in symptoms were reported in individuals exposed to cyanobacteria compared to unexposed counterparts in two Australian cohort studies, though minor morbidity appeared to be the main finding. The four other small studies (three from the UK, one Australian) did not report any significant association. However, the potential for serious injury or death remains, as freshwater cyanobacteria under bloom conditions are capable of producing potent toxins that cause specific and severe dysfunction to hepatic or central nervous systems. The exposure route for these toxins is oral, from ingestion of recreational water, and possibly by inhalation.A range of freshwater microbial agents may cause acute conditions that present with features that resemble illnesses attributed to contact with cyanobacteria and, conversely, acute illness resulting from exposure to cyanobacteria or cyanotoxins in recreational waters could be misdiagnosed. Accurately assessing exposure to cyanobacteria in recreational waters is difficult and unreliable at present, as specific biomarkers are unavailable. However, diagnosis of cyanobacteria-related illness should be considered for individuals presenting with acute illness following freshwater contact if a description is given of a waterbody visibly affected by planktonic mass development.Cyanobacteria are a diverse group of prokaryotes that occupy a broad range of ecological niches by virtue of their age, having first appeared some 2.5 billion years ago, and specialisation. All cyanobacteria are photoautotrophic organisms, yet many can grow heterotrophically, using light for energy and organic compounds as a carbon source [1]. The cyanobacteria are a remarkably widespread and successful group, colonising freshwater, marine and terrestrial ecosystems, inc
Primary irritant and delayed-contact hypersensitivity reactions to the freshwater cyanobacterium Cylindrospermopsis raciborskii and its associated toxin cylindrospermopsin
Ian Stewart, Alan A Seawright, Philip J Schluter, Glen R Shaw
BMC Dermatology , 2006, DOI: 10.1186/1471-5945-6-5
Abstract: Between 8 and 10 female Balb/c mice in each experiment had test material applied to depilated abdominal skin during the induction phase and 10 or 11 control mice had vehicle only applied to abdominal skin. For challenge (day 10) and rechallenge (day 17), test material was applied to a randomly-allocated test ear; vehicle was applied to the other ear as a control. Ear thickness in anaesthetised mice was measured with a micrometer gauge at 24 and 48 hours after challenge and rechallenge. Ear swelling greater than 20% in one or more test mice is considered a positive response. Histopathology examination of ear tissues was conducted by independent examiners.Purified cylindrospermopsin (2 of 9 test mice vs. 0 of 5 control mice; p = 0.51) and the cylindrospermopsin-producing cyanobacterium C. raciborskii (8 of 10 test mice vs. 0 of 10 control mice; p = 0.001) were both shown to produce hypersensitivity reactions. Irritant reactions were seen on abdominal skin at induction. Two other toxic cyanobacteria (Microcystis aeruginosa and Anabaena circinalis) did not generate any responses using this model. Histopathology examinations to determine positive and negative reactions in ear tissues showed excellent agreement beyond chance between both examiners (κ = 0.83).The irritant properties and cutaneous sensitising potential of cylindrospermopsin indicate that these toxicological endpoints should be considered by public health advisors and reservoir managers when setting guidelines for recreational exposure to cyanobacteria.Cyanobacteria, also known as blue-green algae, are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions, certain cyanobacteria can dominate the phytoplankton within a waterbody and form nuisance blooms. Anecdotal and case reports have documented skin rashes associated with contact exposure to freshwater cyanobacteria, from recreational and occupational settings [1]. Some reports and health advisories refer to
Cutaneous hypersensitivity reactions to freshwater cyanobacteria – human volunteer studies
Ian Stewart, Ivan M Robertson, Penelope M Webb, Philip J Schluter, Glen R Shaw
BMC Dermatology , 2006, DOI: 10.1186/1471-5945-6-6
Abstract: A consecutive series of adult patients presenting for diagnostic skin patch testing at a hospital outpatient clinic were invited to participate. A convenience sample of volunteers matched for age and sex was also enrolled. Patches containing aqueous suspensions of various cyanobacteria at three concentrations were applied for 48 hours; dermatological assessment was made 48 hours and 96 hours after application.20 outpatients and 19 reference subjects were recruited into the study. A single outpatient produced unequivocal reactions to several cyanobacteria suspensions; this subject was also the only one of the outpatient group with a diagnosis of atopic dermatitis. No subjects in the reference group developed clinically detectable skin reactions to cyanobacteria.This preliminary clinical study demonstrates that hypersensitivity reactions to cyanobacteria appear to be infrequent in both the general and dermatological outpatient populations. As cyanobacteria are widely distributed in aquatic environments, a better appreciation of risk factors, particularly with respect to allergic predisposition, may help to refine health advice given to people engaging in recreational activities where nuisance cyanobacteria are a problem.Cyanobacteria, commonly but erroneously known as blue-green algae, are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions certain cyanobacteria can dominate the phytoplankton within a waterbody and undergo mass developments, known as blooms. Public health concerns arise because many nuisance cyanobacteria can produce potent toxins. Anecdotal and case reports have documented skin rashes, often described as intensely pruritic, associated with contact exposure to cyanobacteria. While there are relatively few references in the scientific and medical literature since these reports began in 1949, under-diagnosis of cyanobacteria-associated illness was suggested by Schwimmer & Schwimmer [1] in 1968, a suspi
Efficacy of a compulsory homework programme for increasing physical activity and healthy eating in children: the healthy homework pilot study
Scott Duncan, Julia C McPhee, Philip J Schluter, Caryn Zinn, Richard Smith, Grant Schofield
International Journal of Behavioral Nutrition and Physical Activity , 2011, DOI: 10.1186/1479-5868-8-127
Abstract: The six-week 'Healthy Homework' programme and complementary teaching resource was developed under the guidance of an intersectoral steering group. Eight senior classes (year levels 5-6) from two diverse Auckland primary schools were randomly assigned into intervention and control groups. A total of 97 children (57 intervention, 40 control) aged 9-11 years participated in the evaluation of the intervention. Daily step counts were monitored immediately before and after the intervention using sealed multiday memory pedometers. Screen time, sports participation, active transport to and from school, and the consumption of fruits, vegetables, unhealthy foods and drinks were recorded concurrently in a 4-day food and activity diary.Healthy Homework resulted in a significant intervention effect of 2,830 steps.day-1 (95% CI: 560, 5,300, P = 0.013). This effect was consistent between sexes, schools, and day types (weekdays and weekend days). In addition, significant intervention effects were observed for vegetable consumption (0.83 servings.day-1, 95% CI: 0.24, 1.43, P = 0.007) and unhealthy food consumption (-0.56 servings.day-1, 95% CI: -1.05, -0.07, P = 0.027) on weekends but not weekdays, with no interactions with sex or school. Effects for all other variables were not statistically significant regardless of day type.Compulsory health-related homework appears to be an effective approach for increasing physical activity and improving vegetable and unhealthy food consumption in children. Further research in a larger study is required to confirm these initial results.Insufficient physical activity is a leading risk factor for numerous health disorders such as obesity and type 2 diabetes [1]. While methodological differences make it difficult to compare secular trends in children's free-living physical activity, there is evidence that organised physical activity is declining in many countries [2]. Similarly, sedentary behaviours, such as television watching and computer use, h
The Healthy Steps Study: A randomized controlled trial of a pedometer-based Green Prescription for older adults. Trial protocol
Gregory S Kolt, Grant M Schofield, Ngaire Kerse, Nicholas Garrett, Philip J Schluter, Toni Ashton, Asmita Patel
BMC Public Health , 2009, DOI: 10.1186/1471-2458-9-404
Abstract: The Healthy Steps study is a 12-month randomized controlled trial comparing the efficacy of a pedometer-based Green Prescription with the conventional time-based Green Prescription in increasing and maintaining physical activity levels in low-active adults over 65 years of age. The Green Prescription interventions involve a primary care physical activity prescription with 3 follow-up telephone counselling sessions delivered by trained physical activity counsellors over 3 months. Those in the pedometer group received a pedometer and counselling based around increasing steps that can be monitored on the pedometer, while those in the standard Green Prescription group received counselling using time-based goals. Baseline, 3 month (end of intervention), and 12 month measures were assessed in face-to-face home visits with outcomes measures being physical activity (Auckland Heart Study Physical Activity Questionnaire), quality of life (SF-36 and EQ-5D), depressive symptoms (Geriatric Depression Scale), blood pressure, weight status, functional status (gait speed, chair stands, and tandem balance test) and falls and adverse events (self-report). Utilisation of health services was assessed for the economic evaluation carried out alongside this trial. As well, a process evaluation of the interventions and an examination of barriers and motives for physical activity in the sample were conducted. The perceptions of primary care physicians in relation to delivering physical activity counselling were also assessed.The findings from the Healthy Steps trial are due in late 2009. If successful in improving physical activity in older adults, the pedometer-based Green Prescription could assist in reducing utilisation of health services and improve cardiovascular health and reduction of risk for a range of non-communicable lifestyles diseases.Australian and New Zealand Clinical Trials Registry ACTRN012606000023550Many older adults are at risk of lifestyle-related diseases because of a
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