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PubMed2000

Adolescent cigarette smoking in U.S. racial/ethnic subgroups: findings from the National Education Longitudinal Study.

Using nationally representative data for 16,454 8th graders and 13,840 10th graders, we explore racial/ethnic differences in "daily cigarette initiation," beginning to smoke on a daily basis between baseline interviews and reinterviews conducted two years later. In both samples, the initiation rate among whites is more than double the rate among blacks and higher than rates among Asian/Pacific Islanders and Hispanics. Risk factors at the individual, family, and peer-group levels of analysis do not explain most racial/ethnic differences. We develop alternative hypotheses by extending theories of cigarette use to the school level, and we test them using multilevel models: Consistent with social learning theory, cigarette risk among blacks and Hispanics decreases as the percentage of racial/ethnic minority students in the school increases. Consistent with strain theory, cigarette risk increases with the academic competitiveness of the school--especially among females--after controlling for the adolescent's academic performance.

Adolescent↗
PubMed2006

Serial echocardiographic assessment of neo-aortic regurgitation and root dimensions after the modified Ross procedure.

BACKGROUND AND AIM OF THE STUDY: Concern exists regarding progressive root dilatation after the modified Ross procedure. The present prospective echocardiographic study aimed to provide further insight into neo-aortic regurgitation (nAR) and neoaortic root dimensions over time in adult Rotterdam Ross root patients, and to study potential risk factors for nAR and dilatation. METHODS: All Rotterdam Ross patients aged > or = 16 years at surgery were subjected to a prospective biennial standardized echocardiographic protocol. Analysis over time of nAR according to the jet length and jet diameter method, autograft annulus and sinotubular junction (STJ) diameters was carried out using a multilevel linear model in 90 patients who had two or more echocardiographic measurements (mean 5; range 2-9; total 458) up to 14 years (mean 7 years) after surgery. RESULTS: The mean (+/- SE) initial postoperative jet length nAR was grade 0.9 +/- 0.09, and the annual increase 0.1 +/- 0.02 (p < 0.001). Initial annulus and STJ diameters were 25 +/- 0.5 mm and 36 +/- 0.6 mm, while annual increases were 0.4 +/- 0.07 mm and 0.5 +/- 0.09 mm, respectively (p < 0.001). Patients who eventually underwent an autograft reoperation (n = 10) had significantly greater initial nAR and greater progression of nAR, and a greater initial annulus diameter. The annual annulus and STJ diameter increase was greater in patients who underwent autograft reoperation. Compared to freestanding root replacement, patients with inclusion cylinder aortic root replacement had smaller initial annulus and STJ diameters that did not increase over time. Female gender was associated with a greater initial jet length and jet diameter nAR and a greater increase over time in jet diameter nAR. Preoperative aortic regurgitation or combined aortic stenosis and regurgitation were associated with greater initial annulus and STJ diameters. Neither bicuspid valve disease, patient age, preoperative ascending aorta aneurysm, prior aortic valve surgery nor hypertension had an effect on initial or progression of nAR, annulus, and STJ diameter. CONCLUSION: The annual increase in nAR and root dimensions is small, but persistent, after autograft aortic root replacement in adults, and further reoperations should be anticipated. Use of the inclusion cylinder root replacement technique seems to prevent neo-aortic dilatation.

Adolescent↗
PubMed1996

A novel technique for laminoplasty augmentation of spinal canal area using titanium miniplate stabilization. A computerized morphometric analysis.

STUDY DESIGN: Titanium miniplates are used to secure the posterior elements in the open position after expansive open-door laminoplasty. Preoperative and postoperative spinal canal dimensions are measured to assess the effectiveness of this technique. OBJECTIVES: To develop a simple yet effective technique to stabilize the posterior elements after laminoplasty and to compare preoperative and postoperative spinal canal dimensions to accepted normal values. SUMMARY OF BACKGROUND DATA: Expansive open-door laminoplasty has been offered as a simple alternative to laminectomy, which has been associated with postoperative kyphosis. Although the technique of laminoplasty is effective, a simple and reliable method of holding the posterior elements open has not been described. METHODS: Ten myelopathic patients with multilevel cervical canal stenosis secondary to spondylosis or ossification of the posterior longitudinal ligament were treated with an expansive open-door laminoplasty. The posterior elements were stabilized in the open position with titanium miniplates. Computer-assisted morphometric analysis was performed on preoperative and postoperative computed tomography scans to obtain spinal canal dimensions. Plain radiographs were used to monitor construct integrity. RESULTS: The preoperative sagittal canal diameter was 8.2 +/- 0.96 mm, and the canal area was 180.6 +/- 33.7 mm2. These dimensions increased after surgery to 16.6 +/- 1.5 mm and 321.9 +/- 29.7 mm2, respectively. The titanium miniplate constructs did not fail during the follow-up period (mean, 26.4 months), and the decompression was maintained. The single significant complication was transient C5 radiculopathy. CONCLUSIONS: Normal canal dimensions can be reestablished with open-door laminoplasty. Achieving and maintaining an increased sagittal canal diameter is probably the most important change in anatomic parameters to facilitate neurologic recovery. The use of titanium miniplates to stabilize the posterior elements after laminoplasty is a simple, durable, and effective technique to maintain the increased sagittal diameter of the spinal canal.

Adult↗
PubMed2005

Partner aggression and problem drinking across the lifespan: how much do they decline?

Cross-sectional analyses from nationally-representative samples demonstrate significant age-related trends in partner aggression and problem drinking. Both behaviors are most prevalent in the early to mid-twenties and increasingly less common thereafter. Aggregate associations based on percentage of individuals displaying the behavior in each age range are dramatically stronger than those found when correlating individuals' ages and behavior. Multilevel modeling demonstrates that group-level effects do not mask associations found at the level of the individual for either problem drinking or partner aggression. An analysis of recent abstracts from psychology journals showed that issues of aggregate and individual data are rarely if ever discussed, and even well-known statistics books in psychology rarely discuss such issues. The interpretation of aggregate data will become increasing important as psychologists themselves, and in collaboration with epidemiologists and sociologists, have access to large data sets that allow for data aggregation. Both aggregate and individual analyses are valid, although they provide answers to different questions. Individual analyses are necessary for predicting individual behavior; aggregate analyses are useful in policy planning for large scale prevention and intervention. Strengths and limitations of cross-sectional community samples and aggregate data are also discussed.

Adolescent↗
PubMed2006

Public health is an interdiscipline, and about wholes and parts: indeed, critical health psychology needs to join forces.

Hepworth's assessment of critical health psychology's capacity to contribute to public health promotion (this issue) is commented on and supplemented by selected issues relevant to Hepworth's timely call for interdisciplinary research and action in this context. Drawing on eco-epidemiology, multilevel research strategies are suggested that comprehensively account for individual/psychological and population/sociological factors. It is delineated how health promotion policies may be backed by psychologically informed policy analysis. Regarding health, it is argued to keep scrutinizing ill-health and to resist simplistic notions of quality of life or wellness but also to enhance these by incorporating concepts from positive psychology. Finally, it is considered whether trans disciplinarity may be in aid of fully realizing the potentials of blending the merits of health psychology and public health.

Behavioral Medicine↗
PubMed2005

Anterior cervical discectomy and fusion involving a polyetheretherketone spacer and bone morphogenetic protein.

OBJECT: The authors reviewed clinical and radiographic outcomes in patients who had undergone anterior cervical discectomy and fusion (ACDF) involving the placement of polyetheretherketone (PEEK) spacers filled with recombinant human bone morphogenetic protein (rhBMP)-2. METHODS: Data obtained in 24 cases were retrospectively evaluated. The follow-up period ranged from 12 to 16 months (mean 13 months). Fifteen patients presented with radiculopathy, eight with myeloradiculopathy, and one with quadriparesis. Single-level ACDF was performed in 12 patients, two-level ACDF in nine, and three-level ACDF in three. Clinical outcomes were assessed using Odom criteria, and fusion was assessed by examining flexion-extension radiographs and computerized tomography scans in cases in which arthrodesis was questionable. Follow-up data were available for 23 patients. One patient died of medical complications unrelated to surgery 4 weeks after ACDF. Clinical outcomes were rated as good/excellent in 22 patients (95%) and fair in one (5%). Solid radiographically documented fusion, with evidence of solid bridging bone and no instability on flexion-extension x-ray films, was present in all cases. Complications included transient recurrent laryngeal nerve injury in one case, transient C-5 paresis in one, cerebrospinal fluid leakage in one, and transient dysphagia in two. CONCLUSIONS: Analysis of the results indicated that ACDF involving an rhBMP-2-filled PEEK spacer leads to good clinical outcomes (by Odum criteria) and solid fusion (even in multilevel cases) while avoiding the complications associated with harvesting iliac crest bone grafts.

Adult↗
PubMed2001

Ultrastructural morphometric analysis of thymus epithelial cells two months after pinealectomy.

The late effect of surgical ablation of the pineal gland on the morphometric changes of epithelial cells of rat thymus were investigated. The aim of this study was to determine a possible existence of sex related changes in the thymus epithelial cell after pinealectomy and to possibly clarify the correlation between the pineal gland and the thymus. Stereological ultrastructural parameters of the thymus cortical and medullar epithelial cells of male and female rats two months after pinealectomy are reported. A group of animals was submitted to surgery for ablation of pineal gland. The control group (shame-pinealectomized animals) underwent to the same surgical procedure but without removal of pineal gland. Animals were sacrificed 60th days after surgery. Para-sagittal thymus specimens were fixed by immersion in glutaraldehyde and processed for transmission electron microscopy. The volume and surface density (Vv, Sv) of nucleus and cytoplasm of cortical and medullar thymus epithelial cells were calculated using the Weibel's multipurpose test system and multilevel sampling technique on electron micrographs. Volume and surface density of mitochondria (Vvm, Svm), endoplasmic reticulum (Vvr, Svr), vacuole (Vvv) as well as numerical density of mitochondria (Nvm) were evaluated at different magnification levels. Our analysis confirmed a statistically significant increase in Vv of endoplasmic reticulum and vacuoles in both sex of pinealectomized rats. Sv of plasmalema, endoplasmic reticulum and mitochondrial membrane were markedly increased in thymus medullar epithelial cells of pinealectomized rats. Vv of mitochondria was significantly increased in cortical epithelial cells of pinealectomized animals. These results confirm that a correlation between pineal gland and thymus exists. However the present findings seem to support the concept of sex independent inhibitory action of pineal gland on thymus cortical and medullar epithelial cells.

Animals↗
PubMedDate not supplied

Cyclic nucleotides in the development of alcohol tolerance and dependence: a commentary.

This paper aims to outline some of the caveats inherent in studies on first and second messengers in the central nervous system as related to tolerance and dependence. Analysis of systems based on measures of first and second messengers may be an over-simplification, since the actual molecular consequences of neurotransmission might result in a multilevel cascade of many sequential messages including protein kinase activation and protein phosphorylation and/or dephosphorylation.

Adenylyl Cyclases↗
PubMedDate not supplied

An analytic strategy for modeling multiple-item responses: a breast cancer symptom example.

BACKGROUND: Item Response Theory (IRT) is increasingly applied in health research to combine information from multiple-item responses. IRT posits that a person's susceptibility to a symptom is driven by the interaction of the characteristics of the symptom and person. This article describes the statistical background of incorporating IRT into a multilevel framework and extends this approach to longitudinal health outcomes, where the self-report method is used to construct a multi-item scale. METHODS: A secondary analysis of data from 2 descriptive longitudinal studies is performed. The data include 21 symptoms reported across time by 350 women with breast cancer. A 3-level hierarchical linear model (HLM) was used for the analysis. Level 1 models the item responses, consisting of symptom presence or absence. Level 2 models the trajectory of each individual, representing change over time of the IRT-created latent variable symptom experience. Level 3 explains that trajectory using person-specific characteristics such as age and location of care. The purpose of the analysis is to examine if older and younger women with breast cancer differ in their symptom experience trajectory after controlling for location of care. RESULTS: Fatigue and pain were the most prevalent symptoms. The symptom experience of women with breast cancer was found to improve over time. Neither age nor location of care was significantly associated with the symptom experience trajectory. DISCUSSION: Embedding IRT into an HLM framework produces several benefits. The example provided demonstrates benefits through the creation of a latent symptom experience variable that can be used either as an outcome or as a covariate in another model, examining the latent symptom experience trajectory and its relationship with covariates at the individual level, and managing symptom nonresponse.

Adult↗
PubMed2005

Mixed-effects variance components models for biometric family analyses.

Recent substantive research on biometric analyses of twin and family data has used both a biometric path analysis model (PAM) and a biometric variance components model (VCM). Methodological research on these same topics have suggested benefits of using linear structural equation model algorithms (SEMA) as well as mixed effect multilevel algorithms (MEMA). To better understand the potential similarities and differences among these approaches we first highlight the algebraic equivalence between the standard biometric PAM and the corresponding biometric VCM models for family data. Second, we demonstrate how several SEMA programs based on either the PAM or VCM approach produce equivalent estimates for all phenotypic and biometric parameters. Third, we show how the biometric VCM approach (but not the PAM approach) can be easily programmed using current MEMA programs (e.g., SAS PROC MIXED). We then expand the scope of these different approaches to include measured covariates, observed variable interactions and multiple relatives within each family. MEMA software is compared to SEMA software for programming complex models, including the flexibility of data input, treatment of missing data, inclusion of covariates, and ease of accommodating varying numbers of observations (per family or individual).

Algorithms↗
PubMed2001

Conservative management of dynamic equinus in diplegic children treated by gait improvement surgery.

Multilevel surgery for gait improvement was performed on twelve ambulatory children with diplegic type of cerebral palsy and dynamic equinus deformity. Dynamic equinus deformities were defined as those who had an equinus at initial contact during preoperative gait analysis, and where the equinus deformity was correctable passively during physical examination. Ankle function was evaluated by clinical examination and gait analysis before surgery, and at least 3 years after surgery. The ankle showed an increase in dorsal flexion at initial contact, at single stance and in swing. There was an increase in dorsal flexion at the beginning of push-off, without a decrease in the range of motion of the ankle during push-off. Ankle moments demonstrated significant improvement in the maximum flexor moment in the second half of single stance. There was a change from abnormal generation of the energy in mid-stance to the normal pattern of energy absorption. Positive work during push-off was significantly increased. Conservative management of dynamic equinus deformities combined with multilevel surgery to correct other deformities of the locomotion system resulted in significant improvements in ankle function during gait.

Adolescent↗
PubMedDate not supplied

Staphylococcus aureus carrier state among elderly residents of a long-term care facility.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) infections have recently become a major concern in long-term care facilities (LTCF). Patients that have been colonized with MRSA in general hospitals may introduce the organisms into LTCF, and these can become reservoirs for the pathogen. Our objective was to evaluate the rate of colonization by S aureus, especially MRSA, in elderly residents of a large LTCF, and to find factors that predispose to it. METHODS: A nasal culture was obtained from randomly selected patients in an Israeli LTCF. Inclusion criteria were absence of active infection and no antibiotic treatment in the preceding month. The carrier state was defined when two consecutive cultures were positive for S aureus. RESULTS: The study population comprised 270 patients, aged 81 +/- 9.3 years and from all types of wards. Of these, 63 (23.3%) were carriers of S aureus and 17 of those (27%) had MRSA. From univariate analysis, the carrier state was associated with antibiotic treatment or an invasive procedure in the previous 3 months, and with a prior MRSA infection. Subacute LTCF departments had a higher carrier rate than the chronic care wards. CONCLUSIONS: In this large multilevel facility, 6.2% of the patients were MRSA carriers, and came predominantly from the subacute departments, suggesting an influx from general hospitals. This information and the identification of factors associated with MRSA infection permit the development of an institutional infection control program.

Aged↗
PubMed2004

Passive tactile sensibility in edentulous subjects treated with dental implants: a pilot study.

STATEMENT OF PROBLEM: Edentulous patients treated with implant-supported prostheses have shown increased passive tactile sensibility compared with those using conventional complete dentures. This is thought to be due to the close mechanical coupling between the implant and bone via the osseointegrated interface, yet the phenomenon has received little attention. PURPOSE: The purpose of this study was to measure passive tactile sensibility in a group of edentulous subjects treated with dental implants, and to relate the measured sensibility to a range of factors thought to be of possible relevance, namely, patient age, gender, time since implant placement, implant length, and implant separation. MATERIAL AND METHODS: Twenty edentulous subjects successfully treated with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. The inclusion criteria were : (1) age of less than 50 years, (2) a period of at least 12 months since implant placement, (3) implant length of at least 10 mm and of standard diameter (excluding narrow and wide platform designs), and (4) implant separation of at least 18 mm. Using a computer-controlled custom-made device, pushing forces (2.1, 2.4, 2.7, and 3.0 N/s) were applied directly and perpendicular to the long axes of the implant abutments until the subjects felt the first sensation of pressure. The magnitude of these forces was measured with an integral transducer. The applied force had a ramped staircase pattern, and force application rates were varied between 2.1 and 3.0 N/s. Multilevel modeling was used to analyze the collected data (alpha=.05). RESULTS: The threshold values of passive tactile sensibility ranged between 3.1 and 15.7 N (mean 10.9; SD 3.9). Analysis failed to show any significant association between passive tactile sensibility and the variables studied. CONCLUSION: Within the limitations of this study, which included a small sample size, no relationship was found between passive tactile sensibility associated with long-standing implants and any of the variables studied (age, gender, time since implant placement, implant length, and implant separation).

Age Factors↗
PubMed2000

Death and deprivation: an exploratory analysis of deaths in the health and lifestyle survey.

An analysis is undertaken of deaths of respondents in the UK- representative Health and Lifestyle Survey. The sample was originally interviewed in 1984/5 and followed initially until May 1997. Using multilevel logistic and Cox-proportional hazards models, the relationships between death and a wide range of social circumstances and behaviours is explored. It is found that place deprivation interacts with individual social class in accounting for variations in mortality. This is the case even when account is taken of personal health-related behaviour. There appears to be some evidence of a threshold relationship such that the differential effects of social class are only found at high-levels of deprivation. No statistically significant interactions are found for social and behavioural variables, for behavioural and place deprivation variables, and for social and place deprivation variables with the exception of social class. The study is deliberately exploratory and a wide range of models have been fitted which will be subject to more rigorous evaluation as the HALS death study proceeds.

Health Behavior↗
PubMed2001

Hierarchical modeling of paired comparison data.

The method of paired comparisons belongs to a small group of techniques that provide explicit information about the consistency of individual and aggregated choices. This article investigates the link between the individual- and group-level judgments by extending R. D. Luce's (1959) model, which was originally developed for individual choice behavior, to a mixed-effects paired comparison model. It is shown that standard multilevel software for binary data can be used to estimate the model. The interpretation of the paired comparison parameters and statistical model tests are discussed in detail. An extensive analysis of an experimental study illustrates the usefulness of a hierarchical approach in modeling multiple pairwise judgments.

Choice Behavior↗
PubMed2001

Case-control study of leatherwork and male infertility.

OBJECTIVES: To test the hypothesis that leatherwork is associated with male infertility mediated through the development of oligozoospermia. The basis of any association was postulated, at the outset, to be with exposure to the solvents used in leatherwork. METHODS: All new referrals with infertility presenting in Leicestershire hospital clinics between November 1988 and September 1992 and Kettering District General Hospital from August 1990 were eligible to participate; 88.5% agreed to be interviewed. Exposure to leatherwork and work with solvents was defined by job title. Comparisons were made with fertile controls and in an analysis within men from infertile couples with oligozoospermia as the primary outcome. Effects on sperm motility and deformity were investigated secondarily. Analyses used logistic regression for binary outcomes and multilevel modelling for continuous outcomes. RESULTS: 1906 men were interviewed. Compared with the fertile controls the men from infertile couples were 1.10 times (95% confidence interval (95% CI) 0.46 to 2.63; p=0.99) more likely to be leatherworkers and 1.73 times (95% CI 1.26 to 2.38; p<0.001) more likely to work with solvents. Compared with other men, leatherworkers were 1.20 times (95% CI 0.43 to 3.33; p=0.73) more likely to present with oligozoospermia and 1.65 times (95% CI 0.37 to 7.30; p=0.51) more likely to present with teratozoospermia. Being a leatherworker was associated with only a 6% reduction in sperm concentration; motility and deformity were similarly unaffected by this exposure. Work with solvents did not statistically, nor clinically, increase the risk of oligozoospermia, teratozoospermia, or asthenozoospermia. CONCLUSIONS: There was little evidence to support the hypothesis that leatherwork is associated with an increased risk of presenting with infertility or oligozoospermia. There was limited evidence that leatherwork is a risk factor for teratozoospermia. Workers with solvents were at an increased risk of presenting with infertility, although this was not mediated through effects on standard measures of semen quality; this finding merits further investigation.

Adult↗
PubMed1991

Variations on two themes: racial and ethnic patterns in the attainment of suburban residence.

To investigate racial and ethnic diversity in suburbanization, we draw on two complementary theoretical traditions, which we label "assimilation" and "stratification." Our analytic model is multilevel, and includes variables characterizing individuals, households, and metropolitan contexts. We use it to analyze the determinants of suburban versus central-city residence for 11 racial/ethnic groups. The analysis reveals that family status, socioeconomic, and assimilation variables influence the suburbanization process rather consistently. We take this finding as evidence in favor of the assimilation model. These effects display group variations, however, in a manner predicted by the stratification model. There are also suburbanization differences among metropolitan areas, particularly related to the relative economic status of cities and their suburbs, and between the northeast/north central regions and the south/west. Finally, we conclude that suburbanization is variable across the groups in a way that is not captured by broad categories such as "Asian" or "Hispanic."

Acculturation↗