Search PubMed⌕ Search

Biomedical subjects

Beth A Reboussin

Publications and source records attributed to Beth A Reboussin.

At least 19 recordsLinked to original sources
PubMed2007

Long-term cocaine self-administration under fixed-ratio and second-order schedules in monkeys.

RATIONALE: Studies in rodents have demonstrated that increased access to cocaine can result in increases in drug intake per unit time. OBJECTIVES: The present studies characterized long-term changes in cocaine self-administration associated with quantitatively and qualitatively different conditions of cocaine availability in monkeys. MATERIALS AND METHODS: Separate groups of rhesus monkeys (n = 6/group) self-administered cocaine (0.2 mg/kg per injection) under a fixed ratio (FR) 30 schedule for 3 h twice daily for two consecutive days each week for 1 year, or responded under a second-order FR 10 (fixed interval 3-min:S) schedule of 0.2 mg/kg per injection cocaine during daily sessions. After 18 weeks, probe sessions were conducted once per week, in which responding was maintained under a fixed interval (FI) 30-min schedule in the presence of distinct stimuli. RESULTS: Weekly cocaine intakes under the FR schedule were stable in three subjects, but increased progressively in three monkeys over 1 year. In contrast, response rates under the second-order schedule were low and stable over time. Responding under the FI 30-min schedule was higher for monkeys in the FR group and pattern of responding was not indicative of FI performance, perhaps due to experimental history. CONCLUSIONS: These data suggest that increases in cocaine intake can be observed under ratio schedules in monkeys. The use of an FI 30-min "probe" to assess changes in "drug seeking" appeared to be influenced by experimental history. These data may aid in the development of behavioral models of cocaine abuse, which focus on the compulsive nature of drug taking.

Animals↗
PubMed2006

Medical students' attitudes toward underserved patients: a longitudinal comparison of problem-based and traditional medical curricula.

Medical education has been shown to negatively influence student attitudes toward certain types of patient populations. Past research does not inform current educational practice because today's medical school environment is different from when most of the published research was conducted. There are more female students, curricular innovations such as problem-based learning have changed the framework for educational delivery, and longitudinal studies, which could inform when interventions may be needed, are uncommon. The purposes of this longitudinal, prospective cohort study were to compare the attitudes of Problem-based learning and Traditional curriculum students toward providing care for medically indigent patients as they progressed through the four-year undergraduate medical education curriculum, and to determine if gender differences were apparent and persisted over time. Attitudes of one cohort of students enrolled in separate curricula were studied. The outcome measure was the Medical Student Attitudes Toward the Underserved questionnaire, which was administered three times. A linear mixed effects regression analysis was performed to examine changes in factor scores over time and whether these changes differed between Problem-based and Traditional students, and males and females. Longitudinal findings revealed that commitment to caring for the medically underserved was greater when students entered medical school than when they graduated. Students in both curricula, as well as male and female students, experienced increasingly negative attitudes over the four year period. Decline in attitudes toward medically underserved patients was similar to previous research results. This study showed that attitudes of students were not influenced by the preclinical curriculum they experienced.

Adult↗
PubMed2006

Modeling adolescent drug-use patterns in cluster-unit trials with multiple sources of correlation using robust latent class regressions.

PURPOSE: The purpose of the study is to examine variation in adolescent drug-use patterns by using latent class regression analysis and evaluate the properties of an estimating-equations approach under different cluster-unit trial designs. METHODS: A set of second-order estimating equations for latent class models under the cluster-unit trial design are proposed. This approach models the correlation within subclusters (drug-use behaviors), but ignores the correlation within clusters (communities). A robust covariance estimator is proposed that accounts for within-cluster correlation. Performance of this approach is addressed through a Monte Carlo simulation study, and practical implications are illustrated by using data from the National Evaluation of the Enforcing Underage Drinking Laws Randomized Community Trial. RESULTS: The example shows that the proposed method provides useful information about the heterogeneous nature of drug use by identifying two subtypes of adolescent problem drinkers. A Monte Carlo simulation study supports the proposed estimation method by suggesting that the latent class model parameters were unbiased for 30 or more clusters. Consistent with other studies of generalized estimating equation (GEE) estimators, the robust covariance estimator tended to underestimate the true variance of regression parameters, but the degree of inflation in the test size was relatively small for 70 clusters and only slightly inflated for 30 clusters. CONCLUSIONS: The proposed model for studying adolescent drug use provides an alternative to standard diagnostic criteria, focusing on the nature of the drug-use profile, rather than relying on univariate symptom counts. The second-order GEE-type estimation procedure provided a computationally feasible approach that performed well for a moderate number of clusters and was consistent with prior studies of GEE under the generalized linear model framework.

Adolescent↗
PubMed2006

"Gesundheit!" sneezing, common colds, allergies, and Staphylococcus aureus dispersion.

BACKGROUND: Staphylococcus aureus is among the most important pathogens in today's hospital setting. METHODS: The effects of sneezing on the airborne dispersal of S. aureus and other bacteria were assessed in 11 healthy nasal S. aureus carriers with experimentally induced rhinovirus colds. Airborne dispersal was studied by volumetric air sampling in 2 chamber sessions with and without histamine-induced sneezing. After 2 days of preexposure measurements, volunteers were inoculated with a rhinovirus and monitored for 14 days. Daily quantitative nasal- and skin-culture samples for bacteria and nasal-culture samples for rhinovirus were obtained, cold symptoms were assessed, and volunteer activities were recorded during sessions. RESULTS: All participants developed a cold. Sneezing caused a 4.7-fold increase in the airborne dispersal of S. aureus, a 1.4-fold increase in coagulase-negative staphylococci (CoNS), and a 3.9-fold increase in other bacteria (P < .001). An additional 2.83 colony forming units (cfu) of S. aureus/m3/min, 3.24 cfu of CoNS/m3/min, and 474.61 cfu of other bacteria/m3/min were released per sneeze. Rhinovirus exposure did not change the frequency of sneezing or airborne dispersal. Having respiratory allergies increased the spread of S. aureus by 3.8-fold during sneezing sessions (P < .001). CONCLUSION: Nasal S. aureus carriers disperse a significant amount of S. aureus into the air by sneezing. Experimental colds do not alter bacterial dispersal, but respiratory allergies multiply the effect of dispersing S. aureus.

Adult↗
PubMed2006

Is there epidemiological evidence to support the idea that a cocaine dependence syndrome emerges soon after onset of cocaine use?

The present study uses latent class methods and multiple regression to shed light on hypothesized cocaine dependence syndromes experienced by community residents, who initiated cocaine use within 24 months of survey assessment, and explores possible variation in risk. Identified within public use data files from the United States National Household Surveys on Drug Abuse (NHSDA), and with assessments completed between 1995 and 1998, the study sample consists of 927 recent-onset cocaine users, defined as having initiated cocaine use no more than 24 months prior to assessment (approximate median elapsed time since onset of use approximately 12-13 months). The NHSDA included items to assess seven clinical features often associated with cocaine dependence, which were used in latent class modeling. Empirically derived latent classes, in conjunction with prior theory, tend to support a three-class solution, according to which 4% of recent-onset users are members of a class that resembles the DSM-IV cocaine dependence syndrome (mean: 5.4 clinical features (CF)); 16% might be in a cocaine dependence prodrome (mean: 2.4 CF); 80% of recent-onset cocaine users had few or no clinical features (mean<1 CF). Results from latent class regressions indicate that susceptibility to rapid transition from first cocaine use to onset of the LCA-assigned cocaine dependence syndrome might depend upon whether the user starts smoking crack-cocaine and, independently, age at first cocaine use.

Adolescent↗
PubMed2006

Progestins affect mechanism of estrogen-induced C-reactive protein stimulation.

PURPOSE: To determine whether the mechanisms of C-reactive protein production differ depending on the presence or absence of a progestin in the regimen. SUBJECTS AND METHODS: We examined data from the Postmenopausal Estrogen Progestin Intervention (PEPI) study, a 5-group (3 different combined estrogen-progestin regimens, conjugated equine estrogen-only, and placebo) randomized clinical trial. This substudy included 221 postmenopausal women assigned to active treatment groups who took at least 80% of pills and had stored plasma specimens available to assess 12-month changes in estrone, sex hormone binding globulin, interleukin (IL)-6, and C-reactive protein levels. RESULTS: All treatments resulted in increases in estrone, sex hormone binding globulin, and C-reactive protein at 12 months compared with baseline values. In all progestin-containing groups, 12-month change in IL-6 was positively correlated with 12-month change in C-reactive protein (r between 0.34 and 0.65, each P <.010). By contrast, in the conjugated equine estrogen-only group, 12-month change in IL-6 was negatively correlated with 12-month change in C-reactive protein (r value -0.31, P = .055). In adjusted models predicting 12-month C-reactive protein change, an interaction between change in IL-6 and treatment group was highly significant (P=.0008-P <.0001) for each of the progestin-containing groups compared with the conjugated equine estrogen-only group. In the conjugated equine estrogen-only group, the change in C-reactive protein per unit increase in IL-6 was -0.88, whereas in the progestin-containing groups it ranged from 1.46 to 2.85 (P <.0001 for each comparison with conjugated equine estrogen-only). CONCLUSION: Progestins in combination with conjugated equine estrogen potentiate the IL-6 (inflammatory)-mediated stimulation of C-reactive protein. These findings support the hypothesis that progestins plus estrogen, not estrogen alone, generate C-reactive protein through an inflammatory mechanism.

C-Reactive Protein↗
PubMed2006

Predictors of suicide attempts: state and trait components.

The authors examined the state and trait components of 3 predictors of suicide attempts (depression, hopelessness, and anxiety), and their relationship to suicidal behavior. Self-report questionnaire and interview data from 180 adolescents enrolled in a prospective naturalistic study were analyzed. Between 23% and 30% of the variance in the predictors was attributable to subjects' trait levels of these variables; the trait, as well as the state, components of the predictor variables were interrelated; and trait levels of these variables were consistently related to suicide attempts. To reduce long-term risk of suicide attempts, clinicians should focus not only on reducing short-term distress but also on reducing individuals' more enduring patterns (trait levels) of negative affectivity.

Adolescent↗
PubMed2005

A latent class analysis of underage problem drinking: evidence from a community sample of 16-20 year olds.

The aim of this paper is to shed light on the nature of underage problem drinking by using an empirically based method to characterize the variation in patterns of drinking in a community sample of underage drinkers. A total of 4056 16-20-year-old current drinkers from 212 communities in the US were surveyed by telephone as part of the National Evaluation of the Enforcing Underage Drinking Laws (EUDL) Program. Latent class models were used to create homogenous groups of drinkers with similar drinking patterns defined by multiple indicators of drinking behaviors and alcohol-related problems. Two types of underage problem drinkers were identified; risky drinkers (30%) and regular drinkers (27%). The most prominent behaviors among both types of underage problem drinkers were binge drinking and getting drunk. Being male, other drug use, early onset drinking and beliefs about friends drinking and getting drunk were all associated with an increased risk of being a problem drinker after adjustment for other factors. Beliefs that most friends drink and current marijuana use were the strongest predictors of both risky problem drinking (OR=4.0; 95% CI=3.1, 5.1 and OR=4.0; 95% CI=2.8, 5.6, respectively) and regular problem drinking (OR=10.8; 95% CI=7.0, 16.7 and OR=10.2; 95% CI=6.9, 15.2). Young adulthood (ages 18-20) was significantly associated with regular problem drinking but not risky problem drinking. The belief that most friends get drunk weekly was the strongest discriminator of risky and regular problem drinking patterns (OR=5.3; 95% CI=3.9, 7.1). These findings suggest that underage problem drinking is most strongly characterized by heavy drinking behaviors which can emerge in late adolescence and underscores its association with perceptions regarding friends drinking behaviors and illicit drug use.

Adolescent↗
PubMed2005

The Fagerström test for nicotine dependence: a comparison of standard scoring and latent class analysis approaches.

The classification of being tobacco dependent obtained via the established scoring method of the Fagerström test for nicotine dependence (FTND) is compared to a method that bases classification on the pattern of item responses. Young adults participating in a longitudinal study, who indicated they had ever smoked, were asked six standardized items (n = 962; mean age 21 years). By standard scoring, the mean FTND score was 1.9 (S.E.= 2.3): 66% of the smokers qualified for a very low level of dependence, 17% low, 9% moderate, and 9% a high level of dependence. Response patterns detected by latent class analysis (LCA) indicated class differences based on severity gradations and of qualitative content. Three profiles of tobacco dependence were found: a non-dependent class (50%), a class manifesting a moderate number of dependence features (31%), and more severely affected class (19%). The vast majority of smokers (three-fourth) were classified congruently by these two methods. Discrepancies involved LCA classifying smokers into a higher level of dependence when compared to the conventional scoring classification. Patterns of dependence features obtained from population samples that include a wide range of smokers may provide insight into possible phenotypic differences among tobacco smokers, particularly when LCA methods are used to complement standard scoring methods.

Adult↗
PubMed2005

Positive association between mammographic breast density and bone mineral density in the Postmenopausal Estrogen/Progestin Interventions Study.

INTRODUCTION: Mammographic breast density is a strong independent risk factor for breast cancer. We hypothesized that demonstration of an association between mammographic breast density and bone mineral density (BMD) would suggest a unifying underlying mechanism influencing both breast density and BMD. METHODS: In a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions Study (PEPI), participants were aged 45 to 64 years and were at least 1 year postmenopausal. Mammographic breast density (percentage of the breast composed of dense tissue), the outcome, was assessed with a computer-assisted percentage-density method. BMD, the primary predictor, was measured with dual-energy X-ray absorptiometry. Women quitting menopausal hormone therapy to join PEPI were designated recent hormone users. RESULTS: The mean age of the 594 women was 56 years. The average time since menopause was 5.6 years. After adjustment for age, body mass index, and cigarette smoking, in women who were not recent hormone users before trial enrollment (n = 415), mammographic density was positively associated with total hip (P = 0.04) and lumbar (P = 0.08) BMD. Mammographic density of recent hormone users (n = 171) was not significantly related to either total hip (P = 0.51) or lumbar (P = 0.44) BMD. In participants who were not recent hormone users, mammographic density was 4% greater in the highest quartile of total hip BMD than in the lowest. In participants who were not recent hormone users, mammographic density was 5% greater in the highest quartile of lumbar spine BMD than in the lowest. CONCLUSION: Mammographic density and BMD are positively associated in women who have not recently used postmenopausal hormones. A unifying biological mechanism may link mammographic density and BMD. Recent exogenous postmenopausal hormone use may obscure the association between mammographic density and BMD by having a persistent effect on breast tissue.

Bone Density↗
PubMed2005

The association of endogenous sex steroids and sex steroid binding proteins with mammographic density: results from the Postmenopausal Estrogen/Progestin Interventions Mammographic Density Study.

Mammographic density is an independent risk factor for breast cancer. In postmenopausal women, higher levels of endogenous sex steroids are associated with an increased risk of breast cancer. Limited prior data suggest that endogenous sex steroids either are not associated (total estradiol and progesterone) or are negatively associated (free estradiol) with higher mammographic density. To analyze the associations between endogenous sex steroids and mammographic density, the authors conducted a 1998-2005 cross-sectional analysis of baseline clinical trial data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial for US women who had not used hormone therapy for at least 3.1 months prior to baseline. In models adjusted for age, body mass index, parity, prior use of hormone therapy, time since last use of hormone therapy, and the interaction between prior hormone therapy use and time since last hormone therapy use, higher levels of estrone (beta = 0.0013, p = 0.014), estradiol (beta = 0.0009, p = 0.009), and bioavailable estradiol (beta = 0.0021, p = 0.018) were statistically significantly related to greater mammographic density. (Beta coefficients express the increment in mammographic density per-unit increment (pg/ml) of each hormone.) These results suggest that some sex steroids may increase the risk of breast cancer by stimulating breast epithelial or stromal proliferation, which appears on a mammogram as higher density.

Breast↗
PubMed2005

The effects of hormone therapy on the markers of inflammation and endothelial function and plasma matrix metalloproteinase-9 level in postmenopausal women: the postmenopausal estrogen progestin intervention (PEPI) trial.

OBJECTIVE: The objective of this study was to determine whether oral conjugated equine estrogen (CEE) alone or with one of the three progestin regimens causes changes in biomarkers predictive of adverse cardiovascular events: C-reactive protein (CRP), interleukin-6 (IL-6), intercellular adhesion molecule (ICAM) and matrix metalloproteinase-9 (MMP-9). METHODS AND RESULTS: The analysis included 271 postmenopausal women from the postmenopausal estrogen progestin intervention (PEPI) trial. Plasma levels of biomarkers were measured on frozen samples obtained at baseline, 1- and 3-year follow-up visits. Multivariable linear mixed effects models were used to estimate changes in CRP, IL-6, ICAM and MMP-9 levels from baseline to follow-up visits by treatment groups. Women assigned to CEE only or CEE plus a progestin had 121 and 150% 1-year increase in CRP levels, respectively. In contrast, these treatments caused no significant change in IL-6 levels. Women assigned to CEE with or without a progestin had a 6-8% decline in ICAM and a 26-33% decline in MMP-9. CONCLUSIONS: The linkage between CEE alone or with a progestin and increased cardiovascular events may be associated with a rise in CRP level, but not through the mechanisms of IL-6-mediated inflammation, endothelial dysfunction or increased MMP activity.

C-Reactive Protein↗
PubMed2005

The structure of posttraumatic stress disorder: latent class analysis in 2 community samples.

CONTEXT: Latent structure analysis of DSM-IV posttraumatic stress disorder (PTSD) can help clarify how persons who experience traumatic events might be sorted into clusters with respect to their symptom profiles. Classification of persons exposed to traumatic events into clinically homogeneous groups would facilitate further etiologic and treatment research, as well as research on the relationship of trauma and PTSD with other disorders. OBJECTIVES: To examine empirically the structure underlying PTSD criterion symptoms and identify discrete classes with similar symptom profiles. DESIGN: Data on PTSD symptoms from trauma-exposed subsets of 2 community samples were subjected to latent class analysis. The resultant classes were studied in associations with trauma type and indicators of impairment. SETTING: The first sample is from the Detroit Area Survey of Trauma (1899 trauma-exposed respondents with complete data) and the second is from a mid-Atlantic study of young adults conducted by The Johns Hopkins University Prevention Research Center, Baltimore, Md (1377 trauma-exposed respondents with complete data). PARTICIPANTS: Respondents in the 2 community samples who experienced 1 or more qualifying PTSD-level traumatic events. MAIN OUTCOME MEASURES: Number, size, and symptom profiles of latent classes. RESULTS: In both samples, analysis yielded 3 classes: no disturbance, intermediate disturbance, and pervasive disturbance. The classes also varied qualitatively, with emotional numbing distinguishing the class of pervasive disturbance, a class that approximates the subset with DSM-IV PTSD. Members of the pervasive disturbance class were far more likely to report use of medical care and disruptions in life or activities. CONCLUSIONS: The 3-class structure separates trauma-exposed persons with pervasive disturbance (a class that approximates DSM-IV PTSD) from no disturbance and intermediate disturbance, a distinction that also helps identify population subgroups with low risk for any posttrauma disturbance. The results suggest that the structure of PTSD is ordinal and configurational and that emotional numbing differentiates the class with pervasive disturbance. These results should motivate prospective research of persons who have experienced trauma to trace the emergence of posttrauma symptoms and the timing of emotional numbing relative to other symptoms.

Adult↗
PubMed2005

Severity of emotional and behavioral problems among poor and typical readers.

The purpose of this study was to examine the severity of behavioral and emotional problems among adolescents with poor and typical single word reading ability (N = 188) recruited from public schools and followed for a median of 2.4 years. Youth and parents were repeatedly assessed to obtain information regarding the severity and course of symptoms (depression, anxiety, somatic complaints. aggression, delinquent behaviors, inattention), controlling for demographic variables and diagnosis or ADHD. After adjustment for demographic variables and ADHD, poor readers reported higher levels of depression, trait anxiety, and somatic complaints than typical readers, but there were no difference, in reported self-reported delinquent or aggressive behaviors. Parent reports indicated no difference, in depression, anxiety or aggression between the two groups but indicated more inattention, somatic complaints, and delinquent behaviors for the poor readers. School and health professionals should carefully assess youth with poor reading for behavioral and emotional symptoms and provide services when indicated.

Adolescent↗
PubMed2005

Dispersal of Staphylococcus aureus into the air associated with a rhinovirus infection.

OBJECTIVE: To determine whether healthy adult nasal carriers of Staphylococcus aureus can disperse S. aureus into the air after rhinovirus infection. DESIGN: We investigated the "cloud" phenomenon among adult nasal carriers of S. aureus experimentally infected with a rhinovirus. Eleven volunteers were studied for 16 days in an airtight chamber wearing street clothes, sterile garb, or sterile garb plus surgical mask; rhinovirus inoculation occurred on day 2. Daily quantitative air, nasal, and skin cultures for S. aureus; cold symptom assessment; and nasal rhinovirus cultures were performed. SETTING: Wake Forest University School of Medicine, Winston-Salem, North Carolina. PARTICIPANTS: Wake Forest University undergraduate or graduate students who had persistent nasal carriage of S. aureus for 4 or 8 weeks. RESULTS: After rhinovirus inoculation, dispersal of S. aureus into the air increased 2-fold with peak increases up to 34-fold. Independent predictors of S. aureus dispersal included the time period after rhinovirus infection and wearing street clothes (P < .05). Wearing barrier garb but not a mask decreased dispersal of S. aureus into the air (P < .05). CONCLUSION: Virus-induced dispersal of S. aureus into the air may have an important role in the transmission of S. aureus and other bacteria.

Adult↗
PubMed2004

Early childhood misbehavior and the estimated risk of becoming tobacco-dependent.

In this study, the authors focused on signs of early childhood misbehavior that might be linked to the risk of becoming tobacco-dependent. Standardized teacher ratings of misbehavior were obtained for an epidemiologic sample of first graders entering an urban mid-Atlantic public school system in 1985 and 1986. Fifteen years later, 1,692 of the students were reassessed (nearly 75% of the original sample). As adults, 962 participants indicated that they had tried tobacco at least once; 66% of the 962 had become daily users. Latent class analysis of items on the Fagerström Test for Nicotine Dependence gave evidence of three classes pertinent to tobacco dependence syndrome in smokers by young adulthood: one nondependent class of smokers (50% of smokers), a class of smokers experiencing a moderate number of dependence features (31%), and a third class that was more severely affected (19%), as manifest in the need to smoke immediately after waking and smoking when ill. With or without adjustment for covariates, higher levels of teacher-rated childhood misbehavior at entry into primary school were associated with a modest excess risk of becoming tobacco-dependent by young adulthood (risk ratio = 1.6, 95% confidence interval: 1.1, 2.5). Interventions that seek to improve childhood behavior might reduce early onset tobacco smoking and risk of tobacco dependence among smokers.

Adult↗
PubMed2004

Post-treatment change in serum estrone predicts mammographic percent density changes in women who received combination estrogen and progestin in the Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial.

PURPOSE: Postmenopausal estrogen and progestin therapy (EPT) increases mammographic percent density and breast cancer risk substantially more than does estrogen therapy alone. We determined whether increases in serum estrone as a function of treatment predict increases in mammographic percent density. METHODS: We measured mammographic percent density and serum estrone levels in participants in the Postmenopausal Estrogen/Progestin Interventions Trial who were randomly assigned to receive conjugated equine estrogens (CEE) 0.625 mg/d; CEE and medroxyprogesterone acetate (MPA) 10 mg on days 1 to 12 per 28-day cycle; CEE and MPA 2.5 mg/d; or CEE and micronized progesterone (MP) 200 mg on days 1 to 12 per 28-day cycle. We used linear regression to determine whether serum estrone changes predicted mammographic percent density changes from baseline to 1 year. RESULTS: Mammographic percent density increased with increasing change in estrone level in the EPT groups, but not in the CEE group. Combined, the mammographic percent density in the three EPT groups demonstrated an absolute increase of 2.95% per 100 pg/mL increase in serum estrone level (P =.0003). The absolute increases were 4.09% (P =.0018) in the CEE + MPA continuous group, 2.79% (P =.0292) in the CEE + MPA cyclical group, and 1.40% (P =.36) in the CEE + MP group, but the differences among the EPT groups were not statistically significant. CONCLUSION: Greater increase in serum estrone level as a function of treatment is a significant predictor of increase in mammographic percent density in women randomly assigned to the combination of estrogen and progestin.

Breast↗