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PubMedDate not supplied

Secular trend in the development of fatness during childhood and adolescence.

This study examined the development of fatness, as indexed by skinfold thickness, in healthy Caucasian children and adolescents residing in the same location in Canada in the 1960s and the 1990s. The data comes from two longitudinal studies, conducted approximately 30 years apart, of children aged 8-16 years. The first study (1964-1973) annually measured 207 males and 140 females. The second investigation (1991-1997) repeatedly measured 113 males and 115 females. Identical measurement tools and protocols were used for height, body mass, and skinfolds. Maturational age was estimated as a measure in years from age of peak height velocity. Males from the second investigation matured significantly (P < 0.05) earlier. Multilevel regression modeling was utilized to determine developmental curves for the individuals within the two populations. When differences in height, body mass, and maturity were controlled, skinfold thicknesses of the males and females in the second study were significantly greater (P < 0.05) than age- and sex-matched peers in the first study. This was not seen in models of the BMI. The results suggest that when maturity and size were controlled, the fatness of children and adolescents increased over 30 years.

Adipose Tissue↗
PubMed1999

If diabetes is a public health problem, why not treat it as one? A population-based approach to chronic illness.

It is increasingly acknowledged that diabetes and other chronic illnesses are major public health problems. Medicare and many managed health care organizations have recognized the enormous personal and societal costs of uncontrolled diabetes in terms of complications, patient quality of life, and health care system resources. However, the current system of reactive acute-episode focused disease care practiced in many settings does not adequately address this public health problem. An alternative proactive, population-based approach to chronic illnesses such as diabetes is proposed and illustrated. This multilevel systems approach addresses supportive and inhibitory social-environmental factors at multiple levels (personal, family, health care team, work, neighborhood, community). Key disciplines contributing to a population-based approach to diabetes include epidemiology, behavioral science, health care services, public health, health economics, and quality of life professions. Current and potential contributions of each of these disciplines are illustrated and an integrative, population-based systems approach to diabetes management and prevention of complications is proposed. This approach is also seen as applicable to other chronic illnesses.

Chronic Disease↗
PubMed2002

Gamma irradiation alters fatigue-crack behavior and fracture toughness in 1900H and GUR 1050 UHMWPE.

Pitting and delamination remain causative factors of polyethylene failure in total knee replacement. Gamma irradiation induces cross linking in ultra-high-molecular-weight polyethylene, which has been shown to improve wear resistance. Irradiation may reduce fracture toughness and fatigue strength, however, and the effects of irradiation are dependent upon the resin, processing technique, and radiation dose. The effects of varying levels of gamma irradiation (0, 33, 66, and 100 kGy) on the fracture toughness and fatigue-crack resistance of UHMWPE, isostatically molded from 1900H and GUR 1050 resins, were examined. Paris law regressions were performed to quantify fatigue-crack propagation rates as functions of change in stress intensity, and J-integral methods were used to quantify the elastic-plastic fracture toughness. The results indicated that gamma irradiation reduced the resistance of both materials to fatigue-crack growth, and that the reductions were radiation dosage and resin dependent. Irradiation at any level was detrimental to the fracture toughness of the 1900H specimens. Irradiation at 33 kGy increased fracture toughness for the GUR 1050 specimens, and substantial reductions were observed only at the highest irradiation level. Scanning electron microscopy of the fracture surface revealed diamond-like fracture patterns of the nonirradiated specimens indicative of ductile, multilevel fracture. Pronounced striations were apparent on these fracture surfaces, oriented perpendicular to the direction of crack growth. The striations appeared as folds in surface layers of the GUR 1050 specimens. At the highest irradiation levels, the striations were nearly eliminated on the fracture surfaces of the 1900H specimens, and were markedly less severe for the GUR 1050. These results demonstrated that at higher irradiation levels the materials became more brittle in fatigue, with less ductile folding and tearing of the fracture surfaces.

Arthroplasty, Replacement, Knee↗
PubMed2000

[On comparison of hospital performance].

BACKGROUND: The motivation to identify the causes of rising health care cost and variations across providers has intensified in all industrialized countries. These countries have an ongoing debate on efficiency and effectiveness in hospital production. In this debate, national and international comparative studies are important. MATERIAL AND METHODS: There are very few international comparative studies that include Norwegian hospitals. Actually we know very little about how Norwegian hospitals are performing compared to others. This paper gives an introduction to comparative studies and to the DEA model which is often used in such studies and also a multilevel model which is not so common. RESULTS: A short review is given of a comparative study of Norwegian and North American hospitals. I also discuss the feasibility of comparative studies of hospitals from the Nordic countries, with references to several comparative studies performed in these countries. INTERPRETATION: Comparative studies are often closely linked to national health politics, policy making and reforms; thus the outcome of such studies is important for the hospitals included. This makes such studies a sensitive field of research. It is important to be aware of the strength and weaknesses of comparative studies and acknowledge their importance beyond the development of new knowledge.

Cost-Benefit Analysis↗
PubMed2002

Spatial structure of zervamicin IIB bound to DPC micelles: implications for voltage-gating.

Zervamicin IIB is a 16-amino acid peptaibol that forms voltage-dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. The spatial structure of zervamicin IIB bound to dodecylphosphocholine micelles was studied by nuclear magnetic resonance spectroscopy. The set of 20 structures obtained has a bent helical conformation with a mean backbone root mean square deviation value of approximately 0.2 A and resembles the structure in isotropic solvents (Balashova et al., 2000. NMR structure of the channel-former zervamicin IIB in isotropic solvents. FEBS Lett 466:333-336). The N-terminus represents an alpha-helix, whereas the C-terminal part has a mixed 3(10)/alpha(R) hydrogen-bond pattern. In the anisotropic micelle environment, the bending angle on Hyp10 (23 degrees) is smaller than that (47 degrees) in isotropic solvents. In the NOESY (Nuclear Overhauser Effect Spectroscopy) spectra, the characteristic attenuation of the peptide signals by 5- and 16-doxylstearate relaxation probes indicates a peripheral mode of the peptaibol binding to the micelle with the N-terminus immersed slightly deeper into micelle interior. Analysis of the surface hydrophobicity reveals that the zervamicin IIB helix is amphiphilic and well suited to formation of a tetrameric transmembrane bundle, according to the barrel-stave mechanism. The results are discussed in a context of voltage-driven peptaibol insertion into membrane.

Anisotropy↗
PubMed1984

Aortofemoral or femoropopliteal revascularization? A prospective evaluation of the papaverine test.

Proper selection of suprainguinal vs. infrainguinal arterial revascularization in patients with multilevel disease requires hemodynamic assessment. In such patients hemodynamic evaluation of the aortoiliac system cannot be made accurately with either arteriography or current noninvasive techniques. One hundred six lower extremities underwent preoperative triplane arteriography, measurement of Doppler-derived segmental blood pressures, measurement of common femoral intra-arterial pressure, and intra-arterial injection (30 mg) of the vasodilator papaverine hydrochloride prior to arterial bypass. Common femoral intra-arterial pressure was monitored continuously before and after papaverine injection. The resting femoral/brachial pressure index (FBI) and the maximum change in this index (% delta FBI) following papaverine injection were calculated. To be considered improved postoperatively, claudicants required an increase in treadmill walking time of greater than or equal to 50%, whereas patients operated on for limb salvage required an increase in the thigh/brachial pressure index (TBI) of greater than or equal to 0.15 for suprainguinal revascularizations and an increase of TBI to greater than or equal to 0.9 for infrainguinal revascularizations. In the first 41 extremities (phase I), receiver operator characteristic analysis revealed a % delta FBI greater than or equal to 15% to be optimal in the detection of hemodynamically significant aortoiliac disease. In phase II (65 limbs) this discriminant value for % delta FBI was assessed prospectively. In phase I, in which the choice of supra- vs. infrainguinal bypass was determined arteriographically, only 80% of the extremities were improved; in phase II, in which supra- vs. infrainguinal bypass was determined by the papaverine test, 98% of extremities were improved (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1994

Anterior cervical discectomy and fusion using a porous hydroxyapatite bone graft substitute.

OBJECTIVES: This study analyzed the use of a coral hydroxyapatite bone substitute for use in ACDF both with and without an anterior cervical plate. STUDY DESIGN: The healing of multilevel anterior cervical fusions was tested using a goat model. Comparisons were drawn with histologic, radiographic, and biomechanical test data. METHODS: Forty-nine mature alpine goats had three-level anterior discectomies performed. Seven treatment groups of seven goats each were used; Group I with no fusion, Group IIa having tricortical iliac crest autograft, Group IIb having autograft plus an anterior plate, Group IIIa having tricortical iliac crest fresh-frozen allograft, Group IIIb having allograft plus an anterior plate, Group IVa having rectangular-shaped implants of porous hydroxyapatite, and Group IVb having ProOsteon 500 implants with an anterior cervical plate. RESULTS: Histologically, at 12 weeks 48% of the ProOsteon (Interpore, Irvine, CA) implants were rated as incorporated, 10% as possessing a fibrous gap, 29% as collapsed, and 14% as extruded. Anterior cervical plating improved the results with 71% of the implants showing good incorporation, 24% with collapse, and 5% with a fibrous gap. These histologic results compare favorably with autogenous bone and are improved over allograft bone. Fluorochrome analysis showed that none of the implants had complete turnover with host bone, but that all possessed peripheral creeping substitution with cutting cones of new bone formation at 12 weeks. Biomechanically, the spines using the ProOsteon implant were less stiff in torsion than autograft, but equal in stiffness to allograft. Flexion-extension neutral zone stiffness was lower in the ProOsteon implant group than either allograft or autograft. CONCLUSIONS: The use of a coral-based hydroxyapatite bone graft substitute for anterior cervical fusions led to significant rates of implant collapse at 12 weeks but showed excellent biologic compatibility with good early creeping substitution of the implant by host bone. The concomitant use of an anterior cervical plate with the implant prevents extrusion.

Animals↗
PubMed2003

Control for confounding in the presence of measurement error in hierarchical models.

Hierarchical modeling is becoming increasingly popular in epidemiology, particularly in air pollution studies. When potential confounding exists, a multilevel model yields better power to assess the independent effects of each predictor by gathering evidence across many sub-studies. If the predictors are measured with unknown error, bias can be expected in the individual substudies, and in the combined estimates of the second-stage model. We consider two alternative methods for estimating the independent effects of two predictors in a hierarchical model. We show both analytically and via simulation that one of these gives essentially unbiased estimates even in the presence of measurement error, at the price of a moderate reduction in power. The second avoids the potential for upward bias, at the price of a smaller reduction in power. Since measurement error is endemic in epidemiology, these approaches hold considerable potential. We illustrate the two methods by applying them to two air pollution studies. In the first, we re-analyze published data to show that the estimated effect of fine particles on daily deaths, independent of coarse particles, was downwardly biased by measurement error in the original analysis. The estimated effect of coarse particles becomes more protective using the new estimates. In the second example, we use published data on the association between airborne particles and daily deaths in 10 US cities to estimate the effect of gaseous air pollutants on daily deaths. The resulting effect size estimates were very small and the confidence intervals included zero.

Air Pollutants↗
PubMed2005

Who you live with and where you live: setting the context for health using multiple membership multilevel models.

STUDY OBJECTIVE: Previous studies into the effect of area of residence on individuals' health have not accounted for changing residency over time, although few people remain resident in the same area throughout their life. Furthermore, few studies of area effects on health have accounted for the clustering of health at the household level. These methodological problems may have led previous studies to under estimate or over estimate the size of area level effects. This study uses multiple membership multilevel models to investigate whether longitudinal analyses of area effects on health need to take account of clustering at the household level. SETTING AND PARTICIPANTS: A longitudinal survey (1991-1999) of a nationally representative sample of British households (5511 households with 10 264 adult members). DESIGN: Two level (individuals within households or areas) and three level (individuals within households within areas) multiple membership models of SF-36 physical and mental health functioning scores at wave nine were analysed adjusting for age, gender, education, marital, employment, and smoking status from previous waves. RESULTS: Physical and mental health functioning seem to cluster within households. Accounting for changes in household membership over time increases estimates of the clustering in functioning at the household level. The clustering of functioning within area wards is reduced when the clustering within households and risk factors for functioning are taken into account. CONCLUSIONS: Clustered sampling units within study designs should be taken account of in individual level analyses. Changes in these units over time should be accounted for in longitudinal analysis.

Adolescent↗
PubMed2006

Economics methods in the Clinical Outcomes Utilizing percutaneous coronary Revascularization and Aggressive Guideline-driven drug Evaluation (COURAGE) trial.

Percutaneous coronary intervention (PCI) remains a major therapeutic option for the treatment of chronic coronary artery disease. In the COURAGE trial, 2287 patients with chronic coronary disease were randomized between PCI with medical management and medical management alone. Embedded within the COURAGE trial is a detailed economic analysis being conducted in three health care systems: the US Veterans Administration (VA), Canada, and the US non-VA. Resource use and costs are being collected for each system and overall. Survival is assessed internally in the trial with mean follow-up of 4.5 years. Long-term mean survival will be estimated by projecting survival beyond the trial period by extrapolating the in-trial hazard rates. Utility is being assessed at baseline and at 1, 3, and 6 months and annually thereafter, using a computer-administered standard gamble. Quality-adjusted life years are calculated by multiplying survival by utility. The incremental cost-effectiveness ratio of PCI will be defined as the additional cost of PCI divided by the gain in life years and quality-adjusted life years. The 95% confidence regions of efficacy and costs will be determined by bootstrap over a range of acceptability thresholds, which will then be displayed in the cost-effectiveness plane and as a cost-effectiveness acceptability curve. A multilevel regression model will assess cost-effectiveness from a net benefit perspective. These approaches should provide the most detailed assessment available of the cost-effectiveness of PCI for coronary artery disease.

Angioplasty, Balloon, Coronary↗
PubMed2000

Predicting small-area health-related behaviour: a comparison of smoking and drinking indicators.

Health-related behaviours are of central importance to health promotion and to the promotion of enhanced population health. In the UK, localised knowledge of the quantitative dimensions of health-related behaviours is traditionally attained by conducting a costly sample survey. Such surveys seldom generate reliable data at scales more local than that of the health authority, they also need to be repeated regularly. This paper outlines an alternative framework for generating statistics on small-area health related behaviours using routinely available data from the annual Health Survey for England (N = 17,000) and the decennial Population Census. Using a multilevel modelling approach nesting individuals within postcode sectors within health authorities, and focusing on the prevalence of smoking and 'problem' drinking, the paper comprises four sections: a consideration of the modelling strategy, a comparison of the smoking and drinking models, an outline of the estimation strategy, and the presentation and discussion of ward-level estimates of smoking and drinking behaviour for England. The paper concludes that the method is better at estimating smoking than drinking but that it offers a feasible, cheap and more informative alternative to the survey approach to the generation of information on smoking and drinking behaviour.

Alcohol Drinking↗
PubMed2004

Current smoking among young adolescents: assessing school based contextual norms.

OBJECTIVE: To extend research on the relation of school based contextual norms to current smoking among adolescents by using three analytic techniques to test for contextual effects. It was hypothesised that significant contextual effects would be found in all three models, but that the strength of these effects would vary by the statistical rigor of the model. DESIGN: Three separate analytic approaches were conducted on baseline self report student survey data from a larger study to test the relation between school level perceived peer tobacco use and individual current smoking status. PARTICIPANTS: A representative sample of 5399 sixth through eighth grade students in 14 midwestern middle schools completed the survey. All enrolled sixth through eighth grade students were eligible to participate in the survey. The student participation rate was 91.4% for the entire sample, and did not differ significantly between the schools (range 82-100%). MAIN OUTCOME MEASURE: Thirty day cigarette smoking prevalence. RESULTS: A level 2 only model based on aggregated individual responses indicated that students in schools with higher average reported peer tobacco use were more likely to be current smokers than students in schools with lower average peer tobacco use. Using a level 1 only model based on individual responses indicated that the effect of school level perceived peer tobacco use on current smoking was significant when individual perceived peer tobacco use was excluded from the model but was non-significant when individual perceived peer tobacco use was added to the model. A multilevel model also indicated that the effect of school level perceived peer tobacco use on current smoking was not significant when individual perceived peer tobacco use was added to the model. CONCLUSION: The analytic approach used to examine contextual effects using individuals' reports of peer tobacco use norms that were aggregated to obtain a context measure of the school norms may produce statistical artefacts that distort the association of the school context in general, and peer tobacco use norms in particular, with increased risk for current smoking beyond the risk associated with individual factors.

Adolescent↗
PubMed2005

Should treatment of (sub)acute low back pain be aimed at psychosocial prognostic factors? Cluster randomised clinical trial in general practice.

OBJECTIVE: To compare the effects of a minimal intervention strategy aimed at assessment and modification of psychosocial prognostic factors and usual care for treatment of (sub)acute low back pain in general practice. DESIGN: Cluster randomised clinical trial. SETTING: 60 general practitioners in 41 general practices. PARTICIPANTS: 314 patients with non-specific low back pain of less than 12 weeks' duration, recruited by their general practitioner. INTERVENTIONS: In the minimal intervention strategy group the general practitioner explored the presence of psychosocial prognostic factors, discussed these factors, set specific goals for reactivation, and provided an educational booklet. The consultation took about 20 minutes. Usual care was not standardised. MAIN OUTCOME MEASURES: Functional disability (Roland-Morris disability questionnaire), perceived recovery, and sick leave because of low back pain assessed at baseline and after 6, 13, 26, and 52 weeks. RESULTS: The dropout rate was 8% in the minimal intervention strategy group and 9% in the usual care group. Multilevel analyses showed no significant differences between the groups on any outcome measure during 12 months of follow-up in the whole group or in relevant subgroups (patients with high scores on psychosocial measures at baseline or a history of frequent or prolonged low back pain). CONCLUSION: This study provides no evidence that (Dutch) general practitioners should adopt our new treatment strategy aimed at psychosocial prognostic factors in patients with (sub)acute low back pain. Further research should examine why our new strategy was not more effective than usual care.

Cluster Analysis↗
PubMedDate not supplied

Management of type 2 diabetes in the primary care setting: a practice-based research network study.

PURPOSE: We wanted to describe how primary care clinicians care for patients with type 2 diabetes. METHODS: We undertook a cross-sectional study of 95 primary care clinicians and 822 of their established patients with type 2 diabetes from 4 practice-based, primary care research networks in the United States. Clinicians were surveyed about their training and practice. Patients completed a self-administered questionnaire about their care, and medical records were reviewed for complications, treatment, and diabetes-control indicators. RESULTS: Participating clinicians (average age, 45.7 years) saw an average of 32.6 adult patients with diabetes per month. Patients (average age, 59.7 years) reported a mean duration of diabetes of 9.1 years, with 34.3% having had the disease more than 10 years. Nearly one half (47.5%) of the patients had at least 1 diabetes-related complication, and 60.8% reported a body mass index greater than 30. Mean glycosylated hemoglobin (HbA1c) level was 7.6% (SD 1.73), and 40.5% of patients had values <7%. Only 35.3% of patients had adequate blood pressure control (<130/85 mm Hg), and only 43.7% had low-density lipoprotein cholesterol (LDL-C) levels <100 mg/dL. Only 7.0% of patients met all 3 control targets. Multilevel models showed that patient ethnicity, practice type, involvement of midlevel clinicians, and treatment were associated with HbA1c level; patient age, education level, and practice type were associated with blood pressure control; and patient ethnicity was associated with LDL-C control. CONCLUSIONS: Only modest numbers of patients achieve established targets of diabetes control. Reengineering primary care practice may be necessary to substantially improve care.

Cardiovascular Diseases↗
PubMed2004

Work stressors and the quality of life in long-term care units.

PURPOSE: The purpose of this work was to examine how structural factors, residents' needs for physical and psychosocial assistance, and the work stressors experienced by employees are related to the quality of life of elderly residents in long-term care. DESIGN AND METHODS: Cross-sectional survey data were collected from 1,194 employees and 1,079 relatives of residents in 107 residential-home units and health-center bed wards. Data were analyzed using multilevel modeling. RESULTS: The majority of differences in both employees' and relatives' perceptions of residents' quality of life across units could be explained by work stressors such as time pressure. Large unit size was related to both increased time pressure among employees and reduced quality of life of residents. IMPLICATIONS: Long-term care units are encouraged to review their practices so that employee well-being is supported. Attention also should be focused on unit size, as small units appear better able to help employees cope with work stress, resulting in better quality of life for residents.

Finland↗
PubMed2002

The effects of kin on child mortality in rural Gambia.

We analyzed data that were collected continuously between 1950 and 1974 from a rural area of the Gambia to determine the effects of kin on child mortality. Multilevel event-history models were used to demonstrate that having a living mother, maternal grandmother, or elder sisters had a significant positive effect on the survival probabilities of children, whereas having a living father, paternal grandmother, grandfather, or elder brothers had no effect. The mother's remarriage to a new husband had a detrimental effect on child survival, but there was little difference in the mortality rates of children who were born to monogamous or polygynous fathers. The implications of these results for understanding the evolution of human life-history are discussed.

Demography↗
PubMedDate not supplied

An evaluative case study of online learning for healthcare professionals.

BACKGROUND: This evaluation study assessed the pedagogical and instructional design (e-pedagogy) effectiveness of online continuing professional education (CPE) courses offered by a large Australian CPE provider. METHODS: A naturalistic theory approach and a multilevel evaluation were used to examine the impact of web-based learning on more than 300 healthcare professionals. Participant satisfaction, learning achievement, self-reported practice performance change, and e-pedagogical courseware characteristics were assessed by various qualitative and quantitative data collection methods. RESULTS: Findings revealed that learning online was an effective means for increasing CPE knowledge (p < .05) and improving self-reported practice performance change (p < .05). Courses containing a clinical tool resulted in an increased self-reported practice performance change over courses that did not (Zobs = 3.757). CONCLUSION: Online CPE offers a convenient format for healthcare professionals from educationally and geographically diverse populations to update their knowledge and view best practice.

Analysis of Variance↗
PubMed1999

[Prospective 12-year follow-up study of clinical and hemodynamic sequelae of deep venous thromboses in patients with low risk (Zurich Study)].

No prospective study of the long-term sequelae of more than 10 years after acute deep vein thrombosis exists so far. Therefore, 28 patients with DVT were included in a prospective study to evaluate the natural history of postthrombotic syndrome. Clinical and hemodynamic examinations were performed at the time of admission; after 3, 6 and 12 months; after the 2nd, 3rd, 4th, 5th; and finally after the 12th year. All patients received unfractionated heparin initially and oral anticoagulants subsequently. After 12 years, 64% of the patients exhibited normal findings. Mild skin changes were found in 28%, marked trophic changes in 5%, and only 1 venous ulcer occurred. Regular use of compression stockings was reported by 54% of the patients with multilevel disease. Although mean maximum venous outflow was significantly reduced from the acute event to 2 years later (p < 0.003) compared with the contralateral leg, a significant (p < 0.05) improvement was observed 6 months later. Recanalization of calf vein thrombosis was detected by Doppler sonography after 3 months. 64% of the multilevel thromboses were recanalized completely or in part after 1 year; in 69%, valvular incompetence was found. In conclusion, in contrast to earlier reports, this prospective study up to 12 years after DVT demonstrates a low incidence of PTS by administration of initially unfractionated heparin, oral anticoagulation and compression therapy. However, the adverse clinical event rate (mortality 14%) and recurrency rate of 24% show that the prognosis after DVT does not appear favorable even in low-risk patients.

Adult↗