Akaike's information criterion in generalized estimating equations

High-Intensity Drug Use and Health Service Access Among Street-Involved Youth in a Canadian Setting

BACKGROUND/OBJECTIVES

Addiction severity has been associated with numerous social- and health-related harms. This study sought to examine the prevalence and correlates of high-intensity drug use among street-involved youth in a Canadian setting with a focus on high-risk drug use practices and health service access.

METHODS

Data were derived from the At-Risk Youth Study, a Vancouver-based prospective cohort of street-involved youth aged 14-26. We used generalized estimating equations to examine variables associated with high-intensity drug use, defined as daily use of crack cocaine, cocaine, heroin, or crystal methamphetamine.

RESULTS

From September 2005 to November 2012, of 1017 youth included in the analyses, 529 (52%) reported high-intensity drug use as defined above at least once during the study period. In a multivariate analysis, older age (Adjusted Odds Ratio [AOR] = 1.47); residing in the Downtown Eastside of Vancouver (AOR = 1.46); homelessness (AOR = 1.30); recent incarceration (AOR = 1.25); inability to access addiction treatment (AOR = 1.42); and crack pipe sharing and/or used syringe injecting (AOR = 2.64), were all positively and independently associated with high-intensity drug use (p < 0.05). The most common barrier to accessing addiction treatment reported by these youth was long waiting lists.

CONCLUSIONS

High-intensity drug use among street-involved youth was prevalent and associated with structural and geographical disadvantages in addition to high-risk drug administration practices. Youth reporting more frequent drug use also reported barriers to accessing addiction treatment, highlighting the need to expand addiction services tailored to youth at greatest risk of harm from illicit drug use and street-involvement.

Specific aspects of minority stress associated with depression among LDS affiliated non-heterosexual adults

A nation-wide sample of 634 previous or current members of the Church of Jesus Christ of Latter-Day Saints (LDS), non-heterosexual adults (ages 18-33), were surveyed to examine how specific aspects of minority stress are individually and collectively associated with depression, and how such associations differ across sex, sexual orientation, and level of affiliation with the LDS church. When five stressors were examined simultaneously, need for others' acceptance (NA) was the strongest predictor of depression, followed by internalized homophobia (IH). All minority stress factors were found to be individually predictive of depression and did not differ across sex or sexual orientation subgroups. Differences were observed, however, when considering current LDS status, such that participants who were no longer affiliated with the LDS church reported stronger relationships between some minority stressors and depression. Implications of religious identity salience as a potential mediator of relationships between specific stressors and depression are discussed.

The influence of relationship power dynamics on HIV testing in rural Malawi

Using the theory of gender and power (TGP) and data from the Tsogolo la Thanzi (TLT) study, we examined how relationship power shapes young people's decisions to test for HIV in rural Malawi (N=932), a high-HIV prevalence setting undergoing rapid expansions in testing services. We used generalized estimating equations (GEE) to examine associations among five constructs of relationship power (socioeconomic inequalities, relationship dominance, relationship violence, relationship unity, and mistrust), perceived risk, and receiving an HIV test over a 16-month period. The results indicate that young Malawians are testing for HIV at relatively high rates, repeatedly, and not just during pregnancy. Over the study period, 47.3% of respondents received at least one HIV test outside of TLT (range: 0-4). The GEE analysis revealed that men and women with higher levels of relationship unity were less likely to test for HIV. For men, being a victim of sexual coercion was an additional barrier to testing. Women's testing decisions were more strongly influenced by perceptions of a partner's risk for HIV than their own, whereas men relied more on self-assessments. The results highlight that testing decisions are deeply embedded within the relationship context, which should be considered in future HIV testing interventions.

Variation in harbour porpoise activity in response to seismic survey noise

Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency.

Synergistic effects of food insecurity and drug use on medication adherence among people living with HIV infection

Food insecurity and drug use are closely connected in the context of poverty, and both have been suggested to interfere with HIV medication adherence among people living with HIV/AIDS (PLWH). Yet the potential interaction between the two factors on adherence has not been examined. For this study we collected longitudinal data on HIV medication adherence among PLWH in Atlanta, GA, to assess a possible synergistic effect between the two factors on HIV medication adherence. People informed about the study came to the research site and completed an audio computer-assisted self-interview and instructions for pill counting. Over the next 5 weeks participants received three unscheduled follow-up phone assessments conducted 2 weeks apart to collect pill counts of their HIV medication. The prevalence of food insecurity was 60 % (488) and that of drug use was 33 % (274) in the sample of 809 participants. Among 770 participants who completed follow-up phone assessments, both food insecurity and drug use were associated with HIV medication adherence after adjusting for socio-demographic characteristics. The negative association between drug use and adherence persisted after further adjusting for health-related characteristics. Moreover, drug use appeared to moderate the effect of food insufficiency on adherence, with drug users who were food insufficient being the least likely to achieve 85 % adherence. Results from the current study demonstrate a synergism between food insecurity and drug use that may impede adherence among PLWH. The findings imply that the disruptive effects of food insecurity and drug use on adherence are likely to be intensified with the presence of each other, and encourage interventions to address the problem of HIV medication adherence from a multi-faceted perspective that takes into account detrimental combination of problem factors.

Risk factors of pandemic influenza A/H1N1 in a prospective household cohort in the general population: results from the CoPanFlu-France cohort

Background

The CoPanFlu-France household cohort was set up in 2009 to identify risk factors of infection by the pandemic A/H1N1 (H1N1pdm09) virus in the general population.

Objectives

To investigate the determinants of infection during the 2010–2011 season, the first complete influenza season of study follow-up for this cohort.

Patients/Methods

Pre- and post-epidemic blood samples were collected for all subjects, and nasal swabs were obtained in all subjects from households where an influenza-like illness was reported. Cases were defined as either a fourfold increase in the serological titer or a laboratory-confirmed H1N1pdm09 on a nasal swab, with either RT-PCR or multiplex PCR. Risk factors for H1N1pdm09 infections were explored, without any pre-specified hypothesis, among 167 individual, collective and environmental covariates via generalized estimating equations modeling. We adopted a multimodel selection procedure to control for model selection uncertainty.

Results

This analysis is based on a sample size of 1121 subjects. The final multivariable model identified one risk factor (history of asthma, OR = 2·17; 95% CI: 1·02–4·62) and three protective factors: pre-epidemic serological titer (OR = 0·51 per doubling of the titer; 95% CI: 0·39–0·67), green tea consumption a minimum of two times a week (OR = 0·39; 95% CI: 0·18–0·84), and proportion of subjects in the household always covering their mouth while coughing/sneezing (OR = 0·93 per 10% increase; 95% CI: 0·86–1·00).

Conclusion

This exploratory study provides further support of previously reported risk factors and highlights the importance of collective protective behaviors in the household. Further analyses will be conducted to explore these findings.

Prevalence and behavioural risk factors of Staphylococcus aureus nasal colonization in community-based injection drug users

The aims of this study were to identify Staphylococcus aureus nasal colonization prevalence, behavioural risk factors, and to determine staphylococcal protein A (spa) types in community-based injection drug users (IDUs). Nasal swabs were collected and methicillin susceptibility testing and spa/SCCmec typing were performed on S. aureus isolates. Generalized estimating equations were used to report adjusted odds ratios and 95% confidence intervals. Of the 440 participants, 24·1% were colonized and 5·7% had methicillin-resistant S. aureus (MRSA). Colonization was associated with age, employment/marital status, and the presence of scabs but not with sexually transmitted disease co-infection, HIV status, antibiotic use, hospitalization, or drug treatment programme participation. The USA300 MRSA clone spa types were most common, but 15/49 spa types were new to one of the international databases. Community-based IDUs appear to have different risk factors compared to IDUs from clinical studies. In addition, the number of newly identified spa types indicates a diverse, understudied population.

Weighted diagnostic criteria for developmental dysplasia of the hip

OBJECTIVE

To establish clinical diagnostic criteria for developmental dysplasia of the hip (DDH) that model the practices of expert clinicians.

STUDY DESIGN

Of 23 clinical criteria for the diagnosis of DDH, ranked in order of diagnostic importance by international consensus, the 7 most highly ranked were placed in all possible combinations to create unique case vignettes. Twenty-six experts rated 52 vignettes for the presence of DDH. We modeled the data to determine which of the 7 criteria were associated with a clinician's opinion that the vignette represented DDH. From the resulting regression coefficients, for each vignette we calculated a probability of DDH. An independent panel rated the same vignettes using a visual analog scale response. We correlated the visual analog scale ratings with probabilities derived from the model.

RESULTS

Our model identified 4 of 7 criteria as predictive of DDH (P < .001): Ortolani/Barlow test (β = 3.26), limited abduction (β = 1.48), leg length discrepancy (β = 0.74), and first-degree family history of DDH (β = 1.39). There was substantial correlation between the probability of DDH predicted by the model and that derived from an independent expert panel (r = 0.73; P < .001).

CONCLUSION

Weighted clinical criteria for inferring the likelihood of DDH produced consistent results in the judgment of 2 separate groups of experts. Using these weights, nonexperts could establish the probability of DDH in a manner approaching the practice of clinical experts.

Generalized Estimating Equations in Longitudinal Data Analysis: A Review and Recent Developments

Generalized Estimating Equation (GEE) is a marginal model popularly applied for longitudinal/clustered data analysis in clinical trials or biomedical studies. We provide a systematic review on GEE including basic concepts as well as several recent developments due to practical challenges in real applications. The topics including the selection of “working” correlation structure, sample size and power calculation, and the issue of informative cluster size are covered because these aspects play important roles in GEE utilization and its statistical inference. A brief summary and discussion of potential research interests regarding GEE are provided in the end.

Zero adjusted models with applications to analysing helminths count data

Background

It is common in public health and epidemiology that the outcome of interest is counts of events occurrence. Analysing these data using classical linear models is mostly inappropriate, even after transformation of outcome variables due to overdispersion. Zero-adjusted mixture count models such as zero-inflated and hurdle count models are applied to count data when over-dispersion and excess zeros exist. Main objective of the current paper is to apply such models to analyse risk factors associated with human helminths (S. haematobium) particularly in a case where there’s a high proportion of zero counts.

Methods

The data were collected during a community-based randomised control trial assessing the impact of mass drug administration (MDA) with praziquantel in Malawi, and a school-based cross sectional epidemiology survey in Zambia. Count data models including traditional (Poisson and negative binomial) models, zero modified models (zero inflated Poisson and zero inflated negative binomial) and hurdle models (Poisson logit hurdle and negative binomial logit hurdle) were fitted and compared.

Results

Using Akaike information criteria (AIC), the negative binomial logit hurdle (NBLH) and zero inflated negative binomial (ZINB) showed best performance in both datasets. With regards to zero count capturing, these models performed better than other models.

Conclusion

This paper showed that zero modified NBLH and ZINB models are more appropriate methods for the analysis of data with excess zeros. The choice between the hurdle and zero-inflated models should be based on the aim and endpoints of the study.

TAILOR THE LONGITUDINAL ANAYSIS FOR NIH LONGITUDINAL NORMAL BRAIN DEVELOPMENTAL STUDY

There are imminent needs for longitudinal analysis to make physiological inferences on NIH MRI study of normal brain development. But up to date, two critical aspects for longitudinal analysis, namely the selections of mean and covariance structures have not been addressed by the neuroimaging community. For the mean structure, we employed a linear free-knot B-spline regression in combination with quasi-least square estimating equations to approximate a nonlinear growth trajectory with piecewise linear segments for a friendly physiological interpretation. For covariance structure selection, we have proposed a novel time varying correlation structure considering not only the time separation between the repeated measures but also when these acquisitions occurred. We have demonstrated that the proposed covariance structure has a lower Akaike information criterion value than the commonly used Markov correlation structure.

Subconjunctival hemorrhage after intravitreal injection of anti-vascular endothelial growth factor

PURPOSE

To investigate the risk factors for subconjunctival hemorrhage (SCH) after intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) and evaluate the relationship between hemodynamic status at the time of injection and SCH.

METHODS

We retrospectively reviewed the medical records of 598 cases of 173 patients who underwent intravitreal injection of ranibizumab whose hemodynamic status was monitored at the time of the injection. Cases with SCH after the injection were included in the SCH group. We compared systemic factors, including the hemodynamic status between the SCH group and the control group.

RESULTS

The SCH group included 67 cases and the control group included 531 cases without SCH. Baseline hemodynamic status was not significantly related to development of SCH. However, systolic blood pressure (BP) at injection was a significant risk factors for SCH (P = 0.034). Elevated systolic BP, mean arterial pressure (MAP), and pulse rate from baseline to time of injection were significantly related to the development of SCH (P = 0.011, P = 0.014, P = 0.036, respectively). In multivariate analysis, hypertension, a large change in MAP, and a fewer previous injections were significant risk factors for SCH after intravitreal injection (P = 0.030, P = 0.032, P = 0.028, respectively).

CONCLUSIONS

Hemodynamic risk factors exist for SCH after intravitreal injection of anti-VEGF. To reduce the risk of SCH, strategies should seek to decrease patient anxiety, especially in those with hypertension.

Alcohol is longitudinally associated with lower urinary tract symptoms partially via high-density lipoprotein

BACKGROUND

Previous studies on the association of alcohol consumption with lower urinary tract symptoms (LUTS) have been inconsistent, and none took into account the dynamic nature of LUTS, fluctuating over time. The purpose of the study was to determine the longitudinal association of alcohol consumption with LUTS.

METHODS

We used generalized estimating equations to analyze the longitudinal association of alcohol consumption with LUTS in a longitudinal study of 9,712 healthy men 30 years or older who visited our institution multiple times for routine comprehensive health evaluations, with an average follow-up period of 27.9 months.

RESULTS

Light-moderate alcohol consumption (0.1 to 29 g/d) was associated with decreased likelihood of moderate-severe LUTS, whereas heavy alcohol consumption (≥30 g/d) was associated with increased likelihood of moderate-severe LUTS in a dose-dependent manner. Compared to those with 0 g/d alcohol intake, subjects who drank 0.1 to 9.9, 10 to 19.9, 20 to 29.9, 30 to 39.9, or ≥40 g/d of alcohol were in general significantly associated with moderate-severe LUTS with adjusted odds ratio (95% confidence interval) as follows respectively: 0.94 (0.87 to 1.02), 1.00 (0.91 to 1.09), 0.85 (0.77 to 0.93), 1.08 (0.98 to 1.19), and 1.31 (1.19 to 1.44). However, the protective association of light-moderate alcohol consumption with LUTS was greatly attenuated when serum high-density lipoprotein (HDL) was added to the analysis, specifically for voiding symptoms.

CONCLUSIONS

We show strong evidence there is longitudinal association of alcohol consumption with LUTS. The protective effect of light-moderate alcohol consumption on LUTS is in part modulated by HDL as a confounder, similar to its effect on coronary heart disease.

Mosquito surveillance revealed lagged effects of mosquito abundance on mosquito-borne disease transmission: a retrospective study in Zhejiang, China

Mosquito-borne diseases (MBDs) are still threats to public health in Zhejiang. In this study, the associations between the time-lagged mosquito capture data and MBDs incidence over five years were used to examine the potential effects of mosquito abundance on patterns of MBDs epidemiology in Zhejiang during 2008–2012. Light traps were used to collect adult mosquitoes at 11 cities. Correlation tests with and without time lag were performed to investigate the correlations between MBDs incidence rates and mosquito abundance by month. Selected MBDs consisted of Japanese encephalitis (JE), dengue fever (DF) and malaria. A Poisson regression analysis was performed by using a generalized estimating equations (GEE) approach, and the most parsimonious model was selected based on the quasi-likelihood based information criterion (QICu). We identified five mosquito species and the constituent ratio of Culex pipiens pallens, Culex tritaeniorhynchus, Aedes albopictus, Anopheles sinensis and Armigeres subalbatus was 66.73%, 21.47%, 6.72%, 2.83% and 2.25%, respectively. The correlation analysis without and with time lag showed that Culex mosquito abundance at a lag of 0 or 1 month was positively correlated with JE incidence during 2008–2012, Ae. albopictus abundance at a lag of 1 month was positively correlated with DF incidence in 2009, and An. sinensis abundance at a lag of 0–2 months was positively correlated with malaria incidence during 2008–2010. The Poisson regression analysis showed each 0.1 rise of monthly mosquito abundance corresponded to a positive increase of MBD cases for the period of 2008–2012. The rise of mosquito abundance with a lag of 0–2 months increased the risk of human MBDs infection in Zhejiang. Our study provides evidence that mosquito monitoring could be a useful early warning tool for the occurrence and transmission of MBDs.

Gastrointestinal helminths may affect host susceptibility to anthrax through seasonal immune trade-offs

Background

Most vertebrates experience coinfections, and many pathogen-pathogen interactions occur indirectly through the host immune system. These interactions are particularly strong in mixed micro-macroparasite infections because of immunomodulatory effects of helminth parasites. While these trade-offs have been examined extensively in laboratory animals, few studies have examined them in natural systems. Additionally, many wildlife pathogens fluctuate seasonally, at least partly due to seasonal host immune changes. We therefore examined seasonality of immune resource allocation, pathogen abundance and exposure, and interactions between infections and immunity in plains zebra (Equus quagga) in Etosha National Park (ENP), Namibia, a system with strongly seasonal patterns of gastrointestinal (GI) helminth infection intensity and concurrent anthrax outbreaks. Both pathogens are environmentally transmitted, and helminth seasonality is driven by environmental pressures on free living life stages. The reasons behind anthrax seasonality are currently not understood, though anthrax is less likely directly driven by environmental factors.

Results

We measured a complex, interacting set of variables and found evidence that GI helminth infection intensities, eosinophil counts, IgE and IgGb antibody titers, and possibly IL-4 cytokine signaling were increased in wetter seasons, and that ectoparasite infestations and possibly IFN-γ cytokine signaling were increased in drier seasons. Monocyte counts and anti-anthrax antibody titers were negatively associated with wet season eosinophilia, and monocytes were negatively correlated with IgGb and IgE titers. Taken together, this supports the hypothesis that ENP wet seasons are characterized by immune resource allocation toward Th-2 type responses, while Th1-type immunity may prevail in drier seasons, and that hosts may experience Th1-Th2 trade-offs. We found evidence that this Th2-type resource allocation is likely driven by GI parasite infections, and that these trade-offs may render hosts less capable of concurrently mounting effective Th1-type immune responses against anthrax.

Conclusions

This study is one of the first to examine laboratory-demonstrated Th1-Th2 trade-offs in a natural system. It provides evidence that seasonally bound pathogens may affect, through immunology, transmission dynamics of pathogens that might otherwise not be seasonally distributed. It suggests that, by manipulating the internal host ecosystem, GI parasites may influence the external ecosystem by affecting the dynamics of another environmentally transmitted pathogen.

Electronic supplementary material

The online version of this article (doi:10.1186/s12898-014-0027-3) contains supplementary material, which is available to authorized users.

Acute decompensated heart failure patients admitted to critical care units: insights from ASCEND-HF

BACKGROUND

Little is known about global patterns of critical care unit (CCU) care and the relationship with outcomes in patients with acute decompensated heart failure (ADHF). Whether a ward or a CCU admission is associated with better outcomes is unclear.

METHODS

Patients in the Acute Study of Clinical Effectiveness of Nesiritide in Decompensated Heart Failure (ASCEND-HF) trial were initially hospitalized in a ward or CCU (coronary or intensive care unit). Sites were geographically classified: Asia-Pacific (AP), Central Europe (CE), Latin America (LA), North America (NA), and Western-Europe (WE). The primary outcome of 30-day all-cause mortality or all-cause hospital readmission was adjusted using a two-stage multivariable logistic regression model with a generalized estimated equation that took sites within each country as a nested random factor.

RESULTS

Overall, 1944 (38.2%) patients were admitted to a CCU and 3150 (61.8%) to a ward, and this varied by region: 50.6% AP, 63.3% CE, 60.7% WE, 22.1% LA, and 28.6% NA. The 30-day death or readmission rate was 15.2% in ward patients and 17.0% in CCU patients (risk-adjusted Odds Ratio [OR] 1.44: 95% CI, 1.14-1.82). Compared with CCU patients in NA (24.1% 30-day event rate), the primary outcomes were: AP (10.4%, Odds Ratio [OR] 0.63; 95% confidence Interval [CI], 0.35 to 1.15), CE (10.4%, OR 0.56: 95% CI, 0.31 to 1.02), LA (22.4%, OR 0.60: 95% CI, 0.11 to 3.32), and WE (11.2%, OR 0.63, 95% CI, 0.25 to 1.56). No regional differences in 30-day mortality were observed; however, 30-day readmission rates were highest in NA sites.

CONCLUSIONS

Management of patients with ADHF varies significantly, and after adjustment, CCU care was associated with higher risk of early mortality, not explained by international differences. These findings may help to improve the early decisions regarding risk stratification of patients hospitalized with ADHF.

Differences by sexual minority status in relationship abuse and sexual and reproductive health among adolescent females

PURPOSE

Little is known about adolescent relationship abuse (ARA) and related sexual and reproductive health among females who either identify as lesbian or bisexual or engage in sexual behavior with female partners (i.e., sexual minority girls [SMGs]).

METHODS

Baseline data were collected from 564 sexually active girls ages 14-19 years seeking care at eight California school-based health centers participating in a randomized controlled trial. Associations between ARA, sexual minority status and study outcomes (vaginal, oral, and anal sex, number and age of sex partners, contraceptive nonuse, reproductive coercion, sexually transmitted infection [STI] and pregnancy testing) were assessed via logistic regression models for clustered survey data.

RESULTS

SMGs comprised 23% (n = 130) of the sample. Controlling for exposure to ARA, SMGs were less likely to report recent vaginal sex (adjusted odds ratio [AOR], .51; 95% confidence interval [CI], .35-.75) and more likely to report recent oral sex (AOR, 2.01; 95% CI, 1.38-2.92) and anal sex (AOR, 1.76; 95% CI, 1.26-2.46) compared with heterosexual girls. Heterosexual girls with ARA exposure (AOR, 2.85; 95% CI, 1.07-7.59) and SMGs without ARA exposure (AOR, 3.01; 95% CI, 2.01-4.50) were more likely than nonabused heterosexual girls be seeking care for STI testing or treatment than heterosexual girls without recent victimization.

CONCLUSIONS

Findings suggest the need for attention to STI risk among all girls, but SMGs in particular. Clinicians should be trained to assess youth for sexual contacts and sexual identity and counsel all youth on healthy relationships, consensual sex, and safer sex practices relevant to their sexual experiences.

Effects of livestock grazing and well construction on prairie vegetation structure surrounding shallow natural gas wells

Short and sparse vegetation near shallow gas wells has generally been attributed to residual effects from well construction, but other mechanisms might also explain these trends. We evaluated effects of distance to shallow gas wells on vegetation and bare ground in mixed-grass prairies in southern Alberta, Canada, from 2010 to 2011. We then tested three hypotheses to explain why we found shorter vegetation and more bare ground near wells, using cattle fecal pat transects from 2012, and our vegetation quadrats. We evaluated whether empirical evidence suggested that observed patterns were driven by (1) higher abundance of crested wheatgrass (Agropyron cristatum) near wells, (2) residual effects of well construction, or (3) attraction of livestock to wells. Crested wheatgrass occurrence was higher near wells, but this did not explain effects of wells on vegetation structure. Correlations between distance to wells and litter depth were the highest near newer wells, providing support for the construction hypothesis. However, effects of distance to wells on other vegetation metrics did not decline as time since well construction increased, suggesting that other mechanisms explained observed edge effects. Cattle abundance was substantially higher near wells, and this effect corresponded with changes in habitat structure. Our results suggest that both residual effects of well construction and cattle behavior may explain effects of shallow gas wells on habitat structure in mixed-grass prairies, and thus, to be effective, mitigation strategies must address both mechanisms.

Risk of tuberculosis cattle herd breakdowns in Ireland: effects of badger culling effort, density and historic large-scale interventions

Bovine tuberculosis (bTB) continues to be a problem in cattle herds in Ireland and Britain. It has been suggested that failure to eradicate this disease is related to the presence of a wildlife reservoir (the badger). A large-scale project was undertaken in the Republic of Ireland during 1997-2002 to assess whether badger removal could contribute to reducing risk of cattle herd breakdowns in four areas. During the period of that "four area" study, there was a significant decrease in risk in intensively culled (removal) areas relative to reference areas. In the present study, we revisit these areas to assess if there were any residual area effects of this former intervention a decade on (2007-2012). Over the study period there was an overall declining trend in bTB breakdown risk to cattle herds. Cattle herds within former removal areas experienced significantly reduced risk of breakdown relative to herds within former reference areas or herds within non-treatment areas (OR: 0.53; P < 0.001). Increased herd breakdown risk was associated with increasing herd size (OR: 1.92-2.03; P < 0.001) and herd bTB history (OR: 2.25-2.40; P < 0.001). There was increased risk of herd breakdowns in areas with higher badger densities, but this association was only significant early in the study (PD*YEAR interaction; P < 0.001). Badgers were culled in areas with higher cattle bTB risk (targeted culling). Risk tended to decline with cumulative culling effort only in three counties, but increased in the fourth (Donegal). Culling badgers is not seen as a viable long-term strategy. However, mixed policy options with biosecurity and badger vaccination, may help in managing cattle breakdown risk.

Tuberculosis treatment managed by providers outside the Public Health Department: lessons for the Affordable Care Act

INTRODUCTION

Tuberculosis (TB) requires at least six months of multidrug treatment and necessitates monitoring for response to treatment. Historically, public health departments (HDs) have cared for most TB patients in the United States. The Affordable Care Act (ACA) provides coverage for uninsured persons and may increase the proportion of TB patients cared for by private medical providers and other providers outside HDs (PMPs). We sought to determine whether there were differences in care provided by HDs and PMPs to inform public health planning under the ACA.

METHODS

We conducted a retrospective, cross-sectional analysis of California TB registry data. We included adult TB patients with culture-positive, pulmonary TB reported in California during 2007-2011. We examined trends, described case characteristics, and created multivariate models measuring two standards of TB care in PMP- and HD-managed patients: documented culture conversion within 60 days, and use of directly observed therapy (DOT).

RESULTS

The proportion of PMP-managed TB patients increased during 2007-2011 (p = 0.002). On univariable analysis (N = 4,606), older age, white, black or Asian/Pacific Islander race, and birth in the United States were significantly associated with PMP care (p<0.05). Younger age, Hispanic ethnicity, homelessness, drug or alcohol use, and cavitary and/or smear-positive TB disease, were associated with HD care. Multivariable analysis showed PMP care was associated with lack of documented culture conversion (adjusted relative risk [aRR] = 1.37, confidence interval [CI] 1.25-1.51) and lack of DOT (aRR = 8.56, CI 6.59-11.1).

CONCLUSION

While HDs cared for TB cases with more social and clinical complexities, patients under PMP care were less likely to receive DOT and have documented culture conversion. This indicates a need for close collaboration between PMPs and HDs to ensure that optimal care is provided to all TB patients and TB transmission is halted. Strategies to enhance collaboration between HDs and PMPs should be included in ACA implementation.

Effects of tylosin administration on C-reactive protein concentration and carriage of Salmonella enterica in pigs

OBJECTIVE

To evaluate the effects of tylosin on C-reactive protein concentration, carriage of Salmonella enterica, and antimicrobial resistance genes in commercial pigs.

ANIMALS

120 pigs on 2 commercial farms.

PROCEDURES

A cohort of sixty 10-week-old pigs in 4 pens/farm (15 pigs/pen) was randomly selected. Equal numbers of pigs were given feed containing tylosin (40 μg/g of feed) for 0, 6, or 12 weeks. C-reactive protein concentrations were measured, microbial culture for S enterica in feces was performed, and antimicrobial resistance genes in feces were quantified.

RESULTS

No significant associations were detected between C-reactive protein concentration or S enterica status and tylosin treatment. During the 12 weeks of tylosin administration, increased levels of 6 antimicrobial resistance genes did not occur.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment of pigs with tylosin did not affect C-reactive protein concentration or reduce carriage or load of S enterica. There was no evidence that pigs receiving tylosin had increased carriage of the 6 antimicrobial resistance genes measured.

IMPACT FOR HUMAN MEDICINE

S enterica is a public health concern. Use of the antimicrobial growth promoter tylosin did not pose a public health risk by means of increased carriage of S enterica.

Full and home smoking ban adoption after a randomized controlled trial targeting secondhand smoke exposure reduction

INTRODUCTION

The current study examined home and full (i.e., home plus car) smoking ban adoption as secondary outcomes to a randomized controlled trial targeting reduced secondhand smoke exposure (SHSe) for children under treatment for cancer.

METHODS

Families with at least 1 adult smoker who reported SHSe for their children (n = 119) were randomized to control or intervention conditions and followed for 1 year with 5 assessments. Both groups were advised of the negative health outcomes associated with SHSe; the intervention group provided more in-depth counseling from baseline to 3 months. Parents reported on household and car smoking behavior, demographic, psychosocial, and medical/treatment-related information.

RESULTS

Regardless of group assignment, there was an increase in home (odds ration [OR] = 1.16, p = .074) and full (OR = 1.37, p = .001) smoking ban adoption across time. Families in the intervention group were more likely to adopt a full ban by 3 months, but this difference was nonsignificant by 12 months. Married parents (OR = 2.33, p = .006) and those with higher self-efficacy for controlling children's SHSe (OR = 1.11, p = .023) were more likely to have a home smoking ban; parents who reported smoking fewer cigarettes were more likely to adopt a home (OR = 1.62, p < .0001) or full (OR = 7.32, p = .038) ban.

CONCLUSIONS

Smoking bans are in-line with Healthy People 2020's tobacco objectives and may be more feasible for parents with medically compromised children for immediate SHSe reduction. Furthermore, interventions targeting full smoking bans may be a more effective for comprehensive elimination of SHSe.

Male experiences of unintended pregnancy: characteristics and prevalence

STUDY QUESTION

What are the characteristics and circumstances of pregnancies men report as unintended in France?

SUMMARY ANSWER

Pregnancies reported as unintended were most prevalent among young men with insecure financial situations, less stable relationships and inconsistent use of contraception or false assumptions about their partner's use of contraception.

WHAT IS KNOWN ALREADY

Efforts to involve men in family planning have increased over the last decade; however, little is known about factors associated with men's pregnancy intentions and associated contraceptive behaviours.

STUDY DESIGN, SIZE, DURATION

The data presented in this study were drawn from the nationally representative FECOND study, a population-based survey conducted in France in 2010. The sample comprised 8675 individuals (3373 men), aged 15-49 years, who responded to a telephone interview about socio-demographics and topics related to sexual and reproductive health. The total refusal rate was 20%.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study included 2997 men, of whom 664 reported 893 recent pregnancies (in the 5 years preceding the survey). Multivariate Poisson's regression with population-averaged marginal effects was applied to assess the individual and contextual factors associated with men's intentions for recent pregnancies. The contraceptive circumstances leading to the unintended pregnancies were also assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

Of all heterosexually active men, 5% reported they had experienced an unintended pregnancy with a partner in the last 5 years. A total of 20% of recent pregnancies reported by men were qualified to be unintended, of which 45% ended in induced abortion. Of pregnancies following a previous unintended pregnancy, 68% were themselves unintended. Among all heterosexually active men, recent experience of an unintended pregnancy was related to age, mother's education, age at first sex, parity, contraceptive method history, lifetime number of female partners and the relationship situation at the time of survey. Recent unintended pregnancies were also related to pregnancy order and to the financial and professional situation at the time of conception. The majority of unintended pregnancies occurred when men or their partners were using contraceptives; 58% of contraceptive users considered that the pregnancy was due to inconsistent use and 39% considered that it resulted from method failure. Half of the non-users who reported an unintended pregnancy thought that their partner was using a contraceptive method. The relative risk of non-use of a contraceptive method during the month of conception of a recent unintended pregnancy was higher among those without a high school degree (IRR = 2.9, CI 1.6, 5.2) and higher among men for whom the pregnancy interfered with education (IRR = 1.8, CI 1.0, 3.1) or work (IRR = 1.9, CI 1.1, 3.6).

LIMITATIONS, REASONS FOR CAUTION

From the perspective of men, the unintended pregnancy rates may be underestimated due to a combination of underreporting of abortion and post-rationalization of birth intentions. Our use of a dichotomous measure of unintended pregnancy is unlikely to fully capture the multidimensional construct of pregnancy intentions.

WIDER IMPLICATION OF THE FINDINGS

These results call for gender-inclusive family planning programmes, which fully engage men as active participants in their own rights.

STUDY FUNDING/COMPETING INTERESTS

The FECOND study was supported by a grant from the French Ministry of Health, a grant from the French National Agency of Research (#ANR-08-BLAN-0286-01; PIs N.B., C.M.), and funding from National Institute of Health and Medical Research (INSERM) and the National Institute for Demographic Research (INED). None of the authors have competing interests.

Subclinical deterioration of left ventricular function in patients with juvenile-onset systemic lupus erythematosus

OBJECTIVES

Patients with systemic lupus erythematosus (SLE) have a higher risk of myocardial involvement, which can result in ventricular dysfunction. Little is known about the chronic influence of SLE on heart function in children and adolescents. This is the first study to demonstrate long-term changes in left ventricular function in patients with juvenile-onset SLE.

METHODS

This was a longitudinal study of 92 patients with juvenile-onset SLE. Two-dimensional echocardiography was performed by a single pediatric cardiologist at baseline, with follow-up at six-month intervals. Clinical and laboratory parameters, disease activity, treatment, nailfold capillaroscopy, and the traditional risk factors for atherosclerosis were evaluated. The baseline comparison of ventricular function was performed against 50 age-matched controls, and the follow-up results were analyzed using generalized estimating equations.

RESULTS

The patients' mean age at baseline was 15.9 ± 4.3 years, the mean disease duration was 3.6 ± 3.2 years, and the mean follow-up duration was 4.5 ± 1.6 years. At baseline, the mean left ventricular ejection fraction (LVEF) was 74.7 ± 5.6% and the mean E/A ratio of left ventricular diastolic filling was 1.7 ± 0.3 (E: the peak velocity at rapid left ventricular filling; A: the peak velocity during left atrial contraction). The LVEF of the SLE patients was similar to the healthy controls and it did not change during the follow-up period. In contrast, the E/A ratio was lower in the SLE patients than in the healthy controls (1.7 ± 0.3 versus 1.88 ± 0.37; p = 0.002), and it decreased significantly with time (B ± SE, -0.013 ± 0.006, p = 0.023). In multiple analyses, abnormal microvasculature in nailfold capillaroscopy had a negative effect on LVEF progression (p = 0.039). Disease duration of SLE and proteinuria were risk factors associated with the descent of E/A ratio (p = 0.014 and p = 0.015, respectively).

CONCLUSION

In patients with juvenile-onset SLE who were free of cardiac symptoms, there was evidence of declining ventricular diastolic function with time. Abnormal nailfold microvasculature, proteinuria and longer disease duration were the main risk factors for worsening of ventricular function.

A modified γ-retrovirus vector for X-linked severe combined immunodeficiency

BACKGROUND

In previous clinical trials involving children with X-linked severe combined immunodeficiency (SCID-X1), a Moloney murine leukemia virus-based γ-retrovirus vector expressing interleukin-2 receptor γ-chain (γc) complementary DNA successfully restored immunity in most patients but resulted in vector-induced leukemia through enhancer-mediated mutagenesis in 25% of patients. We assessed the efficacy and safety of a self-inactivating retrovirus for the treatment of SCID-X1.

METHODS

We enrolled nine boys with SCID-X1 in parallel trials in Europe and the United States to evaluate treatment with a self-inactivating (SIN) γ-retrovirus vector containing deletions in viral enhancer sequences expressing γc (SIN-γc).

RESULTS

All patients received bone marrow-derived CD34+ cells transduced with the SIN-γc vector, without preparative conditioning. After 12.1 to 38.7 months of follow-up, eight of the nine children were still alive. One patient died from an overwhelming adenoviral infection before reconstitution with genetically modified T cells. Of the remaining eight patients, seven had recovery of peripheral-blood T cells that were functional and led to resolution of infections. The patients remained healthy thereafter. The kinetics of CD3+ T-cell recovery was not significantly different from that observed in previous trials. Assessment of insertion sites in peripheral blood from patients in the current trial as compared with those in previous trials revealed significantly less clustering of insertion sites within LMO2, MECOM, and other lymphoid proto-oncogenes in our patients.

CONCLUSIONS

This modified γ-retrovirus vector was found to retain efficacy in the treatment of SCID-X1. The long-term effect of this therapy on leukemogenesis remains unknown. (Funded by the National Institutes of Health and others; ClinicalTrials.gov numbers, NCT01410019, NCT01175239, and NCT01129544.).

Universal bilirubin screening and health care utilization

OBJECTIVE

To evaluate the impact of the implementation of universal bilirubin screening on neonatal health care use in the context of a large jurisdiction with universal health insurance.

METHODS

We conducted a population-based retrospective cohort study of all newborns discharged after birth between April 2003 and February 2011 from 42 hospitals that implemented universal bilirubin screening between July 2007 and June 2010 in Ontario, Canada. We surveyed hospitals to determine their screening implementation date. We used multiple linked administrative health data sets to measure phototherapy use, length of stay (LOS), jaundice-related emergency department visits, and jaundice-related readmissions. We modeled the relationship between universal bilirubin screening and outcomes using generalized estimating equations to account for clustering by hospital, underlying temporal trends, and important covariates.

RESULTS

Screening was associated with an increase in phototherapy during hospitalization at birth (relative risk, 1.32; 95% confidence interval, 1.09-1.59) and a decrease in jaundice-related emergency department visits (relative risk, 0.79; 95% confidence interval, 0.64-0.96) but no statistically significant difference in phototherapy after discharge, LOS, or jaundice-related readmissions after accounting for preexisting temporal trends in health care service use and other patient sociodemographic and hospital characteristics.

CONCLUSIONS

Universal bilirubin screening may not be associated with increased neonatal LOS or increased subsequent hospital use. Our findings are relevant for determining the resource implications of universal bilirubin screening in Ontario. They highlight the limitations in generalizability of previous research on health care utilization associated with similar programs and underline the importance of context-specific local evaluation of guideline implementation.

Short communication: kidney dysfunction among HIV-infected children in Latin America and the Caribbean

Renal toxicity is a concern in HIV-infected children receiving antiretrovirals. However, the prevalence [1.7%; 95% confidence interval (CI): 1.0-2.6%] and incidence of kidney dysfunction (0.17 cases/100 person-years; 95% CI: 0.04-0.30) were rare in this multicenter cohort study of 1,032 perinatally HIV-infected Latin American and Caribbean children followed from 2002 to 2011.

Risk factors for the progression of cystic fibrosis lung disease throughout childhood

RATIONALE

Previous studies of risk factors for progression of lung disease in cystic fibrosis (CF) have suffered from limitations that preclude a comprehensive understanding of the determinants of CF lung disease throughout childhood. The epidemiologic component of the 27-year Wisconsin Randomized Clinical Trial of CF Neonatal Screening Project (WI RCT) afforded us a unique opportunity to evaluate the significance of potential intrinsic and extrinsic risk factors for lung disease in children with CF.

OBJECTIVES

Describe the most important intrinsic and extrinsic risk factors for progression of lung disease in children with CF.

METHODS

Variables hypothesized at the onset of the WI RCT study to be determinants of the progression of lung disease and potential risk factors previously identified in the WI RCT study were assessed with multivariable generalized estimating equation models for repeated measures of chest radiograph scores and pulmonary function tests in the WI RCT cohort.

MEASUREMENTS AND MAIN RESULTS

Combining all patients in the WI RCT, 132 subjects were observed for a mean of 16 years and contributed 1,579 chest radiographs, and 1,792 pulmonary function tests. The significant determinants of lung disease include genotype, poor growth, hospitalizations, meconium ileus, and infection with mucoid Pseudomonas aeruginosa. The previously described negative effect of female sex was not seen.

CONCLUSIONS

Modifiable extrinsic risk factors are the major determinants of progression of lung disease in children with CF. Better interventions to prevent or treat these risk factors may lead to improvements in lung health for children with CF.

Mastery motivation: a way of understanding therapy outcomes for children with unilateral cerebral palsy

PURPOSE

To investigate the impact of mastery motivation on occupational performance outcomes immediately following upper limb (UL) training and 6 months post-intervention for school-aged children with unilateral cerebral palsy.

METHOD

This prediction study was a post-hoc analysis of a matched pairs randomized comparison trial (COMBiT Trial Registration: ACTRN12613000181707). The Canadian Occupational Performance Measure (COPM) was administered at baseline, 13 and 26 weeks post-intervention. Parents completed the Dimensions of Mastery Questionnaire (DMQ), Parenting Scale and a demographic questionnaire. Children's UL capacity and performance was assessed using the Melbourne Assessment of Unilateral UL Function and assisting hand assessment (AHA). Regression models were fitted using generalized estimating equations to baseline, 13 and 26 week measurements.

RESULTS

Forty-six children (7.78 years SD 2.27 years, 31 males, Manual Ability Classification System I = 23, II = 23) participated. Higher levels of bimanual performance (AHA: β = 0.03, p < 0.001), greater object-oriented persistence (DMQ: β = 0.31, p = 0.05), and treatment group allocation (Standard Care: β = 0.24, p = 0.01) were positively associated with COPM performance scores post-intervention.

CONCLUSIONS

Children's bimanual performance and persistence with object-oriented tasks significantly impact occupational performance outcomes following UL training. Predetermining children's mastery motivation along with bimanual ability may assist in tailoring of intervention strategies and models of service delivery to improve effectiveness. Implications for Rehabilitation Children's object persistence and bimanual performance both impact upper limb training outcomes Working with children's motivational predispositions may optimize engagement and therapy outcomes. Supporting positive parenting styles may enhance a child's mastery motivation and persistence with difficult tasks.

Risk of healthcare associated infections in HIV positive patients

HIV positive patients are a high risk population due to the alteration in their immune status. Health-care associated infections (HAI) have not been well described in this population, with some risk factors reported inconsistently in the literature. The aim of this study was to describe the epidemiology as well as the underlying risk factors for HAI, specifically urinary tract infection (UTI), bloodstream infection (BSI) and respiratory tract infection (RTI). This was a retrospective cohort study conducted at an academic health system in New York City which included three hospitals over a two year period from 2006 to 2008. There were 3,877 HIV positive patient discharges in 1,911 patients. There were a total of 142 UTI, 106 BSI, and 100 RTI. The incidence rates were 4.35 for UTI, 3.16 for BSI and 2.98 for RTI. CD4 count and antiretroviral therapy were not associated with HAI. Significant predictors of UTI included urinary catheter, length of stay, female gender, steroids and trimethoprim-sulphamethoxazole (TMP-SMX); of BSI were steroids and TMP-SMX; and RTI were mechanical ventilation, steroids and TMP-SMX. Multivariable analysis indicated that TMP-SMX was significantly associated with an increased risk of infection for all three types of HAI [BSI odds ratio 2.55, 95% confidence interval (1.22-5.34); UTI odds ratio 3.1, 95% confidence interval (1.41-7.22); RTI odds ratio 5.15, 95% confidence interval (1.70-15.62)]. HIV positive patients are at significant risk for developing HAI, but the risk factors differ depending on the specific type of infection. The fact that TMP-SMX is a risk factor in these patients warrants further research as this may have significant health policy implications.

A Wald test for zero inflation and deflation for correlated count data from dental caries research

Tests of homogeneity in zero-inflated models for count data have been well discussed in the literature, but the existing methodologies have relied primarily on score statistics. An often cited justification for the use of these statistics is that they do not require the model to be fitted under the alternative. But the advent of computer software with robust functions and procedures has made it easy for these alternative models to be fitted routinely in practice. In this article, we exploit this opportunity by using results generated from these analyses to develop a Wald test statistic to evaluate homogeneity in the class of zero-inflated models. We show how the proposed test can be performed with minimal programming effort for the practicing statistician. Technically, the test is based on a reparameterization of the mixing weights that naturally incorporates covariates under heterogeneity, a characteristic often ignored by existing testing procedures. A quasi-likelihood function derived from a working independence model coupled with the so-called sandwich estimator of the covariance matrix of the parameter estimates is used to accommodate correlation in the data. A simulation study is conducted to evaluate the empirical performance of the proposed Wald test and its real life applications are illustrated using correlated dental caries counts in young children.

Effects of naltrexone on adolescent alcohol cue reactivity and sensitivity: an initial randomized trial

Adolescent alcohol use is associated with myriad adverse consequences and contributes to the leading causes of mortality among youth. Despite the magnitude of this public health problem, evidenced-based treatment initiatives for alcohol use disorders in youth remain inadequate. Identifying promising pharmacological approaches may improve treatment options. Naltrexone is an opiate receptor antagonist that is efficacious for reducing drinking in adults by attenuating craving and the rewarding effects of alcohol. Implications of these findings for adolescents are unclear; however, given that randomized trials of naltrexone with youth are non-existent. We conducted a randomized, double-blinded, placebo-controlled cross-over study, comparing naltrexone (50 mg/daily) and placebo in 22 adolescent problem drinkers aged 15-19 years (M = 18.36, standard deviation = 0.95; 12 women). The primary outcome measures were alcohol use, subjective responses to alcohol consumption, and alcohol-cue-elicited craving assessed in the natural environment using ecological momentary assessment methods, and craving and physiological reactivity assessed using standard alcohol cue reactivity procedures. Results showed that naltrexone reduced the likelihood of drinking and heavy drinking (P's ≤ 0.03), blunted craving in the laboratory and in the natural environment (P's ≤ 0.04), and altered subjective responses to alcohol consumption (P's ≤ 0.01). Naltrexone was generally well tolerated by participants. This study provides the first experimentally controlled evidence that naltrexone reduces drinking and craving, and alters subjective responses to alcohol in a sample of adolescent problem drinkers, and suggests larger clinical trials with long-term follow-ups are warranted.

Safety performance models for urban intersections in Brazil

This paper presents a modeling effort for developing safety performance models (SPM) for urban intersections for three major Brazilian cities. The proposed methodology for calibrating SPM has been divided into the following steps: defining the safety study objective, choosing predictive variables and sample size, data acquisition, defining model expression and model parameters and model evaluation. Among the predictive variables explored in the calibration phase were exposure variables (AADT), number of lanes, number of approaches and central median status. SPMs were obtained for three cities: Fortaleza, Belo Horizonte and Brasília. The SPM developed for signalized intersections in Fortaleza and Belo Horizonte had the same structure and the most significant independent variables, which were AADT entering the intersection and number of lanes, and in addition, the coefficient of the best models were in the same range of values. For Brasília, because of the sample size, the signalized and unsignalized intersections were grouped, and the AADT was split in minor and major approaches, which were the most significant variables. This paper also evaluated SPM transferability to other jurisdiction. The SPM for signalized intersections from Fortaleza and Belo Horizonte have been recalibrated (in terms of the Cx) to the city of Porto Alegre. The models were adjusted following the Highway Safety Manual (HSM) calibration procedure and yielded Cx of 0.65 and 2.06 for Fortaleza and Belo Horizonte SPM respectively. This paper showed the experience and future challenges toward the initiatives on development of SPMs in Brazil, that can serve as a guide for other countries that are in the same stage in this subject.

Achieving cannabis cessation -- evaluating N-acetylcysteine treatment (ACCENT): design and implementation of a multi-site, randomized controlled study in the National Institute on Drug Abuse Clinical Trials Network

Despite recent advances in behavioral interventions for cannabis use disorders, effect sizes remain modest, and few individuals achieve long-term abstinence. One strategy to enhance outcomes is the addition of pharmacotherapy to complement behavioral treatment, but to date no efficacious medications targeting cannabis use disorders in adults through large, randomized controlled trials have been identified. The National Institute on Drug Abuse Clinical Trials Network (NIDA CTN) is currently conducting a study to test the efficacy of N-acetylcysteine (NAC) versus placebo (PBO), added to contingency management, for cannabis cessation in adults (ages 18-50). This study was designed to replicate positive findings from a study in cannabis-dependent adolescents that found greater odds of abstinence with NAC compared to PBO. This paper describes the design and implementation of an ongoing 12-week, intent-to-treat, double-blind, randomized, placebo-controlled study with one follow-up visit four weeks post-treatment. Approximately 300 treatment-seeking cannabis-dependent adults will be randomized to NAC or PBO across six study sites in the United States. The primary objective of this 12-week study is to evaluate the efficacy of twice-daily orally-administered NAC (1200 mg) versus matched PBO, added to contingency management, on cannabis abstinence. NAC is among the first medications to demonstrate increased odds of abstinence in a randomized controlled study among cannabis users in any age group. The current study will assess the cannabis cessation efficacy of NAC combined with a behavioral intervention in adults, providing a novel and timely contribution to the evidence base for the treatment of cannabis use disorders.

The magnitude and duration of Clostridium difficile infection risk associated with antibiotic therapy: a hospital cohort study

Antibiotic therapy is the principal risk factor for Clostridium difficile infection (CDI), but little is known about how risks cumulate over the course of therapy and abate after cessation. We prospectively identified CDI cases among adults hospitalized at a tertiary hospital between June 2010 and May 2012. Poisson regression models included covariates for time since admission, age, hospitalization history, disease pressure, and intensive care unit stay. Impacts of antibiotic use through time were modeled using 4 measures: current antibiotic receipt, time since most recent receipt, time since first receipt during a hospitalization, and duration of receipt. Over the 24-month study period, we identified 127 patients with new onset nosocomial CDI (incidence rate per 10,000 patient days [IR] = 5.86). Of the 4 measures, time since most recent receipt was the strongest independent predictor of CDI incidence. Relative to patients with no prior receipt of antibiotics in the last 30 days (IR = 2.95), the incidence rate of CDI was 2.41 times higher (95% confidence interval [CI] 1.41, 4.13) during antibiotic receipt and 2.16 times higher when patients had receipt in the prior 1–5 days (CI 1.17, 4.00). The incidence rates of CDI following 1–3, 4–6 and 7–11 days of antibiotic exposure were 1.60 (CI 0.85, 3.03), 2.27 (CI 1.24, 4.16) and 2.10 (CI 1.12, 3.94) times higher compared to no prior receipt. These findings are consistent with studies showing higher risk associated with longer antibiotic use in hospitalized patients, but suggest that the duration of increased risk is shorter than previously thought.

Model-based estimation of measures of association for time-to-event outcomes

Background

Hazard ratios are ubiquitously used in time to event applications to quantify adjusted covariate effects. Although hazard ratios are invaluable for hypothesis testing, other adjusted measures of association, both relative and absolute, should be provided to fully appreciate studies results. The corrected group prognosis method is generally used to estimate the absolute risk reduction and the number needed to be treated for categorical covariates.

Methods

The goal of this paper is to present transformation models for time-to-event outcomes to obtain, directly from estimated coefficients, the measures of association widely used in biostatistics together with their confidence interval. Pseudo-values are used for a practical estimation of transformation models.

Results

Using the regression model estimated through pseudo-values with suitable link functions, relative risks, risk differences and the number needed to treat, are obtained together with their confidence intervals. One example based on literature data and one original application to the study of prognostic factors in primary retroperitoneal soft tissue sarcomas are presented. A simulation study is used to show some properties of the different estimation methods.

Conclusions

Clinically useful measures of treatment or exposure effect are widely available in epidemiology. When time to event outcomes are present, the analysis is performed generally resorting to predicted values from Cox regression model. It is now possible to resort to more general regression models, adopting suitable link functions and pseudo values for estimation, to obtain alternative measures of effect directly from regression coefficients together with their confidence interval. This may be especially useful when, in presence of time dependent covariate effects, it is not straightforward to specify the correct, if any, time dependent functional form. The method can easily be implemented with standard software.

Complexities of short-term mobility for sex work and migration among sex workers: violence and sexual risks, barriers to care, and enhanced social and economic opportunities

Despite research on the health and safety of mobile and migrant populations in the formal and informal sectors globally, limited information is available regarding the working conditions, health, and safety of sex workers who engage in short-term mobility and migration. The objective of this study was to longitudinally examine work environment, health, and safety experiences linked to short-term mobility/migration (i.e., worked or lived in another city, province, or country) among sex workers in Vancouver, Canada, over a 2.5-year study period (2010-2012). We examined longitudinal correlates of short-term mobility/migration (i.e., worked or lived in another city, province, or country over the 3-year follow-up period) among 646 street and off-street sex workers in a longitudinal community-based study (AESHA). Of 646 sex workers, 10.84 % (n = 70) worked or lived in another city, province, or country during the study. In a multivariate generalized estimating equations (GEE) model, short-term mobility/migration was independently correlated with older age (adjusted odds ratio (AOR) 0.95, 95 % confidence interval (CI) 0.92-0.98), soliciting clients in indoor (in-call) establishments (AOR 2.25, 95 % CI 1.27-3.96), intimate partner condom refusal (AOR 3.00, 1.02-8.84), and barriers to health care (AOR 1.77, 95 % CI 1.08-2.89). In a second multivariate GEE model, short-term mobility for sex work (i.e., worked in another city, province, or country) was correlated with client physical/sexual violence (AOR 1.92, 95 % CI 1.02-3.61). In this study, mobile/migrant sex workers were more likely to be younger, work in indoor sex work establishments, and earn higher income, suggesting that short-term mobility for sex work and migration increase social and economic opportunities. However, mobility and migration also correlated with reduced control over sexual negotiation with intimate partners and reduced health care access, and mobility for sex work was associated with enhanced workplace sexual/physical violence, suggesting that mobility/migration may confer risks through less control over work environment and isolation from health services. Structural and community-led interventions, including policy support to allow for more formal organizing of sex work collectives and access to workplace safety standards, remain critical to supporting health, safety, and access to care for mobile and migrant sex workers.

Bidirectional Syntactic Priming across Cognitive Domains: From Arithmetic to Language and Back

Scheepers et al. [Scheepers, C., Sturt, P., Martin, C. J., Myachykov, A., Teevan, K., & Viskupova, I. (2011). Structural priming across cognitive domains: From simple arithmetic to relative clause attachment. Psychological Science, 22, 1319–1326. doi:10.1177/0956797611416997] showed that the structure of a correctly solved mathematical equation affects how people subsequently complete sentences containing high versus low relative-clause attachment ambiguities. Here we investigated whether such effects generalize to different structures and tasks and, importantly, whether they also hold in the reverse direction (i.e., from linguistic to mathematical processing). In a questionnaire-based experiment, participants had to solve structurally left- or right-branching equations (e.g., 5 × 2 + 7 versus 5 + 2 × 7) and to provide sensicality ratings for structurally left- or right-branching adjective–noun–noun compounds (e.g., alien monster movie versus lengthy monster movie). In the first version of the experiment, the equations were used as primes and the linguistic expressions as targets (investigating structural priming from maths to language). In the second version, the order was reversed (language-to-maths priming). Both versions of the experiment showed clear structural priming effects, conceptually replicating and extending the findings from Scheepers and colleagues (2011). Most crucially, the observed bidirectionality of cross-domain structural priming strongly supports the notion of shared syntactic representations (or recursive procedures to generate and parse them) between arithmetic and language.

Inability to access addiction treatment among street-involved youth in a Canadian setting

From Sept 2005 to May 2012, 1015 street-involved youth were enrolled into the At-Risk Youth Study, a prospective cohort of youth aged 14-26 who use illicit drugs in Vancouver, Canada. Data were collected through semiannual interviewer administered questionnaires. Generalized estimating equation logistic regression was used to identify factors independently associated with being unable to access addiction treatment. The enclosed manuscript notes the implications and limitations of this study, as well as possible directions for future research. This study was funded by the US National Institutes of Health (NIH) and Canadian Institutes of Health (CIHR).

Crack pipe sharing among street-involved youth in a Canadian setting

INTRODUCTION AND AIMS

Crack pipe sharing is a risky practice that has been associated with the transmission of hepatitis C and other harms. While previous research has exclusively focused on this phenomenon among adults, this study examines crack pipe sharing among street-involved youth.

DESIGN AND METHODS

From May 2006 to May 2012, data were collected from the At-Risk Youth Study, a cohort of street-involved youth aged 14-26 in Vancouver, Canada. Survey data from active crack smokers were analysed using generalised estimating equations logistic regression.

RESULTS

Over the study period, 567 youth reported smoking crack cocaine and contributed 1288 observations, among which 961 (75%) included a report of crack pipe sharing. In multivariate analysis, factors that were associated with crack pipe sharing included difficulty accessing crack pipes [adjusted odds ratio (AOR) = 1.58, 95% confidence interval (CI) 1.13-2.20]; homelessness (AOR = 1.87, 95% CI 1.43-2.44); regular employment (AOR = 1.53, 95% CI 1.15-2.04); daily non-injection crystal methamphetamine use (AOR = 2.04, 95% CI 1.11-3.75); daily crack smoking (AOR = 1.37, 95% CI 1.01-1.85); encounters with the police (AOR = 1.42, 95% CI 1.01-1.99); and reporting unprotected sex (AOR = 1.95, 95% CI 1.47-2.58).

DISCUSSION AND CONCLUSIONS

The prevalence of crack pipe sharing was high among our sample and independently associated with structural factors including difficulty accessing crack pipes and homelessness. Crack pipe sharing was also associated with high-intensity drug use and a number of other markers of risk and vulnerability. Collectively, these findings highlight opportunities for health services to better engage with this vulnerable group and reduce this risky behaviour.

Measuring family HRQoL spillover effects using direct health utility assessment

Background. Applications of cost-effectiveness analysis do not typically incorporate effects on caregiver quality of life despite increasing evidence that these effects are measurable. Methods. Using a national sample of US adults, we conducted 2 cross-sectional surveys during December 2011 and January 2012. One version asked respondents to value their own experience as the family member of a person with a chronic illness (experienced sample), and the other version asked respondents to value hypothetical scenarios describing the experience of having a family member with a chronic illness (community sample). Conditions included Alzheimer’s disease/dementia, arthritis, cancer, and depression. Using standard gamble questions, respondents were asked to value the spillover effects of a family member’s illness. We used regression analysis to evaluate the disutility (loss in health-related quality of life) of having a family member with a chronic illness by condition and relationship type, controlling for the respondent’s own conditions and sociodemographic characteristics. Results. For the experienced sample (n = 1389), regression analyses suggested that greater spillover was associated with certain conditions (arthritis, depression) compared with other conditions (Alzheimer’s disease, cancer). For the community sample (n = 1205), regression analyses indicated that lower spillover was associated with condition (cancer) but not the type of relationship with the ill family member (parent, child, spouse). Conclusions. The effects of illness extend beyond the individual patient to include effects on caregivers of patients, parents of ill children, spouses, and other close family and household members. Cost-effectiveness analyses should consider the inclusion of health-related quality of life spillover effects in addition to caregiving time costs incurred by family members of ill individuals.

Does walking speed mediate the association between visual impairment and self-report of mobility disability? The Salisbury Eye Evaluation Study

OBJECTIVES

To determine whether performance speeds mediate the association between visual impairment and self-reported mobility disability over an 8-year period.

DESIGN

Longitudinal analysis.

SETTING

Salisbury, Maryland.

PARTICIPANTS

Salisbury Eye Evaluation Study participants aged 65 and older (N=2,520).

MEASUREMENTS

Visual impairment was defined as best-corrected visual acuity worse than 20/40 in the better-seeing eye or visual field less than 20°. Self-reported mobility disability on three tasks was assessed: walking up stairs, walking down stairs, and walking 150 feet. Performance speed on three similar tasks was measured: walking up steps (steps/s), walking down steps (steps/s), and walking 4 m (m/s).

RESULTS

For each year of observation, the odds of reporting mobility disability was significantly greater for participants who were visually impaired (VI) than for those who were not (NVI) (odds ratio (OR) difficulty walking up steps=1.58, 95% confidence interval (CI)=1.32-1.89; OR difficulty walking down steps=1.90, 95% CI=1.59-2.28; OR difficulty walking 150 feet=2.11, 95% CI=1.77-2.51). Once performance speed on a similar mobility task was included in the models, VI participants were no longer more likely to report mobility disability than those who were NVI (OR difficulty walking up steps=0.84, 95% CI=0.65-1.11; OR difficulty walking down steps=0.96, 95% CI=0.74-1.24; OR difficulty walking 150 feet=1.22, 95% CI=0.98-1.50).

CONCLUSION

Slower performance speed in VI individuals largely accounted for the difference in the odds of reporting mobility disability, suggesting that VI older adults walk slower and are therefore more likely to report mobility disability than those who are NVI. Improving mobility performance in older adults with visual impairment may minimize the perception of mobility disability.

High prevalence and partner correlates of physical and sexual violence by intimate partners among street and off-street sex workers

Objectives

Intimate partner violence (IPV) is associated with increased risk of HIV among women globally. There is limited evidence and understanding about IPV and potential HIV risk pathways among sex workers (SWs). This study aims to longitudinally evaluate prevalence and correlates of IPV among street and off-street SWs over two-years follow-up.

Methods

Longitudinal data were drawn from an open prospective cohort, AESHA (An Evaluation of Sex Workers Health Access) in Metro Vancouver, Canada (2010–2012). Prevalence of physical and sexual IPV was measured using the WHO standardized IPV scale (version 9.9). Bivariate and multivariable logistic regression using Generalized Estimating Equations (GEE) were used to examine interpersonal and structural correlates of IPV over two years.

Results

At baseline, 387 SWs had a male, intimate sexual partner and were eligible for this analysis. One-fifth (n = 83, 21.5%) experienced recent physical/sexual IPV at baseline and 26.2% over two-years follow-up. In multivariable GEE analysis, factors independently correlated with physical/sexual IPV in the last six months include: childhood (<18 years) sexual/physical abuse (adjusted odds ratio [AOR] = 2.05, 95% confidence interval [CI]: 1.14–3.69), inconsistent condom use for vaginal and/or anal sex with intimate partner (AOR = 1.84, 95% CI: 1.07–3.16), <daily prescription opioid use (AOR = 1.72, 95% CI: 1.02–2.89), providing financial support to intimate partner (AOR = 1.65, 95% CI: 1.05–2.59), and sourcing drugs from intimate partner (AOR = 1.62, 95% CI: 1.02–2.26).

Discussion

Our results demonstrate that over one-fifth of SWs in Vancouver report physical/sexual IPV in the last six months. The socio-structural correlates of IPV uncovered here highlight potential HIV risk pathways through SWs’ intimate, non-commercial partner relationships. The high prevalence of IPV among SWs is a critical public health concern and underscores the need for integrated violence and HIV prevention and intervention strategies tailored to this key population.