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PubMed2005

Human factors in matching images to standards: assimilation and time order error.

OBJECTIVES: This study examines recognition performance to depend on image context and time order error. Recognition of standard images is a basic process in medical image analysis. METHODS: After the presentation of a standard square, 20 subjects identified the standard within a variety of 7 squares. The choice was between the standard and either 3 smaller and 3 larger squares, 5 smaller and 1 larger square, or 5 larger and 1 smaller square (context conditions). RESULTS: Multilevel regression analysis showed large individual differences in judgments (P < .001). Context induced assimilation of judgments to the medium-sized square within response options (P < .001). Negative time order error in rapid judgments caused an underestimation of the standard (P < .001). CONCLUSIONS: Assimilation of judgments and time order error might be a threat to the reliability of medical image analysis. Some procedural recommendations are derived to reduce bias and increase patient safety in radiology.

Adult↗

PubMed2003

Patient experiences with information in a hospital setting: a multilevel approach.

BACKGROUND: Patients tend to be critical of poor communication and the provision of information from health professionals. One explanation may be related to organizational aspects characterizing the hospital unit. Studies have indicated quality of contact with nursing staff to be a major determinant of patients' experiences with information. Yet many studies do not simultaneously analyze the effects of patient and unit characteristics. OBJECTIVE: To explore the extent to which variation in patients' experiences with the provision of information from hospital staff are associated with differences between patients, and the extent to which they are associated with differences between hospital wards. RESEARCH DESIGN: Cross-sectional study of patients nested within hospital wards including hospital administrative data and survey data on patients' experiences with hospital care and nurses' assessments of working conditions and job satisfaction. RESULTS: Multilevel regression analysis indicated low intraward correlation and high within ward variability. In explaining variability in experiences with information, patients' sense of coherence was the most important patient-level characteristic. The percentage of nurses satisfied with their work contributed to an additional proportional reduction in variance between hospital wards. CONCLUSIONS: This study has illustrated the use of multilevel methods in analyzing patient perceptions of hospital care. Ward-level factors are at most modestly related to patients' experiences with information. The effect of hospital, department, and ward characteristics is likely to be mediated through the existence of microunits within hospital wards. Quality of contact with nursing staff may be a characteristic of the microunit rather than an organizational characteristic related to hospital wards.

Adolescent↗

PubMed2025

Association Between Ratio of Triglycerides to HDL-C and Cognitive Impairment: A Longitudinal Population-Based Analysis and Mendelian Randomization Study.

OBJECTIVES: This study aimed to explore the longitudinal association between the triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio and cognitive impairment in older adults and further assess potential causality using Mendelian randomization (MR). DESIGN: Longitudinal population-based analysis combined with two-sample MR. Data from Waves 6-8 (2015-2019) of the Survey of Health, Ageing, and Retirement in Europe (SHARE) were analyzed using hierarchical regression models and mixed linear effects models. MR utilized genome-wide association studies (GWAS) summary data. PARTICIPANTS: 11,444 adults aged ≥60 years from SHARE Wave 6, with longitudinal follow-up in Waves 7 (N = 2,775) and 8 (N = 5,469). MEASUREMENTS: TG/HDL-C ratio, cognitive function (orientation, immediate/delayed recall, verbal fluency, numeracy), and cognitive impairment (defined as scores >1.5 SD below age-group mean). Covariates included socio-demographics, health behaviors, comorbidities, and national-level factors. MR employed genetic variants associated with TG/HDL-C as instrumental variables. RESULTS: Higher TG/HDL-C ratios were negatively associated with total cognitive scores (β = -0.115, χ² = 15.44, df = 1, p < 0.001), immediate recall (β = -0.029, χ² = 12.34, df = 1, p < 0.001), delayed recall (β = -0.028, χ² = 7.33, df = 1, p < 0.001), verbal fluency (β = -0.038, χ² = 11.53, df = 1, p < 0.001), and numeracy (β = -0.019, χ² = 4.55, df = 1, p < 0.05) in fully adjusted models. Longitudinal analysis revealed increased cognitive impairment risk in the highest TG/HDL-C quartile (OR=1.43, 95% CI:1.01-2.03, χ² = 9.24, df = 1) over 4 years. MR supported a causal link between elevated TG/HDL-C and cognitive decline. CONCLUSIONS: Elevated TG/HDL-C ratios are longitudinally associated with cognitive decline in older adults. Managing lipid metabolism may mitigate cognitive impairment, highlighting the importance of TG/HDL-C as a modifiable risk factor in aging populations.

Humans↗

PubMed2001

Radiographic defect depth and width for prognosis and description of periodontal healing of infrabony defects.

BACKGROUND: The aims of the present study were to evaluate 1) defect depth and width as a prognostic factor and 2) change in defect width as a describing parameter of periodontal healing in infrabony defects treated by regenerative therapy after 6 and 24 months. METHODS: In 24 patients with advanced periodontitis, 39 infrabony defects were treated by guided tissue regeneration (GTR) using expanded polytetrafluoroethylene (ePTFE) (n = 7) or bioabsorbable barriers (n = 32). Clinical parameters were assessed and 39 standardized radiographs (in triplicate) were taken before and 6 and 24 months after surgery. Using a computer-assisted analysis, the depth, width, and angle of the bony defects were measured. RESULTS: Statistically significant vertical clinical attachment gains (CAL-V: 3.15 +/- 1.63 mm to 3.31 +/- 1.65 mm; P<0.001) and bony fill (1.30 +/- 2.53 mm; P<0.01 to 1.54 +/- 2.70 mm; P<0.005) were observed 6 and 24 months postsurgically. In a multilevel regression analysis CAL-V gain was predicted by baseline CAL-V (P <0.0001), actual smoking (P <0.05), and age (P <0.1). Bony fill could be predicted by baseline height of the infrabony component (P<0.0001), gingival index at baseline (P<0.05), and actual smoking (P <0.01). In narrow (<26 degrees) and deep (> or = 3 mm) infrabony defects bony fill was more pronounced than in wide and shallow defects (P <0.05). CONCLUSIONS: Improvement achieved by guided tissue regeneration in infrabony defects can be maintained up to 24 months after surgery. Narrow and deep infrabony defects respond radiographically and to some extent clinically more favorably to GTR therapy than wide and shallow defects. However, depth of the infrabony component was a stronger prognostic parameter than defect angle. Actual smoking impairs the results of GTR therapy in infrabony defects.

Adult↗

PubMed2005

Analysing the relationship between family planning workers' contact and contraceptive switching in rural Bangladesh using multilevel modelling.

With a population of over 131 million and a fertility rate of 29.9 per 1000, population growth constitutes a primary threat to continued economic growth and development in Bangladesh. One strategy that has been used to cease further increases in fertility in Bangladesh involves using family planning outreach workers who travel throughout rural and urban areas educating women regarding contraceptive alternatives. This study uses a longitudinal database to assess the impact of family planning outreach workers' contact upon contraceptive switching and upon the risk of an unintended pregnancy. Using longitudinal data on contraceptive use from the Operations Research Project (ORP) of the International Centre for Diarrhoeal Disease Research (ICDDR,B) in Bangladesh, multiple decrement life table analysis and multilevel, discrete-time competing risk hazards models were used to estimate the cumulative probabilities of switching to an alternative form of contraceptive use after a woman engaged in a discussion with an outreach worker. After controlling for the effects of socio-demographic and economic characteristics, the analysis revealed that family planning outreach workers' contact with women significantly decreases the risk of transitioning to the non-use of contraceptives. This contact also reduces the risk of an unintended pregnancy. Family planning workers' contact with women is associated with the increased risk of a woman switching from one modern method to another modern method. The study results indicate that side-effects and other method-related reasons are the two primary reasons for contraceptive discontinuation in rural Bangladesh.

Adult↗

PubMed2004

Predicting geographical variations in behavioural risk factors: an analysis of physical and mental healthy days.

STUDY OBJECTIVES: To determine the validity of physical and mental unhealthy days as summary measures for county health status and to forward a method for examining county level health trends using a single year of data from the Behavioral Risk Factor Surveillance System (BRFSS). DESIGN: The study analysed geographical variation in physical and mental unhealthy days at the state and county level using the 2000 BRFSS. Whereas state level analyses used individual level data, this research conducted multilevel regression analysis using county level data as independent variables and individual level reports of physical and mental unhealthy days as dependent variables. SETTING: Population based samples of non-institutionalised civilian adult residents from each of the 50 states and the District of Columbia in the United States. MAIN RESULTS: Socioeconomic variables predicted similar mean numbers of physical and mental unhealthy days at both the state and county level, validating the county level analyses. County level disability rates were strongly associated with county mean unhealthy days. Using the regression method we forward, it is possible to analyse county level trends using a single year of BRFSS data. CONCLUSIONS: Physical and mental unhealthy days may be used as valid summary measures of county health status. Regression models may be used to assist local decision makers in assessing the needs of their communities and may be used to improve health resource allocation within states.

Adolescent↗

PubMed2000

Fast analysis of transient acoustic wave scattering from rigid bodies using the multilevel plane wave time domain algorithm

The analysis of transient wave scattering from rigid bodies using integral equation-based techniques is computationally intensive: if carried out using classical schemes, the evaluation of the velocity potential on the surface of a three-dimensional scatterer, represented in terms of Ns spatial basis functions for Nt time steps, requires O(NtNs2) operations. The recently developed plane wave time domain (PWTD) algorithm permits the rapid evaluation of transient fields that are generated by bandlimited source distributions. It has been shown that incorporation of the PWTD algorithm into integral equation-based solvers in a two-level setting reduces the computational complexity of a transient analysis to O(NtNs1.5 logNs). In this paper, it is shown that casting the PWTD scheme into a multilevel framework permits the analysis of transient acoustic surface scattering phenomena in O(NtNslog2Ns) operations using O(NtNs) memory. Numerical examples that demonstrate the efficacy of the multilevel implementation are also presented.

Journal Article↗

PubMed2006

Men's approval of family planning in Bangladesh.

This article attempts to evaluate men's approval of family planning in Bangladesh using the couple data set from the recent Bangladesh Demographic and Health Survey (BDHS), 1999-2000. Family planning approval is addressed both from individual and couple perspectives. Analysis of BDHS data shows that about 85% of the wives report that their husbands approve of family planning, which is lower than the wives' own approval rate (95%). Using the couple data set, husbands' characteristics were matched to the wives' responses on family planning approval. Regression analyses show that age, education, access to TV, inter-spousal communication, current use of family planning and the number of living children significantly determine family planning approval among both men as well as couples. Family planning approval was found to be much lower in Sylhet than in the other administrative divisions. Multilevel modelling analysis suggests almost negligible variation at the community level. The findings indicate the need for careful evaluation of the DHS questions in order to measure appropriately men's family planning attitudes.

Adolescent↗

PubMed2004

Coverage and costs of childhood immunizations in Cameroon.

OBJECTIVE: To quantify the association between household-level and provider-level determinants and childhood immunization rates in Cameroon while also calculating the cost of childhood immunizations. METHODS: This study uses multilevel regression analysis to calculate these relationships. The 1998 Cameroon Demographic and Health Survey and the 2000 Multiple Indicator Cluster Survey are the main sources of household-level data. These surveys are supplemented by data from a 2002 survey of health facilities conducted in three provinces. At the national level, immunization financing data were collected from the Ministry of Health and donors that support the national Expanded Programme on Immunization. FINDINGS: The 1998 survey found that nationally 37% of children were fully immunized; the 2000 survey found that nationally 34% were fully immunized. These results are strongly correlated with both the mother's level of education and the household's economic status. Multilevel logistic regression shows that maternal education level is a stronger predictor of positive immunization status than is relative economic status. Children of mothers with secondary education or higher education were 3 times more likely to be fully vaccinated than children whose mothers had not completed primary education. At the health-facility level, both having art immunization plan and regular supervisory visits from someone at the health-district level are strongly positively associated with immunization rates. The cost of routine vaccinations for each fully immunized child is 12.73 U.S. dollars when donors' contributions are included but not the costs of immunization campaigns. CONCLUSION: Studies conducted in the 1980s and 1990s found that costs per fully immunized child varied from 2.19 U.S. dollars to 26.59 U.S. dollars (not adjusted for inflation) in a range of low-income and middle-income countries. The relatively low rates of immunization coverage in Cameroon, and the strong influence of the household's socioeconomic status--particularly the mother's level of education--on immunization rates suggest that the effectiveness of the Cameroon programme could be increased by promoting immunization and directing such programmes towards households with limited resources.

Cameroon↗

PubMed1997

Association between ambient air concentrations of nitrogen dioxide and respiratory symptoms in children in Prague, Czech Republic. Preliminary results from the Czech part of the SAVIAH Study. Small Area Variation in Air Pollution and Health.

The primary objective of the SAVIAH, a multi-centre study funded by European Union, was to assess new methodology for study of small area health statistics and to implement it in epidemiological health statistics and geography. In Prague, the study has been conducted in two city districts with large variation in air pollution. Data at individual level (health symptoms and socio-economic circumstances of the family) were collected by questionnaires completed by parents of 3680 children aged 7-10 both resident and attending schools within the area (response rate 88%). Aggregated data for geographical areas were available from census and urban planning sources for 692 enumeration districts in the study area which were aggregated into 75 medium sized areas. Outdoor concentrations of nitrogen dioxide (NO2) were monitored by passive samplers. All these data were integrated into a geographic information system (GIS). Spatial distribution of air pollution was estimated by kriging and multiple regression modelling. These models explained about 80% of the variation in air pollution measured by passive samplers. GIS was then used to assign to individuals an exposure based on place of residence and school in order to conduct individual based analyses. Association between NO2 and life-time prevalence of wheezing and/or whistling, and wheezing/whistling in the last 12 months was studied by logistic regression. For both outcomes, school levels of NO2 were positively related to symptoms but home levels of NO2 showed a negative association. Logistic regression at individual level gives similar results as ecological analysis and multilevel modelling. Hierarchical model yielded somewhat wider confidence limits. Adjustment for parental behavioural and socio-economic factors did not affect these estimates substantially. This study demonstrated the power of the GIS methodology in studying the effects of complex environmental factors on respiratory health of children.

Air Pollution↗

PubMedDate not supplied

Changes in passive tactile sensibility associated with dental implants following their placement.

PURPOSE: This study investigated the changes that might occur in passive tactile sensibility during a period of 3 months following Implant placement in a group of edentulous subjects treated with dental implants. The effect of changing the velocity of force application on passive tactile sensibility was also investigated. MATERIALS AND METHODS: Five edentulous subjects who had been treated (as a part of an immediate loading study) with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. Pushing forces were applied directly and perpendicular to the long axes of the abutments until the subjects felt the first sensation of pressure, using a computer-controlled, custom-made device. The force was measured with an integral transducer. The applied force had a ramped staircase pattern, which was used at 2 different tip velocities. The measurements were taken on 4 occasions: 1, 2, 4, and 12 weeks after fitting the abutments. RESULTS: Statistical analysis, using multilevel modeling, demonstrated that there was a significant decrease In the tactile threshold over successive weeks following implant placement. It also demonstrated that high velocity exhibited a higher threshold than low velocity. DISCUSSION AND CONCLUSION: It could be concluded that there was a significant increase In passive tactile sensibility during the healing phase following implant placement.

Aged↗

PubMed2005

Risk modifying effect of social capital on measures of heavy alcohol consumption, alcohol abuse, harms, and secondhand effects: national survey findings.

STUDY OBJECTIVE: To examine associations between social capital and individual risk for alcohol abuse and harms and identify protective effect mechanisms. DESIGN: Multilevel multivariate analysis with individual level data from a national panel survey of drinking and a contextual measure of social capital reflecting college mean aggregate reports of student volunteerism. Outcomes include heavy episodic (binge) drinking, frequent drinking, frequent drunkenness, diagnosable alcohol abuse, intentional drunkenness, acquisition of binge drinking, harms, secondhand effects from others' drinking. SETTING: United States, 119 four year colleges. PARTICIPANTS: Representative samples of youth ages 18-24 surveyed in 1997 and 1999 using an anonymous mailed questionnaire (total n = 27 687). MAIN RESULTS: Students from colleges with higher levels of social capital reported reduced risks for binge drinking (adjusted OR 0.38, 95% CI 0.20 to 0.69, p = 0.002), frequent drunkenness (adjusted OR 0.58, 95% CI 0.34 to 0.98, p = 0.04), acquisition of binge drinking in college (adjusted OR 0.48, 95% CI 0.24 to 0.95, p = 0.03), and alcohol abuse (adjusted OR 0.55, 95% CI 0.34 to 0.91, p = 0.02) in multilevel multivariate analyses that controlled for individual volunteering, the measure on which social capital was based. Higher levels of social capital protected against multiple drinking related harms (adjusted OR 0.51, 95% CI 0.29 to 0.90, p = 0.02) and secondhand drinking effects (adjusted OR, 0.30, 95% CI 0.16 to 0.58, p = 0.0003). Significant cross level interactions exist between fraternity/sorority membership and social capital for measures of risky drinking. Harm reduction primarily reflects consumption modification. CONCLUSIONS: Social capital exerts strong protective effects on alcohol abuse and harm in college including among high risk students.

Adolescent↗

PubMed2004

Radiographic parameters for prognosis of periodontal healing of infrabony defects: two different definitions of defect depth.

BACKGROUND: The aim of the present study was to evaluate defect width and two different definitions of defect depth as prognostic factors of periodontal healing in infrabony defects treated by regenerative therapy 6 and 24 months after surgery. METHODS: In 32 patients with moderate to advanced periodontitis, 50 infrabony defects were treated by the guided tissue regeneration (GTR) technique using non-resorbable or bioabsorbable barriers. Clinical parameters were assessed, and 50 triplets of standardized radiographs were taken before surgery and 6 and 24 months after surgery. Using a computer-assisted analysis, the distances cemento-enamel junction (CEJ) to alveolar crest (AC), CEJ to bony defect (BD), horizontal projection of the most coronal extension of the bony wall to the root surface to BD, width, and angle of the bony defects were measured. Depth of the bony defect was 1) calculated as CEJ-BD minus CEJ-AC (INFRA1) and 2) measured as horizontal projection of the most coronal extension of the bony wall to the root surface to BD (INFRA2). RESULTS: Whereas statistically significant vertical clinical attachment level gains (CAL-V: 3.36 +/- 1.59 mm/ 3.41 +/- 1.72 mm; P < 0.001) could be found both 6 and 24 months after surgery, bony fill (0.70 +/- 2.52 mm; P = 0.056/1.21 +/- 2.55 mm; P < 0.005) was significant 24 months post-surgically only. In a multilevel regression analysis, CAL-V gain was predicted by bioabsorbable membrane (P = 0.005), baseline probing depths (PD) (P < 0.001), and actual smoking (P < 0.05). Bony fill could be predicted by baseline depth of the infrabony component as determined by INFRA2 (P < 0.05), angulation of bony defect (P < 0.005), and gingival index at baseline (P < 0.001). In narrow (< 37 degrees) and deep (> or = 4 mm) infrabony defects, bony fill was more pronounced than in wide and shallow defects (P < 0.001). CONCLUSIONS: Improvement achieved by GTR in infrabony defects can be maintained up to 24 months after surgery. Narrow and deep infrabony defects respond radiographically and are to some extent clinically more favorable to GTR therapy than are wide and shallow defects. The infrabony component of bony defects, as determined by the distance from the most coronal extension of the lateral bony wall to BD (INFRA2), is a better predictor of bony fill than that determined by AC-BD (INFRA1).

Absorbable Implants↗

PubMed2004

The effects of early prevention programs for families with young children at risk for physical child abuse and neglect: a meta-analysis.

In this article, a meta-analysis is presented on 40 evaluation studies of early prevention programs for families with young children at risk for physical child abuse and neglect with mostly nonrandomized designs. The main aim of all programs was to prevent physical child abuse and neglect by providing early family support. For the meta-analysis, a multilevel approach was used. A significant overall positive effect was found, pointing to the potential usefulness of these programs. The study demonstrated a significant decrease in the manifestation of abusive and neglectful acts and a significant risk reduction in factors such as child functioning, parent-child interaction, parent functioning, family functioning, and context characteristics.

Age Factors↗

PubMedDate not supplied

Determination of florfenicol in fish feed by liquid chromatography.

A simple, accurate, and reproducible assay was developed for the determination of Florfenicol in medicated fish feed. Florfenicol was extracted from ground feed into an acetonitrile-water mixture by shaking and sonication. A portion of the centrifuged extract was passed through an Envi-Carb solid-phase extraction cartridge, through which Florfenicol eluted unretained. The collected eluant was diluted to adjust for analyte concentration, and injected into a reversed-phase liquid chromatography system. Samples were quantitated by external standard analysis versus multilevel calibration solutions. The procedure is suitable for the quantitation of samples medicated with 0.2-4 g/kg Florfenicol. Accuracy was evaluated by 2 analysts, who determined recovery of Florfenicol from feeds fortified over a range of 0.1-6.0 g/kg. The average recovery was 100.5% (relative standard deviation, 1.2%). The linearity, accuracy, precision, reproducibility (interday and analyst), and selectivity of the method are presented. The detection and quantitation limits were determined to be 0.2 and 1.0 mg/kg, respectively.

Animal Feed↗

PubMedDate not supplied

The determinants of delivery care in Kenya.

This paper examines the determinants of place of delivery and childbirth attendant in Kenya based on the 1993 Kenya Demographic and Health Survey data. The analysis utilizes multilevel logistic and multilevel multinomial regression models for the place of delivery and the type of childbirth attendant, respectively. The results show that delivery care in Kenya is determined by a wide range of factors: socioeconomic and cultural factors associated with the individual woman or her household, her demographic status or reproductive behavior relating to a specific birth, as well as availability and accessibility of health services within her community. In addition, a significant variation in delivery care behavior is observed between women and between communities, implying that there are unobserved factors within families and communities that have a significant effect on delivery care. The woman or family effect on delivery care is particularly strong, but varies by distance to the nearest delivery care facility.

Adolescent↗

PubMed2001

Substance use during pregnancy in the state of California, USA.

Most analyses of prenatal substance use focus on individual level correlates and ignore community level variables and the effect of the dependency of respondents within communities. This analysis uses multilevel logistic regression models to more accurately assess the correlates of perinatal substance use in California. Statistical results indicate that a significant portion of substance use can be attributed to neighborhood heterogeneity, and that traditional models of substance use may inaccurately attribute this variation to individual level regression coefficients. Substantive results indicate that levels of neighborhood public assistance had an independent, significant effect on the prevalence of all substances tested for except alcohol. Black women had higher predicted prevalence risks for alcohol and cocaine while White women had higher predicted risks for tobacco, marijuana and amphetamines. Racial contrasts were non-significant for the overall illicit drug category and opiates, after controlling for neighborhood public assistance. Finally, individual level variables, with the exception of age, were not moderated by levels of neighborhood public assistance.

Adolescent↗

PubMed2005

Longitudinal reference charts for growth of the fetal head, abdomen and femur.

OBJECTIVES: The aims of the present study were to establish improved reference charts for growth of the fetal head, abdomen and femur, and to determine the effect of fetal and maternal factors. STUDY DESIGN: This prospective longitudinal study included 650 low-risk pregnancies. Outer-outer biparietal diameter (BPD), head circumference (HC), mean abdominal diameter (MAD), abdominal circumference (AC) and femur length (FL) were measured by ultrasound, and the statistical analysis was based on regression analysis and multilevel modeling. RESULTS: Reference percentiles for the growth of MAD, AC and FL showed continuous growth in gestational week 10-40, while BPD and HC showed a slightly blunted growth toward the end of pregnancy. FL was the only variable that was not influenced by gender. There was a significant negative association between breech presentation and all five biometrical variables, while maternal weight was positively associated with all five variables. Cephalic index significantly influenced BPD and HC. Maternal height had a positive effect on BPD, HC, AC and FL, and parity had a positive effect on MAD and AC, while smoking influenced negatively HC, MAD, and FL. Terms for calculating conditional reference values and customisation for individualised growth assessment are presented. CONCLUSIONS: New reference charts for the growth of fetal head, abdomen and femur are suggested for assessing fetal size and growth, and can be adjusted for maternal and fetal factors to suite individual pregnancies.

Abdomen↗