Relationship between anxiety and dyspnea on exertion in patients with chronic obstructive pulmonary disease

Abstract

Dyspnea limits exercise in patients with chronic obstructive pulmonary disease (COPD) and is known to induce anxiety. Little is known whether anxiety contributes to exercise-induced dyspnea, which in turn might influence the outcome of diagnostic tests. The aim of the present study was to examine the relationship between general anxiety and dyspnea on exertion in patients with COPD.

Ninety patients with stable COPD participated; 44 men, mean age 61 (standard deviation (SD) 10.4), and mean forced expiratory volume in 1 second (%pred.) 40.5 (SD 16.9). All participants performed pulmonary function tests and an incremental cycle ergometry. The Modified Borg Scale was used to measure the level of dyspnea on exertion. Anxiety symptoms were assessed with the Hospital Anxiety and Depression Scale. Data were analyzed using Spearman's correlations and multivariate regression. Dyspnea on exertion was correlated with general anxiety (r=.31), age (r=–.30), and exercise capacity (r=.27). Regression analysis showed that general anxiety was associated with dyspnea on exertion, adjusted for sex, age, baseline dyspnea, and exercise capacity. Consequently, it is reasoned that results of exercise training and activities in daily living may be influenced negatively by anxiety-worsened dyspnea. Attention should be given to anxiety management in patients with COPD to optimize exercise training.     

Multiple Imputation of Item Scores in Test and Questionnaire Data,and Influence on Psychometric Results

The performance of five simple multiple imputation methods for dealing with missing data were compared. In addition, random imputation and multivariate normal imputation were used as lower and upper benchmark, respectively. Test data were simulated and item scores were deleted such that they were either missing completely at random, missing at random, or not missing at random. Cronbach's alpha, Loevinger's scalability coefficient H, and the item cluster solution from Mokken scale analysis of the complete data were compared with the corresponding results based on the data including imputed scores. The multiple-imputation methods, two-way with normally distributed errors, corrected item-mean substitution with normally distributed errors, and response function, produced discrepancies in Cronbach's coefficient alpha, Loevinger's coefficient H, and the cluster solution from Mokken scale analysis, that were smaller than the discrepancies in upper benchmark multivariate normal imputation.     

Outlier Detection in Test and Questionnaire Data

Classical methods for detecting outliers deal with continuous variables. These methods are not readily applicable to categorical data, such as incorrect/correct scores (0/1) and ordered rating scale scores (e.g., 0, …, 4) typical of multi-item tests and questionnaires. This study proposes two definitions of outlier scores suited for categorical data. One definition combines information on outliers from scores on all the items in the test, and the other definition combines information from all pairs of item scores. For a particular item-score vector, an outlier score expresses the degree to which the item-score vector is unusual. For ten real-data sets, the distribution of each of the two outlier scores is inspected by means of Tukey's fences and the extreme studentized deviate procedure. It is investigated whether the outliers that are identified are influential with respect to the statistical analysis performed on these data. Recommendations are given for outlier identification and accommodation in test and questionnaire data.     

Explanatory,Multilevel Person-Fit Analysis of Response Consistency on the Spielberger State-Trait Anxiety Inventory

Self-report measures are vulnerable to concentration and motivation problems, leading to responses that may be inconsistent with the respondent's latent trait value. We investigated response consistency in a sample (N = 860) of cardiac patients with an implantable cardioverter defibrillator and their partners who completed the Spielberger State-Trait Anxiety Inventory on five measurement occasions. For each occasion and for both the state and trait subscales, we used the l ^p _z person-fit statistic to assess response consistency. We used multilevel analysis to model the between-person and within-person differences in the repeated observations of response consistency using time-dependent (e.g., mood states) and time-invariant explanatory variables (e.g., demographic characteristics). Respondents with lower education, undergoing psychological treatment, and with more post-traumatic stress disorder symptoms tended to respond less consistently. The percentages of explained variance in response consistency were small. Hence, we conclude that the results give insight into the causes of response inconsistency but that the identified explanatory variables are of limited practical value for identifying respondents at risk of producing invalid test results. We discuss explanations for the small percentage of explained variance and suggest alternative methods for studying causes of response inconsistency.     

Pre- and Postpartum Fear of Childbirth in Nulliparous and Parous Women

The link between fear of childbirth and theories of anxiety in general is discussed. A possible expression of trait (T-fear) and state (S-fear) aspects of fear of childbirth was investigated in 77 nulliparous and 85 parous women based on data from gestational week 32, at 2 hours and at 5 weeks after childbirth. Data are based on the State Trait Anxiety Inventory and the Wijma Delivery Expectancy/Experience Questionnaire. According to their scores on the Wijma Delivery Expectancy/Experience Questionnaire during late pregnancy, women were divided into 3 groups: high, moderate and low levels of fear of childbirth. In gestational week 32, women in the low level of fear of childbirth group had lower trait anxiety than those in the moderate level of fear of childbirth group, who had lower trait anxiety than the women in the high level of fear of childbirth group. Nulliparous women had a higher level of fear of childbirth but a lower level of trait anxiety than did parous women. There was a significant decreasing trend in fear of childbirth from 2 hours to 5 weeks after delivery, in a parallel way for all 3 groups. Differences in fear of childbirth between nulliparous and parous women disappeared after delivery. These findings suggest that fear of childbirth comprises a considerable part of T-fear, with the risk of a vicious cycle, i.e. that during labour women experience what they are afraid of, which also influences the women's postpartum cognitive appraisal of the delivery.     

The Factor Structure of ADHD – Different Models,Analyses and Informants in a Bifactor Framework

The methodological approach of exploratory structural equation modelling (ESEM) has only been applied once to the construct of Attention-deficit/hyperactivity disorder (ADHD). We decided to compare bifactor models based on confirmatory factor analyses (Bi-CFA) and exploratory equation modeling (Bi-ESEM) only, as there is a growing support of a bifactor structure of ADHD. To examine the factorial validity of the construct we compared three possible bifactor models. One model with two specific factors (inattention and hyperactivity/impulsivity), another model with three specific factors (inattention, hyperactivity and impulsivity) and an alternative, incomplete model with one general ADHD and two specific factors (inattention and impulsivity). We used parent- (N = 1386; Age: M = 11.70, SD = 3.18; Sex: 74.5 % male) and teacher-ratings (N = 110; Age: M = 11.27, SD = 3.04; Sex: 77.5 % male) from clinically referred children between the age of 6 and 18. The results indicate that both methods lead to equally good model fit and for both informants the reliable variance of the specific factor hyperactivity is almost completely explained by the general factor. However, in the teacher condition cross-loadings seem to be of particular importance. Across both methods and informants covariation among ADHD symptom items can be in most part attributed to a general ADHD factor as well as to three (inattention, hyperactivity and impulsivity) or two (inattention and impulsivity) weakly defined specific factors. Further research regarding associations between the specific factors of ADHD and other disorders (e.g. conduct disorder) should be conducted.     

Relationship between anxiety and dyspnea on exertion in patients with chronic obstructive pulmonary disease

Dyspnea limits exercise in patients with chronic obstructive pulmonary disease (COPD) and is known to induce anxiety. Little is known whether anxiety contributes to exercise-induced dyspnea, which in turn might influence the outcome of diagnostic tests. The aim of the present study was to examine the relationship between general anxiety and dyspnea on exertion in patients with COPD. Ninety patients with stable COPD participated; 44 men, mean age 61 (standard deviation (SD) 10.4), and mean forced expiratory volume in 1 second (%pred.) 40.5 (SD 16.9). All participants performed pulmonary function tests and an incremental cycle ergometry. The Modified Borg Scale was used to measure the level of dyspnea on exertion. Anxiety symptoms were assessed with the Hospital Anxiety and Depression Scale. Data were analyzed using Spearman's correlations and multivariate regression. Dyspnea on exertion was correlated with general anxiety (r=.31), age (r=-.30), and exercise capacity (r=.27). Regression analysis showed that general anxiety was associated with dyspnea on exertion, adjusted for sex, age, baseline dyspnea, and exercise capacity. Consequently, it is reasoned that results of exercise training and activities in daily living may be influenced negatively by anxiety-worsened dyspnea. Attention should be given to anxiety management in patients with COPD to optimize exercise training.     

On measurement properties of continuation ratio models

Three classes of polytomous IRT models are distinguished. These classes are the adjacent category models, the cumulative probability models, and the continuation ratio models. So far, the latter class has received relatively little attention. The class of continuation ratio models includes logistic models, such as the sequential model (Tutz, 1990), and nonlogistic models, such as the acceleration model (Samejima, 1995) and the nonparametric sequential model (Hemker, 1996). Four measurement properties are discussed. These are monotone likelihood ratio of the total score, stochastic ordering of the latent trait by the total score, stochastic ordering of the total score by the latent trait, and invariant item ordering. These properties have been investigated previously for the adjacent category models and the cumulative probability models, and for the continuation ratio models this is done here. It is shown that stochastic ordering of the total score by the latent trait is implied by all continuation ratio models, while monotone likelihood ratio of the total score and stochastic ordering on the latent trait by the total score are not implied by any of the continuation ratio models. Only the sequential rating scale model implies the property of invariant item ordering. Also, we present a Venn-diagram showing the relationships between all known polytomous IRT models from all three classes.     

The person response function as a tool in person-fit research

Item responses that do not fit an item response theory (IRT) model may cause the latent trait value to be inaccurately estimated. In the past two decades several statistics have been proposed that can be used to identify nonfitting item score patterns. These statistics all yieldscalar values. Here, the use of the person response function (PRF) for identifying nonfitting item score patterns was investigated. The PRF is afunction and can be used for diagnostic purposes. First, the PRF is defined in a class of IRT models that imply an invariant item ordering. Second, a person-fit method proposed by Trabin & Weiss (1983) is reformulated in a nonparametric IRT context assuming invariant item ordering, and statistical theory proposed by Rosenbaum (1987a) is adapted to test locally whether a PRF is nonincreasing. Third, a simulation study was conducted to compare the use of the PRF with the person-fit statistic ZU3. It is concluded that the PRF can be used as a diagnostic tool in person-fit research.The authors are grateful to Coen A. Bernaards for preparing the figures used in this article, and to Wilco H.M. Emons for checking the calculations.