Akaike's information criterion in generalized estimating equations

Core symptoms not meeting criteria for delirium are associated with cognitive and functional impairment and mood and behavior problems in older long-term care residents

BACKGROUND

The immediate clinical significance of Confusion Assessment Method (CAM)-defined core symptoms of delirium not meeting criteria for delirium is unclear. This study proposed to determine if such symptoms are associated with cognitive and functional impairment, mood and behavior problems and increased Burden of Care (BOC) in older long-term care (LTC) residents.

METHODS

The study was a secondary analysis of data collected for a prospective cohort study of delirium. Two hundred and fifty-eight LTC residents aged 65 years and older in seven LTC facilities had monthly assessments (for up to six months) of CAM - defined core symptoms of delirium (fluctuation, inattention, disorganized thinking, and altered level of consciousness) and five outcome measures: Mini-Mental State Exam, Barthel Index, Cornell Scale for Depression, Nursing Home Behavioral Problems Scale, and Burden of Care. Associations between core symptoms and the five outcome measures were analyzed using generalized estimating equations.

RESULTS

Core symptoms of delirium not meeting criteria for delirium among residents with and without dementia were associated with cognitive and functional impairment and mood and behavior problems but not increased BOC. The associations appear to be intermediate between those of full delirium and no core symptoms and were greater for residents with than without dementia.

CONCLUSION

CAM-defined core symptoms of delirium not meeting criteria for delirium appear to be associated with cognitive and functional impairment and mood and behavior problems in LTC residents with or without dementia. These findings may have implications for the prevention and management of such impairments and problems in LTC settings.

Uniting statistical and individual-based approaches for animal movement modelling

The dynamic nature of their internal states and the environment directly shape animals' spatial behaviours and give rise to emergent properties at broader scales in natural systems. However, integrating these dynamic features into habitat selection studies remains challenging, due to practically impossible field work to access internal states and the inability of current statistical models to produce dynamic outputs. To address these issues, we developed a robust method, which combines statistical and individual-based modelling. Using a statistical technique for forward modelling of the IBM has the advantage of being faster for parameterization than a pure inverse modelling technique and allows for robust selection of parameters. Using GPS locations from caribou monitored in Québec, caribou movements were modelled based on generative mechanisms accounting for dynamic variables at a low level of emergence. These variables were accessed by replicating real individuals' movements in parallel sub-models, and movement parameters were then empirically parameterized using Step Selection Functions. The final IBM model was validated using both k-fold cross-validation and emergent patterns validation and was tested for two different scenarios, with varying hardwood encroachment. Our results highlighted a functional response in habitat selection, which suggests that our method was able to capture the complexity of the natural system, and adequately provided projections on future possible states of the system in response to different management plans. This is especially relevant for testing the long-term impact of scenarios corresponding to environmental configurations that have yet to be observed in real systems.

Systemic glucose variability predicts cerebral metabolic distress and mortality after subarachnoid hemorrhage: a retrospective observational study

Introduction

Cerebral glucose metabolism and energy production are affected by serum glucose levels. Systemic glucose variability has been shown to be associated with poor outcome in critically ill patients. The objective of this study was to assess whether glucose variability is associated with cerebral metabolic distress and outcome after subarachnoid hemorrhage.

Methods

A total of 28 consecutive comatose patients with subarachnoid hemorrhage, who underwent cerebral microdialysis and intracranial pressure monitoring, were studied. Metabolic distress was defined as lactate/pyruvate ratio (LPR) >40. The relationship between daily glucose variability, the development of cerebral metabolic distress and hospital outcome was analyzed using a multivariable general linear model with a logistic link function for dichotomized outcomes.

Results

Daily serum glucose variability was expressed as the standard deviation (SD) of all serum glucose measurements. General linear models were used to relate this predictor variable to cerebral metabolic distress and mortality at hospital discharge. A total of 3,139 neuromonitoring hours and 181 days were analyzed. After adjustment for Glasgow Coma Scale (GCS) scores and brain glucose, SD was independently associated with higher risk of cerebral metabolic distress (adjusted odds ratio = 1.5 (1.1 to 2.1), P = 0.02). Increased variability was also independently associated with in hospital mortality after adjusting for age, Hunt Hess, daily GCS and symptomatic vasospasm (P = 0.03).

Conclusions

Increased systemic glucose variability is associated with cerebral metabolic distress and increased hospital mortality. Therapeutic approaches that reduce glucose variability may impact on brain metabolism and outcome after subarachnoid hemorrhage.

Excessive daytime sleepiness among rural residents in Saskatchewan

BACKGROUND

Obstructive sleep apnea (OSA) is a common diagnosis in clinical practice. Excessive daytime sleepiness may be a warning for possible OSA.

OBJECTIVES

To assess the prevalence of excessive daytime sleepiness as measured by the Epworth Sleepiness Scale (ESS) in a rural community population; potential risk factors for OSA were also assessed.

METHODS

In 2010, a baseline respiratory health questionnaire within the Saskatchewan Rural Health Study was mailed to 11,982 households in Saskatchewan. A total of 7597 adults within the 4624 (42%) respondent households completed the ESS questionnaire. Participants were categorized according to normal or high (>10) ESS scores. Data obtained included respiratory symptoms, doctor-diagnosed sleep apnea, snoring, hypertension, smoking and demographics. Body mass index was calculated. Multivariable logistic regression analysis examined associations between high ESS scores and possible risk factors. Generalized estimating equations accounted for the two-tiered sampling procedure of the study design.

RESULTS

The mean age of respondents was 55.0 years and 49.2% were male. The prevalence of ESS>10 and 'doctor diagnosed' OSA were 15.9% and 6.0%, respectively. Approximately 23% of respondents reported loud snoring and 30% had a body mass index >30 kg⁄m2. Of those with 'doctor-diagnosed' OSA, 37.7% reported ESS>10 (P<0.0001) and 47.7% reported loud snoring (P<0.0001). Risk of having an ESS>10 score increased with age, male sex, obesity, lower socioeconomic status, marriage, loud snoring and doctor-diagnosed sinus trouble.

CONCLUSIONS

High levels of excessive daytime sleepiness in this particular rural population are common and men >55 years of age are at highest risk. Examination of reasons for residual sleepiness and snoring in persons with and without sleep apnea is warranted.

Distribution of Culicoides sonorensis (Diptera: Ceratopogonidae) in Alberta, Canada

The distribution of Culicoides sonorensis Wirth and Jones was examined in Alberta, Canada. Sampling was conducted weekly using blacklight traps at eight locations in 2009, and 10 locations during 2010-2012. Nine supplemental sites were sampled twice annually during both 2011 and 2012. Abundance of C. sonorensis was consistently greatest at a site near the U.S. border, and declined in a northerly direction. Mean annual abundance at this site ranged from 6.4- to > 1,000-fold greater across positive sites. Data from a less extensive survey conducted during 2002-2006 were included in the remaining analyses. C. sonorensis was distributed below a diagonal spanning 49 degrees 30' N, 113 degrees 0' W to 51 degrees 21' N, 110 degrees 40' W. The relationship between the proportion of weekly samples positive and mean annual abundance at a site was determined and indicated that the proportion of positive samples could be used as a surrogate measure of abundance to overcome issues associated with the extreme variation in abundance. A series of logistic regression models were developed and evaluated to determine the effects of spatial (latitude and longitude), climatic (historic temperature and precipitation during the warmest quarter), and weather (temperature during the sample interval and spring precipitation) on abundance as measured by the proportion of positive samples. Spatial and climatic variables set the overall level of abundance, while weather variables added seasonal fluctuations within years, and also fluctuations between years. These data will be useful for long-term monitoring of C. sonorensis and as a baseline for detecting shifts in abundance that might occur because of climate change.

Increases and decreases in drug use attributed to housing status among street-involved youth in a Canadian setting

Background

Among a cohort of drug-using street-involved youth, we sought to identify the prevalence of reporting increases and decreases in illicit drug use due to their current housing status and to identify factors associated with reporting these changes.

Findings

This longitudinal study was based on data collected between June 2008 and May 2012 from a prospective cohort of street-involved youth aged 14–26 in Vancouver, Canada. At semi-annual study follow-up visits, youth were asked if their drug use was affected by their housing status. Using generalized estimating equations, we identified factors associated with perceived increases and decreases in drug use attributed to housing status. Among our sample of 536 participants at baseline, 164 (31%) youth reported increasing their drug use due to their housing situation and 71 (13%) reported decreasing their drug use. In multivariate analysis, factors that were positively associated with perceived increases in drug use attributed to housing status included the following: being homeless, engaging in sex work and drug dealing. Regular employment was negatively associated with increasing drug use due to housing status. Among those who reported decreasing their drug use, only homelessness was significant in bivariate analysis.

Conclusion

Perceived changes in drug use due to housing status were relatively common in this setting and were associated with being homeless and, among those who increased their drug use, engaging in risky income generation activities. These findings suggest that structural factors, particularly housing and economic opportunities, may be crucial interventions for reducing or limiting drug use among street-involved youth.

Evaluation of serum thyroid-stimulating hormone as indicator for fine-needle aspiration in patients with thyroid nodules

BACKGROUND

Recently, it has been reported that the risk of thyroid malignancy increases with increasing concentrations of serum thyroid-stimulating hormone (TSH). The purpose of this study was to determine whether or not serum TSH can be a predictor for thyroid malignancy when considering the relevant ultrasound features and clinical risk factors.

METHODS

This retrospective study included 1200 euthyroid patients with 1269 thyroid nodules who underwent ultrasound-guided fine-needle aspiration (FNA) biopsy between January and June 2009. Serum TSH, ultrasound feature, and clinical parameters were compared according to final diagnosis. Subgroup analyses were performed according to nodule size.

RESULTS

Serum TSH did not show a positive association with malignancy for all nodules and the micronodule subgroup in multivariate analysis, although they showed significant association with thyroid malignancy for the macronodule subgroup. For all nodules and the 2 subgroups, suspicious ultrasound features and younger age were significantly associated with malignancy in univariate and multivariate analyses.

CONCLUSION

Our study suggests that TSH alone is not as useful as ultrasound features in deciding whether or not to perform FNA in patients with micronodules.

Parasite-mediated selection drives an immunogenetic trade-off in plains zebras (Equus quagga)

Pathogen evasion of the host immune system is a key force driving extreme polymorphism in genes of the major histocompatibility complex (MHC). Although this gene family is well characterized in structure and function, there is still much debate surrounding the mechanisms by which MHC diversity is selectively maintained. Many studies have investigated relationships between MHC variation and specific pathogens, and have found mixed support for and against the hypotheses of heterozygote advantage, frequency-dependent or fluctuating selection. Few, however, have focused on the selective effects of multiple parasite types on host immunogenetic patterns. Here, we examined relationships between variation in the equine MHC gene, ELA-DRA, and both gastrointestinal (GI) and ectoparasitism in plains zebras (Equus quagga). Specific alleles present at opposing population frequencies had antagonistic effects, with rare alleles associated with increased GI parasitism and common alleles with increased tick burdens. These results support a frequency-dependent mechanism, but are also consistent with fluctuating selection. Maladaptive GI parasite 'susceptibility alleles' were reduced in frequency, suggesting that these parasites may play a greater selective role at this locus. Heterozygote advantage, in terms of allele mutational divergence, also predicted decreased GI parasite burden in genotypes with a common allele. We conclude that an immunogenetic trade-off affects resistance/susceptibility to parasites in this system. Because GI and ectoparasites do not directly interact within hosts, our results uniquely show that antagonistic parasite interactions can be indirectly modulated through the host immune system. This study highlights the importance of investigating the role of multiple parasites in shaping patterns of host immunogenetic variation.

Alcohol craving in adolescents: bridging the laboratory and natural environment

RATIONALE

Initial lab studies suggest that adolescent drinkers crave alcohol when presented with alcohol cues. Whether this effect generalizes to the natural environment, however, remains unknown, and studies have not examined whether craving predicts drinking among youths.

OBJECTIVES

This study builds on existing research by pairing controlled lab-based cue reactivity assessments (CRAs) with data collected in the natural environment using ecological momentary assessment (EMA) methods. We examined whether alcohol cues evoke craving among adolescent drinkers in the lab and natural environment, and tested the clinical relevance of craving during adolescence by examining the prospective association between craving and alcohol use.

METHODS

Non-treatment-seeking adolescent drinkers (N = 42; ages 15 to 20 years) completed a lab-based CRA followed by a 1-week EMA monitoring period. During the EMA period, youth were prompted randomly throughout the day to record momentary data on craving and contextual factors (e.g., alcohol cues, peers present).

RESULTS

Alcohol cues elicited craving in the lab, and this effect generalized to the natural environment, especially among adolescents with more alcohol problems. In addition, craving predicted subsequent drinking levels in the natural environment.

CONCLUSIONS

This study demonstrates the utility of pairing lab paradigms with EMA methods to better characterize adolescents' reactivity to alcohol cues. Results implicate craving as a clinically meaningful motivator for drinking among adolescents and highlight a potentially important target of pharmacological or behavioral intervention.

Exploring the variation in state-level prescription utilization using a triangulation of analytic methods

BACKGROUND

Retail prescription fill data have consistently shown wide variation in prescription drug utilization across states, with state-level rates ranging from 8.5 to 19.3 filled prescriptions per capita per year. Empirical explanations for this wide variation have not yet been sought.

OBJECTIVES

To examine which factors potentially explain the wide variation in prescription drug utilization across US states.

METHODS

Summary data (proportions, counts, rates, etc) on sociodemographics, health, insurance, provider density, health service use, and retail prescription drug fills for each of the 50 states and the District of Columbia, from 2008 to 2010, were retrieved from multiple national data sources, such as the Kaiser Family Foundation's "State Health Facts" Web Portal. Pooled cross-sectional linear, negative binomial, and ordered logit multivariable regressions were used to model states' prescription utilization as a function of the aforementioned possible explanatory variables. Principal components analysis also was employed so as to overcome high correlations among some of the covariates.

RESULTS

Among US states, higher levels of employer-sponsored insurance or Medicaid coverage were associated with both higher levels of prescription utilization and a higher likelihood of being in upper utilization quartiles. A higher density of nurse practitioners was also positively associated with both the level of utilization and the likelihood of higher utilization, whereas a higher density of active physicians was associated with opposite effects. Higher prevalence of physical activity was associated with lower utilization levels as well as a lower likelihood of high utilization. State-level prevalence of chronic conditions and poor health mattered only for the level of prescription utilization. States' sociodemographics were not significantly associated with prescription utilization.

CONCLUSIONS

This study suggests that higher prescription utilization across states was associated with the variations in provider types, Medicaid and private insurance coverage, as well as the prevalence of chronic diseases. Further investigation of how each of these factors may contribute to a particular state's prescription drug utilization level is needed.

Cumulative mechanical low-back load at work is a determinant of low-back pain

OBJECTIVES

Reported associations of physical exposures during work (eg, lifting, trunk flexion or rotation) and low-back pain (LBP) are rather inconsistent. Mechanical back loads (eg, moments on the low back) as a result of exposure to abovementioned risk factors have been suggested to be important as such loads provide a more direct relationship with tissue failure and thus LBP. Since information on the effect of such load metrics with LBP is lacking yet, we aimed to assess this effect in a prospective study.

METHODS

Of 1131 workers, categorised into 19 groups, LBP was prospectively assessed over 3 years. Video and hand force recordings of 4-5 workers per group (93 in total) were used to estimate mechanical low-back loads (peak load and three cumulative load metrics, ie, linear weighted load, squared weighted load and load weighted to the tenth power) during manual materials handling (MMH) tasks using a video analysis method. These data were combined with static mechanical load estimates based on structured observation of non-MMH tasks. Associations of mechanical loads and LBP were tested using generalised estimating equations.

RESULTS

Significant effects on LBP were found for cumulative low-back moments (linear and squared weighted; both p<0.01 and ORs of 3.01 and 3.50, respectively) but not for peak and cumulative moments weighted to the tenth power.

CONCLUSIONS

Results of this first prospective study on the effect of mechanical low-back load on LBP support a LBP aetiology model of cumulative loads, potentially due to accumulation of microdamage or fatigue. Therefore, prevention of LBP should focus on reducing cumulative low-back loads, especially in highly exposed occupational groups, for example, by reducing handling of heavy loads and working in awkward body postures.

Trends in live birth rates and adverse neonatal outcomes among HIV-positive women in Ontario, Canada, 2002-2009: a descriptive population-based study

To characterise trends in live birth rates, adverse neonatal outcomes and socio-demographic characteristics of pregnant women with diagnosed HIV between the ages of 18 and 49 in Ontario, Canada from 1 April 2002 to 31 March 2010, we conducted a population-based study. Utilising linked administrative healthcare databases we used generalised estimating equations to characterise secular trends and examine the association between live births and socio-demographic characteristics, including age, region of birth and neighbourhood income quintile. Between 2002/2003 and 2009/2010, there were 551 live births during 15,610 person-years of follow-up. The proportion of HIV-positive mothers originally from Africa or the Caribbean increased from 26.7% to 51.6% over the study period. The risk of pre-term (risk ratio 2.13, 95% confidence interval 1.74 to 2.61) and small for gestational age births (risk ratio 1.53, 95% confidence interval 1.20 to 1.94) was higher in women with HIV compared with provincial estimates for these outcomes. Women with HIV have rates of pre-term and small for gestational age births that exceed provincial estimates for these outcomes. Further research is required to identify factors mediating these disparities that are amenable to pre-natal risk reduction initiatives.

Frequent and seasonally variable sublethal anthrax infections are accompanied by short-lived immunity in an endemic system

Few studies have examined host-pathogen interactions in wildlife from an immunological perspective, particularly in the context of seasonal and longitudinal dynamics. In addition, though most ecological immunology studies employ serological antibody assays, endpoint titre determination is usually based on subjective criteria and needs to be made more objective. Despite the fact that anthrax is an ancient and emerging zoonotic infectious disease found world-wide, its natural ecology is not well understood. In particular, little is known about the adaptive immune responses of wild herbivore hosts against Bacillus anthracis. Working in the natural anthrax system of Etosha National Park, Namibia, we collected 154 serum samples from plains zebra (Equus quagga), 21 from springbok (Antidorcas marsupialis) and 45 from African elephants (Loxodonta africana) over 2-3 years, resampling individuals when possible for seasonal and longitudinal comparisons. We used enzyme-linked immunosorbent assays to measure anti-anthrax antibody titres and developed three increasingly conservative models to determine endpoint titres with more rigourous, objective mensuration. Between 52 and 87% of zebra, 0-15% of springbok and 3-52% of elephants had measurable anti-anthrax antibody titres, depending on the model used. While the ability of elephants and springbok to mount anti-anthrax adaptive immune responses is still equivocal, our results indicate that zebra in ENP often survive sublethal anthrax infections, encounter most B. anthracis in the wet season and can partially booster their immunity to B. anthracis. Thus, rather than being solely a lethal disease, anthrax often occurs as a sublethal infection in some susceptible hosts. Though we found that adaptive immunity to anthrax wanes rapidly, subsequent and frequent sublethal B. anthracis infections cause maturation of anti-anthrax immunity. By triggering host immune responses, these common sublethal infections may act as immunomodulators and affect population dynamics through indirect immunological and co-infection effects. In addition, with our three endpoint titre models, we introduce more mensuration rigour into serological antibody assays, even under the often-restrictive conditions that come with adapting laboratory immunology methods to wild systems. With these methods, we identified significantly more zebras responding immunologically to anthrax than have previous studies using less comprehensive titre analyses.

Importance of social and cultural factors for attitudes, disclosure and time off work for depression: findings from a seven country European study on depression in the workplace

OBJECTIVES

Depression is experienced by a large proportion of the workforce and associated with high costs to employers and employees. There is little research on how the social costs of depression vary by social and cultural context. This study investigates individual, workplace and societal factors associated with greater perceived discomfort regarding depression in the workplace, greater likelihood of employees taking time off of work as a result of depression and greater likelihood of disclosure of depression to one's employer.

METHODS

Employees and managers (n = 7,065) were recruited from seven European countries to participate in the IDEA survey. Multivariable logistic regression models were used to examine associations between individual characteristics and country contextual characteristics in relation to workplace perceptions, likelihood of taking time off work and disclosing depression to an employer.

RESULTS

Our findings suggest that structural factors such as benefit systems and flexible working hours are important for understanding workplace perceptions and consequences for employees with depression. However, manager responses that focus on offering help to the employee with depression appear to have stronger associations with positive perceptions in the workplace, and also with openness and disclosure by employees with depression.

CONCLUSION

This study highlights the importance of individual, workplace and societal factors that may be associated with how people with depression are perceived and treated in the workplace, and, hence, factors that may be associated with openness and disclosure among employees with depression. Some responses, such as flexible working hours, may be helpful but are not necessarily sufficient, and our findings also emphasise the importance of support and openness of managers in addition to flexible working hours.

Model selection criterion for causal parameters in structural mean models based on a quasi-likelihood

Structural mean models (SMMs) have been proposed for estimating causal parameters in the presence of non-ignorable non-compliance in clinical trials. To obtain a valid causal estimate, we must impose several assumptions. One of these is the correct specification of the structural model. Building on Pan's work (2001, Biometrics 57, 120-125) on developing a model selection criterion for generalized estimating equations, we propose a new approach for model selection of SMMs based on a quasi-likelihood. We provide a formal model selection criterion that is an extension of Akaike's information criterion. Using subset selection of baseline covariates, our method allows us to understand whether the treatment effect varies across the available baseline covariate levels, and/or to quantify the treatment effect on a specific covariates level to target specific individuals to maximize treatment benefit. We present simulation results in which our method performs reasonably well compared to other testing methods in terms of both the probability of selecting the correct model and the predictive performances of the individual treatment effects. We use a large randomized clinical trial of pravastatin as a motivation.

Does electroencephalogram phase variability account for reduced P3 brain potential in externalizing disorders?

OBJECTIVE

Amplitude deficits of the P3 event-related potential (ERP) are associated with externalizing psychopathology but little is known about the nature of underlying brain electrical activity that accounts for this amplitude reduction. We sought to understand if group differences in task-induced phase-locking in electroencephalographic (EEG) delta and theta frequencies may account for P3-externalizing associations.

METHODS

Adult males (N=410) completed a visual oddball task and frontal and parietal P3-related delta- and theta-band phase-invariant evoked energy and inter-trial phase-locking measures were investigated with respect to the externalizing spectrum, including substance dependence, adult antisociality, and childhood disruptive disorders. We hypothesized that P3-related phase-locking is weaker in externalizing-diagnosed individuals and this might mediate prior findings of reduced evoked P3 energy.

RESULTS

Reductions in both evoked energy and phase-locking, in both frequency bands, at both scalp sites, were associated with greater odds of externalizing diagnoses. Generally, adding phase-locking to evoked energy came with better prediction model fit. Moreover, reduced theta-band phase-locking partially mediated the effects of within-frequency evoked energy on externalizing prediction.

CONCLUSIONS

Inter-trial phase-locking underlying P3 appears to be an important distinction between externalizing and control subjects.

SIGNIFICANCE

This cross-trial phase-variability for externalizing-diagnosed individuals might reflect deficient top-down "tuning" by neuromodulatory systems.

Associations between injection risk and community disadvantage among suburban injection drug users in southwestern Connecticut, USA

Increases in drug abuse, injection, and opioid overdoses in suburban communities led us to study injectors residing in suburban communities in southwestern Connecticut, US. We sought to understand the influence of residence on risk and injection-associated diseases. Injectors were recruited by respondent-driven sampling and interviewed about sociodemographics, somatic and mental health, injection risk, and interactions with healthcare, harm reduction, substance abuse treatment, and criminal justice systems. HIV, hepatitis B and C (HBV and HCV) serological testing was also conducted. Our sample was consistent in geographic distribution and age to the general population and to the patterns of heroin-associated overdose deaths in the suburban towns. High rates of interaction with drug abuse treatment and criminal justice systems contrasted with scant use of harm reduction services. The only factors associated with both dependent variables-residence in less disadvantaged census tracts and more injection risk-were younger age and injecting in one's own residence. This contrasts with the common association among urban injectors of injection-associated risk behaviors and residence in disadvantaged communities. Poor social support and moderate/severe depression were associated with risky injection practices (but not residence in specific classes of census tracts), suggesting that a region-wide dual diagnosis approach to the expansion of harm reduction services could be effective at reducing the negative consequences of injection drug use.

Identifying factors associated with changes in physical functioning in an older population

AIM

The present study evaluated the association between changes in physical functioning and a variety of factors in an older population in Taiwan.

METHODS

The data of 907 participants were derived from a three-wave cohort study of aging, the Functioning and Aging Study in Taipei, with a study period from 2005 to 2009. Functional status was assessed using activities of daily living, instrumental activities of daily living and mobility tasks, and classified as being normal, with mild disability, moderate disability, and severe disability. All potential factors were allocated into five groups including demography, chronic diseases, geriatric conditions, lifestyle and physical assessments. Generalized estimating equations and generalized linear mixed-effects models were used to identify factors responsible for changes in physical functioning across different waves of data.

RESULTS

The proportion of elderly participants with normal function decreased with time throughout the study period. The results of Generalized estimating equations and mixed effects models showed nearly identical sets of factors. These included age, living arrangements, social support, self-rated health, stroke, diabetes, Parkinson's disease, osteoporosis, depression, cognition, vision, history of fracture and falls, incontinence of urine and feces, physical activity, body mass index, and short physical performance battery.

CONCLUSIONS

Older persons with stroke, Parkinson's disease, diabetes, osteoporosis, geriatric conditions and poor short physical performance battery score should be considered as the target of prevention against functional decline. Those not living with spouses, with poor self-rated health, with low social support, being underweight or obese and with a sedentary lifestyle might also require major attention.

Prevalence of hypertension and associated factors in an indigenous community of central Brazil: a population-based study

Objective

The aim of the present study was to assess the prevalence of hypertension and cardiovascular risk factors among the native indigenous of Jaguapiru village in Dourados, Mato Grosso do Sul, Brazil.

Method

A cross-sectional, population-based study was conducted with adult indigenous aged 18 years or more. The subjects' blood pressure was measured twice, and the mean of the two measurements was calculated. Body weight, height, capillary blood glucose and waist circumference were measured. Pregnant women, individuals using glucocorticoids, and non-indigenous villagers and their offspring were excluded. Multivariate regression analyses were conducted on the socio-demographic and clinical independent variables. Interactions between independent variables were also tested.

Results

We included 1,608 native indigenous eligible to the research. The prevalence of hypertension was 29.5% (95% CI: 27–31.5), with no significant difference between the genders. For both men and women, diastolic hypertension was more common than systolic hypertension. The prevalence of hypertension was higher among obese, diabetic, and older participants, as well as those who consumed alcohol, had a lower educational level, or had a family history of hypertension. There was no association between hypertension and tobacco smoking or family income.

Conclusion

Hypertension among the indigenous from Jaguapiru village was similar to the prevalence in the Brazilians, but may have a more negative effect in such disadvantaged population. The associated factors we found can help drawing prevention policies.

Patient-specific computer-based decision support in primary healthcare--a randomized trial

BACKGROUND

Computer-based decision support systems are a promising method for incorporating research evidence into clinical practice. However, evidence is still scant on how such information technology solutions work in primary healthcare when support is provided across many health problems. In Finland, we designed a trial where a set of evidence-based, patient-specific reminders was introduced into the local Electronic Patient Record (EPR) system. The aim was to measure the effects of such reminders on patient care. The hypothesis was that the total number of triggered reminders would decrease in the intervention group compared with the control group, indicating an improvement in patient care.

METHODS

From July 2009 to October 2010 all the patients of one health center were randomized to an intervention or a control group. The intervention consisted of patient-specific reminders concerning 59 different health conditions triggered when the healthcare professional (HCP) opened and used the EPR. In the intervention group, the triggered reminders were shown to the HCP; in the control group, the triggered reminders were not shown. The primary outcome measure was the change in the number of reminders triggered over 12 months. We developed a unique data gathering method, the Repeated Study Virtual Health Check (RSVHC), and used Generalized Estimation Equations (GEE) for analysing the incidence rate ratio, which is a measure of the relative difference in percentage change in the numbers of reminders triggered in the intervention group and the control group.

RESULTS

In total, 13,588 participants were randomized and included. Contrary to our expectation, the total number of reminders triggered increased in both the intervention and the control groups. The primary outcome measure did not show a significant difference between the groups. However, with the inclusion of patients followed up over only six months, the total number of reminders increased significantly less in the intervention group than in the control group when the confounding factors (age, gender, number of diagnoses and medications) were controlled for.

CONCLUSIONS

Computerized, tailored reminders in primary care did not decrease during the 12 months of follow-up time after the introduction of a patient-specific decision support system.

TRIAL REGISTRATION

ClinicalTrial.gov NCT00915304.

Risk factor analysis for capsular contracture: a 5-year Sientra study analysis using round, smooth, and textured implants for breast augmentation

BACKGROUND

Although there are a few broadly agreed on contributory factors, the multifaceted causes of capsular contracture have remained unresolved for decades. This study investigates a variety of potential risk factors that contribute to capsular contracture in primary augmentation patients.

METHODS

The data used for this analysis include 5109 implants in 2560 primary augmentation patients implanted by 34 surgeons based on 5-year results from Sientra's clinical study. Patients were evaluated at annual visits where the capsular contracture Baker grade was recorded. Potential risk factors, including patient attributes, implant attributes, surgery characteristics, pocket irrigation, and postsurgery characteristics, were analyzed using frequency and multivariate models.

RESULTS

A total of 265 capsular contracture events in 179 patients were reported through 5 years. The overall Kaplan-Meier rate for capsular contracture was 7.6 percent by device. The unadjusted analysis showed increased odds of capsular contracture in smooth devices, periareolar incision, subglandular placement, antibiotic and steroid pocket irrigation, recommended massage, and surgical bra (p<0.05 for all). Results from the multivariate analysis, adjusting for all variables in the model, found six factors to be independently associated with capsular contracture (i.e., implant placement, implant surface, incision site, hematoma or seroma development, device size, and surgical bra; p<0.05 for all).

CONCLUSION

This analysis has provided evidence that submuscular placement and textured implants, in addition to other factors, are significant in reducing the incidence of capsular contracture.

Integrated assessment of behavioral and environmental risk factors for Lyme disease infection on Block Island, Rhode Island

Peridomestic exposure to Borrelia burgdorferi-infected Ixodes scapularis nymphs is considered the dominant means of infection with black-legged tick-borne pathogens in the eastern United States. Population level studies have detected a positive association between the density of infected nymphs and Lyme disease incidence. At a finer spatial scale within endemic communities, studies have focused on individual level risk behaviors, without accounting for differences in peridomestic nymphal density. This study simultaneously assessed the influence of peridomestic tick exposure risk and human behavior risk factors for Lyme disease infection on Block Island, Rhode Island. Tick exposure risk on Block Island properties was estimated using remotely sensed landscape metrics that strongly correlated with tick density at the individual property level. Behavioral risk factors and Lyme disease serology were assessed using a longitudinal serosurvey study. Significant factors associated with Lyme disease positive serology included one or more self-reported previous Lyme disease episodes, wearing protective clothing during outdoor activities, the average number of hours spent daily in tick habitat, the subject’s age and the density of shrub edges on the subject’s property. The best fit multivariate model included previous Lyme diagnoses and age. The strength of this association with previous Lyme disease suggests that the same sector of the population tends to be repeatedly infected. The second best multivariate model included a combination of environmental and behavioral factors, namely hours spent in vegetation, subject’s age, shrub edge density (increase risk) and wearing protective clothing (decrease risk). Our findings highlight the importance of concurrent evaluation of both environmental and behavioral factors to design interventions to reduce the risk of tick-borne infections.

Binge Drug Use among Street-Involved Youth in a Canadian Setting

BACKGROUND

Binge drug use has been associated with increased risk of HIV infection and other serious health-related harms among adult drug user populations. This study sought to determine the prevalence and correlates of binge drug use among street-involved youth in a Canadian setting.

METHODS

From Sept 2005 to May 2012, data were collected from the At-Risk Youth Study (ARYS), a prospective cohort of street-involved youth aged 14 - 26 who use illicit drugs. Multivariate generalized estimating equations (GEE) was used to identify factors associated with binge drug use.

RESULTS

Of the 987 participants included in this analysis, 41.5% reported binge drug use at baseline, and another 59.1% reported binge drug use at some point during the study. In multivariate GEE analysis, older age (adjusted odds ratio [AOR] = 1.11), homelessness (AOR = 1.67), drug injecting (AOR = 1.63), non-fatal overdose (AOR = 1.98), public injecting (AOR 1.42), being a victim of violence (AOR = 1.38), sex work (AOR = 2.51) and participation in drug dealing (AOR = 2.04) were independently associated with binge drug use in the previous 6 months (all p<0.05).

DISCUSSION

The prevalence of reporting binge drug use among the youth was high in this setting and was independently associated with a range of high-risk activities and markers of vulnerability. Querying high-risk youth about binge drug use may help prioritize those in greatest need of addiction treatment strategies and public health interventions.

Locally efficient estimation of marginal treatment effects when outcomes are correlated: is the prize worth the chase?

Semiparametric methods have been developed to increase efficiency of inferences in randomized trials by incorporating baseline covariates. Locally efficient estimators of marginal treatment effects, which achieve minimum variance under an assumed model, are available for settings in which outcomes are independent. The value of the pursuit of locally efficient estimators in other settings, such as when outcomes are multivariate, is often debated. We derive and evaluate semiparametric locally efficient estimators of marginal mean treatment effects when outcomes are correlated; such outcomes occur in randomized studies with clustered or repeated-measures responses. The resulting estimating equations modify existing generalized estimating equations (GEE) by identifying the efficient score under a mean model for marginal effects when data contain baseline covariates. Locally efficient estimators are implemented for longitudinal data with continuous outcomes and clustered data with binary outcomes. Methods are illustrated through application to AIDS Clinical Trial Group Study 398, a longitudinal randomized clinical trial that compared the effects of various protease inhibitors in HIV-positive subjects who had experienced antiretroviral therapy failure. In addition, extensive simulation studies characterize settings in which locally efficient estimators result in efficiency gains over suboptimal estimators and assess their feasibility in practice.

Obsessions and Time of Day: A Self-Monitoring Study in Individuals With Obsessive-Compulsive Disorder

Deepening our understanding of the basic mechanisms underlying obsessive-compulsive disorder (OCD) often leads to advances in clinical practice. And, as noted by Kazdin (2008), clinical experiences are an important resource for identifying novel targets for empirical study. One potential target for furthering our understanding of OCD is to investigate clinical reports of within-day symptom fluctuations. Self-monitoring data from 17 adults with OCD were used to test for a diurnal pattern in obsessions. Results from generalized estimating equations revealed that obsessions were most common during midday and that the midday exacerbation was briefer in males. In combination with prior findings of similar diurnal patterns for other anxious symptoms (e.g., panic), these findings suggest that daily social rhythms and/or circadian influences may influence levels of obsessions. Furthermore, treatment may be improved by attending to these heightened symptom periods and integrating this information into therapy (e.g., when developing the exposure hierarchy).

Assessing habitat connectivity for ground-dwelling animals in an urban environment

To ensure viable species populations in fragmented landscapes, individuals must be able to move between suitable habitat patches. Despite the increased interest in biodiversity assessment in urban environments, the ecological relevance of habitat connectivity in highly fragmented landscapes remains largely unknown. The first step to understanding the role of habitat connectivity in urban ecology is the challenging task of assessing connectivity in the complex patchwork of contrasting habitats that is found in cities. We developed a data-based framework, minimizing the use of subjective assumptions, to assess habitat connectivity that consists of the following sequential steps: (1) identification of habitat preference based on empirical habitat-use data; (2) derivation of habitat resistance surfaces evaluating various transformation functions; (3) modeling of different connectivity maps with electrical circuit theory (Circuitscape), a method considering all possible pathways across the landscape simultaneously; and (4) identification of the best connectivity map with information-theoretic model selection. We applied this analytical framework to assess habitat connectivity for the European hedgehog Erinaceus europaeus, a model species for ground-dwelling animals, in the city of Zurich, Switzerland, using GPS track points from 40 individuals. The best model revealed spatially explicit connectivity “pinch points,” as well as multiple habitat connections. Cross-validation indicated the general validity of the selected connectivity model. The results show that both habitat connectivity and habitat quality affect the movement of urban hedgehogs (relative importance of the two variables was 19.2% and 80.8%, respectively), and are thus both relevant for predicting urban animal movements. Our study demonstrates that even in the complex habitat patchwork of cities, habitat connectivity plays a major role for ground-dwelling animal movement. Data-based habitat connectivity maps can thus serve as an important tool for city planners to identify habitat corridors and plan appropriate management and conservation measures for urban animals. The analytical framework we describe to model such connectivity maps is generally applicable to different types of habitat-use data and can be adapted to the movement scale of the focal species. It also allows evaluation of the impact of future landscape changes or management scenarios on habitat connectivity in urban landscapes.

Do intensive care data on respiratory infections reflect influenza epidemics?

OBJECTIVES

Severe influenza can lead to Intensive Care Unit (ICU) admission. We explored whether ICU data reflect influenza like illness (ILI) activity in the general population, and whether ICU respiratory infections can predict influenza epidemics.

METHODS

We calculated the time lag and correlation between ILI incidence (from ILI sentinel surveillance, based on general practitioners (GP) consultations) and percentages of ICU admissions with a respiratory infection (from the Dutch National Intensive Care Registry) over the years 2003-2011. In addition, ICU data of the first three years was used to build three regression models to predict the start and end of influenza epidemics in the years thereafter, one to three weeks ahead. The predicted start and end of influenza epidemics were compared with observed start and end of such epidemics according to the incidence of ILI.

RESULTS

Peaks in respiratory ICU admissions lasted longer than peaks in ILI incidence rates. Increases in ICU admissions occurred on average two days earlier compared to ILI. Predicting influenza epidemics one, two, or three weeks ahead yielded positive predictive values ranging from 0.52 to 0.78, and sensitivities from 0.34 to 0.51.

CONCLUSIONS

ICU data was associated with ILI activity, with increases in ICU data often occurring earlier and for a longer time period. However, in the Netherlands, predicting influenza epidemics in the general population using ICU data was imprecise, with low positive predictive values and sensitivities.

Errors in after-hours phone consultations: a simulation study

BACKGROUND

After-hours out-of-hospital phone consultations require physicians to make decisions based on information provided by a nurse over the phone.

METHODS

We conducted a simulation study to evaluate physicians' actions following communication of key information. 22 nurses were asked to call physicians with six cases based on the six most common reasons for after-hours phone calls. We evaluated physicians' actions following the communication of key clinical information: A situation cue described a patient's problem (eg, confusion). A background cue described a specific clinical finding regarding the cause of the problem (eg, patient's sodium is low). For each cue we defined a list of indicators, based on the medical literature, to ascertain whether physicians acted upon the provided information (which was defined as addressing at least one of the indicators).

RESULTS

A total of 108 phone consultations (containing 88 situation and 93 background cues) were analysed. Situation cues were communicated in 90% (79/88) of the calls and background cues in 33% (31/93). Physician acted upon the provided information in 57% (45/79) and 48% (15/31) of the communicated situation and background cues, respectively. When the background cues were not communicated, physicians asked questions expected to elicit the cue in 12% of the cases. Responding to the situation cue was associated with longer conversations and active inquiry by the physician.

CONCLUSIONS

After-hours phone calls are error prone. Both nurse communication and physician decision-making are problematic. Efforts to improve patient safety in this setting must address both communication and decision-making.

Victims of infanticide and conspecific bite wounding in a female-dominant primate: a long-term study

The aggression animals receive from conspecifics varies between individuals across their lifetime. As poignantly evidenced by infanticide, for example, aggression can have dramatic fitness consequences. Nevertheless, we understand little about the sources of variation in received aggression, particularly in females. Using a female-dominant species renowned for aggressivity in both sexes, we tested for potential social, demographic, and genetic patterns in the frequency with which animals were wounded by conspecifics. Our study included 243 captive, ring-tailed lemurs (Lemur catta), followed from infancy to adulthood over a 35-year time span. We extracted injury, social, and life-history information from colony records and calculated neutral heterozygosity for a subset of animals, as an estimate of genetic diversity. Focusing on victims rather than aggressors, we used General Linear Models to explain bite-wound patterns at different life stages. In infancy, maternal age best predicted wounds received, as infants born to young mothers were the most frequent infanticide victims. In adulthood, sex best predicted wounds received, as males were three times more likely than females to be seriously injured. No relation emerged between wounds received and the other variables studied. Beyond the generally expected costs of adult male intrasexual aggression, we suggest possible additive costs associated with female-dominant societies - those suffered by young mothers engaged in aggressive disputes and those suffered by adult males aggressively targeted by both sexes. We propose that infanticide in lemurs may be a costly by-product of aggressively mediated, female social dominance. Accordingly, the benefits of female behavioral 'masculinization' accrued to females through priority of access to resources, may be partially offset by early costs in reproductive success. Understanding the factors that influence lifetime patterns of conspecific wounding is critical to evaluating the fitness costs associated with social living; however, these costs may vary substantially between societies.

Pseudo-value approach for comparing survival medians for dependent data

Survival median is commonly used to compare treatment groups in cancer-related research. The current literature focuses on developing tests for independent survival data. However, researchers often encounter dependent survival data such as matched pair data or clustered data. We propose a pseudo-value approach to test the equality of survival medians for both independent and dependent survival data. We investigate the type I error and power of the proposed method by a simulation study, in which we examine independent and dependent data. The simulation study shows that the proposed method performs equivalently to the existing methods for independent survival data and performs better for dependent survival data. A study comparing survival median times for bone marrow transplants illustrates the proposed method.

Recent reproductive coercion and unintended pregnancy among female family planning clients

OBJECTIVE

Reproductive coercion (RC)--birth control sabotage and coercion by male partners to become pregnant and to control the outcome of a pregnancy--has been associated with a history of both intimate partner physical and sexual violence (IPV) and unintended pregnancy among females utilizing reproductive health services. The temporal nature of associations of RC and unintended pregnancy (distinct from the impact of IPV), however, has remained less clear.

STUDY DESIGN

A survey was administered to females aged 16-29 years seeking care in 24 rural and urban family planning clinics in Pennsylvania (n=3539).

RESULTS

Five percent of respondents reported RC in the past 3 months, and 12% reported an unintended pregnancy in the past year. Among those who reported recent RC, 21% reported past-year unintended pregnancy. Compared to women exposed to neither condition, exposure to recent RC increased the odds of past-year unintended pregnancy, both in the absence of a history of IPV [adjusted odds ratio (AOR) 1.79, 1.06-2.03] and in combination with a history of IPV (AOR 2.00, 1.15-3.48); history of IPV without recent RC was also associated with unintended pregnancy (AOR 1.80, 1.42-2.26).

CONCLUSIONS

Findings indicate the temporal proximity of the association of RC and unintended pregnancy, with recent RC related to past-year unintended pregnancy, both independently and in combination with a history of IPV. Recent RC is relatively prevalent among young women using family planning clinics and is associated with increased risk for past-year unintended pregnancy even in the absence of IPV.

IMPLICATIONS

Recent RC and a history of IPV are prevalent among female family planning clients, particularly younger women, and these experiences are each associated with unintended pregnancy. Pregnancy prevention counseling should include not only assessment for physical and sexual partner violence but also specific inquiry about RC.

Associations between race, lifecourse socioeconomic position and prevalence of diabetes among US women and men: results from a population-based panel study

BACKGROUND

Few studies have examined the degree to which racial disparities in the development of diabetes are accounted by differences in lifecourse socioeconomic position (SEP). We assessed the association between race, lifecourse SEP measures and prevalence of diabetes in a representative US sample of black and white adults.

METHODS

A generalised estimating equations approach was used with a sample of 3497 adults from the Americans' Changing Lives study. Sex-specific models were calculated to compute prevalence ratios (PR) for associations of race and SEP with self-reported diagnoses of diabetes.

RESULTS

For men, childhood and adult SEP were unrelated to diabetes, and adjustment for lifecourse SEP had little effect on the excess diabetes in blacks (PR=1.56, 95% CI 1.11 to 2.21). Adjustment for measures of lifecourse SEP reduced the PR for the association between race and diabetes in women from 1.96 (95% CI 1.52 to 2.54) to 1.40 (95% CI 1.04 to 1.87) with the respondent's education responsible for most of the reduction in the association. However, diabetes was also inversely associated with father's education, and low SEP throughout the lifecourse was associated with a nearly threefold increase in diabetes (PR=2.89, 95% CI 2.10 to 3.99).

CONCLUSIONS

Racial disparities in diabetes existed among both men and women, but lifecourse SEP was related to diabetes only among women. The pathway and cumulative hypotheses for lifecourse SEP effects on diabetes may be especially salient for women.