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PubMed2004

SPSS and SAS programs for addressing interdependence and basic levels-of-analysis issues in psychological data.

Levels-of-analysis issues arise whenever individual-level data are collected from more than one person from the same dyad, family, classroom, work group, or other interaction unit. Interdependence in data from individuals in the same interaction units also violates the independence-of-observations assumption that underlies commonly used statistical tests. This article describes the data analysis challenges that are presented by these issues and presents SPSS and SAS programs for conducting appropriate analyses. The programs conduct the within-and-between-analyses described by Dansereau, Alutto, and Yammarino (1984) and the dyad-level analyses described by Gonzalez and Griffin (1999) and Griffin and Gonzalez (1995). Contrasts with general multilevel modeling procedures are then discussed.

Analysis of Variance↗
PubMed1986

[Psycholinguistic analysis of the speech of senile dementia patients].

The author has studied 17 patients with senile dementia and its combination (in case of an underlying atrophic process) with cerebral atherosclerosis but without local pathomorphological changes. It has been found that in senile dementia the multilevel and multiaspect functional system of speech is impaired at both, a lower, phonetic, and higher speech (a phonological analysis) levels. Other findings with regard to the speech level include disturbances of programming a speech statement or internal speech (dynamic aphasia), impairment of grammatical structuring and damaged lexical choice. The above disturbances (above all programming of the internal speech) are linked with intellectual deviations and are secondary to atrophy of the frontal lobes.

Aged↗
PubMed2004

Decomposing the total variation in a nested random effects model of neighborhood, household, and individual components when the dependent variable is dichotomous: implications for adolescent marijuana use.

Multilevel modeling techniques have become a useful tool that enables substance abuse researchers to more accurately identify the contribution of multiple levels of influence on drug-related attitudes and behaviors. However, it is difficult to determine the relative importance of the different hierarchical levels because, in the case of dichotomous outcomes, the variance components estimation involves calculations using a log-odds metric at the lowest level of estimation. We present methods introduced by Goldstein and Rasbash [Goldstein, H., Rasbash, J., 1996. Improved approximations for multilevel models with binary responses. J. Roy. Stat. Soc. A 159, 505-513.] to convert the variance components from the log-odds to the probability metric. This method provides a more logical and interpretable way to examine variation for nonlinear outcomes, which tend to be heavily utilized in substance use research. Using data from the National Household Survey on Drug Abuse [Substance Abuse and Mental Health Services Administration (SAMHSA), 2001. 1999 National Household Survey on Drug Abuse. Data Collection Final Report. Office of Applied Studies (OAS), Rockville, MD. Available at . Accessed on July 1, 2003.], we partition variation among individual, household, and neighborhood levels for the binary outcome of past year marijuana use to illustrate this approach. We also conduct a stability analysis to examine the robustness across different estimation procedures commonly available in commercial multilevel software packages. Finally, we partition the variance components using a conventional continuously distributed outcome and compare the relative magnitudes across binary and continuous outcomes.

Adolescent↗
PubMed2024

Small noncoding RNAs and sperm nuclear basic proteins reflect the environmental impact on germ cells.

BACKGROUND: Molecular techniques can complement conventional spermiogram analyses to provide new information on the fertilizing potential of spermatozoa and to identify early alterations due to environmental pollution. METHODS: Here, we present a multilevel molecular profiling by small RNA sequencing and sperm nuclear basic protein analysis of male germ cells from 33 healthy young subjects residing in low and high-polluted areas. RESULTS: Although sperm motility and sperm concentration were comparable between samples from the two sites, those from the high-pollution area had a higher concentration of immature/immune cells, a lower protamine/histone ratio, a reduced ability of sperm nuclear basic proteins to protect DNA from oxidative damage, and an altered copper/zinc ratio in sperm. Sperm levels of 32 microRNAs involved in intraflagellar transport, oxidative stress response, and spermatogenesis were different between the two areas. In parallel, a decrease of Piwi-interacting RNA levels was observed in samples from the high-polluted area. CONCLUSIONS: This comprehensive analysis provides new insights into pollution-driven epigenetic alterations in sperm not detectable by spermiogram.

Male↗
PubMedDate not supplied

[National immunization day evaluation in Colombia, 2001: an ecological approach].

OBJECTIVES: To determine OPV coverage impact of the 2001 national immunization day in different geographic regions and its association with the Unsatisified Basic Needs Index (NBI), forced displacement and armed conflict. METHODS: This is an analytical ecological study of multiple groups using multilevel observation units such as region, department, province and municipality. A bivariate analysis with difference between proportions between paired samples (McNemar test), estimation of OR, lineal regression and relative risk determination (Morgenstern) was carried out. In addition, protected and susceptible populations in each observation unit were compared. RESULTS: The OPV3 coverage increase between October and December, 2001, was 15 to 19% (p<0.05) and the final coverage was 78-84%. The provincial analysis demonstrated a 25.8% of total population with OPV3 coverage greater than 95%. An increase of 4 to 7 departments and 281 to 328 cities with at least 95% coverage (p<0.05) was observed. The risk of having incomplete immunization schedules decreased in armed conflict zones, remained stable in areas with high NBI and increased in areas with a high proportion of displaced families. The booster goal of the OPV had reached a median of 61%. CONCLUSIONS: The national immunization day diminished immunization access barriers for children under 5 years. The analysis of different geographic units controls the effect of the unknown population denominators. The ecological studies improved routine data analysis.

Child, Preschool↗
PubMed2003

Elective non-instrumented anterior cervical diskectomy and fusion in Ghana: a preliminary report.

BACKGROUND: This study is a retrospective analysis of forty-one consecutive patients who underwent elective single or multilevel anterior cervical diskectomy and fusion (ACDF) in Ghana. All the patients had been followed up for at least six months. METHODS: The medical records of forty-one consecutive cases were analysed retrospectively. The parameters reviewed included patient demographics and presentations, number of fusion levels, complications and clinical outcome. RESULT: Non-instrumented ACDF constituted 22% of all the neurosurgical procedures performed during the study period. A total of 41 patients underwent the procedure. Seventy-eight percent of the patients were male; the mean age of all the patients was 52 years; follow-up was for an average of 21 months. Preoperative assessment revealed that 98% had myelopathy and 2% had radiculopathy only. No patient was operated on for only pain. There were no repeat operations performed. All levels operated on were fused for a total of 67 levels; 37% at one level only and 63% at two levels; no patient was fused or operated on at three levels. Ninety percent of the fusions were at the C4-5 and C5-6 levels. The mean ages of males and females fused at one level only were 48 and 60 years respectively; the difference was statistically significant (P<0.05). For patients fused at two levels; 81% were males and 19% were females, the difference was statistically significant (P<0.05). However, there was no statistical difference between the ages of males and females operated on at two levels (P>0.05). In addition there was no statistical difference between the ages of males operated on at one level or two levels nor was there a difference between the ages of females operated on at one or two levels (P>0.05). The mean preoperative Nurick grade was 2.3 (SD, 1.9); the mean Nurick grade postoperation was 1.3 (SD, 1.3). The difference is significant (P<0.001). There was also a significant relationship between the preoperative and postoperative Nurick grades for males operated on at either one or two levels (P<0.01); however none could be demonstrated for females (P>0.01). The total operative complication rate was 12%; the most common complication was graft/donor site infection (7%). There was no operative or postoperative mortality. Eighty six percent of the patients had an excellent or good clinical outcome as defined by Odom's criteria. Of the 34% who did not have excellent or good clinical outcome, follow up radiologic studies showed excellent graft fusion in all of them. CONCLUSION: The majority of patients undergoing non-instrumented ACDF in Ghana have cervical myelopathy involving two cervical levels. However, a large majority of them have excellent or good clinical results after surgery. The most common complication is graft/donor site infection.

Cervical Vertebrae↗
PubMed2001

Cigarette diffusion and sex differences in smoking.

Because the recent narrowing of the sex differential in smoking (and mortality from smoking-related causes) coincides with movement toward gender equality and independence among women, it suggests that rising status among women has contributed to their adoption of male smoking behavior (and ultimately to worsening longevity). However, an alternative "cigarette diffusion" explanation suggests that convergence in male and female smoking is the byproduct of a female lag in the process of cigarette adoption, diffusion, and abatement. Using multilevel models and data for 16 European nations from 1988-1995, the analysis demonstrates consistent support for the predictions of the cigarette diffusion explanation. Smoking of men and women becomes more similar in nations that have the longest history of cigarette use rather than the greatest gender equality.

Developed Countries↗
PubMed2005

Bayesian analysis of clustered interval-censored data.

The recording of multiple interval-censored failure times is common in dental research. Modeling multilevel data has been a difficult task. This paper aims to use the Bayesian approach to analyze a set of multilevel clustered interval-censored data from a clinical study to investigate the effectiveness of silver diamine fluoride and sodium fluoride varnish in arresting active dentin caries in Chinese pre-school children. The time to arrest dentin caries on a surface was measured. A three-level random-effects Weibull regression model was used. Analysis was performed with WinBUGS. Results revealed a strong positive correlation (0.596) among the caries lesions' arrest times on different surfaces from the same child. The software WinBUGS made the above complicated estimation simple. In conclusion, the annual application of silver diamine fluoride on caries lesions, and caries removal before the application, were found to shorten the arrest time.

Bayes Theorem↗
PubMed2006

An ecometric analysis of neighbourhood cohesion.

BACKGROUND: It is widely believed that the social environment has an important influence on health, but there is less certainty about how to measure specific factors within the social environment that could link the neighbourhood of residence to a health outcome. The objectives of the study were to examine the underlying constructs captured by an adapted version of Buckner's neighbourhood cohesion scale, and to assess the reliability of the scale at the small-area-level by combining ecometric methodology with ordinal modelling of a five-point scale. METHODS: Data were analysed from 11,078 participants in the Caerphilly Health and Social Needs Study, who were sampled from within 325 UK census enumeration districts in Caerphilly county borough, Wales, UK. The responses of interest came from 15 question items designed to capture different facets of neighbourhood cohesion. Factor analysis was used to identify constructs underlying the neighbourhood cohesion item responses. Using a multilevel ecometric model, the variability present in these ordinal responses was decomposed into contextual, compositional, item-level and residual components. RESULTS: Two constructs labelled neighbourhood belonging and social cohesion were identified, and variability in both constructs was modelled at each level of the multilevel structure. The intra-neighbourhood correlations were 6.4% and 1.0% for the neighbourhood belonging and social cohesion subscales, respectively. Given the large sample size, contextual neighbourhood cohesion scores can be estimated reliably. The wide variation in the observed frequency of occurence of the scale item activities suggests that the two subscales have desirable ecometric properties. Further, the majority of between-neighbourhood variation is not explained by the socio-demographic characteristics of the individual respondents. CONCLUSION: Assessment of the properties of the adapted neighbourhood cohesion scale using factor analysis and ecometric analysis extended to an ordinal scale has shown that the items allow fine discrimination between individuals. However, large sample sizes are needed in order to accurately estimate contextual neighbourhood cohesion. The scale is therefore appropriate for use in the measurement of neighbourhood cohesion at small-area-level in future studies of neighbourhoods and health.

Journal Article↗
PubMed1999

Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis.

BACKGROUND: We studied the incidence, prevalence, and radiographic progression of symptomatic adjacent-segment disease, which we defined as the development of new radiculopathy or myelopathy referable to a motion segment adjacent to the site of a previous anterior arthrodesis of the cervical spine. METHODS: A consecutive series of 374 patients who had a total of 409 anterior cervical arthrodeses for the treatment of cervical spondylosis with radiculopathy or myelopathy, or both, were followed for a maximum of twenty-one years after the operation. The annual incidence of symptomatic adjacent-segment disease was defined as the percentage of patients who had been disease-free at the start of a given year of follow-up in whom new disease developed during that year. The prevalence was defined as the percentage of all patients in whom symptomatic adjacent-segment disease developed within a given period of follow-up. The natural history of the disease was predicted with use of a Kaplan-Meier survivorship analysis. The hypothesis that new disease at an adjacent level is more likely to develop following a multilevel arthrodesis than it is following a single-level arthrodesis was tested with logistic regression. RESULTS: Symptomatic adjacent-segment disease occurred at a relatively constant incidence of 2.9 percent per year (range, 0.0 to 4.8 percent per year) during the ten years after the operation. Survivorship analysis predicted that 25.6 percent of the patients (95 percent confidence interval, 20 to 32 percent) who had an anterior cervical arthrodesis would have new disease at an adjacent level within ten years after the operation. There were highly significant differences among the motion segments with regard to the likelihood of symptomatic adjacent-segment disease (p<0.0001); the greatest risk was at the interspaces between the fifth and sixth and between the sixth and seventh cervical vertebrae. Contrary to our hypothesis, we found that the risk of new disease at an adjacent level was significantly lower following a multilevel arthrodesis than it was following a single-level arthrodesis (p<0.001). More than two-thirds of all patients in whom the new disease developed had failure of nonoperative management and needed additional operative procedures. CONCLUSIONS: Symptomatic adjacent-segment disease may affect more than one-fourth of all patients within ten years after an anterior cervical arthrodesis. A single-level arthrodesis involving the fifth or sixth cervical vertebra and preexisting radiographic evidence of degeneration at adjacent levels appear to be the greatest risk factors for new disease. Therefore, we believe that all degenerated segments causing radiculopathy or myelopathy should be included in an anterior cervical arthrodesis. Although our findings suggest that symptomatic adjacent-segment disease is the result of progressive spondylosis, patients should be informed of the substantial possibility that new disease will develop at an adjacent level over the long term.

Adolescent↗
PubMed2006

Correction of severe crouch gait in patients with spastic diplegia with use of multilevel orthopaedic surgery.

BACKGROUND: Severe crouch gait in patients with spastic diplegia causes excessive loading of the patellofemoral joint and may result in anterior knee pain, gait deterioration, and progressive loss of function. Multilevel orthopaedic surgery has been used to correct severe crouch gait, but no cohort studies or long-term results have been reported, to our knowledge. METHODS: In order to be eligible for the present retrospective cohort study, a patient had to have a severe crouch gait, as defined by sagittal plane kinematic data, that had been treated with multilevel orthopaedic surgery as well as a complete clinical, radiographic, and instrumented gait analysis assessment. The surgical intervention consisted of lengthening of contracted muscle-tendon units and correction of osseous deformities, followed by the use of ground-reaction ankle-foot orthoses until stable biomechanical realignment of the lower limbs during gait was achieved. Outcome at one and five years after surgery was determined with use of selected sagittal plane kinematic and kinetic parameters and valid and reliable scales of functional mobility. Knee pain was recorded with use of a Likert scale, and all patients had radiographic examination of the knees. RESULTS: Ten subjects with severe crouch gait and a mean age of 12.0 years at the time of surgery were studied. After surgery, the patients walked in a more extended posture, with increased extension at the hip and knee and reduced dorsiflexion at the ankle. Pelvic tilt increased, and normalized walking speed was unaltered. Knee pain was diminished, and patellar fractures and avulsion injuries healed. Improvements in functional mobility were found, and, at the time of the five-year follow-up, fewer patients required the use of wheelchairs or crutches in the community than had been the case prior to intervention. CONCLUSIONS: Multilevel orthopaedic surgery for older children and adolescents with severe crouch gait is effective for relieving stress on the knee extensor mechanism, reducing knee pain, and improving function and independence.

Adolescent↗
PubMed2004

[A role of segmental disturbances in formation of movement disorders in patients with infantile cerebral palsy].

Clinico-electromyographical analysis has been conducted in patients with a late residual stage of cerebral palsy (CP). Multilevel CNS lesion with upper segmental and segmental involvement was detected in 19.1% of the patients with CP combined with progressive deformations of lower extremities joints in need of orthopedic-surgical treatment. The presence of segmental motoneuron disturbances in CP patients considerably worsens the clinical pattern of the disease that demands changes in policy of rehabilitation and surgical treatment. Electromyography with assessment of motor units activity potentials and turn-amplitude analysis with assessment of needle electrodes are the most informative diagnostic methods for CP patients suspected to have segmental motorneuron disturbances.

Adolescent↗
PubMed2001

Impact of smoking on the outcome of anterior cervical arthrodesis with interbody or strut-grafting.

BACKGROUND: An increased rate of pseudarthrosis has been documented following posterolateral lumbar spine grafting in patients who smoke. This same relationship has been assumed for anterior cervical interbody grafting, but to our knowledge it has never been proven. This study compared the long-term radiographic and clinical results of smokers and nonsmokers who had undergone arthrodesis with autogenous bone graft following multi-level anterior cervical decompression for the treatment of cervical radiculopathy or myelopathy, or both. METHODS: One hundred and ninety patients were followed clinically and radiographically for at least two years (range, two to fifteen years). Fifty-nine of the patients had corpectomy with strut-grafting, and 131 patients had multiple discectomies and interbody grafting. Fifty-five of the 190 patients had a history of active cigarette-smoking; fifteen of the fifty-five had corpectomy with strut-grafting, and forty had multilevel discectomies and interbody grafting. Internal fixation was not used in any patient. The reconstruction techniques and postoperative bracing regimen were similar between smokers and nonsmokers. Osseous union was judged on dynamic lateral radiographs made at least two years following surgery, and clinical outcomes were judged on the basis of pain level, medication usage, and daily activity level. RESULTS: Of the forty smokers who had undergone multilevel interbody grafting, twenty had a solid fusion at all levels, whereas sixty-nine of the ninety-one nonsmokers had solid fusion at all levels (p < 0.02; chi-square test). This difference was especially pronounced among patients who had had a two-level interbody grafting procedure (p < 0.002; chi-square test). With the numbers available, there was no difference in the rate of fusion between smokers (fourteen of fifteen) and nonsmokers (forty-one of forty-four) who had undergone corpectomy and strut-grafting, as 93% of both groups had a solid union. In addition, clinical outcomes were significantly worse among smokers when compared with nonsmokers (p < 0.03; rank-sum analysis). CONCLUSIONS: Smoking had a significant negative impact on healing and clinical recovery after multilevel anterior cervical decompression and fusion with autogenous interbody graft for radiculopathy or myelopathy. Since smoking had no apparent effect upon the healing of autogenous iliac-crest or fibular strut grafts, subtotal corpectomy and autogenous strut-grafting should be considered when a multilevel anterior cervical decompression and fusion is performed in patients who are unable or unwilling to stop smoking prior to surgical treatment.

Bone Transplantation↗
PubMed2006

Levels of analysis for the study of environmental health disparities.

Reducing racial/ethnic and socioeconomic environmental health disparities requires a comprehensive multilevel conceptual and quantitative approach that recognizes the various levels through which environmental health disparities are produced and perpetuated. We propose a conceptual framework that incorporates the micro level, contained within the local level, which in turn is contained within the macro level. We discuss the utility of multilevel techniques to examine environmental level (both physical and social) and individual-level factors to appropriately quantify and improve our understanding of environmental health disparities. We discuss the reasoning and the methodological approach behind multilevel modeling, including differentiating between individual and contextual influences on individual outcomes. Next we address the questions and principles that guide the choice of levels or geographic units in multilevel studies. Finally, we address the ways in which different data sources can be combined to produce suitable data for multilevel analyses. We provide some examples of how such data sources can be linked to create multilevel data structures, and offer suggestions to facilitate the integration of multilevel techniques in environmental health disparities research and monitoring.

Environmental Exposure↗
PubMed1998

Strategies for analyzing ecological momentary assessment data.

Studies incorporating repeated observations of momentary phenomena are becoming more common in behavioral and medical science. Analysis of such data requires the use of statistical techniques that are unfamiliar to many investigators. Some common ways of analyzing momentary data are reviewed--aggregation strategies, repeated measures analysis of variance, pooled within-person regression, and two-stage estimation procedures for multilevel models--and are found to be usually suboptimal, possibly leading to incorrect inferences. A broad class of statistical models for multilevel data that can address many research questions typically asked of momentary data are then described. Analytic issues that merit careful consideration include the scaling of momentary variables, allowance for serial autocorrelation of residuals, and the treatment of coefficients that vary across individuals as fixed versus random effects.

Analysis of Variance↗
PubMed2001

Single event multilevel botulinum toxin type A treatment and surgery: similarities and differences.

The present study attempts to provide objective evidence of two treatment options for children with cerebral palsy (CP): multilevel botulinum toxin type A (BTX-A) injections and multilevel surgery. The purpose of the study was to clarify the differences and the similarities, and common treatment principles of both treatment strategies. Objective three dimensional gait analysis data were studied retrospectively in two patient groups pre- and post-treatment (randomly selected from a group of children that were treated between 1998 and 1999). In the first group, 29 children with CP were managed with BTX-A injections according to an integrated multilevel approach (Molenaers et al., 1999a). A second group of 23 children with CP were managed by a more traditional single event multilevel surgery, also according to an integrated approach. Our aim was to evaluate the differences as well as the similarities between both patient groups, using a set of 56 parameters selected from three-dimensional gait analysis. The unifying concept between management with BTX-A injections and orthopaedic surgery was the adoption of a multilevel approach at one session. The groups demonstrated considerable differences with respect to age, pretreatment condition and amount and level of improvement after treatment. The children who received BTX-A were typically younger, and showed primary gait problems in the distal joints, whereas the children who underwent surgery demonstrated a higher frequency of gait deviations in the transverse plane and had more complications. Although the benefit of both treatments was confirmed by the present study, a difference in the amount and level of improvement was also demonstrated. In conclusion, these treatment modalities should be regarded as complementary rather than mutually exclusive treatments, with both calling for an integrated approach.

Adult↗
PubMed2006

Electromyographic patterns in children with cerebral palsy: do they change after surgery?

The purpose of this study was to investigate the changes in electromyographic (EMG) patterns after multilevel surgical treatment in children with spastic cerebral palsy. Children with diplegia (n=18) and hemiplegia (n=16) aging from 6 to 16 years participated in the study. Twenty healthy children within the same age span are presented as reference. Gait analysis and surface electromyograms of seven major lower limb muscles were assessed before and 1-5 years after the multilevel surgery. The most frequent procedures were equinus correction, distal rectus femoris transfer, femoral derotation osteotomy and hamstrings lengthening. The results showed that the EMG pattern of the soleus, lateral gastrocnemius and tibialis anterior muscles became closer to normal after the surgery, while no differences were detected between diplegic and hemiplegic patients. Furthermore, a subgroup of 10 patients showed an increase in medial hamstrings activation during preswing that decreased postoperatively. These findings indicate that changes in EMG patterns should not be ruled out after surgical treatment, although the extent of these changes is limited compared to changes in the kinematics. Abnormal muscle activation before the operation can be related to a compensatory response in some patients and this can be manipulated after surgery.

Adolescent↗
PubMed2005

Couples at risk following the death of their child: predictors of grief versus depression.

This longitudinal study examined the relative impact of major variables for predicting adjustment (in terms of both grief and depression) among bereaved parents following the death of their child. Couples (N = 219) participated 6, 13, and 20 months postloss. Use of multilevel regression analyses enabled assessment of the impact of several predictors and facilitated analysis of factors that were either shared by parents or individual. Grief was predicted mainly by shared parent factors: child's age, cause and unexpectedness of death, and number of remaining children. By contrast, depression was predicted by individual parent factors: gender, religious affiliation, and professional help seeking. Theoretical implications of these findings are discussed.

Adult↗