Biomedical subjects

T D Wade

Publications and source records attributed to T D Wade.

At least 19 recordsLinked to original sources

PubMed2003

The genetic epidemiology of body attitudes, the attitudinal component of body image in women.

BACKGROUND: There were four purposes of the current study, including the investigation of the: (i) adequacy of a multidimensional measure of body image; (ii) genetic and environmental epidemiology of this measure; (iii) shared variance between genetic and environmental risk factors for body mass index (BMI) and body image; and (iv) Equal Environment Assumption (EEA) as it related to body attitudes. METHOD: Six types of body attitudes, as measured by the Body Attitudes Questionnaire (BAQ) and reported by 894 complete female-female twin pairs (mean age 32.35 years, S.D. = 41.8) from the Australian Twin Registry, were analysed. RESULTS: Confirmatory factor analysis of the BAQ supported the adequacy of the measure. Additive genetic and unique environmental influences best accounted for the variance of all six of the BAQ subscales. The relationship between BMI and body attitudes was primarily due to shared genes rather than environment but the majority of genetic and environmental effects on body attitudes were independent of BMI, with the exception of the Feeling Fat subscale, which shared 53% of its genetic risk factors with BMI. One violation of the EEA was suggested, namely similarity of childhood treatment influenced similarity on Lower Body Fatness subscale. CONCLUSIONS: Findings support the notion that: (i) body image is a multidimensional concept; (ii) it is relatively independent of BMI; and (iii) both genetic and non-shared environment are influential determinants of body attitudes.

Adult↗

PubMed2001

Characteristics of monozygotic twins discordant for bulimia nervosa.

OBJECTIVE: We studied monozygotic (MZ) twins who were discordant for bulimia nervosa in order to identify environmental factors that could have contributed to the expression of bulimia nervosa in only one member of these genetically identical twin pairs. METHOD: Female twin pairs from the Virginia Twin Registry were identified. One twin met DSM-III-R criteria for bulimia nervosa (excluding the frequency and duration criterion) and the co-twin either reported some symptoms of bulimia nervosa but never met full diagnostic criteria (n = 20 pairs) or reported no symptoms of bulimia nervosa (n = 10). We compared the twins on demographic, developmental, personality, and psychiatric dimensions using self- and maternal report. RESULTS: Affected twins were more likely to report lifetime generalized anxiety disorder and were described by their mothers as more anxious and fearful as children. They also had significantly lower mastery, optimism, and self-esteem, and significantly greater obsessive and compulsive symptoms than their unaffected co-twins. Affected twins recalled greater discord in their families but viewed their parents as more warm toward them than toward their unaffected co-twin. DISCUSSION: Given that MZ twins are genetically identical and share a common family background, differences between them must be attributable to unique environmental factors. Although it is difficult to disentangle predisposing risk factors from sequelae of psychiatric illness in a retrospective co-twin control design, the affected twins were perceived to have been more anxious as children by their mothers-possibly reflecting a predisposing trait. More extensive interviews are required to determine the nature of environmental events that contribute to the expression of the observed personality, behavioral, anxious, and eating-related traits in the affected twins.

Adult↗

PubMed2001

Investigation of quality of the parental relationship as a risk factor for subclinical bulimia nervosa.

OBJECTIVE: Previous literature suggests a link between the quality of the parental relationship and disordered eating in offspring. We investigated the relationship between offspring pyschopathology and the parental relationship using a population-based twin registry that contained 766 complete twin pairs. METHOD: We used reports of twin lifetime psychopathology from the twins and quality of parental relationship and parental lifetime psychopathology from both parents. RESULTS: Poorer quality of the marital relationship predicted the presence of subclinical bulimia nervosa (SBN) using both mother's (odds ratio [OR] = 0.83, 95% confidence interval [CI]: 0.71-0.97) and father's (OR = 0.78, 95% CI: 0.62-0.97) reports. It also predicted the presence of generalized anxiety disorder (GAD) and alcohol dependence. SBN was still strongly predicted by the marital relationship when parental psychopathology was included as a covariate. DISCUSSION: These results are supportive of the notion that a conflictual and distant marital relationship can, at least partially, act as an environmental risk factor for SBN.

Adolescent↗

PubMed2001

Parent, child, and social correlates of parental discipline style: a retrospective, multi-informant investigation with female twins.

BACKGROUND: The type of parental discipline used in families appears to be related to parental characteristics, child temperament, and aspects of the social context. Within these three areas, we examine specific correlates of parental discipline (namely, limit setting and physical discipline) using a multiple informant model. METHOD: Using interview data from 2003 female twins from a population-based twin registry and 1472 of their parents, we examined retrospective reports of parental discipline from three perspectives. First, father and mother reporting separately on the type of discipline they provided for their offspring; second, each twin reporting on the type of discipline they received from their parents; and third, each parent reporting on the discipline provided by their spouse. Using a mixed model regression, we examined the impact on parental discipline of 25 potential predictor variables, as reported by parents, from three domains: social context, parental factors, and childhood vulnerability factors. RESULTS: There was a great deal of overlap between the independent variables for the two types of discipline in the areas of child vulnerability factors and family relationships, with similar effect sizes for child disobedience, teenage rebelliousness, and family discord. However, the profiles of parental characteristics associated with each type of discipline were quite different. Greater use of physical discipline was associated with less parental warmth, a higher incidence of parental lifetime generalised anxiety disorder, and more frequent religious attendance. Greater use of limit setting was associated with more years of parental education, younger age, and greater parental extroversion and authoritarianism. CONCLUSIONS: Parental characteristics, child temperament, and social context may all contribute to the frequency of discipline used in families, but parental characteristics may be most influential in determining the type of discipline used.

Adult↗

PubMed2001

Relating body mass index to figural stimuli: population-based normative data for Caucasians.

OBJECTIVE: To establish body mass index (BMI) norms for standard figural stimuli using a large Caucasian population-based sample. In addition, we sought to determine the effectiveness of the figural stimuli to identify individuals as obese or thin. DESIGN: All Caucasian twins born in Virginia between 1915 and 1971 were identified by public birth record. In addition, 3347 individual twins responded to a letter published in the newsletter of the American Association of Retired Persons (AARP). All adult twins (aged 18 and over) from both of these sources and their family members were mailed a 16 page 'Health and Lifestyle' questionnaire. SUBJECTS: BMI and silhouette data were available on 16 728 females and 11 366 males ranging in age from 18-100. MEASUREMENTS: Self-report information on height-weight, current body size, desired body size and a discrepancy score using standard figural stimuli. RESULTS: Gender- and age-specific norms are presented linking BMI to each of the figural stimuli. Additional norms for desired body size and discrepancy scores are also presented. Receiver operating curves (ROC) indicate that the figural stimuli are effective in classifying individuals as obese or thin. CONCLUSIONS: With the establishment of these norms, the silhouettes used in standard body image assessment can now be linked to BMI. Differences were observed between women and men in terms of desired body size and discrepancy scores, with women preferring smaller sizes. The figural stimuli are a robust technique for classifying individuals as obese or thin.

Adolescent↗

PubMed2001

Integrating workplace exposure databases for occupational medicine services and epidemiologic studies at a former nuclear weapons facility.

We outline methods for integrating epidemiologic and industrial hygiene data systems for the purpose of exposure estimation, exposure surveillance, worker notification, and occupational medicine practice. We present examples of these methods from our work at the Rocky Flats Plant--a former nuclear weapons facility that fabricated plutonium triggers for nuclear weapons and is now being decontaminated and decommissioned. The weapons production processes exposed workers to plutonium, gamma photons, neutrons, beryllium, asbestos, and several hazardous chemical agents, including chlorinated hydrocarbons and heavy metals. We developed a job exposure matrix (JEM) for estimating exposures to 10 chemical agents in 20 buildings for 120 different job categories over a production history spanning 34 years. With the JEM, we estimated lifetime chemical exposures for about 12,000 of the 16,000 former production workers. We show how the JEM database is used to estimate cumulative exposures over different time periods for epidemiological studies and to provide notification and determine eligibility for a medical screening program developed for former workers. We designed an industrial hygiene data system for maintaining exposure data for current cleanup workers. We describe how this system can be used for exposure surveillance and linked with the JEM and databases on radiation doses to develop lifetime exposure histories and to determine appropriate medical monitoring tests for current cleanup workers. We also present time-line-based graphical methods for reviewing and correcting exposure estimates and reporting them to individual workers.

Colorado↗

PubMed2001

A comparison of family functioning, temperament, and childhood conditions in monozygotic twin pairs discordant for lifetime bulimia nervosa.

OBJECTIVE: The authors investigated differences between twins in nine pairs of female monozygotic twins in the Australian Twin Registry who were discordant for lifetime bulimia nervosa. METHOD: The twins affected and unaffected by lifetime bulimia nervosa were compared on self-report measures, including a measure of parental bonding, four measures of temperament, and six early-childhood medical conditions. RESULTS: No twins had current bulimia nervosa, and there was no difference in weight or eating status between the affected and unaffected twins. The affected twins reported significantly lower self-esteem and less warmth but more overprotection by their mothers during childhood. CONCLUSIONS: Although limited by the small number of discordant twin pairs and the inability to detect causal relationships, these results suggest that environmental influences that promote low self-esteem may also increase the risk for bulimia nervosa. These temperamental differences may explain the discrepancies in parenting or perceived parenting.

Adult↗

PubMed2001

The influence of genetic and environmental factors in estimations of current body size, desired body size, and body dissatisfaction.

The objective was to investigate the genetic epidemiology of figural stimuli. Standard figural stimuli were available from 5,325 complete twin pairs: 1,751 (32.9%) were monozygotic females, 1,068 (20.1%) were dizygotic females, 752 (14.1%) were monozygotic males, 495 (9.3%) were dizygotic males, and 1,259 (23.6%) were dizygotic male-female pairs. Univariate twin analyses were used to examine the influences on the individual variation in current body size and ideal body size. These data were analysed separately for men and women in each of five age groups. A factorial analysis of variance, with polychoric correlations between twin pairs as the dependent variable, and age, sex, zygosity, and the three interaction terms (age x sex, age x zygosity, sex x zygosity) as independent variables, was used to examine trends across the whole data set. Results showed genetic influences had the largest impact on the individual variation in current body size measures, whereas non-shared environmental influences were associated with the majority of individual variation in ideal body size. There was a significant main effect of zygosity (heritability) in predicting polychoric correlations for current body size and body dissatisfaction. There was a significant main effect of gender and zygosity in predicting ideal body size, with a gender x zygosity interaction. In common with BMI, heritability is important in influencing the estimation of current body size. Selection of desired body size for both men and women is more strongly influenced by environmental factors.

Adolescent↗

PubMed2000

Twin studies of eating disorders: a review.

OBJECTIVE: Twin methodology has been used to delineate etiological factors in many medical disorders and behavioral traits including eating disorders. Although twin studies are powerful tools, their methodology can be arcane and their implications easily misinterpreted. METHOD: The goals of this study are to (a) review the theoretical rationale for twin studies; (b) provide a framework for their interpretation and evaluation; (c) review extant twin studies on eating disorders; and (d) explore the implications for understanding etiological issues in eating disorders. DISCUSSION: On the basis of this review, it is not possible to draw firm conclusions regarding the precise contribution of genetic and environmental factors to anorexia nervosa. Twin studies confirm that bulimia nervosa is familial and reveal significant contributions of additive genetic effects and of unique environmental factors in liability to bulimia nervosa. The magnitude of the contribution of shared environment is less clear, but in the studies with the greatest statistical power, it appears to be less prominent than additive genetic factors.

Anorexia Nervosa↗

PubMed2000

Absence of interactions between social support and stressful life events in the prediction of major depression and depressive symptomatology in women.

BACKGROUND: While high levels of social support (SS) are associated with a decreased risk for major depression (MD) or less depressive symptomatology, and stressful life events (SLEs) have a substantial causal relationship with MD, uncertainty remains as to whether a main-effect or a buffering model best explains the nature of the relationship among SS, MD and SLEs. METHOD: Using two waves of interview data on 2,163 female twin pairs from a population-based twin registry, and discrete time survival analysis with both logistic and linear regression models, we examine the ability of interactions between eight dimensions of SS and 16 categories of stressful life events to predict MD onset and levels of depressive symptomatology. RESULTS: In the presence of a significant effect of a SLE on MD (beta > or = 100), we found evidence for seven interactions out of a possible 93, of which none involved buffering effects. Similarly, examination of depressive symptomatology detected a total of two interactions (both buffering) out of possible 28. We found no evidence, beyond what would be expected by chance, for the existence of buffering effects where either MD or depressive symptomatology was used as the dependent variable. CONCLUSIONS: There is little evidence to suggest the presence of the buffering effect of social support in the face of adverse life events for women. We suggest that it is important to use alternative models (multiplicative and additive) to examine data, to investigate the match between stressors and social resources, and to investigate fully whether detected interactions actually represent a buffering effect.

Adaptation, Psychological↗

PubMed2000

The genetic epidemiology of parental discipline.

BACKGROUND: Previous studies of parental discipline have identified little influence of heritability on parental control, and some influence of gene-environment correlations, shared environment and child temperament. METHOD: Using interview data from 2003 female twins from a population-based twin registry and 1472 of their parents, we examined reports of parental discipline from four perspectives: (1) father and mother reporting separately on the type of discipline they provided for their offspring; (2) each twin reporting on the type of discipline they received from their parents; (3) each parent reporting on the discipline provided by their spouse; and, (4) each twin reporting on the discipline they provided for their own offspring. Using factor analysis and univariate structural equation modelling, we examined the structure of parental discipline, and the genetic and environmental influences thereon. RESULTS: The seven discipline items yielded two factors, physical discipline and limit setting, which were moderately positively correlated. Parents perceived discipline as largely a common environmental experience for the twins, whereas the twins indicated that discipline was influenced by unique environmental factors and the genotype of the child. Twins as parents indicated no influence of shared environment on discipline, with the majority of influence accounted for by non-shared environment and parental genotype. CONCLUSIONS: Parents recall providing similar discipline to their children, whereas children emphasize the differences in parental discipline. Sources of individual variation in parental discipline vary according to which family member report is examined. In total, parental discipline is partially influenced by the genotype of both the parent and child, and by environmental factors shared by the twins and unique to the individual.

Adolescent↗

PubMed2000

The relation between risk factors for binge eating and bulimia nervosa: a population-based female twin study.

This study investigated the differential risk factors for the initiation of binge eating and the transition from binge eating to bulimia nervosa. Women from a population-based twin registry (850 complete pairs) were assessed with respect to specific measured variables (including demographics, religiosity, lifetime psychopathology, current symptomatology, and personality) and latent genetic and environmental variables. Because of the relative rarity of bulimia nervosa, statistical power was low, but findings suggested considerable overlap between the genetic risk factors for the development of binge eating and the genetic risk factors for the transition from binge eating to bulimia nervosa. Genetic risk factors for binge eating and bulimia nervosa may be largely similar, whereas nonshared environment may be important in influencing the risk for bulimia nervosa once binge eating is initiated.

Adult↗

PubMed2000

The relationship between social support and major depression: cross-sectional, longitudinal, and genetic perspectives.

Although social support (SS) is associated with risk for major depression (MD), we are uncertain of the extent to which a) low SS increases risk for MD, b) MD lowers SS, or c) both variables reflect a common genetic liability. Using two waves of interview data on female twin pairs from a population-based registry, we examine the cross-sectional and longitudinal association of eight dimensions of perceived SS and MD. Risk for MD in the last year was inversely associated with supportive spouse and relative relationships, and directly associated with problems in these relationships (e.g., too many demands, criticism, tension, and disagreements). Significant cross-time associations were seen only for spousal variables. The history of MD in one twin significantly predicted low relative and spouse support, and relative and friend problems, in her co-twin (MZ > DZ pairs). The relationship between SS and MD in women is complex and due to at least the three separate mechanisms outlined above that operate to varying degrees in different dimensions of SS.

Adolescent↗

PubMed2000

Anorexia nervosa and major depression: shared genetic and environmental risk factors.

OBJECTIVE: The authors sought to derive heritability estimates for anorexia nervosa and to explore the etiology of the comorbid relationship between anorexia nervosa and major depression. METHOD: They applied bivariate structural equation modeling to a broad definition of anorexia nervosa and lifetime major depression as assessed in a population-based sample of 2,163 female twins. RESULTS: Anorexia nervosa was estimated to have a heritability of 58% (95% confidence interval=33%-84%). The authors were unable to completely rule out a contribution of shared environment. The comorbidity between anorexia nervosa and major depression is likely due to genetic factors that influence the risk for both disorders. CONCLUSIONS: Although the study was limited by the small number of affected twins, the results suggest that genetic factors significantly influence the risk for anorexia nervosa and substantially contribute to the observed comorbidity between anorexia nervosa and major depression.

Adult↗

PubMed2000

Reliability of lifetime history of bulimia nervosa. Comparison with major depression.

BACKGROUND: Previous studies have found that the reliability of the lifetime prevalence of bulimia nervosa is low to moderate. However, the reasons for poor reliability remain unknown. AIMS: We investigated the ability of a range of variables to predict reliability, sensitivity, and specificity of reporting of both bulimia nervosa and major depression. METHOD: Two interviews, approximately 5 years apart, were completed with 2163 women from the Virginia Twin Registry. RESULTS: After accounting for different base rates, bulimia nervosa was shown to be as reliably reported as major depression. Consistent with previous studies of major depression, improved reliability of bulimia nervosa reporting is associated with more severe bulimic symptomatology. CONCLUSIONS: Frequent binge eating and the presence of salient behavioural markers such as vomiting and laxative misuse are associated with more reliable reporting of bulimia nervosa. In the absence of the use of fuller forms of assessment, brief interviews should utilise more than one prompt question, thus increasing the probability that memory of past disorders will be more successfully activated and accessed.

Adolescent↗

PubMed1998

Computer-generated time lines for visualizing and editing epidemiological and biomedical data.

Most biomedical data have a temporal dimension. Time-line displays spatialize this dimension and help the viewer comprehend large sets of complex data. If we add ways for users to selectively expand the details of data visible on a time line, even more information can be organized and accessed. Design issues for this kind of display include: how to display time scales that are often wider than the physical display space; how to display events with brief duration; how to display data for two or more events that overlap in time; how to manage the display of data details; how to allow database editing from a time line; and how to facilitate time-based analytical techniques. We describe a time-line display system that addresses each of these issues, and show how it can be used to organize data for an epidemiological study of parental radiation exposure and childhood leukemia. We also suggest further refinements of the time line technique for other biomedical applications.

Child↗

PubMed1994

Finding temporal patterns--a set-based approach.

We created an inference engine and query language for expressing temporal patterns in data. The patterns are represented by using temporally-ordered sets of data objects. Patterns are elaborated by reference to new objects inferred from original data, and by interlocking temporal and other relationships among sets of these objects. We found the tools well-suited to define scenarios of events that are evidence of inappropriate use of prescription drugs, using Medicaid administrative data that describe medical events. The tools' usefulness in research might be considerably more general.

Artificial Intelligence↗

PubMed1988

Using smoothing splines to make inferences about the shape of gas-exchange curves.

Respiratory gas-exchange data from progressive exercise tests are typically interpreted by visual inspection. Attempts to objectify such interpretation have applied particular parametric models which limit the measures which can be studied and the inferences which can be made. We use a known spline-smoothing procedure which fits a continuous curve to such data, yielding confidence intervals for the curve and for its first and second derivatives. Rules can be made which use the derivatives to infer features of a curve's shape and to relate features from different curves in the same data set. In this way complex interpretations can be made objective, so that they may be adequately tested.

Algorithms↗