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PubMed1987

Analysis of longitudinal "time series" data in toxicology.

Studies focusing on chronic toxicity or on the time course of toxicant effect often involve repeated measurements or longitudinal observations of endpoints of interest. Experimental design considerations frequently necessitate between-group comparisons of the resulting trends. Typically, procedures such as the repeated-measures analysis of variance have been used for statistical analysis, even though the required assumptions may not be satisfied in some circumstances. This paper describes an alternative analytical approach which summarizes curvilinear trends by fitting cubic orthogonal polynomials to individual profiles of effect. The resulting regression coefficients serve as quantitative descriptors which can be subjected to group significance testing. Randomization tests based on medians are proposed to provide a comparison of treatment and control groups. Examples from the behavioral toxicology literature are considered, and the results are compared to more traditional approaches, such as repeated-measures analysis of variance.

Analysis of Variance↗
PubMed1999

[Nucleotide sequence analysis for high variance region of hepatitis C virus in patients with hemodialysis].

OBJECTIVE: To investigate the route of transmission for hepatitis C virus (HCV) infection in patients on hemodialysis (HD). METHODS: Nucleotide sequence of high variance region (HVR) of HCV was analyzed with nucleotide sequencing technique in 15 HD patients, and its homology was compared. RESULTS: Comparison of the nucleotide sequences of HCV HVR in 15 HD patients showed that their homologies in isolates 8, 12 and 14 reached 97.50%, 95.00% in isolates 4, 5 and 10, and more than 80.00% in isolates 1, 3 - 8 and 10 - 14. Clinical data showed that all these patients were hemodialyzed in the same room with the same HD machine. Isolates 2 and all others were 61.25% - 66.25% in homology, and 57.50% - 67.50% in isolates 9 and all others, and both the patients had histories of large-quantity blood transfusion. CONCLUSION: Blood transfusion was the primary risk factor for HCV infection in HD patients, but iatrogenic transmission of HCV through HD environment could also exist.

Adult↗
PubMed1997

Assessment of physicians' ability to prescribe parenteral nutrition support in a community teaching hospital.

OBJECTIVE: To assess the knowledge and skill base of the physicians in our hospital in prescribing parenteral nutrition support. DESIGN: Physicians completed parenteral nutrition orders for three mock patients. A range of clinically appropriate responses was established before the survey by the hospital Nutrition Support Team. Each case was scored according to set criteria, and the three case scores were averaged to yield a total score of 0 to 100. SUBJECTS/SETTING: Forty-eight attending, resident, and student physicians in the departments of family practice, internal medicine, and general surgery in a community teaching hospital. STATISTICAL ANALYSIS: Student's t test was used to compare interval data between two groups, and analysis of variance was used to compare interval data among three or more groups. If Bartlett's test for homogeneity of variance showed differences between the groups, the Kruskal-Wallis one-way analysis of variance was used. If analysis of variance revealed a significant difference, the data were reanalyzed using three different multiple-comparison procedures (Tukey, Scheffe, and Bonferroni) to decrease the possibility of a type I error. RESULTS: The mean total score was 48.6 +/- 20.8. Total score differed according to the number of nutrition lectures attended during residency. Total score tended to differ by specialty and number of patients treated with parenteral nutrition; however, these differences did not reach statistical significance. APPLICATIONS/CONCLUSIONS: This tool can be adapted and used by other hospitals, medical schools, and residency programs to assess physicians' knowledge base, design educational programs, and improve the parenteral nutrition ordering process.

Analysis of Variance↗
PubMed1998

Gyri of the human neocortex: an MRI-based analysis of volume and variance.

This magnetic resonance imaging (MRI)-based morphometric analysis of cortical topography in the human brain is based upon the segmentation and parcellation of volumetric T1-weighted MRI data for a set of 20 young adult brains including 10 males and 10 females. For the most part, each parcellation unit (PU) of the neocortex corresponds to a single or a portion of a single gyrus. The volumes of each PU were computed for each brain. Subsets of PUs were also grouped so as to represent the neocortex for the frontal, temporal, parietal and occipital lobes. The coefficient of variation of the mean volume of total neocortex and that of the neocortex assigned to individual lobes cluster around 10%, whereas that of neocortex assigned to the individual gyri (PU) is more than twice that value. Approximately 80% of the total variance in gyral volume arises from determinants interactive for individual and specific gyri, while only approximately 10% of the total variance appears to be a reflection of uniform scaling to total neocortical volume. Sexual dimorphism contributes a pervasive though relatively small component of this variance. These results have implications for the study of structure-function correlation, and the proper statistical methods of handling volumetric data in morphometric studies. In addition, the nature of the covariance structure of the data will lead to future hypotheses regarding the relationships between the various potential genetic and epigenetic gyral influencing factors.

Adult↗
PubMed2001

Characteristics and work experiences of hospitalists in the United States.

BACKGROUND: Little is known about the personal characteristics, work-related attitudes, or professional experiences of hospitalists. In considering the future of hospital medicine as a viable career choice for physicians (primarily, internists), these issues should be examined in a systematic fashion. Learning more about hospitalists and their work can enhance dialogue about the advantages and shortcomings of such a career from the perspective of the individual physician. METHODS: A self-administered mail survey was sent to 820 hospitalists who are dues-paying members of the National Association of Inpatient Physicians and who spend 50% or more of their time doing clinical work, teaching, or research related to hospital medicine. Attitudes about topics such as job-related burnout and job satisfaction were tapped, as well as information about different professional and social experiences. The analyses were performed using descriptive statistics and analysis of variance techniques. RESULTS: Analysis was based on 393 responses (48% response rate). Results show hospitalists to be a group of younger, mostly male, early-career individuals with high levels of job satisfaction and autonomy, low levels of burnout, and a long-term commitment to remaining in the role. Hospital medicine is a source of positive social and professional work experiences related to interactions with physician peers, patients and their families, and nonphysician hospital coworkers. Key components of hospitalists' jobs, practices, and workload are coalescing. However, certain developments, such as changing patterns of compensation and the enlisting of more general internists and women as hospitalists, merit further examination. CONCLUSIONS: The results offer insight into the physicians who are becoming hospitalists, the jobs and settings in which they work, and how hospitalists experience their everyday work lives. Valuable baseline data are provided for assessment of attitudes, such as burnout, that should be examined regularly in this fledgling group. This study complements research looking at the performance-related outcomes of hospitalists, and it can be used by various stakeholders to better understand and assess the long-term potential of what is being proposed as a new career path.

Adult↗
PubMed1997

Hospital infant formula discharge packages. Do they affect the duration of breast-feeding?

OBJECTIVE: To determine whether the duration of breast-feeding is affected by the contents of the hospital discharge package. DESIGN: A randomized clinical trial with 2 experimental interventions (a discharge package containing a manual breast pump only and a discharge package containing a commercially prepared infant formula and a manual breast pump) and a control group who received a commercially prepared infant formula discharge package only. Sociodemographic characteristics and information concerning prior births (including feeding methods) were obtained from each mother within 48 hours of her infant's birth. Sources of influence on the mother's feeding decision, maternal attitudes concerning breast-feeding, and maternal feeding preferences were also assessed. PARTICIPANTS: The sample consisted of 763 women who had given birth who were admitted to the maternal-fetal unit of a midwestern community hospital. MAIN OUTCOME MEASURES: Information concerning current method of infant feeding was obtained from telephone interviews conducted at 2-week intervals until the infant was 16 weeks old. The data were analyzed using descriptive statistics, multivariate analysis of variance, logistic regression analysis, and survival analysis. RESULTS: The content of the hospital discharge package did not affect whether the mother engaged in exclusive or partial breast-feeding during the 16-week follow-up interval. However, there was some evidence that providing formula samples at discharge from the hospital increased the duration of exclusive breast-feeding compared with providing a manual breast pump. CONCLUSION: This study does not support the assumption that inclusion of infant formula in hospital discharge packages decreases the duration of breast-feeding.

Adult↗
PubMed1996

Size and location of the human temporomandibular joint.

The literature abounds with conflicting data on various morphometric aspects of the temporomandibular joint (TMJ). The purpose of this study was to observe the effects of sex, ethnic group, and edentulism on TMJ osseous morphology and to define possible factors which might influence variation in this structure. TMJs and related craniofacial structures were measured directly on 229 dry skulls and matching mandibles. Analysis of variance, principal component analysis, and cluster analysis were performed. Our results indicate that 1) the anteroposterior-related TMJ dimensions are independent of sex, ethnic group, and edentulism; 2) the transverse TMJ dimension is related to cranial breadth measures; and 3) the projected distance, along a midsagittal plane, between the TMJ and foramen magnum is independent of sex, ethnicity, and edentulism. It is our assertion that the TMJ must not be considered as a single morphological structure but rather viewed as a functional unit with component parts which are subordinate to completely different sets of influences.

Africa↗
PubMed1999

Craniofacial morphology of the first Americans: Pattern and process in the peopling of the New World.

The peopling of the New World has been the focus of anthropological attention since the last century. Proponents of multiple migration models have claimed that patterns of variation among extant New World populations reflect ancient, discrete migrations to the Americas during the terminal Pleistocene. Although multiple migration models appear to explain patterns of both past and present craniometric variation, this interpretation rests on a number of key assumptions that require further investigation. We examined a series of Paleoindian (n = 11) and Archaic (n = 384) crania from North and South America, and compare these early samples to a large world-wide sample of late Holocene (n = 6,742) remains to assess within- and among-group variability in early samples, and to determine how patterns of variation could be viewed as a reflection of both population history and population structure. Analyses included univariate and multivariate analysis of variance, principal component analysis, calculation of biological distances, and multivariate allocation methods. We also performed model-bound analyses of these data, including Relethford-Blangero analysis and calculation of F(ST). Our results indicate that under the assumptions of migration/founder models, the data are consistent with Paleoindians having derived from an undifferentiated Asian population that was not ancestral to modern American Indians. This view can be accommodated into existing models of multiple founders (migrations) in the New World. However, the assumptions required for such an interpretation are not realistic, and the diversity of early populations could as easily reflect population structuring processes such as genetic drift, demographic growth, and other phenomena. When the data were analyzed controlling for the effects of genetic drift (i.e., with smaller long-term effective population sizes for Paleoindians), the Paleoindian samples were no longer distinct from modern Native American populations. Other factors that need to be considered include processes involved in craniofacial change and adaptation during the past 10,000 years. Finally, patterns of variation in the North and South American Paleoindian samples are different, suggesting that the process of New World colonization is more complex than previously assumed.

Anthropometry↗
PubMed1983

Identification of suicide attempters by means of MMPI profiles.

Used multivariate procedures to determine whether psychiatric patients who had made a suicide attempt immediately prior to hospitalization (N = 161) could be differentiated from nonsuicidal psychiatric patients (N = 161). Multivariate analysis of variance and cluster analysis failed to identify differences in the MMPI data of suicidal and nonsuicidal patients. In contrast, discriminant analysis produced a modest degree of differentiation that generally was maintained in the cross-validation.

Adult↗
PubMed2002

Depressive symptomatology differentiates subgroups of patients with seasonal affective disorder.

Patients with seasonal affective disorder (SAD) may vary in symptoms of their depressed winter mood state, as we showed previously for nondepressed (manic, hypomanic, hyperthymic, euthymic) springtime states [Goel et al., 1999]. Identification of such differences during depression may be useful in predicting differences in treatment efficacy or analyzing the pathogenesis of the disorder. In a cross-sectional analysis, we determined whether 165 patients with Bipolar Disorder (I, II) or Major Depressive Disorder (MDD), both with seasonal pattern, showed different symptom profiles while depressed. Assessment was by the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version (SIGH-SAD), which includes a set of items for atypical symptoms. We identified subgroup differences in SAD based on categories specified for nonseasonal depression, using multivariate analysis of variance and discriminant analysis. Patients with Bipolar Disorder (I and II) were more depressed (had higher SIGH-SAD scores) and showed more psychomotor agitation and social withdrawal than those with MDD. Bipolar I patients had more psychomotor retardation, late insomnia, and social withdrawal than bipolar II patients. Men showed more obsessions/compulsions and suicidality than women, while women showed more weight gain and early insomnia. Whites showed more guilt and fatigability than blacks, while blacks showed more hypochondriasis and social withdrawal. Darker-eyed patients were significantly more depressed and fatigued than blue-eyed patients. Single and divorced or separated patients showed more hypochondriasis and diurnal variation than married patients. Employed patients showed more atypical symptoms than unemployed patients, although most of the subgroup distinctions lay on the Hamilton Scale. These results comprise a set of biological and sociocultural factors-including race, gender, and marital and employment status-which contribute to depressive symptomatology in SAD. Significant mood and sociocultural factors, in contrast to biological factors of gender and eye color, were similar to those reported for nonseasonal depression. Lightly pigmented eyes, in particular, may serve to enhance photic input during winter and allay depressive symptoms in vulnerable populations.

Adolescent↗
PubMed2006

Functional imaging analysis contest (FIAC) analysis according to AFNI and SUMA.

The Functional Imaging Analysis Contest (FIAC) datasets were analyzed with the AFNI software package. Two types of linear regression analyses were carried out: "fixed shape" hemodynamic response, where a preselected incomplete gamma function is used to model each brief activation episode, and "variable shape" analysis, where the temporal shape of the response model in each stimulus block class is allowed to vary separately in each voxel. These time series regressions were carried out both in the volume and on the original data projected to individual standardized cortical surface models. Intersubject analyses were carried out voxel-wise on the regression amplitudes obtained from these time series results, using a multi-way within-subject analysis of variance (ANOVA). Group analysis of the block design demonstrated a significant repetition suppression of the BOLD signal within blocks in the superior and middle temporal gyrus. This effect may represent differences in the response to the first stimulus following a period of silence compared to the remaining sentences in the block. Analyzing the event-related data, Brodmann area 31 showed significant sentence effect and consecutive-sentence repetition effect. However, no significant speaker effect was found; these results may be consistent with the instructions to the subjects that they would be tested on the sentence content. Sentence by speaker interaction effects were found in bilateral middle temporal gyrus, left inferior frontal, and left inferior temporal gyrus.

Brain Mapping↗
PubMed1996

Use of Cluster and Discriminant Analyses to Compare Rhizosphere Bacterial Communities Following Biological Perturbation

We present an approach to comparing the diversity and composition of bacterial communities from different habitats and for identifying which members of a community are most affected by an introduced bacterium. We use this method to explore both previously published and new data from field and growth chamber experiments in which we isolated heterotrophic bacteria from samples of root-free soil, roots of nontreated soybean seedlings, and from the roots of soybean seedlings grown from Bacillus cereus UW85n1-treated seeds. We characterize bacterial isolates for 40 physiological attributes, and grouped the isolates hierarchically using two-stage density-linkage cluster analysis. Multivariate analysis of variance and discriminant analysis of the relative frequencies of the clusters in the soil and rhizosphere habitats were then used to determine whether there were differences among the bacterial communities from the various habitats, and which of the clusters were most useful in discriminating among the communities. We used rarefied estimates of richness as a measure of community diversity in the various habitats. Introduction of UW85n1 affected the composition and/or diversity of rhizosphere communities in three of four experiments.

Journal Article↗
PubMed1989

Spreading of cells on various substrates evaluated by Fourier analysis of shape.

In order to evaluate in mathematical terms the morphological changes occurring in the course of cell spreading, Fourier analysis of shape was applied. Human urothelial Hu 961 b cells plated on type IV collagen, fibronectin, laminin, glass and bovine serum albumin (BSA) were studied. Fourier parameters describing cell shape as well as surface areas covered by the cells on the substrate were subjected to statistical analysis. Using analysis of variance and discriminant analysis it was found that parameters describing cell shape (both gross shape of cells and their fine scale contour foldings) possessed a higher power of discrimination between the cells spread on various substrates than the differences in cell surface areas. In the course of observation (75 and 150 min) the highest number of attached cells and highest degree of spreading were found when cells were plated on type IV collagen. Moderate alterations in cell shape and moderate increase of surface area were seen in the group of cells seeded on fibronectin, whereas the cells plated on laminin, glass and BSA revealed a moderate increase of surface area, but no changes in their shape were observed. The differences in attachment of cells and in the degree of their spreading might be due to the variation in expression of plasma membrane receptors for various substrates. The Fourier analysis of cell shape coupled with measurement of surface area is a good tool for quantitative evaluation of cell spreading and can be used for discrimination between cells spread on different substrates.

Cell Adhesion↗
PubMed1995

Rhythm alteration in patients with metastatic breast cancer and poor prognostic factors.

Circulating blood cell counts, serum cortisol, proteins, alkaline phosphatase, carcinoembryonic antigen and CA15.3 displayed significant circadian rhythms in a group of 13 women with metastatic breast cancer. Statistical significance (P < 0.05) was assessed with both analysis of variance and cosinor analysis. All patients had been previously treated with chemo-and/or radiotherapy and/or antiestrogens. All patients had been treatment-free for 1 month prior to the study. Each patient had blood drawn every 4 h for 48 h. Circadian rhythms were examined as a function of performance status, graded according to the World Health Organization, liver involvement and number of metastatic sites. Group circadian rhythms in serum cortisol or proteins were abolished in patients with liver metastases, and were altered in cases of poor performance status. Circulating leukocytes, neutrophils or platelets did not exhibit synchronized circadian rhythmicity in patients with poor performance status or liver metastases. The number of metastatic organs had a minor influence on circadian rhythmicity. These results suggest that rhythm alteration may be associated with both poor performance status and liver metastases in patients with advanced breast cancer. Such alteration of the normal circadian time structure may favor and/or result from cancer spread.

Adult↗
PubMed1995

Prognostic factors for the operative correction of stress urinary incontinence.

Investigating the reliability of using some clinical and laboratory parameters as long-term prognostic factors in properly selected patients for stress urinary surgery could help in the prediction of the long-term result in each case. Toward this goal 51 women were examined prospectively, after they were assessed by clinical and laboratory exams with particular emphasis on urodynamic studies. Out of this group, 41 patients had genuine stress incontinence, and 10 had mixed stress incontinence. Twenty-seven women underwent Burch colposuspension while 24 had Stamey endoscopic bladder neck suspension. In all patients clinical and urodynamic evaluation was done with the same methodology before the operation, and after one month and six months, respectively. The study indicated that 73% of the incontinent women were cured. According to the "analysis of variance" and "correlation analysis" methods the factors which were found to influence the operative result were as follows: (1) Clinical factors including preoperative urgency, U.T.I. and previous gynaecological operations. These factors had negative prognostic value, while the grade of incontinence did not influence at all the outcome of surgery. (2) Urodynamic factors including preoperative residual urine, immediate operative first sensation of micturition, maximum urine flow rate, pre- and immediate postoperative bladder capacity and functional length. These factors influence the operative result negatively or positively according to the deviation from the normal values. Furthermore, the important immediate postoperative change of the urodynamic values was found to determine the result of the operation.

Female↗
PubMed1997

Characteristics of long-surviving men: results from a nine-year longitudinal study.

Although the life expectancy of men is commonly less than that of women, previous analyses of a longitudinal data set revealed a sub-sample of older men whose survival curves over twenty years are similar to those of the women in the sample. The main purpose of this research is to identify factors which differentiate this group of "successful" males from the other males in the sample. Data from the two groups of males (and two groups of females) were examined using analysis of variance, chi 2 analysis, and survival analysis. Data include measures in a variety of biomedical, functional, behavioral, and psychological areas collected during in-home and hospital examinations. Results show that "successful" males have significantly higher scores in both cognitive abilities and health, initially and at longitudinal follow-ups. The combination of overall high scores in the multiple domains evidently gives this group of men an advantage over the others. The results emphasize the importance of recognizing the sub-groups in the aging population with different developmental patterns, and tailoring both research and services to the uniqueness of these groups.

Aged↗
PubMed2003

Changes in bone mineral density in the hip and spine before, during, and after the menopause in elite runners.

This study was undertaken to determine the degree of interaction between hormonal and athletic effects on changes in bone mineral density (BMD, g/cm(2)) with time in women around the menopause. Thirty-five elite female runners aged over 40 participated in a longitudinal cohort study of hip and spine bone density changes and had two measurements a mean of 4.1 years apart. Eighteen remained estrogenized throughout the study (E+ to +), ten remained postmenopausal throughout (E- to -), while seven showed a change in status (E- to +) or (E+ to -). At study exit, both postmenopausal E+ and E- subjects had significantly higher than expected broadband ultrasound attenuation (BUA) and velocity of sound (VOS) values at the calcaneus. However, Z-score 95% confidence intervals for BMD of the hip and spine embraced zero except at the femoral trochanter in E+ women. The E+ to + group did not lose bone at any site. The E- to - group lost bone significantly, but only at the femoral neck and spine at rates close to 1% annually. Multiple analysis of variance repeated measures analysis showed a significant interaction in the effects of estrogen exposure with DXA measurement site, with the femoral trochanter being less affected by E- status than the spine and femoral neck. Body mass index (BMI: weight/height(2), kg/m(2)) had a significantly positive effect on total hip and femoral neck BMD independently of estrogen status. In conclusion, in this pilot study, postmenopausal elite runners not on hormone replacement therapy lost BMD from the femoral neck and spine at the expected rates but in the femoral trochanter bone loss appeared reduced and in the calcaneus BUA and VOS were maintained close to young normal values.

Absorptiometry, Photon↗
PubMed1998

Effect of altered sensory conditions on multivariate descriptors of human postural sway.

Multivariate descriptors of sway were used to test whether altered sensory conditions result not only in changes in amount of sway but also in postural coordination. Eigenvalues and directions of eigenvectors of the covariance of shnk and hip angles were used as a set of multivariate descriptors. These quantities were measured in 14 healthy adult subjects performing the Sensory Organization test, which disrupts visual and somatosensory information used for spatial orientation. Multivariate analysis of variance and discriminant analysis showed that resulting sway changes were at least bivariate in character, with visual and somatosensory conditions producing distinct changes in postural coordination. The most significant changes were found when somatosensory information was disrupted by sway-referencing of the support surface (P = 3.2 x 10(-10)). The resulting covariance measurements showed that subjects not only swayed more but also used increased hip motion analogous to the hip strategy. Disruption of vision, by either closing the eyes or sway-referencing the visual surround, also resulted in altered sway (P = 1.7 x 10(-10)), with proportionately more motion of the center of mass than with platform sway-referencing. As shown by discriminant analysis, an optimal univariate measure could explain at most 90% of the behavior due to altered sensory conditions. The remaining 10%, while smaller, are highly significant changes in posture control that depend on sensory conditions. The results imply that normal postural coordination of the trunk and legs requires both somatosensory and visual information and that each sensory modality makes a unique contribution to posture control. Descending postural commands are multivariate in nature, and the motion at each joint is affected uniquely by input from multiple sensors.

Adult↗