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PubMed2005

Longitudinal profiling of health care units based on continuous and discrete patient outcomes.

Monitoring health care quality involves combining continuous and discrete outcomes measured on subjects across health care units over time. This article describes a Bayesian approach to jointly modeling multilevel multidimensional continuous and discrete outcomes with serial dependence. The overall goal is to characterize trajectories of traits of each unit. Underlying normal regression models for each outcome are used and dependence among different outcomes is induced through latent variables. Serial dependence is accommodated through modeling the pairwise correlations of the latent variables. Methods are illustrated to assess trends in quality of health care units using continuous and discrete outcomes from a sample of adult veterans discharged from 1 of 22 Veterans Integrated Service Networks with a psychiatric diagnosis between 1993 and 1998.

Bayes Theorem↗
PubMed1989

Economic stress and suicide: multilevel analyses. Part 2: Cross-level analyses of economic stress and suicidal ideation.

This paper reports the second of two studies of the hypothesis that the economy affects suicide; both studies were based in the same community during approximately the same time period. Although many aggregate-level tests have been conducted using archival measures of unemployment and suicide (the approach used in Part 1), the impact of economic climate on suicidal ideation has not been measured at the individual level. In the study reported here, aggregate economic indicators were combined with individual-level measures of stressful events, symptoms, and suicidal ideation obtained in a survey of Los Angeles from 1978 to 1982. Each of the two studies revealed small associations between economic stress and suicide or suicidal ideation, but they were inconsistent with respect to specific subgroups.

Adult↗
PubMed1996

Assessment of left ventricular volume and mass by cine magnetic resonance imaging in patients with anterior myocardial infarction intra-observer and inter-observer variability on contour detection.

Remodeling of the left ventricle after myocardial infarction can be documented by calculation of left ventricular volume and mass, using endocardial and epicardial tracings of multilevel multiphase short-axis cine magnetic resonance (MR) imaging series. We assessed left ventricular volume and mass from 8 slices and during 12 phases of the cardiac cycle in seven patients with an anterior wall myocardial infarction; one patient was studied twice, leaving eight MR examinations to be evaluated. Purpose of this study was to assess the intra-observer and inter-observer variability of epicardial volume, endocardial volume, and left ventricular mass from contours manually traced by two independent observers. For the eight MR examinations, epicardial volume was found to be 292 +/- 51 ml (mean +/- SD) at end-diastole, which decreased to 237 +/- 55 ml at end-systole. Endocardial volume was 141 +/- 31 ml at end-diastole, which decreased to 79 +/- 27 ml at end-systole. Left ventricular ejection fraction was 45 +/- 8%. Mean left ventricular mass, when averaged over all patient studies and all phases, was 159 +/- 30 g. Intra-observer and inter-observer variability were found to be 3.5% and 5.2% for endocardial volume, 2.0% and 2.5% for epicardial volume, and 3.6% and 3.6% for left ventricular mass, respectively. The contour analysis showed a statistically significant phase effect in the endocardial contour in the midventricular slices, which was resolved after establishing a more precise definition for the tracing of the endocardial border. In conclusion, left ventricular volume and mass in patients with an anterior wall myocardial infarction can be assessed with high reproducibility and reliability from manual contour tracings. A precise protocol for the definition of endocardial and epicardial contours is required to obtain reproducible and reliable results.

Humans↗
PubMed2005

Neodymium neutron cross section measurements.

Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute LINAC using metallic neodymium samples. The capture measurements were made at the 25-m-long flight station with a 16-segment NaI(Tl) multiplicity detector, and the transmission measurements were performed at 15 and 25 m flight stations with a 6Li glass scintillation detector. After the data were collected and reduced, resonance parameters were determined by simultaneously fitting the transmission and capture data with the multilevel R-matrix Bayesian code SAMMY. The resonance parameters for all naturally occurring neodymium isotopes lie within the energy range of 1.0-500 eV. The resulting resonance parameters were used to calculate the capture resonance integral with this energy region and were compared to calculations obtained when using the resonance parameters from ENDF-B/VI. The RPI parameters gave a resonance integral value of 32 +/- 0.5 b that is approximately 7% lower than that obtained with the ENDF-B/VI parameters. The current measurements significantly reduce the statistical uncertainties on the resonance parameters when compared with previously published parameters.

Chromium Isotopes↗
PubMed2005

Workplace levels of psychosocial factors as prospective predictors of registered sickness absence.

OBJECTIVE: We sought to investigate whether workplace levels of psychosocial work environment factors predict individual sickness absence. METHODS: Data were collected in a prospective study in 52 Danish workplaces in three organizations: municipal care, technical services, and a pharmaceutical company. Psychosocial factors were aggregated as workplace means. We used multilevel Poisson regression models with psychosocial factors as predictors and individual level sickness absence from absence registries as outcome. RESULTS: High workplace levels of decision authority predicted low sickness absence in the technical services (rate ratio = 0.66, 95% confidence interval = 0.51-0.86) and high workplace levels of skill discretion predicted low sickness absence in the pharmaceutical company (rate ratio = 0.74, 95% confidence interval = 0.62-0.88) after control for relevant confounders. Workplaces in municipal care did not differ with respect to the psychosocial factors. CONCLUSIONS: Psychosocial factors at the workplace level may be important predictors of sickness absence.

Absenteeism↗
PubMed1999

Racial and ethnic variation in low birthweight in the United States: individual and contextual determinants.

Using the Linked Birth and Death data set for 1990, the County-City Plus for 1993, and Summary Tape Files (STF) for 1990, a multilevel model is utilized to examine the influence of county and individual-level characteristics on low birthweight risk for white, black, Mexican, Cuban and Puerto Rican infants in the United States. Logistic regression results show that the racial and ethnic differences in low birthweight are not only the result of the individual-level characteristics of the mother, but also are a function of the characteristics of the county where the mother resides. Support for the contention that contextual factors work directly and indirectly to affect low birthweight risk was found. Separate racial/ethnic models indicate that the specific contextual variables that account for low birthweight risk vary across racial/ethnic groups.

Adolescent↗
PubMedDate not supplied

Individual and neighbourhood determinants of health care utilization. Implications for health policy and resource allocation.

OBJECTIVES: To investigate the importance of both individual and neighbourhood socioeconomic characteristics for health care utilization. METHODS: Various linkage procedures generated a longitudinal dataset with information on 2,116 Nova Scotians, their residential neighbourhoods, 8 years of health care utilization and vital status. Unilevel and multilevel regression analyses were employed to examine the effects of both individual and neighbourhood characteristics on health care use. RESULTS: Individual income and education determined physician and hospital use. Also, neighbourhood characteristics, specifically average income and percentage of single mother families, were found to determine health care use. When considering individual and neighbourhood characteristics simultaneously, individual income and education determined physician and hospital use independently, while neighbourhood income determined physician use independently. CONCLUSIONS: Both individual and neighbourhood socioeconomic characteristics determine health care use. Acknowledging this allows better targeting of health policy and planning, and enables more accurate needs-based resource allocation.

Adolescent↗
PubMed2006

What do we learn from binding features? Evidence for multilevel feature integration.

Four experiments were conducted to investigate the relationship between the binding of visual features (as measured by their aftereffects on subsequent binding) and the learning of feature-conjunction probabilities. Both binding and learning effects were obtained, but they did not interact. Interestingly, (shape-color) binding effects disappeared with increasing practice, presumably because of the fact that only 1 of the features involved was relevant to the task. However, this instability was only observed for arbitrary, not highly overlearned combinations of simple geometric features and not for real objects (colored pictures of a banana and strawberry), where binding effects were strong and resistant to practice. These findings suggest that learning has no direct impact on the strength or resistance of bindings or on speed with which features are bound; however, learning does affect the amount of attention particular feature dimensions attract, which again can influence which features are considered in binding.

Analysis of Variance↗
PubMed1999

Incremental growth charts for condylar growth between 6 and 16 years of age.

This study provides sex specific reference data for the incremental growth of the mandibular condyle. The results pertain to a mixed-longitudinal sample of 113 males and 108 females followed annually between 6 and 16 years of age (total of 1647 observations). Growth of condylion was evaluated using naturally stable mandibular reference structures. The mean growth curves were estimated by multilevel models using iterative least squares procedures; between subject variation was estimated based on the sample's percentile distributions. Mean yearly velocities of condylar growth for males ranged between 2.1 and 3.1 mm/year. Growth rates decreased during childhood, increased during adolescence, and attained a maximum of 3.1 mm/year at approximately 14.3 years of age. Females showed a more constant rate of condylar growth during childhood (2.0-2.7 mm/year), a smaller adolescent peak (2.3 mm/year) at approximately 12.2 years and rapid deceleration after the peak. These reference data offer orthodontists an objective means of evaluating growth potential and treatment outcome in individual patients. Charts are provided for evaluating condylar growth of individual patients.

Adolescent↗
PubMed1999

Migradollars and mortality: the effects of migration on infant survival in Mexico.

We apply multilevel methods to data from Mexico to examine how village migration patterns affect infant survival outcomes in origins. We argue that migration is a cumulative process with varying health effects at different stages of its progression, and test several related hypotheses. Findings suggest higher rates of infant mortality in communities experiencing intense U.S. migration. However, two factors diminish the disruptive effects of migration: migradollars, or migrant remittances to villages, and the institutionalization of migration over time. Mortality risks are low when remittances are high and decrease as migration becomes increasingly salient to livelihoods of communities. Together, the findings indicate eventual benefits to all infants, irrespective of household migration experience, as a result of the development of social and economic processes related to U.S. migration.

Adult↗
PubMedDate not supplied

Selection of ecologic covariates in the American Cancer Society study.

The American Cancer Society (ACS) Study of the effects of long-term exposure to ambient air pollution on mortality used metropolitan areas to assign exposures to individual cohort members (Pope et al., 1995); these authors did not, however, control for any other place-specific variables in their analysis. Consequently, the study has been criticized on the basis that the association observed between air pollution and mortality may be confounded by other unmeasured ecologic covariates. To address this criticism, the reanalysis team selected a set of place-specific variables that measured determinants of health ranging from the biophysical environment to the social environment and the healthcare system. This article outlines the process by which place-specific ecologic covariates were selected; data measuring these variables were obtained and geographic boundaries for places were delineated. Issues involved in obtaining and using geographically based ecological data are examined within the context of the reanalysis of the ACS study. Both the ecological fallacy and the atomistic fallacy are addressed and an argument is made for the importance of studying the effects of place-specific variables that are integral or contextual in nature. Issues relating to the Modifiable Areal Unit Problem (MAUP) are explored with reference to using ZIP codes and data from a variety of sources. It is argued that differences in the geographical scale of variability for various pollutants may prove to be the key to distinguishing between their relative impacts on health and that multilevel analyses are essential for understanding the impact of social and environmental determinants of health. A number of determinants of health are then briefly examined in terms of their association with mortality, the appropriateness of their being measured at the metropolitan scale, and the availability of data for the 1980s from U.S. sources. Finally, the article presents the database of place-specific ecologic covariates that was incorporated into the ACS models during the reanalysis in order to account for the influence that place may have above and beyond ambient air pollution.

Air Pollutants↗
PubMed2005

Physicians' attitudes and preventive care delivery: insights from the DOPC study.

BACKGROUND: Interventions that modify physician attitudes to enhance preventive service delivery are common, yet other factors may be relatively more important in determining whether these services are provided. We assessed associations between physicians' attitudes and delivery of preventive care, compared with factors related to the patient, visit, or practice. METHODS: One hundred twenty-eight primary care physicians rated the importance of five preventive services and their effectiveness at delivering them. We assessed whether their patients had received cervical smears, prostate-specific antigen (PSA) testing, smoking cessation advice, recommendation to use aspirin to prevent myocardial infarction, or weight-maintenance counseling, when appropriate. Multilevel models assessed associations between physician attitudinal characteristics and a patient's likelihood of being up to date for each service. RESULTS: Importance of PSA screening and tobacco cessation counseling were weakly associated with patients' receipt of preventive care; no association between attitudes and other services was observed. Factors such as having a visit for well care and use of prevention flowcharts were associated with delivery of preventive services to a greater extent. CONCLUSIONS: Physicians' attitudes toward prevention are necessary, but not sufficient in ensuring the delivery of preventive services. Future interventions should address visit- and practice-specific factors more closely associated with preventive care.

Adult↗
PubMed2003

Contemporary longitudinal methods for the study of trauma and posttraumatic stress disorder.

Traditional methods for analyzing trends in longitudinal data have typically emphasized average group change over time. In this article, we propose multilevel, regression-based methods for examining inter-individual differences in intra-individual change and apply these methods to research in trauma and posttraumatic stress disorder (PTSD). The outcome or dependent variable of interest is reconceptualized as an index of dynamic change reflecting the trend or trajectory of an individual's PTSD symptom severity scores across time. A basic statistical model is presented, and analyses and findings are demonstrated with an existing database used in previously published studies. The methods offer promise for future study of the natural course of PTSD chronicity or recovery, risk and resilience factors that influence individual growth or decline, and critical timepoints for intervention.

Adaptation, Psychological↗
PubMed1994

Functional compartments of the tensor veli palatini muscle.

OBJECTIVE: To evaluate a dual role for the tensor veli palatini muscle in tubal and palatal function. MATERIALS AND METHODS: The eustachian tube region of guinea pigs and macaques was fixed and processed for analysis by serial section histologic examination, micro-dissection, or both. The attachment, fiber direction, and regional relations of potentially discrete functional compartments in eustachian tube muscles were noted. RESULTS: The tensor veli palatini muscle in macaques has two anatomic sub-bellies. One appears to be a tubal dilator, the other to make the tube rigid along its longitudinal axis. No other muscle is directly associated with the eustachian tube in macaques. The tensor veli palatini muscle in guinea pigs has one gross belly that may affect palatal tensing and tubal dilation, rigidification, and stabilization. Other muscles of the eustachian tube in guinea pigs are a medial sub-belly of the medial pterygoid muscle, not previously described, and the levator veli palatini muscle. CONCLUSIONS: The muscular elements underlying tubal-palatal function in guinea pigs are more distinct and spatially separated than in macaques or humans. These differences may explain the confusion about the role of accessory muscles in tubal function. Muscular compartments of the eustachian tube complex in guinea pigs are easily accessible, which facilitates a more discrete and confident placement of electromyography electrodes. The guinea pig may be a useful model to better understand the interaction of multilevel compartmentalized physiologic sequences that underlie coordination of swallowing, breathing, and middle ear aeration.

Anatomy, Comparative↗
PubMed2006

An educational programme for peer review groups to improve treatment of chronic heart failure and diabetes mellitus type 2 in general practice.

RATIONALE, AIMS AND OBJECTIVES: Peer review groups are considered helpful for quality improvement in primary care. An interactive educational programme for small peer groups was developed, focusing on the implementation of newly developed treatment guidelines. The aim is to evaluate the effect of the programme on adherence to treatment guidelines in general practice. METHODS: A cluster randomized trial using a balanced incomplete block design was used; one arm received a programme on treatment of chronic heart failure (CHF), the other on hypertension treatment in diabetes mellitus type 2 (T2DM). A random sample of 10 CHF and 10 T2DM patients per GP was drawn, for whom data were extracted from electronic patient records 1 years before and 6 months after the intervention. The outcomes were prescribing of ACE inhibitors, and antihypertensive treatment in T2DM. The effect was analysed separately for both programmes using multilevel regression models. RESULTS: All 27 peer review groups in one region in the Netherlands were randomized, of which 16 participated. No significant effects were observed in the CHF group or in the T2DM group. The opportunity for change was limited, as only 53% of the CHF patients and 60% of the T2DM patients had a contact with their GP between the intervention and follow-up measurement. CONCLUSION: The peer review programme was not successful for changing the treatment of chronic patients, although the programme focused on dealing with barriers perceived by the participants. Not all problems perceived can be solved in a peer group discussion.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Ecological and individual predictors of birthweight in a northern Finland birth cohort 1986.

This multilevel study of spatial variability in, and determinants of, birthweight was conducted using individual and ecological data in a geographically defined prospective birth cohort for 1986 in northern Finland. The study area comprises three large areas defined by latitude: Northern Lapland (NL), Southern Lapland (SL) and Oulu province (OP), comprising 74 localities with a total study population of 9216 singleton births. The mean birthweight was 3482 g for NL, 3537 g for SL and 3587 g for OP (NL vs. OP and SL vs. OP: P < 0.05). The crude rate for stillbirths was highest in NL. The women in the northernmost area were socially less privileged and the localities less prosperous compared with those in the southernmost area. Significant spatial clustering of mean birthweights was found (P = 0.0016), with highest birthweight in the south-western part of the study area. A variable expressing the wealth of each locality, the financial capacity category (FCC), had its lowest mean value in NL, with a range of one to six for the localities studied here. A multilevel multiple regression model showed that, after allowing for sex, gestational age, mother's age, height and hypertensive disorders, parity, body mass index, previous low birthweight child and smoking as individual determinants of birthweight, part of the residual variation could be explained by the locality wealth parameter. Using the multilevel model, the differences in mean birthweight across the three latitude areas persisted but were reduced (difference OP vs. NL reduced from 105 g to 86.5 g). The relationship between birthweight and FCC was inverse U-shaped with the highest mean birthweight estimated for localities occurring in the middle of the range (FCC = 3). The wealthiest urban localities (FCC = 6) and the most deprived localities (FCC = 1) both had a predicted birthweight about 60 g below the maximum at FCC = 3, if all other factors were held constant. This result, taken together with the spatial clustering of birthweights, suggests that there may be important social and environmental determinants of birthweight that have yet to be identified.

Adult↗
PubMedDate not supplied

Enhancing cultural competence among hospice staff.

A critical component in making hospice and palliative care services accessible and acceptable to diverse communities is preparation of all providers to enhance cultural competence. This article reports a study designed to test an educational intervention aimed at expanding cultural awareness, sensitivity, and competence with a multi-disciplinary and multilevel team of hospice workers. The purpose of this quasi-experimental, longitudinal, crossover design was to test the effects of an educational intervention for multidisciplinary hospice providers. Findings demonstrated that even with a modest face-to-face intervention, cultural competence scores were significantly greater after the educational intervention for participants in both groups. Although the intervention proved successful at enhancing cultural competence scores among diverse types of hospice workers, limitations and logistic insights gained from this pilot suggest the need for examination of alternative methods of program delivery.

Adult↗
PubMed2005

The role of school context in the increase in young people's health complaints in Finland.

According to biological indicators trends in young people's health appear favourable, but the psychosocial aspects suggest a different pattern. We studied the differences across schools in common health complaints and in three groups of factors behind them: pupils' individual characteristics, family related factors and school-related factors. Multilevel linear regression models were used to analyse repeated cross-sectional data from Finnish 8th and 9th graders (14- and 15-year-olds, n=60347) in 109 schools that were surveyed in 1996, 1998 and 2000. Common health complaints increased steadily during the follow-up for all schools and they varied across schools. Both individual and school-level factors contributed significantly to the variation in common health complaints. The study suggests that young people's psychosocial health involves a range of influences deriving from individual susceptibility and from the social and educational functioning of schools. However, none of these factors can account for the rapid decrease in young people's psychosocial health.

Adolescent↗