Detecting variable responses in time-series using repeated measures ANOVA: Application to physiologic challenges.

We present an approach to analyzing physiologic timetrends recorded during a stimulus by comparing means at each time point using repeated measures analysis of variance (RMANOVA). The approach allows temporal patterns to be examined without an a priori model of expected timing or pattern of response. The approach was originally applied to signals recorded from functional magnetic resonance imaging (fMRI) volumes-of-interest (VOI) during a physiologic challenge, but we have used the same technique to analyze continuous recordings of other physiological signals such as heart rate, breathing rate, and pulse oximetry. For fMRI, the method serves as a complement to whole-brain voxel-based analyses, and is useful for detecting complex responses within pre-determined brain regions, or as a post-hoc analysis of regions of interest identified by whole-brain assessments. We illustrate an implementation of the technique in the statistical software packages R and SAS. VOI timetrends are extracted from conventionally preprocessed fMRI images. A timetrend of average signal intensity across the VOI during the scanning period is calculated for each subject. The values are scaled relative to baseline periods, and time points are binned. In SAS, the procedure PROC MIXED implements the RMANOVA in a single step. In R, we present one option for implementing RMANOVA with the mixed model function "lme". Model diagnostics, and predicted means and differences are best performed with additional libraries and commands in R; we present one example. The ensuing results allow determination of significant overall effects, and time-point specific within- and between-group responses relative to baseline. We illustrate the technique using fMRI data from two groups of subjects who underwent a respiratory challenge. RMANOVA allows insight into the timing of responses and response differences between groups, and so is suited to physiologic testing paradigms eliciting complex response patterns

Aboriginal and Torres Strait Islander oral health and its impact among adults: a cross-sectional study

Robust oral health epidemiological information for Aboriginal and Torres Strait Islander adults is scant. Set within a large urban population, this study describes self-reported oral health behaviours, status and impact assessed through computerized health checks (HC), stratified by age groups and sex, and identifies associations with dental appearance satisfaction.This was a cross-sectional study of Aboriginal and Torres Strait Islander adults (aged ≥20\ua0years) attending the Southern Queensland Centre of Excellence in Aboriginal and Torres Strait Islander Primary Health Care between 1\ua0January 2014 and 31\ua0December 2015 who had HC and provided research consent.There were 945 patients, 466 (49.3%) female, with an average age of 41.3\ua0years (range, 20-82). Overall, 97.3% owned a toothbrush and 56.2% brushed two or more times/day. Despite self-reporting a significant oral health burden, only 28.8% visited a dentist within 12\ua0months, mostly due to problems (84.3%). Surprisingly, only 28.4% reported dental appearance dissatisfaction, likely a result of community normalization whereby people are resigned to poor oral health.Under-utilization of dental services remains problematic for Aboriginal and Torres Strait Islander adults. To close the oral heath gap, culturally appropriate, acceptable and safe integrated primary health systems, with co-located dental services, demand consideration

Epidemiology of recreational exposure to freshwater cyanobacteria – an international prospective cohort study

BACKGROUND: Case studies and anecdotal reports have documented a range of acute illnesses associated with exposure to cyanobacteria and their toxins in recreational waters. The epidemiological data to date are limited; we sought to improve on the design of some previously conducted studies in order to facilitate revision and refinement of guidelines for exposure to cyanobacteria in recreational waters. METHODS: A prospective cohort study was conducted to investigate the incidence of acute symptoms in individuals exposed, through recreational activities, to low (cell surface area <2.4 mm(2)/mL), medium (2.4–12.0 mm(2)/mL) and high (>12.0 mm(2)/mL) levels of cyanobacteria in lakes and rivers in southeast Queensland, the central coast area of New South Wales, and northeast and central Florida. Multivariable logistic regression analyses were employed; models adjusted for region, age, smoking, prior history of asthma, hay fever or skin disease (eczema or dermatitis) and clustering by household. RESULTS: Of individuals approached, 3,595 met the eligibility criteria, 3,193 (89%) agreed to participate and 1,331 (37%) completed both the questionnaire and follow-up interview. Respiratory symptoms were 2.1 (95%CI: 1.1–4.0) times more likely to be reported by subjects exposed to high levels of cyanobacteria than by those exposed to low levels. Similarly, when grouping all reported symptoms, individuals exposed to high levels of cyanobacteria were 1.7 (95%CI: 1.0–2.8) times more likely to report symptoms than their low-level cyanobacteria-exposed counterparts. CONCLUSION: A significant increase in reporting of minor self-limiting symptoms, particularly respiratory symptoms, was associated with exposure to higher levels of cyanobacteria of mixed genera. We suggest that exposure to cyanobacteria based on total cell surface area above 12 mm(2)/mL could result in increased incidence of symptoms. The potential for severe, life-threatening cyanobacteria-related illness is likely to be greater in recreational waters that have significant levels of cyanobacterial toxins, so future epidemiological investigations should be directed towards recreational exposure to cyanotoxins

Adolescents and oral health service utilisation in Canterbury, New Zealand : a geospatial cross-sectional study.

Objective: Non-utilisation of dental care during adolescence can result in poorer oral health and subsequently higher expenditures on dental services. This study examined the geospatial and epidemiological factors associated with utilisation of the publicly funded Adolescent Oral Health Services (AOHS) in Canterbury, Aotearoa New Zealand (NZ). Methods: A secondary analysis of prospectively collected routine data from AOHS visits of adolescents in school Year 9 (13-14 years) for the financial year 2019-2020. Geographic Information Systems examined distance from home to dental practices. Multilevel mixed-effects Poisson regression models investigated associations between geospatial, demographic and clinical factors and non-utilisation of dental services. Models were adjusted for sex, ethnicity, area-level deprivation, rural/urban classification, previous caries experience, and the distance from home address to dental practice referred. Results: Dental practices were concentrated in large urban areas and in the least deprived neighbourhoods, with several service area gaps identified. Rural areas and the most deprived areas of Christchurch City had the highest non-utilisation rates. After adjustment, adolescents residing in the most deprived areas had a higher risk of non-utilisation (adjusted risk ratio [aRR]=1.38 (95% CI 1.26-1.51) compared to adolescents in the least deprived areas. Adolescents in remote areas also had an increased risk of non-utilisation (aRR=1.36; 95% CI 1.20-1.54) compared to adolescents in urban core areas. Finally, Māori (aRR=1.37; 95% CI 1.29-1.46) and Pasifika (aRR=1.46; 95% CI 1.35-1.59) adolescents had significantly higher risks of non-utilisation compared to their NZ European counterparts. Conclusion: Inequitable access to dental care exists among adolescents in Canterbury, NZ, which negatively impacts Māori, Pasifika, and those living in rural and most deprived areas. Adolescents at the greatest oral health risk are geographically underserved by current oral health services. The current health system should also explore the possibility of partnering with Māori and Pasifika communities to provide services within culturally appropriate settings

Frailty of Māori, Pasifika, and non-Māori/non-Pasifika older people in New Zealand: a national population study of older people referred for home care services

Little is known about the prevalence of frailty in indigenous populations. We developed a frailty index for older New Zealand Māori and Pasifika who require publicly funded support services.A frailty index (FI) was developed for New Zealand adults aged ≥65 years who had an interRAI-Home Care assessment between 1 June 2012 and 30 October 2015. A frailty score for each participant was calculated by summing the number of deficits recorded and dividing by the total number of possible deficits. This created a FI with a potential range from 0 to 1. Linear regression models for FIs with ethnicity were adjusted for age and sex. Cox proportional hazards models were used to assess the association between the FI and mortality for Māori, Pasifika, and non-Māori/non-Pasifika.Of 54,345 participants, 3,096 (5.7%) identified as Māori, 1,846 (3.4%) were Pasifika, and 49,415 (86.7%) identified as neither Māori nor Pasifika. New Zealand Europeans (48,178, 97.5%) constituted most of the latter group. Within each sex, the mean FIs for Māori and Pasifika were greater than the mean FIs for non-Māori and non-Pasifika, with the difference being more pronounced in females. The FI was associated with mortality (Māori SHR 2.53, 95% CI 1.63 to 3.95; Pasifika SHR 6.03, 95% CI 3.06 to 11.90; non-Māori and non-Pasifika SHR 2.86, 95% 2.53 to 3.25).This study demonstrated differences in FI between the ethnicities in this select cohort. After adjustment for age and sex, increases in FI were associated with increased mortality. This suggests that FI is predictive of poor outcomes in these ethnic groups

Population-Attributable Risk Estimates for Risk Factors Associated with Campylobacter Infection

In 2001-2002, a multicenter, prospective case-control study involving 1,714 participants ≥5 years of age was conducted in Australia to identify risk factors for Campylobacter infection. Adjusted population-attributable risks (PARs) were derived for eac

Population-Attributable Risk Estimates for Risk Factors Associated with Campylobacter Infection, Australia

One-sentence summary: Each year, an estimated 50,500 cases in persons >5 years of age can be directly attributed to consumption of chicken

A multivariate hierarchical Bayesian approach to measuring agreement in repeated measurement method comparison studies

Background. Assessing agreement in method comparison studies depends on two fundamentally important components; validity (the between method agreement) and reproducibility (the within method agreement). The Bland-Altman limits of agreement technique is one of the favoured approaches in medical literature for assessing between method validity. However, few researchers have adopted this approach for the assessment of both validity and reproducibility. This may be partly due to a lack of a flexible, easily implemented and readily available statistical machinery to analyse repeated measurement method comparison data. Methods. 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). Results. 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. Conclusion. 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

Drug burden index and its association with hip fracture among older adults:a national population-based study

Background: The Drug Burden Index (DBI) calculates the total sedative and anticholinergic load of prescribed medications and is associated with functional decline and hip fractures in older adults. However, it is unknown if confounding factors influence the relationship between the DBI and hip fractures. The objective of this study was to evaluate the association between the DBI and hip fractures, after correcting for mortality and multiple potential confounding factors. Methods: A competing-risks regression analysis conducted on a prospectively recruited New Zealand community-dwelling older population who had a standardized (International Resident Assessment Instrument) assessment between September 1, 2012, and October 31, 2015, the study's end date. Outcome measures were survival status and hip fracture, with time-varying DBI exposure derived from 90-day time intervals. The multivariable competing-risks regression model was adjusted for a large number of medical comorbidities and activities of daily living. Results: Among 70,553 adults assessed, 2,249 (3.2%) experienced at least one hip fracture, 20,194 (28.6%) died without experiencing a fracture, and 48,110 (68.2%) survived without a fracture. The mean follow-up time was 14.9 months (range: 1 day, 37.9 months). The overall DBI distribution was highly skewed, with median time-varying DBI exposure ranging from 0.93 (Q = 0.0, Q = 1.84) to 0.96 (Q = 0.0, Q = 1.90). DBI was significantly related to fracture incidence in unadjusted (

Cutaneous hypersensitivity reactions to freshwater cyanobacteria – human volunteer studies

BACKGROUND: Pruritic skin rashes associated with exposure to freshwater cyanobacteria are infrequently reported in the medical and scientific literature, mostly as anecdotal and case reports. Diagnostic dermatological investigations in humans are also infrequently described. We sought to conduct a pilot volunteer study to explore the potential for cyanobacteria to elicit hypersensitivity reactions. METHODS: 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. RESULTS: 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. CONCLUSION: 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