GEE type inference for clustered zero-inflated negative binomial regression with application to dental caries

Use of zero-inflated count data models is common in applications where the number of zero counts exceeds that predicted from a traditional count data model such as Poisson or negative binomial. When count data exhibiting inflated zero counts are correlated among subjects, a natural approach will be to fit a marginal model with the help of generalized estimating equations (GEE) that can incorporate subject-to-subject correlations. A GEE based zero-inflated negative binomial (ZINB) model is proposed to fit clustered counts with excessive zeros. However, the corresponding sandwich variance estimator appears to underestimate the true variance. The theoretical reasons for its failure are explained and a correction under additional modeling assumptions is offered. In addition, a clustered resampling (bootstrap) procedure is proposed to estimate the variance and it is shown that the bootstrap procedure captures the correct variance under no additional model assumptions. Utility of this marginal GEE based ZINB model over two other competing models has been assessed using a thorough simulation study. The resulting inference procedure is applied to study the association between the dental caries and fluoride exposures using a dataset extracted from the Iowa Fluoride Study. A number of risk factors of clinical significance are reliably identified using the proposed model.     

Family-Focused Preventive Interventions: Evaluating Parental Risk Moderation of Substance Use Trajectories.

Four years of longitudinal data from 373 families participating in a randomized intervention-control clinical trial were used to examine whether intervention effects on adolescent alcohol and tobacco use trajectories were moderated by family risk, as defined by parental social emotional maladjustment. Consistent with earlier outcome evaluations based on analyses of covariance, analyses confirmed that both the Preparing for the Drug Free Years program and the Iowa Strengthening Families Program favorably influenced alcohol use index trajectories across the time frame of the study; only the latter program, however, evidenced positive effects on a tobacco use index. Concerning the primary research question, analyses provided no support for family risk moderation of any intervention effect. Findings indicate the feasibility of developing universal preventive interventions that offer comparable benefits to all families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Universal intervention effects on substance use among young adults mediated by delayed adolescent substance initiation.

In this article, the authors examine whether delayed substance initiation during adolescence, achieved through universal family-focused interventions conducted in middle school, can reduce problematic substance use during young adulthood. Sixth-grade students enrolled in 33 rural midwestern schools and their families were randomly assigned to 3 experimental conditions. Self-report questionnaires provided data at 7 time points for the Iowa Strengthening Families Program (ISFP), Preparing for the Drug Free Years (PDFY), and control groups through young adulthood. Five young adult substance frequency measures (drunkenness, alcohol-related problems, cigarettes, illicit drugs, and polysubstance use) were modeled as distal outcomes affected by the average level and rate of increase in substance initiation across the adolescent years in latent growth curve analyses. Results show that the models fit the data and that they were robust across outcomes and interventions, with more robust effects found for ISFP. The addition of direct intervention effects on young adult outcomes was not supported, suggesting long-term effects were primarily indirect. Relative reduction rates were calculated to quantify intervention-control differences on the estimated proportion of young adults indicating problematic substance use; they ranged from 19% to 31% for ISFP and from 9% to 16% for PDFY. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hope and skepticism: Farmer and local community views on the socio-economic benefits of agricultural bioenergy

U.S. government policies and programs promoting agricultural bioenergy development have tended to prioritize national goals of energy security, economic growth and environmental improvement, while marginalizing the local experiences, views and concerns of farmers and rural communities that will produce the needed energy crops. Based on qualitative field interviews with 48 farming and non-farming participants in two switchgrass bioenergy projects (in southern Iowa and in northeastern Kentucky), this paper examines local perspectives on the potential opportunities, drawbacks, and tradeoffs of the emerging agricultural bioeconomy for rural people and places. Individual project participants expressed both positive and negative perceptions about the impacts of the agricultural bioeconomy, with local and regional revitalization being the benefit most desired and also least expected. Skepticism about the social impacts of the agricultural bioeconomy often stemmed from observations of corporate control in agriculture more generally. This research suggests that narrow instrumental views of farmers and rural communities as technical providers of energy feedstocks can be misleading, because they omit the local social and cultural context that complicates rural responses and receptivity to the development of the agricultural bioeconomy.     

Adolescents' Performance on the Iowa Gambling Task: Implications for the Development of Decision Making and Ventromedial Prefrontal Cortex.

Healthy adolescents (79 girls, 66 boys), ages 9-17, completed the Iowa Gambling Task (IGT; A. Bechara, A. R. Damasio, H. Damasio, & S. W. Anderson, 1994) as well as working memory (digit span) and behavioral inhibition (go/no-go) tasks. Cross-sectional age-related changes were seen on all 3 tasks. Gender differences were seen in IGT deck preference and attentional variables (i.e., go/no-go hit rate and forward digit span). After age, gender, and general intellectual abilities were controlled for, IGT performance was not predicted by working memory or behavioral inhibition scores. Findings suggest that the ventromedial prefrontal cortex or its connections are functionally maturing during adolescence in a manner that can be distinguished from maturation of other prefrontal regions. Development of these functions may continue into young adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Third Natures: Incubators of Public Space

Cristina Díaz Moreno and Efrén García Grinda , founders of the Madrid-based office AMID.cero9, shift the notion of the urban from the classic idea of the complete or ideal city, to one which engages with essential urban phenomena: the dynamics of confrontation, dispute and agreement between individuals, social groups and subcultures. In this way, public spaces are transformed from empty spaces into a real context for social interaction; and active involvement with social exchange becomes the main purpose of a project for a new architecture of the city.     

Is decision making really impaired in eating disorders?

Objective: Decision making has been reported to be reduced in eating disorders. However, studies are sparse and have been carried out in various selected populations. In the current study we arranged to confirm previous observations and to assess the relationship between decision making and dimensions relevant to eating disorders. Method: Patients suffering from anorexia nervosa (n = 49), bulimia nervosa (n = 38), and healthy controls (n = 83) were assessed using the Iowa Gambling Task (IGT). All patients were euthymic and free of psychotropic medication. Self-questionnaires (Eating Disorder Inventory–2; Gardner, 1991; and Eating Attitude Test; Garner & Garfinkel, 1979) were used to assess clinical dimensions relevant to eating disorders. Results: No significant differences in IGT performance were observed between patients and healthy controls or between restrictive and purging types of anorexia nervosa. No correlations were found between IGT performance and eating disorder questionnaires. Conclusion: These results do not support reduced decision making in patients with eating disorders, and suggest that previously reported alterations could be related to other clinical characteristics. This should stimulate new topic-related studies designed to reach a firm conclusion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further validation of the Iowa Sleep Disturbances Inventory.

This study examined the reliability and validity of an expanded version of the Iowa Sleep Disturbances Inventory (ISDI; Koffel & Watson, 2010) in 2 samples (219 college students and 200 psychiatric patients). The expanded ISDI includes the scales Sleep Paralysis and Sleep Hallucinations. These scales, along with the Nightmares scale, help define a higher order factor entitled Unusual Sleep Experiences. This factor was distinct from the Insomnia and Lassitude factors that were reported previously. The expanded ISDI showed strong evidence of convergent and discriminant validity with the corresponding interview ratings on a clinician rating version of the ISDI. Mean convergent correlations were .68 in students and .70 in patients. Convergent correlations were significantly higher than discriminant correlations in 99.8% of the 624 comparisons. This study also reports the associations of higher order sleep factors with questionnaire and interview measures of pathological symptoms (e.g., depression, anxiety, dissociation, and schizotypy). The Lassitude factor was specific to dysphoria, whereas the Unusual Sleep Experiences factor was specific to posttraumatic stress disorder (PTSD) and dissociation. Finally, several ISDI scales showed strong evidence of specificity in relation to pathological symptoms; in particular, there were strong associations between (a) ISDI Fatigue and measures of dysphoria, (b) ISDI Nightmares and measures of PTSD, and (c) ISDI Sleep Hallucinations and measures of dissociation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Potential Impact of Climate Change on Subsurface Drainage in Iowa’s Subsurface Drained Landscapes

The study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage and its pattern in Iowa’s subsurface drained landscapes. The contemporary (representing the decade of 1990s) and future (representing the decade of 2040s) climatic scenarios were generated by downscaling the projections of global climatic model HadCM through two regional climatic models RegCM2 and HIRHAM to a regional grid box of 52–55?km2, which contains Perry, IA. These climatic scenarios were used to drive the field scale deterministic hydrologic model DRAINMOD to simulate subsurface drainage from one of Iowa’s predominant hydric soils, WEBSter, cultivated with Continuous Corn (WEBS_CC), and equipped with a conventional drainage system (30-m drain spacing at 1.2-m drain depth). The simulation results consistently indicate an increase in subsurface drainage from WEBS_CC under future climatic scenario as compared to contemporary climatic scenario. This increase in subsurface drainage would be more in the winter months (from December to March) and early spring months (from April to May) than summer and fall months. Since subsurface drainage is a primary carrier of nitrate-nitrogen (NO3–N) from the agricultural lands, the extrapolation of this study simulations suggest that there would be a potential for increased NO3–N loss from Iowa’s subsurface drained landscapes under future (in the decade of 2040s) climatic conditions.