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PubMed2003

The relation of retail tobacco availability to initiation and continued smoking.

Used an ecological analysis employing multilevel random-effects regression analyses to model Level 1 (individual and social) and Level 2 (environmental) correlates of smoking initiation and continued smoking among 6th-, 7th-, and 8th-grade students. Data from 5,234 youth in 11 Midwestern communities were examined. Results indicate higher levels of retail tobacco availability (RTA) were associated with increased odds that a youth initiated smoking but not continued smoking. Among the Level 1 factors, youth who were older, male, had an adult tobacco user in the home, and had more peers who use tobacco had increased odds of initiating smoking. In contrast, only the presence of an adult tobacco user in the home and the number of peers who use tobacco were associated with increased odds that a youth continued smoking. Examining individual, social, and environmental factors simultaneously provides a clearer and more accurate model of these complex ecological influences.

Adolescent↗
PubMed2003

Intranasal sumatriptan in cluster headache: randomized placebo-controlled double-blind study.

BACKGROUND: Current evidence-based acute treatments of cluster headache are limited to oxygen inhalation and subcutaneous sumatriptan. Intranasal sumatriptan is a new formulation with better tolerability than the subcutaneous route. Two open-label studies suggested efficacy of intranasal sumatriptan in cluster headache. METHODS: In a double-blind placebo-controlled randomized trial, patients with episodic or chronic cluster headache whose attacks lasted at least 45 minutes each treated one attack with 20 mg sumatriptan nasal spray and another one, at least 24 hours later, with matching placebo. They scored their headache on a five-point scale (very severe, severe, moderate, mild, or none) at 5, 10, 15, 20, and 30 minutes. The primary outcome measure was headache response (a decrease in pain from very severe, severe, or moderate to mild or none) at 30 minutes. Secondary outcome measures included pain-free rates, relief of associated symptoms, and rates of adverse events. Multilevel multivariate analysis was used for statistical analysis. RESULTS: Five study centers enrolled 118 patients in whom 154 attacks were treated: 77 with sumatriptan and 77 with placebo. The responder rates at 30 minutes were 57% for sumatriptan and 26% for placebo (p = 0.002). Pain-free rates at 30 minutes were 47% for sumatriptan and 18% for placebo (p = 0.003). Sumatriptan was also superior to placebo considering initial response, meaningful relief, and relief of associated symptoms. There were no serious adverse events. CONCLUSION: Sumatriptan nasal spray is effective and well tolerated in the acute treatment of cluster headache attacks of at least 45 minutes' duration.

Administration, Intranasal↗
PubMed2004

Longitudinal changes of maximal short-term peak power in girls and boys during growth.

PURPOSE: The aims of this study are twofold: first, to analyze the influence of age, body mass, and lean leg volume (LLV) on short-term leg peak power (Pmax) of young females and males during growth using multilevel regression analysis and, second, to compare the regression results of boys and girls. METHODS: The individuals were 100 girls and 109 boys aged 7.5-17.5 yr old. Pmax, LLV, and mass were determined on two occasions using the cycling force-velocity test. The optimal force (Fopt) and pedaling frequency (Vopt) corresponded to the force and pedaling frequency at Pmax. RESULTS: It was observed that the increase of Pmax doesn't depend on gender until the age of 14. From that age, Pmax values are significantly lower in girls than in boys. In girls, LLV is the main predictor of Pmax variance (68%; P < 0.001), whereas in boys it is age (57%; P < 0.001). Results of ANCOVA were that for the same leg length (LL), Vopt is significantly (P < 0.001) higher in boys than in girls. It also indicated that for the same LLV, there are no significant (P > 0.05) gender differences of Fopt. CONCLUSION: These results illustrated that during the growth period, the increase of Pmax is significantly higher in boys than in girls. Qualitative muscular factors (Type II fiber, glycolytic ability, motor coordination, and motor unit activation) may account for the significantly higher Pmax production in boys than in girls. Precisely, the gender differences might be explained by neuromuscular determinants of contraction velocity. In conclusion, children should develop their neuromuscular determinants of contraction velocity rather than their lean leg volume.

Adolescent↗
PubMed2004

Factors of the physical environment associated with walking and bicycling.

PURPOSE: The purpose of this study was to identify factors of the physical environment that may influence time spent on walking and bicycling. METHODS: Demographic factors and time spent on walking and bicycling (during leisure time and for commuting purposes) were assessed with a self-administered questionnaire. GIS databases were used to objectively measure the total square area of green space and recreational space (woods, parks, sport grounds, allotments for vegetable gardens, and grounds for day trips) in a circle around the postal code of a respondent with a radius of 300 and 500 m. Multilevel regression analysis was used to study the association between walking and bicycling on the one hand, and green and recreational space on the other hand. Analyses were adjusted for gender, age, and educational level. RESULTS: In a neighborhood defined as a circle with a 300-m radius, the square area of sport grounds was associated with bicycling in general and the square area of parks was associated with bicycling for commuting purposes. It is, however, very likely that these results reflect the association of living in the outskirts of town and time spent on bicycling. CONCLUSION: The present study showed green and recreational space, specifically sport grounds and parks, to be associated with time spent on bicycling.

Adult↗
PubMed2005

Patient- and ward-level determinants of nursing time in nursing facilities.

OBJECTIVES: To explore the patient- and ward-level determinants of wage-adjusted nursing time in long-term care wards for the elderly with a view to improving efficiency of the use of labour resources. METHODS: The wage-adjusted nursing time given to patients was obtained from a time measurement study. Patient characteristics were based on the Minimum Data Set 2.0 of the Resident Assessment Instrument for nursing homes. Ordinary least-squares regression analysis and multilevel modelling were used to disentangle the effect of patient- and ward-level factors on nursing time. RESULTS: A significant difference in wage-adjusted nursing time between wards was detected, which was partly explained by characteristics of patients in wards. The combination of patients' physical functioning and cognition and the Resource Utilization Groups RUG-III/22 resource use classification explained 20-25% of patients' nursing time over a 24-hour period. Variables related to the operational environment of the ward did not explain differences in wage-adjusted nursing time once the patient profile of the ward had been controlled for. The results also showed notable unmeasured patient and ward level effects, inefficiency and randomness in the allocation of nursing time. CONCLUSIONS: By improving the allocation and use of labour resources, the substantial variation in nursing time between wards could be diminished. Managers should allocate their staff primarily according to patients' resource needs.

Benchmarking↗
PubMedDate not supplied

[Multilevel model applications to the analysis of longitudinal data].

This work is an introduction to repeated measurement analysis for longitudinal studies. It uses a two stage modelling framework, using hierarchical linear models with two levels. The first level pertains to the repeated measures, the second level pertains to the individual. For the last 25 years, hierarchical linear models have been used in the Social Sciences to analyse data coming from organizations with multiple levels. Their applications have been extended to the study of change in populations, both to describe the average change in an outcome variable in a population and to analyse the factors associated with variability in the individual trajectories of change. In this article, the basic concepts are introduced: between subjects and within subjects variability, the person-specific model for the individual trajectory and the between person model to describe how individuals vary in their trajectories, fixed and random effects, linear and quadratic growth models. At the end of each section, an illustration is given for the study of cognitive function of the older people cohort "Aging in Leganés", followed in four occasions between 1993 and 1999. Results from fitting the models to answer the most frequently asked research questions in the descriptions and analysis of individual change are presented. Lastly, we present possible generalizations of these linear models to non linear situations which arise when outcomes are dichotomous, nominal or ordinal.

Aging↗
PubMed2003

Power relations and premature mortality in Spain's autonomous communities.

This trends ecological study analyzes, across 17 autonomous communities of Spain from 1989 to 1998, the relationship between mortality (total and by main causes of death) and power relations (type of government: social democratic (SDP), conservative (CDP), and others), labor market variables, welfare state variables, income inequality, absolute income, poverty, and number of civil associations. The authors conducted a descriptive analysis; a bivariate analysis (Pearson correlation coefficients) between mortality and each of the independent variables; and a multivariate analysis, adjusting multilevel linear regression models. All dimensions of the conceptual power relations model were related to premature mortality in the direction hypothesized. The cross-pooled multilevel regression models show that total premature mortality in males, male and female cerebrovascular mortality, male and female cirrhosis mortality, and male lung cancer mortality decreased somewhat more in communities where primary health care reform was implemented more quickly. Premature mortality decreased somewhat more in SDP than in CDP communities for male and female total premature mortality, cerebrovascular mortality, and cirrhosis mortality, and male lung cancer mortality. These results are in accord with earlier studies that found a relationship among health indicators and variables related to labor market, welfare state, income inequalities, civil associations, and power relations.

Adolescent↗
PubMed2004

Impact of early lactation somatic cell count in heifers on somatic cell counts over the first lactation.

The objective of this study was to estimate the impact of somatic cell count in early lactation (SCCel) from Belgian dairy heifers on test-day somatic cell count (SCC) in first lactation. Geometric mean SCCel [5 to 14 d in milk (DIM)] of the 14,766 available samples was 104,000 cells/mL, and decreased from 178,000 at 5 DIM to 74,000 cells/mL at 14 DIM. Proportion of SCCel >200,000 cells/mL was 27.5. Heifers calving in the period April-June had highest SCCel. In total, 117,496 monthly SCC were measured. A multilevel regression analysis revealed that an increase of the natural log-transformed SCCel (LnSCCel) by one unit on average resulted in an increase of test-day natural log-transformed SCC (LnSCC) by 0.22 unit. The impact of LnSCCel on LnSCC depended on when LnSCCel was measured; an elevated LnSCCel at 14 DIM was more consequential than an equally elevated LnSCCel at 5 DIM. The probability of having a test-day SCC >200,000 cells/mL during the first lactation, also increased with an increasing LnSCCel. The negative effect of an elevated LnSCCel was still present, although to a lesser extent, in heifers with a second test-day SCC <or=50,000 cells/mL. This study indicates that udder health problems in heifers in early lactation have a high prevalence and stresses that heifers should have a low SCCel, because an elevated SCCel will negatively influence test-day SCC during the whole first lactation.

Animals↗
PubMed2005

Impact of early lactation somatic cell count in heifers on milk yield over the first lactation.

The objective of this study was to estimate the impact of somatic cell count (SCC) in early lactation (SCCel) [measured between 5 to 14 d in milk (DIM)] of dairy heifers on test-day milk yield (MY) during the first lactation. In total, 117,496 four-weekly test-day records of 14,243 heifers were used. A multilevel regression analysis, which included test-day SCC among the explanatory variables, revealed that an increase by one unit of the natural log-transformed SCCel (LnSCCel) was on average associated with a decrease in MY of 0.13 kg/d later in lactation. As an example, a heifer with an SCCel of 50,000 cells/mL measured at 10 DIM was estimated to produce 119 and 155 kg more milk during its first lactation than heifers with a SCCel of 500,000 and 1,000,000 cells/mL, respectively. When not accounting for test-day SCC, the effect of LnSCCel on MY was larger, indicating that part of the negative impact of elevated SCCel was associated with elevated test-day SCC later in lactation.Furthermore, an elevated SCCel at 14 DIM had a larger impact than an equally elevated SCCel measured at an earlier DIM. In addition, the negative effect of an elevated SCCel remained present during almost the entire first lactation in a subgroup of heifers with a second test-day SCC </=50,000 cells/mL, suggesting that prevention rather than cure of an elevated SCCel should be preferred. This study stresses the importance of heifers having low SCCel, as an elevated SCCel will negatively affect milk production during the first lactation, probably via impairment of mammary function and, to a smaller extent, via elevated test-day SCC later in lactation.

Animals↗
PubMed2002

Secondary traumatization in Dutch couples of World War II survivors.

This study examined whether signs of secondary traumatic stress were present in a community sample of couples who experienced World War II. The authors hypothesized that symptoms of posttraumatic stress disorder (PTSD) in either spouse may be predicted not only by his or her own war experiences but also by the war experiences and posttraumatic symptoms of the partner. Approximately 50 years after the end of World War II, 444 couples from a community sample of elderly Dutch citizens answered a questionnaire. A multilevel regression analysis was performed with symptoms of PTSD as the dependent variable. The most important predictors of PTSD symptoms were the number of war events reported by the participant and the current level of PTSD symptoms of his or her spouse. The results lend empirical support to the notion that posttraumatic stress reactions of both members of a couple are not independent from each other. Several explanations of the findings are discussed.

Aged↗
PubMed2002

[Prognostication of occurrence of the organ dysfunction and course of traumatic disease in injured persons with severe combined trauma].

The course of traumatic disease (TD) was studied up in 415 injured persons with severe combined trauma. There were analyzed 82 parameters, reflecting peculiarities of anatomic traumatization, age of injured person, proceeding diseases, functional state of main systems of the life support. The data obtained were processed using multilevel statistical analysis. There were determined parameters, defining severity of the TD course and probability of syndrome of the polyorgan dysfunction (SPOD) occurrence, original scale of the SPOD prognostication was elaborated, permitting to prognosticate the TD course, to change the tactics and to improve the results of treatment of injured persons.

Abdominal Injuries↗
PubMed2004

Does improved access to care affect utilization and costs for patients with chronic conditions?

OBJECTIVE: To determine whether a major improvement in access (ie, implementing an open access system) in a large multispecialty medical group during 2000 was associated with changes in utilization or costs for patients with diabetes, coronary heart disease (CHD), or depression. STUDY DESIGN: Multilevel regression analysis of health plan administrative data. PATIENTS AND METHODS: Approximately 7000 patients with diabetes, 3800 with CHD, and 6000 with depression who received all of their care in this care system served as the subjects for this study. Utilization and costs between 1999 and 2001 (before and after implementation of open access) were compared for these patients. The main outcome measures were rates of inpatient admissions and various types of outpatient encounters as well as associated costs for these subjects. RESULTS: Between 1999 and 2001, total office visit changes were small and varied with condition, but the proportion of these visits made to primary care physicians increased significantly by an absolute 5% to 9% and primary care physician continuity increased for each condition. Urgent care visits also decreased significantly by an absolute 5% to 9%, but there was no change in emergency department visits or hospital admissions. Total costs of care for these patients were much larger than those for the overall population of the medical group, but increased at a similar rate. CONCLUSION: A major improvement in patient access to primary care clinics was associated with increased use and continuity of primary care for patients with 3 chronic conditions, but did not affect overall resource use.

Aged↗
PubMed2005

Implementation of clinical guidelines on physical therapy for patients with low back pain: randomized trial comparing patient outcomes after a standard and active implementation strategy.

BACKGROUND AND PURPOSE: An active strategy was developed for the implementation of the clinical guidelines on physical therapy for patients with low back pain. The effect of this strategy on patients' physical functioning, coping strategy, and beliefs regarding their low back pain was studied. SUBJECTS: One hundred thirteen primary care physical therapists treated a total of 500 patients. METHODS: The physical therapists were randomly assigned to 1 of 2 groups. The control group received the guidelines by mail (standard passive method of dissemination). The intervention group, in contrast, received an additional active training strategy consisting of 2 sessions with education, group discussion, role playing, feedback, and reminders. Patients with low back pain, treated by the participating therapists, completed questionnaires on physical functioning, pain, sick leave, coping, and beliefs. RESULTS: Physical functioning and pain in the 2 groups improved substantially in the first 12 weeks. Multilevel longitudinal analysis showed no differences between the 2 groups on any outcome measure during follow-up. DISCUSSION AND CONCLUSION: The authors found no additional benefit to applying an active strategy to implement the physical therapy guidelines for patients with low back pain. Active implementation strategies are not recommended if patient outcomes are to be improved.

Education, Continuing↗
PubMed2005

Changes in patients' attitudes towards the management of minor ailments.

BACKGROUND: Patients' attitudes towards the management of minor ailments influence help-seeking behaviour. Up-to-date information about patients' attitudes is valuable for understanding changes in help-seeking behaviour. AIM: To describe changes in patients' attitudes between 1987 and 2001, and to explain the relationship between patients' attitudes and attributes of practices, practitioners and patients. DESIGN: Two cross-sectional, Dutch National Surveys of General Practice (1987 and 2001; n = 9579 and n = 8405 patients, respectively). SETTING: General practice in the Netherlands. METHOD: Patients' attitudes were evaluated in health interviews. Data were analysed using multilevel regression analysis. RESULTS: In 2001, patients' attitudes showed a shift away from consulting their GP for minor ailments. Attitudes are uniform across different types of practice, and mainly differ between patients. In 1987 as well as in 2001 the factors associated with firm beliefs about the benefits of GP's care in case of minor ailments were male, older age, lower educational level, a non-Western cultural background, and a visit to the GP in the past 2 months. Furthermore, the association between health status and beliefs about GPs dealing with minor ailments is more marked in 2001. Compared to 1987, the influences of GPs and the practice are more intertwined in 2001. CONCLUSIONS: Patients' attitudes towards the management of minor ailments have changed over the years, which implies that strategic action by the profession and the government has affected the way the public uses primary care. However, a marginal group of patients (elderly, less-educated, non-Western) is lagging behind this trend, and continuing to consult GPs for minor ailments.

Adult↗
PubMed2001

Laminoplasty versus laminectomy and fusion for multilevel cervical myelopathy: an independent matched cohort analysis.

STUDY DESIGN: A matched cohort clinical and radiographic retrospective analysis of laminoplasty and laminectomy with fusion for the treatment of multilevel cervical myelopathy. OBJECTIVES: To compare the clinical and radiographic outcomes of two procedures increasingly used to treat multilevel cervical myelopathy. SUMMARY OF BACKGROUND DATA: Traditional methods of treating multilevel cervical myelopathy (laminectomy and corpectomy) are reported to have a notable frequency of complications. Laminoplasty and laminectomy with fusion have been advocated as superior procedures. A comparative study of these two techniques has not been reported. METHODS: Medical records of all patients treated for multilevel cervical myelopathy with either laminoplasty or laminectomy with fusion between 1994 and 1999 at our institution were reviewed. Thirteen patients that underwent laminectomy with fusion were matched with 13 patients that underwent laminoplasty. All patients and radiographs were independently evaluated at latest follow-up by a single physician. RESULTS: Cohorts were well matched based on patient age, duration of symptoms, and severity of myelopathy (Nurick grade) before surgery. Mean independent follow-up was similar (25.5 and 26.2 months). Both objective improvement in patient function (Nurick score) and the number of patients reporting subjective improvement in strength, dexterity, sensation, pain, and gait tended to be greater in the laminoplasty cohort. Whereas no complications occurred in the laminoplasty cohort, there were 14 complications in 9 patients that underwent laminectomy with fusion patients. Complications included progression of myelopathy, nonunion, instrumentation failure, development of a significant kyphotic alignment, persistent bone graft harvest site pain, subjacent degeneration requiring reoperation, and deep infection. CONCLUSIONS: The marked difference in complications and functional improvement between these matched cohorts suggests that laminoplasty may be preferable to laminectomy with fusion as a posterior procedure for multilevel cervical myelopathy.

Adult↗
PubMed2003

The use of multilevel models for the prediction of road accident outcomes.

An important problem in road traffic accident research is the resolution of the magnitude by which individual accident characteristics affect the risk of fatality for each person involved. This article introduces the potential of a recently developed form of regression models, known as multilevel models, for quantifying the various influences on casualty outcomes. The application of multilevel models is illustrated by the analysis of the predictors of outcome amongst over 16,000 fatally and seriously injured casualties involved in accidents between 1985 and 1996 in Norway. Risk of fatality was found to be associated with casualty age and sex, as well as the type of vehicles involved, the characteristics of the impact, the attributes of the road section on which it took place, the time of day, and whether alcohol was suspected. After accounting for these factors, the multilevel analysis showed that 16% of unexplained variation in casualty outcomes was between accidents, whilst approximately 1% was associated with the area of Norway in which each incident occurred. The benefits of using multilevel models to analyse accident data are discussed along with the limitations of traditional regression modelling approaches.

Accidents, Traffic↗
PubMed2004

Multilevel linear modelling for FMRI group analysis using Bayesian inference.

Functional magnetic resonance imaging studies often involve the acquisition of data from multiple sessions and/or multiple subjects. A hierarchical approach can be taken to modelling such data with a general linear model (GLM) at each level of the hierarchy introducing different random effects variance components. Inferring on these models is nontrivial with frequentist solutions being unavailable. A solution is to use a Bayesian framework. One important ingredient in this is the choice of prior on the variance components and top-level regression parameters. Due to the typically small numbers of sessions or subjects in neuroimaging, the choice of prior is critical. To alleviate this problem, we introduce to neuroimage modelling the approach of reference priors, which drives the choice of prior such that it is noninformative in an information-theoretic sense. We propose two inference techniques at the top level for multilevel hierarchies (a fast approach and a slower more accurate approach). We also demonstrate that we can infer on the top level of multilevel hierarchies by inferring on the levels of the hierarchy separately and passing summary statistics of a noncentral multivariate t distribution between them.

Bayes Theorem↗
PubMed2004

Fusion rate: a time-to-event phenomenon.

OBJECT: The term "fusion rate" is generally denoted in the literature as the percentage of patients with successful fusion over a specific range of follow up. Because the time to fusion is a time-to-event phenomenon a more accurate method of representation may be made using the Kaplan-Meier method of estimation. METHODS: The current study was performed to illustrate that fusion rate is more accurately represented by median times as calculated using survival analysis. Patients undergoing a cervical decompressive corpectomy and reconstruction formed the basis of the primary analysis. A secondary analysis was made to evaluate the difference in the fusion times for one- compared with multilevel corpectomy cases. Data were collected at a tertiary care institution over a 5-year period with 6-month follow up after the last recruitment. Descriptive statistics of baseline patient characteristics, the extent of disease, and the surgical intervention were obtained. Fusion was the final outcome, and it was defined as the "event." The presence of any trabeculae bridging between the vertebral body and allograft signified the occurrence of an event. Postoperative static radiographs were evaluated by independent neuroradiologists to assess the presence of fusion. Fusion rate was determined using the Kaplan-Meier estimate. The median time to fusion was calculated, as were the 95% confidence intervals (CIs). These were stratified for patients who underwent one- and two-level vertebrectomy. The log-rank test was used to differentiate between one-level and multilevel corpectomy. Multivariate analysis was performed using Cox regression for further evaluation, by adjusting for covariates (age, sex, smoking history). Fifty-seven patients underwent single- or multilevel corpectomy and fusion. The male/female ratio was similar, with a median age of 53 years. Fourteen patients had a history of cigarette smoking. Thirty-six patients underwent a one-level corpectomy, 20 a two-level corpectomy, and one patient underwent a three-level corpectomy. The analysis was restricted to one- and two-level cases. The median time to fusion for the cephalad and caudad aspect of the graft-host interface was 88 days (95% CI 82-94 days) and 85 days (95% CI 77-93 days), respectively. As generally reported in the literature, this translates to a 92% (by 2.1 years) and 93% (by 1.5 years) fusion rate, for the cephalad and caudad, respectively. The median time to fusion for the cephalad aspect of the graft for one-level vertebrectomy was 87 days (95% CI 83-91 days), whereas for two-level vertebrectomy was 90 days (95% CI 59-121 days). The median time to fusion for the caudal aspect of the graft-host interface was 85 days (95% CI 80-90 days) for one-level corpectomy and 90 days (95% CI 83-97 days) for the two-level cases. There was no statistically significant difference in the median time to fusion for one- and two-level corpectomy at either the superior or inferior aspect of the graft (p = 0.19 and 0.84, respectively). This held true even after adjusting for covariates. CONCLUSIONS: Fusion rate is a time-to-event phenomenon and is more accurately represented using the Kaplan-Meier method of estimation.

Bone Transplantation↗