Showing papers by "D. Leann Long published in 2015"

A Marginalized Zero-inflated Poisson Regression Model with Random Effects

Abstract: Public health research often concerns relationships between exposures and correlated count outcomes. When counts exhibit more zeros than expected under Poisson sampling, the zero-inflated Poisson (ZIP) model with random effects may be used. However, the latent class formulation of the ZIP model can make marginal inference on the sampled population challenging. This article presents a marginalized ZIP model with random effects to directly model the mean of the mixture distribution consisting of 'susceptible' individuals and excess zeroes, providing straightforward inference for overall exposure effects. Simulations evaluate finite sample properties, and the new methods are applied to a motivational interviewing-based safer sex intervention trial, designed to reduce the number of unprotected sexual acts.

Blood levels of the heavy metal, lead, and caries in children aged 24-72 months: NHANES III.

Abstract: Lead remains a significant pollutant. It has acute toxic and chronic effects on many tissues and accumulates in teeth and bones. The researchers for this study investigated the association of blood lead levels with the extent/severity of caries as measured by the number of decayed/filled teeth of children aged 24-72 months using data from NHANES III (the Third National Health and Nutrition Examination Survey), accounting for the excess zero caries in the analysis and using less than 2 µg/dl as the reference blood lead level (n = 3,127). Zero-inflated negative binomial regression models indicated unadjusted extent/severity mean ratios of 1.79, 1.88 and 1.94 for the number of decayed/filled teeth in children whose blood lead levels were 2-5, 5-10 and >10 µg/dl, respectively, compared with children having 10 µg/dl levels of exposure. The adjusted extent/severity mean ratios were 1.84, 2.14 and 1.91, respectively, for the categories. This study indicated a strong association of blood lead levels with increasing numbers of carious teeth in children aged 24-72 months. These findings support other studies in an innovative analysis handling cases of children with no caries. The findings may inform caries risk assessment.

Parent and Metabolite Opioid Drug Concentrations in Unintentional Deaths Involving Opioid and Benzodiazepine Combinations.

Abstract: Effects of benzodiazepines on postmortem opioid parent and parent/metabolite blood concentration ratios were determined for fentanyl-, hydrocodone-, methadone-, or oxycodone-related accidental deaths. These opioids are partially metabolized by the CYP3A4 enzyme system, which is also affected by diazepam and alprazolam. Opioid/metabolite combinations examined were as follows: fentanyl/norfentanyl, hydrocodone/dihydrocodeine, methadone/EDDP, and oxycodone/oxymorphone. Parent opioid concentrations were analyzed for 877 deaths. Parent/metabolite concentration ratios were analyzed for 349 deaths, excluding cases with co-intoxicants present known to interfere with opioid elimination. Alprazolam in combination with diazepam significantly decreased median hydrocodone concentrations by 48% (p = 0.01) compared to hydrocodone alone. The methadone parent/metabolite concentration ratio was reduced by 35% in the presence of diazepam compared to methadone alone (p = 0.03). Benzodiazepines did not statistically significantly affect fentanyl or oxycodone concentrations. Possible factors affecting opioid concentrations and possible toxicity development, including any differential effects on specific opioids, should continue to be explored.

Characterization of Diphenhydramine-Related Accidental Overdose Deaths

Abstract: Characteristics of diphenhydramine (DPH)-induced accidental overdose deaths were compared to deaths without DPH present. Data from 4702 drug-induced deaths during 2005 to 2011 in four states were r...