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Results for “Structural equation modeling”

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PubMedDate not supplied

Depressive symptoms and metabolic risk in adult male twins enrolled in the National Heart, Lung, and Blood Institute twin study.

OBJECTIVE: To determine the extent to which depressive symptoms are associated with metabolic risk factors and whether genetic or environmental factors account for this association. METHOD: Twin structural equation modeling was employed to estimate genetic and environmental contributions to the covariation of depressive symptoms, as indexed by the Centers for Epidemiological Studies-Depression Scale, and common variance among blood pressure, body mass index, waist-to-hip ratio, and serum triglycerides and glucose among 87 monozygotic and 86 dizygotic male twin pairs who participated in the NHLBI twin study. RESULTS: Depressive symptoms were associated with individual components of the metabolic syndrome and common variance among the risk factors. Twin structural equation modeling indicated that the associations were attributable to environmental (nongenetic) factors. CONCLUSIONS: These results support the hypothesis that depressive symptoms may increase risk for a pattern of physiological risk consistent with the metabolic syndrome.

Aged↗

PubMed2002

Homesickness among students in two cultures: antecedents and consequences.

Review of the theoretical and empirical literature on homesickness showed that despite recent advances, scientific understanding of the impact on students of leaving home for college is still limited. Further empirical investigation using standardized measures, structural equation models and including additional mediating/moderating variables is needed. Two studies were thus conducted, one in the Netherlands, and one in the UK. Homesickness was investigated among recent-intake students, using a newly developed instrument, the Utrecht Homesickness Scale. Variables investigated in relationship to homesickness included depression, personality factors (self-liking, competence, self-esteem) and family situation (attachment to family). Homesickness was found to be a common though differentially prevalent phenomenon (approximately 50% in the Netherlands; 80% in the UK). Structural equation models showed that students missed family and friends and had difficulties adjusting to college life. These difficulties were associated with ruminations about home and loneliness, which themselves were associated with depression. There were differences in intensity (UK students were more homesick) and there were gender differences (UK females experienced more homesickness). Both the personality and family situation factors had an impact on homesickness. The results supported the conceptualization of homesickness as a 'mini-grief', to be viewed from theoretical perspectives in the field of loss and bereavement.

Adult↗

PubMed2000

Adolescent individuation and alcohol use in multi-ethnic youth.

OBJECTIVE: A structural equation modeling approach is used to assess adolescent alcohol use as a function of two measures of individuation in the context of other family and peer psychosocial factors for adolescents in three ethnic groups. The separation measure captures aspects of individuation related to detachment or rebelliousness. Intergenerational individuation measures increasing self-reliance and control with maintenance of supportive family bonds. METHOD: A sample of 1,200 sixth through eighth grade black, Mexican-American and non-Hispanic white adolescents participated. A structural equation model describing adolescent alcohol use as a function of two measures of individuation, family conflict, communication with mother, stress and peer use of alcohol was tested and compared for the three ethnic groups. RESULTS: Significant direct and indirect paths to adolescent alcohol use were indicated for individuation measures and family use, peer use and stress variables. The proposed model fit for each of the groups, although the way in which separation related to stress was different in the black group. CONCLUSIONS: The findings support the role of individuation as a contributing factor in adolescent alcohol use for each ethnic group. They indicate the importance of family and parent-adolescent relationships in adolescent alcohol use and suggest directions for both family-based and school-based preventive interventions.

Adolescent↗

PubMed1998

Medical outcomes study short form 36: testing and cross-validating a second-order factorial structure for health system employees.

OBJECTIVE: To test the factorial validity of the SF-36. DATA SOURCE: Sample data collected in 1995 and 1996 using telephone interviews with health system employees as part of a study of health status. METHODS OF ANALYSIS: Confirmatory factor analysis and structural equation modeling techniques were used to evaluate the data. PRINCIPAL FINDINGS: The results of this study suggest that (1) Mental Health and Physical Health are not independent; (b) Mental Health cross-loads onto Physical Health; (c) general health loads onto Mental Health instead of Physical Health; (d) many of the error terms are correlated; (e) the physical function subscale is not reliable across the samples or the "age" or "education" subgroups; and (f) the mental health subscale path from Mental Health is not reliable across some subgroups. This hierarchical factor pattern was replicated across both samples. CONCLUSIONS: This study supports the second-order factorial structure of the SF-36. Adding the covariance path between the variables Physical Health and Mental Health improved model fit. Two paths from the second-order latent variables to the first-order latent variables differ from the original hypothesized structure of the SF-36. Health perception was influenced by Mental Health rather than Physical Health, and mental health was influenced by both Mental Health and Physical Health. This cross-loading suggests that the perception of Physical Health greatly affects mental health. Scale instabilities in the SF-36 across subgroups suggest that a comparison of mean scores or summary scores is inappropriate. Data interpretation can be improved if multigroups structural equation modeling is used.

Activities of Daily Living↗

PubMed1999

Social, emotional, and behavioral functioning of children with cancer.

OBJECTIVE: It was hypothesized that children with cancer would have more social problems and difficulties with emotional well-being than case control, same race/gender, similarly aged classmates. STUDY DESIGN: Using a case controlled design, children with any type of cancer requiring chemotherapy except brain tumors (n = 76), currently receiving chemotherapy, ages 8 to 15, were compared with case control classroom peers (n = 76). Peer relationships, emotional well-being, and behavior were evaluated based on peer, teacher, parent, and self-report, and were compared using analysis of variance and structural equation modeling. RESULTS: Relative to case controls, children with cancer were perceived by teachers as being more sociable; by teachers and peers as being less aggressive; and by peers as having greater social acceptance. Measures of depression, anxiety, loneliness, and self-concept showed no significant differences, except children with cancer reported significantly lower satisfaction with current athletic competence. There were also no significant differences in mother or father perceptions of behavioral problems, emotional well-being, or social functioning. Scores on all standardized measures were in the normal range for both groups. Comparisons of the correlation matrices of children with cancer and to the correlation matrix of the comparison children using structural equation modeling suggested they were not significantly different. CONCLUSIONS: Children with cancer currently receiving chemotherapy were remarkably similar to case controls on measures of emotional well-being and better on several dimensions of social functioning. These findings are not supportive of disability/stress models of childhood chronic illness and suggest considerable psychologic hardiness.

Adolescent↗

PubMed2002

Statistical techniques for the analysis of change in longitudinal studies of the menopause.

OBJECTIVE: Critical review of statistical techniques used to analyze data from longitudinal studies. METHOD: Literature search and classification of statistical methods and their utilization evaluated against known underlying assumptions. RESULTS: One hundred and twenty-three papers found: 1. cross-sectional reduction of data (56%); 2. multifactorial techniques (26%); 3. repeated measurement analysis of variance (14%); 4. other (time series and structural equation modelling) (4%). CONCLUSIONS: Cross-sectional reduction violates underlying statistical assumptions. A simple and powerful technique is to mean values prior to and following an event such as the final menstrual period. To allow for the influence of multiple factors, linear regression is preferred to logistic regression where continuous data are available. For more information about evolution in time, more complex techniques are needed. A suitable technique is repeated measurement multivariate analysis of variance using a number of contrasts to estimate various effects. Split plot or randomized block designs cannot be recommended as they violate compound symmetry assumptions. For series involving more than 100 observations for each subject, time series and spectral analysis techniques should be considered. Structural equation modelling is recommended for examination in detail of a range of factors that may influence the studied end-point, the presence of feedback and of latent or non-measurable variables.

Adult↗

PubMed2006

Do the SF-36 and WHOQOL-BREF measure the same constructs? Evidence from the Taiwan population*.

BACKGROUND: The SF-36 and WHOQOL-BREF are available for international use, but it is not clear if they measure the same constructs. We compared the psychometric properties and factor structures of these two instruments. METHODS: Data were collected from a national representative sample (n=11,440) in the 2001 Taiwan National Health Interview Survey, which included Taiwan versions of the SF-36 and WHOQOL-BREF. We used Cronbach's alpha coefficient to estimate scale reliability. We conducted exploratory factor analysis to determine factor structure of the scales, and applied multi trait analysis to evaluate convergent and discriminant validity. We used standardized effect size to compare known-groups validity for health-related variables (including chronic conditions and health care utilization) and self-reported overall quality of life. Structural equation modeling was used to analyze relationships among the two SF-36 component scales (PCS and MCS) and the four WHOQOL subscales (physical, psychological, social relations, and environmental). RESULTS: Cronbach's alpha coefficients were acceptable ([Symbol: see text]0.7) for all subscales of both instruments. The factor analysis yielded two unique factors: one for the 8 SF-36 subscales and a second for the 4 WHOQOL subscales. Pearson correlations were weak (<0.3) among subscales of both instruments. Correlations for subscales hypothesized to measure similar constructs differed little from those measuring heterogeneous subscales. Effect sizes suggested greater discrimination by the SF-36 for health status and services utilization known groups, but greater discrimination by the WHOQOL for QOL-defined groups. Structural equation modeling suggested that the SF-36 PCS and MCS were weakly associated with WHOQOL. CONCLUSIONS: In this Taiwan population sample, the SF-36 and WHOQOL-BREF appear to measure different constructs: the SF-36 measures health-related QOL, while the WHOQOL-BREF measures global QOL. Clinicians and researchers should carefully define their research questions related to patient-reported outcomes before selecting which instrument to use.

Adult↗

PubMed1999

Medication adherence in rheumatoid arthritis patients: older is wiser.

OBJECTIVES: To create a profile of individuals nonadherent to their medications in an age-stratified sample (ages 34-84) of community-dwelling rheumatoid arthritis patients. The relative contributions of age, cognitive function, disability, emotional state, lifestyle, and beliefs about illness to nonadherence were assessed. DESIGN: A direct observation approach was used in conjunction with structural equation modeling. All participants were administered a preliminary assessment battery. Medications were then transferred to vials with microelectronic caps that recorded medication events for all medications for the next 4 weeks. PARTICIPANTS AND SETTING: A volunteer sample of 121 community-dwelling rheumatoid arthritis (RA) patients were recruited from newspaper ads, posters, and via informal physician contact from private rheumatology practices in Atlanta and Athens, Georgia. Written verification of the RA diagnosis and a disease severity rating were obtained from personal physicians before patients were enrolled in the study. Patients were tested in a private physician's office, and their medication adherence was monitored electronically for a month in their every-day work and home settings. MEASUREMENTS AND RESULTS: Structural equation modeling techniques were used to develop a model of adherence behavior. Cognitive and psychosocial measures were used to construct latent variables to predict adherence errors. The model of medication adherence explained 39% of the variance in adherence errors. The model demonstrated that older adults made the fewest adherence errors, and middle-aged adults made the most. A busy lifestyle, age, and cognitive deficits predicted nonadherence, whereas coping with arthritis-related moods predicted adherence. Illness severity, medication load, and physical function did not predict adherence errors. Omission of medication accounted for nearly all errors. CONCLUSION: Despite strong evidence for normal, age-related cognitive decline in this sample, older adults had sufficient cognitive function to manage medications. A busy lifestyle and middle age were more determinant of who was at risk of nonadherence than beliefs about medication or illness. Thus, practicing physicians should not assume that older adults have insufficient cognitive resources to manage medications and that they will be the most likely to make adherence errors. Very busy middle-aged adults seem to be at the greatest risk of managing medications improperly.

Adaptation, Psychological↗

PubMed2002

Rethinking and rescoring the SF-12.

OBJECTIVES: To derive and assess the validity of an Australian version of the SF-12 quality-of-life questionnaire. METHODS: Using regression methods and structural equation modelling to obtain item weights, an Australian version of the SF-12 was derived from Australian population survey data and compared to the existing United States (US) SF-12 variable set. RESULTS: The Australian version of the SF-12 explained 94% of the variation for physical components summary (PCS) and the mental components summary (MCS) of the SF-36 questionnaire. There was high level of agreement on the MCS and PCS summary scores between both versions of the SF-12 and the SF-36. CONCLUSIONS: Although it is possible to derive a valid Australian version of the SF-12 it is concluded the US version of the SF-12 be used for reasons of international comparability, but using item weights derived from structural equation modelling.

Adolescent↗

PubMed1995

Functional network interactions between parallel auditory pathways during Pavlovian conditioned inhibition.

Using covariance structural equation modeling and fluorodeoxyglucose (FDG) autoradiography this study examined auditory system interactions when the learned associative effects of a tone were inhibited by a light. Two groups of rats received pairings of a tone (conditioned excitor: T+) with a mild footshock. Group TL- was trained in a Pavlovian conditioned inhibition paradigm (T+/TL-) where the tone-light compound signaled the absence of footshock, making the light the inhibitor (L-). Group TL degree was trained with the tone as the excitor and the light as a 'neutral' stimulus. After FDG injection, all rats were presented with the tone-light compound. Group differences in auditory system FDG uptake were observed only in the ventral division medial geniculate nucleus (MGV), where group TL- had relatively lower incorporation. Structural equation modeling was used with the covariances of FDG activity to determine the functional influences through the auditory system anatomic connections. Differences were noted mainly at the level of the inferior colliculus (IC) and medial geniculate, possibly reflecting the unique anatomic relation of these regions with extraauditory areas. Ascending and descending influences from the IC differed with stronger influences for group TL-. Intracollicular and the ascending influence influences of MGV and medial division of the medial geniculate nucleus (MGM) on the auditory cortex also differed mainly in the sign of the functional interaction. These results demonstrate how interactions among parallel auditory pathways can code the behavioral significance of auditory stimuli and emphasize that a full appreciation of neural operations underlying learning can only be gained through examination of both regional activity and interregional interactions.

Animals↗

PubMed2001

Non-small cell lung cancer. The role of chemoimmunoradiotherapy after surgery.

The aim of this study was to determine expediency of adjuvant chemoimmunoradiotherapy for radically operated non-small cell lung cancer patients (LCP) with pathologic stage II-III (T1-4N0-2M0G1-3). In retrospective trial (1985-1998) a 5-year survival of 54 consecutive radically operated LCP after adjuvant chemoimmunoradiotherapy (group A) was compared with 5-year survival of 264 LCP, after radical procedures (group C) and with 5-year survival of 86 radically operated LCP after postoperative radiotherapy (group B) (45-50 Gy). I cycle of chemoimmunotherapy was given on day 10-14 after complete resections. Radiotherapy (45-50 Gy) was administered since day 7 after 1 cycle. After irradiation 3-4 courses of CAVT were repeated every 21-28 day. Variables selected for 5-year survival and life span study were sex, age, TNMG, cell type, tumor size. Survival curves were estimated by the Kaplan-Meier method. Differences in curves between groups of LCP were evaluated using a log-rank test. Multivariate proportional hazard Cox regression, multi-factor clustering, structural equation modeling and Monte Carlo simulation were used to determine any significant overall regularity. 5-year survival was superior in group A (64.8%: 35 out of 54 LCP with N0-2; life span=1998.2+/-156.9 days) compared with group B (45.3%: 39 out of 86 LCP with N0-2; life span=1296.4+/-109.5 days) (P<0.001). 5-year survival of group C was 63.6% (168 out of 264 LCP with N0-2; life span=1738.3+/-63.4 days) (P>0.05 for group A and P<0.001 for group B). For LCP with N1-2 5-year survival was significantly superior for group A (63.6%: 21 from 33; life span=1934.0+/-180.9 days) compared with group C (28.1%: 25 out of 89; life span=1056.9+/-91.1 days) (P<0.001) and with group B (35.6%: 21 out of 59; life span=1051.7+/-119.6 days) (P<0.001). Structural equation modeling and Monte Carlo simulation confirmed significant overall differences between 5-year survival (P<0.05) and life span (P<0.001) of LCP with N1-2 in group A with respect to group C or B; however, 5-year survival of LCP for N0 in groups A, B and C were not significantly different.

Antineoplastic Agents↗

PubMed1999

The Assessment of Quality of Life (AQoL) instrument: a psychometric measure of health-related quality of life.

This paper describes constructing the Assessment of Quality of Life (AQoL) instrument; designed to measure health-related quality of life (HRQoL), and to be the descriptive system for a multi-attribute utility instrument. Unlike previous utility instruments' descriptive systems, the AQoL's has been developed using state-of-the-art psychometric procedures. The result is a descriptive system which emphasizes five different facets of HRQoL and which can claim to have construct validity. Based on the WHO's definition of health a model of HRQoL was developed. Items were written by focus groups of doctors and the researchers. These were administered to a construction sample, comprising hospital patients, and community members chosen at random. Final construction was through an iterative process of factor and reliability analyses. The AQoL measures 5 dimensions: illness, independent living, social relationships, physical senses and psychological wellbeing. Each has three items. Exploratory factor analysis showed the dimensions were orthogonal, and each was unidimensional. Internal consistency was alpha = 0.81. Structural equation modeling explored its internal structure; the comparative fit index was 0.90. These preliminary results indicate the AQoL has the prerequisite qualities for a psychometric HRQoL instrument for evaluation; replication with a larger sample is needed to verify these findings. Scaling it for economic evaluation using utilities is being undertaken. Respondents have indicated the AQoL is easy to understand and is quickly completed. Its initial properties suggest it may be widely applicable.

Adult↗

PubMed1990

Alternative common factor models for multivariate biometric analyses.

In prior research we have shown how linear structural equation models and computer programs (e.g., LISREL) may be simply and directly used to provide alternatives for the traditional biometric twin design. We use structural equations and path models to define biometric group differences, we write traditional common-factor models in the same way, and then we take a detailed look at some alternative multivariate and biometric models. We contrast the biometric-factors covariance structure approach used by Loehlin and Vandenberg (1968), Martin and Eaves (1977), and others with the psychometric-factors approach used by McArdle et al. (1980) and others. We use the multivariate primary mental abilities data on monozygotic (MZ) and dizygotic (DZ) twins from Loehlin and Vandenberg (1968) to detail fundamental differences in model specification and results. We extend both multivariate biometric approaches using exploratory and confirmatory multiple-factor models. These comparisons show that each alternative multivariate methodology has useful features for empirical applications.

Humans↗

PubMed1995

Unified Neurological Stroke Scale is valid in ischemic and hemorrhagic stroke.

BACKGROUND AND PURPOSE: The growing interest in testing new therapeutic agents for acute brain injury has lead to increased use of stroke scales. The reliability and validity of these measures need to be examined more completely. We used structural equation modeling, a technique that merges the analytic procedures of factor analysis and multiple regression, to examine the reliability and construct validity of the Middle Cerebral Artery Neurological Scale and the Scandinavian Neurological Stroke Scale used together as the Unified Neurological Stroke Scale. We also analyzed the predictive validity, sensitivity, and specificity of the scales in predicting mortality and functional outcome. METHODS: We prospectively studied 84 consecutive patients admitted to a neurology/neurosurgery intensive care unit with intracerebral hemorrhage (n = 30), subarachnoid hemorrhage (n = 15), ischemic stroke (n = 15), and traumatic brain injury (n = 24). Patients were evaluated within 24 hours of admission and at 48-hour intervals until intensive care unit discharge. A total of 386 assessments were obtained. The Functional Independence Measure was administered by telephone 3 months after hospital discharge. RESULTS: High levels of reliability and construct validity were observed for the majority of the Unified Stroke Scale items. Facial palsy and eye movement items had the lowest reliability and validity. Both the Middle Cerebral Artery and Scandinavian Scales were significant predictors of outcome. Sensitivity and specificity varied by diagnosis. Predictive validity of functional outcome was best in groups with ischemic and hemorrhagic stroke rather than traumatic brain injury and subarachnoid hemorrhage. CONCLUSIONS: The Unified Stroke Scale demonstrates reliability and construct and predictive validity, and its use is supported in ischemic and hemorrhagic stroke. Structural equation modeling is an appropriate technique for use with scales of this type.

Activities of Daily Living↗

PubMed2005

Telomeric length varies with age and polymorphisms of the MAOA gene promoter in peripheral blood cells obtained from a community in Taiwan.

OBJECTIVE: Telomere shortening and increased MAOA gene activity both occur with aging. We undertook to develop a predictive model of telomere shortening and to investigate the possible association between MAOA gene promoter polymorphisms and telomere length as influenced by age and gender. METHODS: A stratified random household sample was selected from a community in southern Taiwan. Of 1231 subjects attending our health-screening program, 441 agreed to have additional venous blood withdrawn for DNA extraction and genetic study. Exactly 433 subjects completed the questionnaires and genetic analysis. Their telomere lengths were distributed (6.4-11.63 kb). RESULTS: The rate of shortening per year was 69 base pairs, and the gender difference in length was not statistically significant (F = 0.091, P = 0.763). The lognormal distribution of telomere lengths was linear. The polynomial regression analysis showed Ln (telomere length) = -2.57-0.007 x age - 0.34 MAOA (adjusted R-square = 0.60). The gender effect on telomere length was not statistically significant (P = 0.52). No interaction effects were found between age, gender and MAOA gene polymorphisms. The high-activity allele of the MAOA promoter polymorphisms were negatively associated with telomere length (P = 0.013). Structural equation modeling confirmed the null model structure. The present data suggest that high-activity MAOA promoter gene polymorphisms, as in aging, are a risk factor for telomeric shortening. CONCLUSIONS: Central nervous system serotonergic activity correlates with human aggressive behavior and depression in many studies, and the MAOA promoter gene may also serve as a clinical marker in the treatment of cardiovascular disease. The predictive model and table of telomere length presented in this study will provide a quick reference for future studies.

Adult↗

PubMed2002

The cognitive-behavioral model of bulimia nervosa: a direct evaluation.

OBJECTIVE: This study represented the first attempt to directly evaluate Fairburn et al's (1986) cognitive-behavioral model of bulimia nervosa--the model on which the most widely used treatment for bulimia nervosa is based. METHOD: The major predictions of the model were tested using structural equation modeling. Data were collected from the responses of 526 subjects to a number of self-report measures. RESULTS: The factors of self-esteem, overconcern with weight and shape, and dietary restraint accounted for a large proportion of the variance in binge eating and purging. The key pathway in the model was the link between overconcern with weight and shape and the adoption of purgative behaviors, which then fed into a vicious cycle of binge eating and purging. Contrary to Fairburn's hypothesis, high levels of dietary restraint did not predict increased binge eating. DISCUSSION: The results suggest that the components of Fairburn's model may operate to maintain the bulimic cycle in a slightly different way to that originally proposed.

Body Image↗

PubMed1989

Personality as modifier of the life change-distress relationship. A longitudinal modelling approach.

We present a structural equation model of the way in which personality factors may modify the response to changes in life situation, based on two-wave panel data from a random sample of 296 Dutch adults. Three definitions of vulnerability were studied: high neuroticism (N), low self-esteem (SE), and an external locus of control (LC). The multigroup LISREL analysis led to the following conclusions: First, previous symptom level was strongly related to current symptom level. The strength of this relationship was independent of SE and LC but modified by N. Secondly, the impact of life situation changes on distress level was moderately strong and similar to what others have reported. Thirdly, a marked modifier effect was found for neuroticism; responsiveness significantly increased with N level. For SE and LC we observed reduced responsiveness among low vulnerability subjects, but the differences did not reach statistical significance. The implications of the findings are discussed.

Adult↗

PubMed2004

Perceived work demands, felt stress, and musculoskeletal neck/shoulder symptoms among elderly female computer users. The NEW study.

The aim of the present study was to test a structural model of the relationship between the perceived quantitative (time pressure and unevenly distributed workload) and emotional work demands and self-reported musculoskeletal symptoms from the neck and shoulder region with felt stress (rested, relaxed, calm, tense, stressed, and pressured at the end of a normal workday) as a mediating variable. As part of the NEW (Neuromuscular assessment in the Elderly Worker) study, a European case-control study, the present cross-sectional study was based on a questionnaire survey among Danish, Dutch, Swedish and Swiss female computer users aged 45 or older (n =148). The hypothesized structural model was tested using structural equation modelling. The results indicate that perceived work demands influence neck/shoulder musculoskeletal symptoms through their effect on felt stress. The results further indicate complete mediation, which means that all of the effect of the perceived work demands on symptoms could be attributed to the stress mechanism. As regards the percentage of explained variance in the endogenous variables, 36% of the variation in felt stress was explained by the perceived work demands, and about 20% of the variation in musculoskeletal neck/shoulder symptoms was explained by the combination of the perceived work demands and the felt stress.

Case-Control Studies↗