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The role of panic-fear in comorbid asthma and panic disorder
Journal of Anxiety Disorders 23 (2009) 178–184
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Journal of Anxiety Disorders
The role of panic-fear in comorbid asthma and panic disorder Jonathan M. Feldman a,*, Mahmood I. Siddique b,c, Nigel S. Thompson a, Paul M. Lehrer d a
Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ, USA c Robert Wood Johnson University Hospital at Hamilton, Hamilton, NJ, USA d Department of Psychiatry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ, USA b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 December 2007 Received in revised form 7 June 2008 Accepted 20 June 2008
We examined mediational models of panic-fear, panic disorder (PD), and asthma outcomes among adult asthma patients. PD was assessed by the Anxiety Disorders Interview Schedule. Twenty-one asthma-PD patients and 27 asthma-only patients completed spirometry and questionnaires. Asthma-PD patients reported greater illness-specific and generalized panic-fear than asthma-only patients, despite no differences in asthma severity or physical symptoms during asthma attacks. Illness-specific panic-fear mediated the relationship between PD and poorer health-related quality of life, including emotional disturbance due to asthma. Illness-specific panic-fear was associated with more primary care office visits for asthma. Asthma-PD patients reported greater irritability during asthma attacks than asthma-only patients. Generalized panic-fear was directly associated with restriction of activities due to asthma and use of rescue medication for asthma. Neither measure of panic-fear was associated with asthma severity. Panic-fear experienced during asthma attacks may be an important area to target for improving healthrelated quality of life among asthma-PD patients. ß 2008 Elsevier Ltd. All rights reserved.
Keywords: Asthma Generalized panic-fear Illness-specific panic-fear Panic disorder Quality of life
1. Introduction Panic-fear has been established as a risk factor for greater asthma morbidity, independent of objective measures of pulmonary function (Dirks, Fross, & Evans, 1977; Dirks, Horton, Kinsman, Fross, & Jones, 1978; Dirks, Kinsman, et al., 1977; Dirks, Kinsman, Horton, Fross, & Jones, 1978; Dirks, Schraa, Brown, & Kinsman, 1980; Kleiger & Dirks, 1979). Most of this research was conducted in the 1970s on inpatients with asthma at National Jewish Medical and Research Center. Two types of panic-fear have been identified with each having a unique association with asthma morbidity. Illness-specific panic-fear refers to anxiety elicited in response to asthma symptoms. Generalized panic-fear is a stable, personality construct that reflects trait anxiety extending beyond asthma symptoms. Illness-specific panic-fear has been shown to be adaptive for asthma and the mechanism might involve vigilance to asthma symptoms (Kinsman, Dirks, Jones, & Dahlem, 1980). Patients with high illness-specific panic-
* Corresponding author at: Ferkauf Graduate School of Psychology, Rousso Building, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA. Tel.: +1 718 430 3968; fax: +1 718 430 3960. E-mail addresses: [email protected], [email protected] (J.M. Feldman). 0887-6185/$ – see front matter ß 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.janxdis.2008.06.005
fear were rehospitalized for asthma half as frequently within 6 months after discharge, compared with patients having low illness-specific panic-fear (Staudenmayer, Kinsman, Dirks, Spector, & Wangaard, 1979). Low illness-specific panic-fear was also a robust predictor of future asthma attacks and emergency health care use among patients who suffered a recent asthma attack (Greaves, Eiser, Seamark, & Halpin, 2002). Earlier research suggested that high illness-specific panic-fear was associated with overuse of PRN (i.e., as-needed) b2-agonist medications for asthma (Dahlem, Kinsman, & Horton, 1977). However, subsequent analyses of these data (Kinsman, Dirks, Jones, & Dahlem, 1980) and other research (Dirks, Fross, et al., 1977; Dirks, Jones, & Kinsman, 1977) have shown that high generalized panic-fear explains more variance than high illness-specific panic-fear in these maladaptive health outcomes. Kinsman, Dirks, and Jones (1982) concluded that high illness-specific panic-fear might mobilize the patient to carry out asthma self-management plans among patients with only moderate levels of generalized panicfear. However, patients with high levels of both types of panic-fear are the most likely to panic during asthma attacks, use excessive asthma medications, and hyperventilate (Kinsman, Dirks, & Dahlem, 1980; Kinsman, Dirks, & Jones, 1980). Both high and low levels of generalized panic-fear have been linked to greater asthma morbidity. High levels of generalized panic-fear have been associated with overuse of PRN b2-agonist
J.M. Feldman et al. / Journal of Anxiety Disorders 23 (2009) 178–184
medications (Kinsman, Dirks, & Dahlem, 1980), stronger prescriptions of corticosteroids (Dirks, Horton, et al., 1978), longer hospitalizations (Dirks, Kinsman et al., 1977), and more frequent hospital readmissions for asthma (Dirks et al., 1980). The dependent and helpless nature of patients with high generalized panic-fear has been hypothesized as being particularly detrimental for asthma self-management (Kinsman, Dirks, Jones, & Dahlem, 1980). In contrast, the excessively independent nature characterized by low generalized panic-fear may result in failure to seek appropriate medical assistance for asthma. Low levels of generalized panic-fear have predicted high rates of rehospitalization (Dirks, Kinsman, et al., 1978) and underutilization of asthma medications (Kleiger & Dirks, 1979). All of these findings on panicfear were independent of objective measures of asthma severity. More recently, attention in the asthma field has shifted toward panic disorder (PD). A growing body of clinical (Brown, Khan, & Mahadi, 2000; Carr, Lehrer, & Hochron, 1992; Carr, Lehrer, Rausch, & Hochron, 1994; Davis, Ross, & MacDonald, 2002; Lavoie et al., 2005; Nascimento et al., 2002; Shavitt, Gentil, & Mandetta, 1992; Yellowlees, Haynes, Potts, & Ruffin, 1988) and community studies (Goodwin, Jacobi, & Thefeld, 2003; Hasler et al., 2005) have shown that there is significant comorbidity between asthma and PD. A 20year longitudinal, community-based study showed that adults with asthma were 41/2 times more likely to develop PD than adults without asthma (Hasler et al., 2005). Conversely, PD was also associated with subsequent asthma morbidity. Data on an overlapping sample of participants from the present study showed that asthma patients with PD (asthma-PD) had greater perceived impairment from asthma and health care utilization for asthma than patients without asthma (Feldman, Lehrer, Borson, Hallstrand, & Siddique, 2005). No differences were found on asthma severity. Models have been proposed addressing hypothesized mediators in this relationship between PD and adverse asthma outcomes (Feldman, Giardino, & Lehrer, 2000; Katon, Richardson, Lozano, & McCauley, 2004). However, there has been a gap in the literature addressing empirical support for these proposed mechanisms (Katon et al., 2004). The overarching goal of the present study was to bridge the gap in the asthma literature between panic-fear and PD by examining these anxiety constructs in the same sample of patients. The construct of health-related quality of life was never examined in the original panic-fear studies. Furthermore, illness-specific and generalized panic-fear have not been examined in asthma-PD patients. Although illness-specific panic-fear may be adaptive for some asthma outcome measures, high levels of anxiety focused on asthma may drive excessive worry between episodes and impair health-related quality of life among PD patients. We hypothesized that asthma-PD patients would report greater illness-specific and generalized panic-fear than asthma patients without PD (asthmaonly). We also hypothesized that the previously reported link between PD and health-related quality of life (Feldman, Lehrer, et al., 2005) would be mediated by illness-specific panic-fear. Although this study includes a reanalysis of data previously reported (Feldman, Lehrer et al., 2005), we have not reported analyses on panic-fear data. 2. Methods 2.1. Subjects Patients with asthma were recruited from primary care and specialized asthma clinics, newspaper advertisements, and flyers in the community (see Feldman, Lehrer et al., 2005 for criteria for asthma diagnosis). Inclusion criteria also required a diagnosis of PD at least 12 months prior to the testing session in order to coincide
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with the minimum duration of asthma and the dependent variable of health care use. Exclusion criteria were emphysema or any nonasthma respiratory disease, heart disease, stroke, neurological disorder, cancer, or organ transplant; bipolar disorder, alcohol/ substance dependence, or psychosis; mental retardation, inability to read English, and pregnancy. Informed consent was obtained and the study was approved by institutional review boards. 2.2. Measures The Autonomic Nervous System Questionnaire (Stein et al., 1999) and the Patient Health Questionnaire (Spitzer, Kroenke, & Williams, 1999) were administered to asthma patients in clinic waiting rooms as an initial screen for targeting patients with PD for the purposes of over-sampling. The Anxiety Disorders Interview Schedule (ADIS-IV) is a semistructured psychological interview (Brown, Di Nardo, & Barlow, 1994) that was administered to all patients to establish psychiatric diagnoses using DSM-IV criteria (American Psychiatric Association, 2000). Furthermore, interviewers followed guidelines to carefully differentiate between asthma and PD to ensure accurate diagnoses (Feldman et al., 2000). For example, symptoms of wheezing, mucus production, and coughing characterize asthma (Schmaling & Bell, 1997). Panic attacks are more likely to have a rapid onset (i.e., peak of symptoms within 10 min) and shorter overall duration. Interviewers also focused on assessment of triggers, situations where attacks occurred, and whether panic occurred exclusively within the context of asthma exacerbation. Advanced graduate students conducted these interviews under the supervision of a licensed clinical psychologist and psychiatrist. The Asthma Quality of Life Questionnaire (AQLQ), a 32-item scale, was used to measure functional impairment due to asthma during the past week across the following domains: emotions, activity limitation, and asthma symptoms (Juniper, Guyatt, Ferrie, & Griffith, 1993). Numerous studies have demonstrated that the AQLQ is a well-validated instrument for assessment of healthrelated quality of life in asthma (Juniper et al., 1993; Juniper, Norman, Cox, & Roberts, 2001; Leidy & Coughlin, 1998; Sanjuas et al., 2002). Lower scores on the AQLQ indicate poorer healthrelated quality of life. The Asthma Symptom Checklist (ASC) was used to assess illness-specific panic-fear experienced during asthma attacks, in addition to irritability, fatigue, hyperventilation, and bronchoconstriction (Brooks et al., 1989; Kinsman, Luparello, O’Banion, & Spector, 1973). The panic-fear subscale of the Minnesota Multiphasic Personality Inventory (MMPI) was used to assess generalized panic-fear (Dirks, Jones, et al., 1977). Both the ASC and MMPI were the measures used in the earlier panic-fear studies and both have excellent reliability and validity (Brooks et al., 1989; Dirks, Jones, et al., 1977; Kinsman et al., 1973). Health care utilization was assessed via medical chart review to determine the number of primary care office visits for asthma during the past 12 months. The chart review was conducted by a research assistant, who was blind to patients’ levels of panic-fear and the hypotheses of the study. An office visit was coded as asthma-related if progress notes indicated that asthma symptoms or medications were discussed, or if pulmonary function testing was conducted. Asthma severity classification was based on National Heart Lung and Blood Institute (NHLBI) guidelines (NHLBI, 1997, 2002). Spirometry was conducted using American Thoracic Society (1995) standards to obtain %FEV1, which is recommended for assessment of pulmonary function (NHLBI, 1997, 2002). Asthma medication and symptom severity were categorized using NHLBI guidelines and based on patients’ self-report. Mild intermittent and persistent
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were combined into one severity class due to the small number of participants taking medications appropriate for mild persistent asthma. Participants reported the average number of days that they used PRN b2-agonist medication during a typical week. Sociodemographic information, including health insurance, was collected by a self-report questionnaire. 2.3. Procedure Participants were instructed to refrain from taking asthma medications, caffeine, or alcohol for 12 h prior to the testing session in order to avoid biases between groups on measurement of lung function. If participants needed to use asthma medications due to symptoms, then the appointment was rescheduled. Spirometry, questionnaires, and the ADIS-IV interview were completed in one session at a laboratory setting. Subjects received $25 for their participation. 2.4. Statistical analyses Between-groups differences were examined by the use of independent-samples t tests, analysis of variance (ANOVA), or chisquare analyses, as appropriate. Effect sizes were calculated as Cohen’s d (Cohen, 1988). A multivariate analysis of variance (MANOVA) was conducted to examine the effect of PD on the five subscales of the ASC. ANOVAs on each subscale were conducted as follow-up tests with a Bonferroni correction (p < .01). Hierarchical multiple regression analyses were used to test the mediational model that illness-specific panic-fear mediates the relationship between PD and health-related quality of life. Diagnosis of PD was entered into the model at step 1 as a predictor, and also at step 2 in combination with illness-specific panic-fear. According to Baron and Kenny (1986), the following conditions must be met to demonstrate mediation: (1) the predictor variable (presence of PD) is associated with the mediator variable (illness-specific panicfear), (2) the predictor is associated with the dependent measure (health-related quality of life) in the absence of the mediator, (3) the mediator must be associated with the dependent measure, and (4) adding the mediator to the overall model significantly reduces the association between the predictor and the dependent variable. The natural logarithm was calculated for the panic-fear and hyperventilation subscales of the ASC in order to normalize the distribution of these data. A median split was conducted for the number of asthma-related primary care visits (1 versus 2) due to non-normality of the distribution. The ASC and MMPI panic-fear scale were treated as continuous measures for primary analyses. However, participants were classified into low, medium, and high panic-fear groups following the methodology of Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977). These secondary analyses allowed for comparison to the original panic-fear literature and examination of the relative distribution of asthma-PD and asthmaonly patients in these panic-fear groups. Illness-specific panic-fear was categorized based upon Z-scores: low (Z < .5), moderate ( .5 Z .5), and high (Z > .5). Generalized panic-fear was split according to empirically derived cutoff scores: low ( 2), moderate (3–8), and high (9). An alpha level of .05 was used for analyses and a Bonferroni correction (p < .017) was used when post-hoc tests were conducted for these analyses. 3. Results 3.1. Patient characteristics The sample consisted of 21 asthma-PD patients (with or without agoraphobia) and 27 asthma-only patients. Ninety percent
Table 1 Participants’ characteristics Age (years, mean S.D.) Gender (% female)
39.2 13.8 66.7
Race/ethnicity (%) White/non-Latino Black/non-Latino Asian White/Latino
72.8 16.7 6.3 4.2
Marital status (%) Single (never married) Married Divorced
56.2 37.5 6.3
Employed (%) Income ($, median)
70.8 30,000
Education (%) <12 years High school graduate >12 years
10.4 54.2 35.4
Health insurance (%) Private Medicaid Medicare None
64.6 16.7 10.4 8.3
Table 2 Asthma Symptom Checklist: asthma-PD versus asthma-only (mean S.D.)
Panic-fear*** Irritability** Hyperventilation Fatigue Bronchoconstriction ** ***
Asthma-PD (N = 21)
Asthma-only (N = 27)
3.50 1.02 3.20 .76 1.99 .66 3.31 1.19 3.62 .60
2.29 1.04 2.39 1.17 1.67 .58 2.86 1.11 3.61 .75
p < .01. p < .001.
of asthma-PD patients met criteria for PD with agoraphobia. The demographic characteristics of the sample are presented in Table 1. The majority of participants were Caucasian females and the mean age was 39.2. No differences were found between asthma-PD and asthma-only participants on any of these sociodemographic variables. 3.2. Illness-specific panic-fear The effect of PD on the ASC subscales was significant [F (5,42) = 4.47, p < .01]. Asthma-PD patients reported greater illness-specific panic-fear than asthma-only patients [F (1,46) = 15.43, p < .001, d = 1.20]. Table 2 presents the mean values for each of the ASC subscales. Asthma-PD patients also reported greater irritability during asthma attacks than asthma-only participants [F (1,46) = 7.45, p < .01, d = .78]. These two findings on the emotional subscales of the ASC were significant with a Bonferroni correction (p < .01). No significant differences were found on the physical symptom subscales of the ASC: hyperventilation (p = .07), fatigue (p = .18), and bronchoconstriction (p = .93). None of the sociodemographic variables were related to any of the ASC subscales and, therefore, none of these measures were treated as covariates. Illness-specific panic-fear, defined in the same categorical manner as Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977), was associated with PD [x2 (2, N = 48) = 11.69, p < .01]. Fig. 1 depicts the opposite pattern found between the two groups. Follow-up chi-square tests using a Bonferroni correction (p < .017) revealed that more asthma-PD patients were categorized with high illness-specific panic-fear (52.4%) versus asthma-only patients
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Fig. 1. Categories of illness-specific panic-fear for asthma-PD and asthma-only participants.
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(18.5%), whereas more asthma-only patients were classified as having low illness-specific panic-fear (55.6%) than asthma-PD patients (9.5%) [x2 (1, N = 33) = 11.21, p < .017]. The comparison between low and moderate groups [x2 (1, N = 32) = 6.41, p < .017] was also significant. The health-related quality of life data were reanalyzed to examine whether previous findings showing poorer health-related quality of life among asthma-PD patients are mediated by illnessspecific panic-fear. Fig. 2a shows that support for the mediational model was found for the total score on the AQLQ. PD was associated with illness-specific panic-fear [r = .50, p < .001, pathway a] and poorer health-related quality of life [r = .37, p < .01, pathway c]. Greater illness-specific panic-fear was associated with poorer health-related quality of life [r = .48, p < .001, pathway b]. The effect of PD on health-related quality of life was significantly reduced (b = .18, ns) when illness-specific panic-fear was added
Fig. 2. Mediational models for: (a) total score on health-related quality of life, (b) emotional disturbance due to asthma, (c) activity limitations, and (d) asthma symptoms.
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to the model. The mediation effect was significant using Sobel’s (1982) first-order solution test for the product of coefficients (Z = 2.15, p < .05). The entire model including PD and illnessspecific panic-fear accounted for 25% of the variance in healthrelated quality of life. Fig. 2b depicts that support for the mediational model was also found for emotional disturbance related to asthma. Greater illnessspecific panic-fear was associated with greater emotional disturbance (r = .53, p < .001, pathway b). The association between PD and emotional disturbance was no longer significant after entering illness-specific panic-fear into the model (b = .07, ns). Sobel’s test confirmed that the mediation effect was significant (Z = 2.55, p = .01). The full model accounted for 28% of the variance in emotional disturbance. Fig. 2c shows that support for mediation was not found for the activity limitations subscale of the AQLQ. Greater illness-specific panic-fear was associated with greater activity limitations due to asthma (r = .41, p < .01, pathway b). The effect of PD was reduced, but remained significant after including illness-specific panic-fear in the model (b = .32, p < .05). The product of coefficients was not significant (Z = 1.54, p = .13). This finding is consistent with the very high rate (90%) of PD with agoraphobia that was diagnosed in this sample. The entire model accounted for 25% of the variance in activity limitations. Fig. 2d presents analyses involving the asthma symptoms subscale of the AQLQ. The model including PD only (pathway c) was not statistically significant (p = .07) and thus the criteria for mediation were not met. Nevertheless, adding illness-specific panic-fear to the model did reduce the association further between PD and symptoms (b = .09, ns). The product of coefficients was not significant (Z = 1.93, p = .053). Given the nonsignificant trend and small sample size, mediation might be demonstrated among larger samples. The combined model accounted for 16% of the variance in asthma symptoms. These findings suggest that illness-specific panic-fear appears to mediate the relationship between PD and health-related quality of life due to asthma and more specifically, emotional disturbance due to asthma. Illness-specific panic-fear was associated with more asthmarelated primary care visits. Patients with two or more visits (N = 19) had greater illness-specific panic-fear (M = 1.09) than patients with less than two visits (N = 28; M = .80; t (45) = 2.10, p < .05, d = .66). Illness-specific panic-fear was not associated with use of PRN b2-agonist medication, %FEV1, or NHLBI severity class for asthma medications or symptoms. 3.3. Generalized panic-fear Asthma-PD participants reported greater generalized panicfear (M = 7.4) than asthma-only patients [(M = 3.8; t (45) = 4.63, p < .001, d = 1.41]. Age (r = .29, p < .05) was associated with generalized panic-fear, and statistically controlling for age in the model did not alter this finding [F (1,43) = 17.16, p < .001]. Using cutoffs established by Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977), PD was associated with generalized panic-fear [x2 (2, N = 47) = 13.25, p = .001]. Fig. 3 shows that an approximately equal percentage of patients in both groups were categorized with moderate generalized panic-fear. However, more asthma-PD patients had high generalized panic-fear (33.3%) versus asthmaonly participants (3.8%), whereas more asthma-only patients had low generalized panic-fear (34.6%) than asthma-PD patients (0%) [x2 (1, N = 17) = 13.39, p < .001]. Other follow-up chi-square tests using a Bonferroni correction showed that the pairwise comparison between low and moderate generalized panic-fear groups was also significant [x2 (1, N = 39) = 6.55, p < .017].
Fig. 3. Categories of generalized panic-fear for asthma-PD and asthma-only patients.
Greater generalized panic-fear was associated with greater activity limitation due to asthma (r = .36, p < .05), but only a trend was found for the total AQLQ score (r = .26, ns) and the emotional disturbance due to asthma scale (r = .27, ns). Generalized panic-fear was not associated with asthma symptoms (r = .10) on the AQLQ. No significant association was present between generalized panic-fear and asthma-related primary care office visits. However, patients with two or more visits tended to have higher generalized panic-fear (M = 6.26) versus patients with less than two visits (M = 4.67) [d = .53, p = .09]. Use of PRN b2-agonist medication was associated with generalized panic-fear (r = .34, p < .05). No association was found between generalized panic-fear and %FEV1 (r = .08) or NHLBI asthma medication or symptom severity class. 3.4. Illness-specific panic-fear and generalized panic-fear Generalized panic-fear was associated with the panic-fear (r = .37, p < .05), irritability (r = .46, p = .001), fatigue (r = .31, p < .05), and hyperventilation (r = .29, p < .05) subscales of the ASC. The only ASC subscale not associated with generalized panicfear was the bronchoconstriction scale (r = .01, ns). These findings demonstrate that trait anxiety has stronger associations with the emotional experience of asthma exacerbations than the physical correlates. 4. Discussion This study showed that asthma-PD patients have higher rates of both illness-specific panic-fear and generalized panic-fear than asthma-only patients, despite no differences in asthma severity. The two panic-fear constructs were associated differentially with asthma outcomes. Illness-specific panic-fear mediated the relationship between PD and health-related quality of life, including emotional disturbance due to asthma. Thus, illness-specific panicfear may be maladaptive for asthma-PD patients by increasing the perceived emotional burden attributed to asthma. Generalized panic-fear was associated with activity limitation due to asthma and use of PRN b2-agonist medication. The greater use of quickrelief medication in the absence of differences in asthma severity might reflect over-reliance on b2-agonist medication. These findings show the importance of teasing apart panic-fear constructs among patients with asthma-PD comorbidity. Both types of panic-fear were associated with patients’ subjective assessment of asthma, but not objective markers. To our knowledge, this is the first study to extend the panic-fear literature to a sample of asthma patients with clinically diagnosed PD. The research and clinical implications are discussed below.
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These findings indicate that emotions experienced by asthmaPD patients during asthma exacerbation may play a key role in contributing to poorer health-related quality of life. Asthma-PD patients reported high levels on the emotional subscales of the ASC (panic-fear and irritability), but their scores on the physical symptom subscales (fatigue, hyperventilation, and bronchoconstriction) closely approximated norms reported for outpatients (Brooks et al., 1989). It is important to note that the ASC does not measure overall frequency of symptoms, but rather frequency of occurrence during asthma attacks. The emotional disturbance during asthma attacks may generalize between episodes and affect health-related quality of life, as supported by the mediational analyses. The emotional function subscale of the AQLQ contains items measuring asthma-related concerns and frustrations, and fears related to breathlessness and not having asthma medications available (Juniper et al., 1993). Therefore, the frightening nature of dyspnea, higher levels of threat appraisal, and feelings of dependence on rescue medication may be key elements involved in the link between PD, illness-specific panic-fear and healthrelated quality of life. Asthma-PD patients appear to feel subjectively more impaired and bothered by their asthma symptoms, despite no differences on markers of asthma severity. This finding is consistent with studies of chest pain (Bull Bringager, Arnesen, Friis, Husebye, & Dammen, 2007) and general somatic symptoms (Hoehn-Saric, McLeod, Funderburk, & Kowalski, 2004) among PD patients. Generalized panic-fear may affect self-management of asthma via decisions about use of rescue medication and avoidance of activities. Excessive trait anxiety might lead patients to treat their emotional distress with short-acting b2-agonists, particularly if they mistake respiratory symptoms of anxiety as asthma (Feldman, Siddique, et al., 2005). Conversely, excessive use of shortacting b2-agonists might also contribute to greater levels of anxiety via side effects, such as tachycardia and tremor (Cazzola, Matera, & Donner, 2005; Scalabrin, Sole, & Naspitz, 1996). The association between generalized panic-fear and avoidance of activities due to asthma may reflect agoraphobic avoidance and extend well beyond adaptive avoidance of asthma triggers (Yellowlees & Kalucy, 1990). The absence of associations between generalized panic-fear and pulmonary function or asthma medication severity class supports this notion. However, the very high rate of PD with agoraphobia (90%) in this sample prevents teasing apart the independent effects of generalized panic-fear from agoraphobia, although this may be difficult if this high rate of agoraphobia is replicated among asthma-PD patients. Although a significant association was found between generalized and illness-specific panic-fear, the size of the correlation (r = .37) was modest. The findings in this study suggest that both types of panic-fear may contribute to the finding that asthma-PD patients are at risk for greater asthma morbidity across time (Hasler et al., 2005). However, differential pathways may be involved and, thus it is important to examine both illness-specific and generalized panic-fear. The present study extends the large body of literature on panicfear to asthma-PD patients. The original studies at National Jewish Medical and Research Center were conducted primarily on inpatients with severe asthma and health care measures included length of hospitalizations and number of readmissions. A key difference in the present study was the milder disease severity of asthma among outpatients and thus, the use of primary care visits as the measure of health care use. The original panic-fear studies concluded that illness-specific panic-fear may be adaptive for asthma by focusing attention on asthma symptoms (Kinsman, Dirks, Jones, & Dahlem, 1980). However, the present data show that this heightened vigilance concerning asthma symptoms may also
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bear a cost for PD patients in terms of emotional distress. It is difficult to interpret whether the link between primary care office visits and illness-specific panic-fear represents appropriate or excessive use of health care resources. The present finding linking generalized panic-fear to PRN b2-agonist medication is consistent with the earlier research (Dirks et al., 1980; Kinsman, Dirks, & Dahlem, 1980). Our hypotheses concerning higher levels of illnessspecific and generalized panic-fear among asthma-PD patients versus asthma-only patients were supported. These findings are strengthened by the absence of between-group differences in asthma severity and the trend showing that asthma-PD patients had higher levels of %FEV1 (Feldman, Lehrer et al., 2005). AsthmaPD patients may use a common appraisal process that is applied to both narrower cues of asthma (illness-specific) and wider physiological cues in general. Therefore, the risk factors originally attributed to panic-fear from earlier studies also appear relevant to asthma-PD patients. There are limitations that should be considered in the context of these results. The use of a small, homogenous, and non-random sample is a major limitation of this study. The small sample size prevented examination of subgroups of panic-fear patients within asthma-PD patients. A question to address in future research is whether differences exist on asthma outcomes between asthmaPD patients with moderate versus high panic-fear. Despite the small sample, significant findings were present due to large effect sizes. Although the multiple comparisons conducted in the present study might increase the chance of a Type I error, a Bonferroni correction was employed and effect sizes were reported. Future research should examine associations between both panic-fear constructs and activity limitation due to asthma among PD patients without agoraphobia, which was not possible due to the high rate of agoraphobia in this sample. Additionally, self-report of short-acting b2-agonist use was a limitation in the present study. Daily, electronic measures of pulmonary function and short-acting b2-agonist use would provide information on whether rescue medication use and health care use are appropriate or excessive. In conclusion, there are several clinical implications for the assessment and treatment of panic-fear and PD among patients with asthma. Both the panic-fear subscale of the ASC and the MMPI panic-fear scale might be useful screening devices, particularly for asthma patients whose subjective report does not match objective measures of asthma control. Whereas treatments were not formally developed for panic-fear, empirically validated treatments are available for PD (Barlow, Gorman, Shear, & Woods, 2000). Furthermore, a psychological treatment has been specifically developed for patients with asthma and PD that combines cognitive behavioral therapy and asthma education (Feldman et al., 2000). A pilot study of this protocol showed that asthma-PD patients reported fewer asthma and panic symptoms, improvements in health-related quality of life, and decreased use of rescue medications at post-treatment (Lehrer et al., 2008). The cognitiveaffective dimensions of asthma are particularly important to target among patients with PD and illness-specific panic-fear. These patients may not only worry about when their next panic episode might occur, but they may also have excessive fear about the occurrence of their next asthma attack. Reducing illness-specific panic-fear and excessive restriction of activities among asthma-PD patients may be beneficial in improving health-related quality of life and reducing emotional distress. However, this goal must be balanced by maintaining potentially adaptive features of illnessspecific panic-fear, such as vigilance to asthma symptoms and medication regimens and avoidance of asthma triggers. An initial treatment goal should be to distinguish between anxiety that mobilizes appropriate asthma self-management versus panic that is mistaken as an asthma exacerbation.
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Contents lists available at ScienceDirect
Journal of Anxiety Disorders
The role of panic-fear in comorbid asthma and panic disorder Jonathan M. Feldman a,*, Mahmood I. Siddique b,c, Nigel S. Thompson a, Paul M. Lehrer d a
Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, New York, NY, USA Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ, USA c Robert Wood Johnson University Hospital at Hamilton, Hamilton, NJ, USA d Department of Psychiatry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ, USA b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 December 2007 Received in revised form 7 June 2008 Accepted 20 June 2008
We examined mediational models of panic-fear, panic disorder (PD), and asthma outcomes among adult asthma patients. PD was assessed by the Anxiety Disorders Interview Schedule. Twenty-one asthma-PD patients and 27 asthma-only patients completed spirometry and questionnaires. Asthma-PD patients reported greater illness-specific and generalized panic-fear than asthma-only patients, despite no differences in asthma severity or physical symptoms during asthma attacks. Illness-specific panic-fear mediated the relationship between PD and poorer health-related quality of life, including emotional disturbance due to asthma. Illness-specific panic-fear was associated with more primary care office visits for asthma. Asthma-PD patients reported greater irritability during asthma attacks than asthma-only patients. Generalized panic-fear was directly associated with restriction of activities due to asthma and use of rescue medication for asthma. Neither measure of panic-fear was associated with asthma severity. Panic-fear experienced during asthma attacks may be an important area to target for improving healthrelated quality of life among asthma-PD patients. ß 2008 Elsevier Ltd. All rights reserved.
Keywords: Asthma Generalized panic-fear Illness-specific panic-fear Panic disorder Quality of life
1. Introduction Panic-fear has been established as a risk factor for greater asthma morbidity, independent of objective measures of pulmonary function (Dirks, Fross, & Evans, 1977; Dirks, Horton, Kinsman, Fross, & Jones, 1978; Dirks, Kinsman, et al., 1977; Dirks, Kinsman, Horton, Fross, & Jones, 1978; Dirks, Schraa, Brown, & Kinsman, 1980; Kleiger & Dirks, 1979). Most of this research was conducted in the 1970s on inpatients with asthma at National Jewish Medical and Research Center. Two types of panic-fear have been identified with each having a unique association with asthma morbidity. Illness-specific panic-fear refers to anxiety elicited in response to asthma symptoms. Generalized panic-fear is a stable, personality construct that reflects trait anxiety extending beyond asthma symptoms. Illness-specific panic-fear has been shown to be adaptive for asthma and the mechanism might involve vigilance to asthma symptoms (Kinsman, Dirks, Jones, & Dahlem, 1980). Patients with high illness-specific panic-
* Corresponding author at: Ferkauf Graduate School of Psychology, Rousso Building, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA. Tel.: +1 718 430 3968; fax: +1 718 430 3960. E-mail addresses: [email protected], [email protected] (J.M. Feldman). 0887-6185/$ – see front matter ß 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.janxdis.2008.06.005
fear were rehospitalized for asthma half as frequently within 6 months after discharge, compared with patients having low illness-specific panic-fear (Staudenmayer, Kinsman, Dirks, Spector, & Wangaard, 1979). Low illness-specific panic-fear was also a robust predictor of future asthma attacks and emergency health care use among patients who suffered a recent asthma attack (Greaves, Eiser, Seamark, & Halpin, 2002). Earlier research suggested that high illness-specific panic-fear was associated with overuse of PRN (i.e., as-needed) b2-agonist medications for asthma (Dahlem, Kinsman, & Horton, 1977). However, subsequent analyses of these data (Kinsman, Dirks, Jones, & Dahlem, 1980) and other research (Dirks, Fross, et al., 1977; Dirks, Jones, & Kinsman, 1977) have shown that high generalized panic-fear explains more variance than high illness-specific panic-fear in these maladaptive health outcomes. Kinsman, Dirks, and Jones (1982) concluded that high illness-specific panic-fear might mobilize the patient to carry out asthma self-management plans among patients with only moderate levels of generalized panicfear. However, patients with high levels of both types of panic-fear are the most likely to panic during asthma attacks, use excessive asthma medications, and hyperventilate (Kinsman, Dirks, & Dahlem, 1980; Kinsman, Dirks, & Jones, 1980). Both high and low levels of generalized panic-fear have been linked to greater asthma morbidity. High levels of generalized panic-fear have been associated with overuse of PRN b2-agonist
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medications (Kinsman, Dirks, & Dahlem, 1980), stronger prescriptions of corticosteroids (Dirks, Horton, et al., 1978), longer hospitalizations (Dirks, Kinsman et al., 1977), and more frequent hospital readmissions for asthma (Dirks et al., 1980). The dependent and helpless nature of patients with high generalized panic-fear has been hypothesized as being particularly detrimental for asthma self-management (Kinsman, Dirks, Jones, & Dahlem, 1980). In contrast, the excessively independent nature characterized by low generalized panic-fear may result in failure to seek appropriate medical assistance for asthma. Low levels of generalized panic-fear have predicted high rates of rehospitalization (Dirks, Kinsman, et al., 1978) and underutilization of asthma medications (Kleiger & Dirks, 1979). All of these findings on panicfear were independent of objective measures of asthma severity. More recently, attention in the asthma field has shifted toward panic disorder (PD). A growing body of clinical (Brown, Khan, & Mahadi, 2000; Carr, Lehrer, & Hochron, 1992; Carr, Lehrer, Rausch, & Hochron, 1994; Davis, Ross, & MacDonald, 2002; Lavoie et al., 2005; Nascimento et al., 2002; Shavitt, Gentil, & Mandetta, 1992; Yellowlees, Haynes, Potts, & Ruffin, 1988) and community studies (Goodwin, Jacobi, & Thefeld, 2003; Hasler et al., 2005) have shown that there is significant comorbidity between asthma and PD. A 20year longitudinal, community-based study showed that adults with asthma were 41/2 times more likely to develop PD than adults without asthma (Hasler et al., 2005). Conversely, PD was also associated with subsequent asthma morbidity. Data on an overlapping sample of participants from the present study showed that asthma patients with PD (asthma-PD) had greater perceived impairment from asthma and health care utilization for asthma than patients without asthma (Feldman, Lehrer, Borson, Hallstrand, & Siddique, 2005). No differences were found on asthma severity. Models have been proposed addressing hypothesized mediators in this relationship between PD and adverse asthma outcomes (Feldman, Giardino, & Lehrer, 2000; Katon, Richardson, Lozano, & McCauley, 2004). However, there has been a gap in the literature addressing empirical support for these proposed mechanisms (Katon et al., 2004). The overarching goal of the present study was to bridge the gap in the asthma literature between panic-fear and PD by examining these anxiety constructs in the same sample of patients. The construct of health-related quality of life was never examined in the original panic-fear studies. Furthermore, illness-specific and generalized panic-fear have not been examined in asthma-PD patients. Although illness-specific panic-fear may be adaptive for some asthma outcome measures, high levels of anxiety focused on asthma may drive excessive worry between episodes and impair health-related quality of life among PD patients. We hypothesized that asthma-PD patients would report greater illness-specific and generalized panic-fear than asthma patients without PD (asthmaonly). We also hypothesized that the previously reported link between PD and health-related quality of life (Feldman, Lehrer, et al., 2005) would be mediated by illness-specific panic-fear. Although this study includes a reanalysis of data previously reported (Feldman, Lehrer et al., 2005), we have not reported analyses on panic-fear data. 2. Methods 2.1. Subjects Patients with asthma were recruited from primary care and specialized asthma clinics, newspaper advertisements, and flyers in the community (see Feldman, Lehrer et al., 2005 for criteria for asthma diagnosis). Inclusion criteria also required a diagnosis of PD at least 12 months prior to the testing session in order to coincide
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with the minimum duration of asthma and the dependent variable of health care use. Exclusion criteria were emphysema or any nonasthma respiratory disease, heart disease, stroke, neurological disorder, cancer, or organ transplant; bipolar disorder, alcohol/ substance dependence, or psychosis; mental retardation, inability to read English, and pregnancy. Informed consent was obtained and the study was approved by institutional review boards. 2.2. Measures The Autonomic Nervous System Questionnaire (Stein et al., 1999) and the Patient Health Questionnaire (Spitzer, Kroenke, & Williams, 1999) were administered to asthma patients in clinic waiting rooms as an initial screen for targeting patients with PD for the purposes of over-sampling. The Anxiety Disorders Interview Schedule (ADIS-IV) is a semistructured psychological interview (Brown, Di Nardo, & Barlow, 1994) that was administered to all patients to establish psychiatric diagnoses using DSM-IV criteria (American Psychiatric Association, 2000). Furthermore, interviewers followed guidelines to carefully differentiate between asthma and PD to ensure accurate diagnoses (Feldman et al., 2000). For example, symptoms of wheezing, mucus production, and coughing characterize asthma (Schmaling & Bell, 1997). Panic attacks are more likely to have a rapid onset (i.e., peak of symptoms within 10 min) and shorter overall duration. Interviewers also focused on assessment of triggers, situations where attacks occurred, and whether panic occurred exclusively within the context of asthma exacerbation. Advanced graduate students conducted these interviews under the supervision of a licensed clinical psychologist and psychiatrist. The Asthma Quality of Life Questionnaire (AQLQ), a 32-item scale, was used to measure functional impairment due to asthma during the past week across the following domains: emotions, activity limitation, and asthma symptoms (Juniper, Guyatt, Ferrie, & Griffith, 1993). Numerous studies have demonstrated that the AQLQ is a well-validated instrument for assessment of healthrelated quality of life in asthma (Juniper et al., 1993; Juniper, Norman, Cox, & Roberts, 2001; Leidy & Coughlin, 1998; Sanjuas et al., 2002). Lower scores on the AQLQ indicate poorer healthrelated quality of life. The Asthma Symptom Checklist (ASC) was used to assess illness-specific panic-fear experienced during asthma attacks, in addition to irritability, fatigue, hyperventilation, and bronchoconstriction (Brooks et al., 1989; Kinsman, Luparello, O’Banion, & Spector, 1973). The panic-fear subscale of the Minnesota Multiphasic Personality Inventory (MMPI) was used to assess generalized panic-fear (Dirks, Jones, et al., 1977). Both the ASC and MMPI were the measures used in the earlier panic-fear studies and both have excellent reliability and validity (Brooks et al., 1989; Dirks, Jones, et al., 1977; Kinsman et al., 1973). Health care utilization was assessed via medical chart review to determine the number of primary care office visits for asthma during the past 12 months. The chart review was conducted by a research assistant, who was blind to patients’ levels of panic-fear and the hypotheses of the study. An office visit was coded as asthma-related if progress notes indicated that asthma symptoms or medications were discussed, or if pulmonary function testing was conducted. Asthma severity classification was based on National Heart Lung and Blood Institute (NHLBI) guidelines (NHLBI, 1997, 2002). Spirometry was conducted using American Thoracic Society (1995) standards to obtain %FEV1, which is recommended for assessment of pulmonary function (NHLBI, 1997, 2002). Asthma medication and symptom severity were categorized using NHLBI guidelines and based on patients’ self-report. Mild intermittent and persistent
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were combined into one severity class due to the small number of participants taking medications appropriate for mild persistent asthma. Participants reported the average number of days that they used PRN b2-agonist medication during a typical week. Sociodemographic information, including health insurance, was collected by a self-report questionnaire. 2.3. Procedure Participants were instructed to refrain from taking asthma medications, caffeine, or alcohol for 12 h prior to the testing session in order to avoid biases between groups on measurement of lung function. If participants needed to use asthma medications due to symptoms, then the appointment was rescheduled. Spirometry, questionnaires, and the ADIS-IV interview were completed in one session at a laboratory setting. Subjects received $25 for their participation. 2.4. Statistical analyses Between-groups differences were examined by the use of independent-samples t tests, analysis of variance (ANOVA), or chisquare analyses, as appropriate. Effect sizes were calculated as Cohen’s d (Cohen, 1988). A multivariate analysis of variance (MANOVA) was conducted to examine the effect of PD on the five subscales of the ASC. ANOVAs on each subscale were conducted as follow-up tests with a Bonferroni correction (p < .01). Hierarchical multiple regression analyses were used to test the mediational model that illness-specific panic-fear mediates the relationship between PD and health-related quality of life. Diagnosis of PD was entered into the model at step 1 as a predictor, and also at step 2 in combination with illness-specific panic-fear. According to Baron and Kenny (1986), the following conditions must be met to demonstrate mediation: (1) the predictor variable (presence of PD) is associated with the mediator variable (illness-specific panicfear), (2) the predictor is associated with the dependent measure (health-related quality of life) in the absence of the mediator, (3) the mediator must be associated with the dependent measure, and (4) adding the mediator to the overall model significantly reduces the association between the predictor and the dependent variable. The natural logarithm was calculated for the panic-fear and hyperventilation subscales of the ASC in order to normalize the distribution of these data. A median split was conducted for the number of asthma-related primary care visits (1 versus 2) due to non-normality of the distribution. The ASC and MMPI panic-fear scale were treated as continuous measures for primary analyses. However, participants were classified into low, medium, and high panic-fear groups following the methodology of Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977). These secondary analyses allowed for comparison to the original panic-fear literature and examination of the relative distribution of asthma-PD and asthmaonly patients in these panic-fear groups. Illness-specific panic-fear was categorized based upon Z-scores: low (Z < .5), moderate ( .5 Z .5), and high (Z > .5). Generalized panic-fear was split according to empirically derived cutoff scores: low ( 2), moderate (3–8), and high (9). An alpha level of .05 was used for analyses and a Bonferroni correction (p < .017) was used when post-hoc tests were conducted for these analyses. 3. Results 3.1. Patient characteristics The sample consisted of 21 asthma-PD patients (with or without agoraphobia) and 27 asthma-only patients. Ninety percent
Table 1 Participants’ characteristics Age (years, mean S.D.) Gender (% female)
39.2 13.8 66.7
Race/ethnicity (%) White/non-Latino Black/non-Latino Asian White/Latino
72.8 16.7 6.3 4.2
Marital status (%) Single (never married) Married Divorced
56.2 37.5 6.3
Employed (%) Income ($, median)
70.8 30,000
Education (%) <12 years High school graduate >12 years
10.4 54.2 35.4
Health insurance (%) Private Medicaid Medicare None
64.6 16.7 10.4 8.3
Table 2 Asthma Symptom Checklist: asthma-PD versus asthma-only (mean S.D.)
Panic-fear*** Irritability** Hyperventilation Fatigue Bronchoconstriction ** ***
Asthma-PD (N = 21)
Asthma-only (N = 27)
3.50 1.02 3.20 .76 1.99 .66 3.31 1.19 3.62 .60
2.29 1.04 2.39 1.17 1.67 .58 2.86 1.11 3.61 .75
p < .01. p < .001.
of asthma-PD patients met criteria for PD with agoraphobia. The demographic characteristics of the sample are presented in Table 1. The majority of participants were Caucasian females and the mean age was 39.2. No differences were found between asthma-PD and asthma-only participants on any of these sociodemographic variables. 3.2. Illness-specific panic-fear The effect of PD on the ASC subscales was significant [F (5,42) = 4.47, p < .01]. Asthma-PD patients reported greater illness-specific panic-fear than asthma-only patients [F (1,46) = 15.43, p < .001, d = 1.20]. Table 2 presents the mean values for each of the ASC subscales. Asthma-PD patients also reported greater irritability during asthma attacks than asthma-only participants [F (1,46) = 7.45, p < .01, d = .78]. These two findings on the emotional subscales of the ASC were significant with a Bonferroni correction (p < .01). No significant differences were found on the physical symptom subscales of the ASC: hyperventilation (p = .07), fatigue (p = .18), and bronchoconstriction (p = .93). None of the sociodemographic variables were related to any of the ASC subscales and, therefore, none of these measures were treated as covariates. Illness-specific panic-fear, defined in the same categorical manner as Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977), was associated with PD [x2 (2, N = 48) = 11.69, p < .01]. Fig. 1 depicts the opposite pattern found between the two groups. Follow-up chi-square tests using a Bonferroni correction (p < .017) revealed that more asthma-PD patients were categorized with high illness-specific panic-fear (52.4%) versus asthma-only patients
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Fig. 1. Categories of illness-specific panic-fear for asthma-PD and asthma-only participants.
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(18.5%), whereas more asthma-only patients were classified as having low illness-specific panic-fear (55.6%) than asthma-PD patients (9.5%) [x2 (1, N = 33) = 11.21, p < .017]. The comparison between low and moderate groups [x2 (1, N = 32) = 6.41, p < .017] was also significant. The health-related quality of life data were reanalyzed to examine whether previous findings showing poorer health-related quality of life among asthma-PD patients are mediated by illnessspecific panic-fear. Fig. 2a shows that support for the mediational model was found for the total score on the AQLQ. PD was associated with illness-specific panic-fear [r = .50, p < .001, pathway a] and poorer health-related quality of life [r = .37, p < .01, pathway c]. Greater illness-specific panic-fear was associated with poorer health-related quality of life [r = .48, p < .001, pathway b]. The effect of PD on health-related quality of life was significantly reduced (b = .18, ns) when illness-specific panic-fear was added
Fig. 2. Mediational models for: (a) total score on health-related quality of life, (b) emotional disturbance due to asthma, (c) activity limitations, and (d) asthma symptoms.
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to the model. The mediation effect was significant using Sobel’s (1982) first-order solution test for the product of coefficients (Z = 2.15, p < .05). The entire model including PD and illnessspecific panic-fear accounted for 25% of the variance in healthrelated quality of life. Fig. 2b depicts that support for the mediational model was also found for emotional disturbance related to asthma. Greater illnessspecific panic-fear was associated with greater emotional disturbance (r = .53, p < .001, pathway b). The association between PD and emotional disturbance was no longer significant after entering illness-specific panic-fear into the model (b = .07, ns). Sobel’s test confirmed that the mediation effect was significant (Z = 2.55, p = .01). The full model accounted for 28% of the variance in emotional disturbance. Fig. 2c shows that support for mediation was not found for the activity limitations subscale of the AQLQ. Greater illness-specific panic-fear was associated with greater activity limitations due to asthma (r = .41, p < .01, pathway b). The effect of PD was reduced, but remained significant after including illness-specific panic-fear in the model (b = .32, p < .05). The product of coefficients was not significant (Z = 1.54, p = .13). This finding is consistent with the very high rate (90%) of PD with agoraphobia that was diagnosed in this sample. The entire model accounted for 25% of the variance in activity limitations. Fig. 2d presents analyses involving the asthma symptoms subscale of the AQLQ. The model including PD only (pathway c) was not statistically significant (p = .07) and thus the criteria for mediation were not met. Nevertheless, adding illness-specific panic-fear to the model did reduce the association further between PD and symptoms (b = .09, ns). The product of coefficients was not significant (Z = 1.93, p = .053). Given the nonsignificant trend and small sample size, mediation might be demonstrated among larger samples. The combined model accounted for 16% of the variance in asthma symptoms. These findings suggest that illness-specific panic-fear appears to mediate the relationship between PD and health-related quality of life due to asthma and more specifically, emotional disturbance due to asthma. Illness-specific panic-fear was associated with more asthmarelated primary care visits. Patients with two or more visits (N = 19) had greater illness-specific panic-fear (M = 1.09) than patients with less than two visits (N = 28; M = .80; t (45) = 2.10, p < .05, d = .66). Illness-specific panic-fear was not associated with use of PRN b2-agonist medication, %FEV1, or NHLBI severity class for asthma medications or symptoms. 3.3. Generalized panic-fear Asthma-PD participants reported greater generalized panicfear (M = 7.4) than asthma-only patients [(M = 3.8; t (45) = 4.63, p < .001, d = 1.41]. Age (r = .29, p < .05) was associated with generalized panic-fear, and statistically controlling for age in the model did not alter this finding [F (1,43) = 17.16, p < .001]. Using cutoffs established by Dirks, Fross, et al. (1977) and Dirks, Jones, et al. (1977), PD was associated with generalized panic-fear [x2 (2, N = 47) = 13.25, p = .001]. Fig. 3 shows that an approximately equal percentage of patients in both groups were categorized with moderate generalized panic-fear. However, more asthma-PD patients had high generalized panic-fear (33.3%) versus asthmaonly participants (3.8%), whereas more asthma-only patients had low generalized panic-fear (34.6%) than asthma-PD patients (0%) [x2 (1, N = 17) = 13.39, p < .001]. Other follow-up chi-square tests using a Bonferroni correction showed that the pairwise comparison between low and moderate generalized panic-fear groups was also significant [x2 (1, N = 39) = 6.55, p < .017].
Fig. 3. Categories of generalized panic-fear for asthma-PD and asthma-only patients.
Greater generalized panic-fear was associated with greater activity limitation due to asthma (r = .36, p < .05), but only a trend was found for the total AQLQ score (r = .26, ns) and the emotional disturbance due to asthma scale (r = .27, ns). Generalized panic-fear was not associated with asthma symptoms (r = .10) on the AQLQ. No significant association was present between generalized panic-fear and asthma-related primary care office visits. However, patients with two or more visits tended to have higher generalized panic-fear (M = 6.26) versus patients with less than two visits (M = 4.67) [d = .53, p = .09]. Use of PRN b2-agonist medication was associated with generalized panic-fear (r = .34, p < .05). No association was found between generalized panic-fear and %FEV1 (r = .08) or NHLBI asthma medication or symptom severity class. 3.4. Illness-specific panic-fear and generalized panic-fear Generalized panic-fear was associated with the panic-fear (r = .37, p < .05), irritability (r = .46, p = .001), fatigue (r = .31, p < .05), and hyperventilation (r = .29, p < .05) subscales of the ASC. The only ASC subscale not associated with generalized panicfear was the bronchoconstriction scale (r = .01, ns). These findings demonstrate that trait anxiety has stronger associations with the emotional experience of asthma exacerbations than the physical correlates. 4. Discussion This study showed that asthma-PD patients have higher rates of both illness-specific panic-fear and generalized panic-fear than asthma-only patients, despite no differences in asthma severity. The two panic-fear constructs were associated differentially with asthma outcomes. Illness-specific panic-fear mediated the relationship between PD and health-related quality of life, including emotional disturbance due to asthma. Thus, illness-specific panicfear may be maladaptive for asthma-PD patients by increasing the perceived emotional burden attributed to asthma. Generalized panic-fear was associated with activity limitation due to asthma and use of PRN b2-agonist medication. The greater use of quickrelief medication in the absence of differences in asthma severity might reflect over-reliance on b2-agonist medication. These findings show the importance of teasing apart panic-fear constructs among patients with asthma-PD comorbidity. Both types of panic-fear were associated with patients’ subjective assessment of asthma, but not objective markers. To our knowledge, this is the first study to extend the panic-fear literature to a sample of asthma patients with clinically diagnosed PD. The research and clinical implications are discussed below.
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These findings indicate that emotions experienced by asthmaPD patients during asthma exacerbation may play a key role in contributing to poorer health-related quality of life. Asthma-PD patients reported high levels on the emotional subscales of the ASC (panic-fear and irritability), but their scores on the physical symptom subscales (fatigue, hyperventilation, and bronchoconstriction) closely approximated norms reported for outpatients (Brooks et al., 1989). It is important to note that the ASC does not measure overall frequency of symptoms, but rather frequency of occurrence during asthma attacks. The emotional disturbance during asthma attacks may generalize between episodes and affect health-related quality of life, as supported by the mediational analyses. The emotional function subscale of the AQLQ contains items measuring asthma-related concerns and frustrations, and fears related to breathlessness and not having asthma medications available (Juniper et al., 1993). Therefore, the frightening nature of dyspnea, higher levels of threat appraisal, and feelings of dependence on rescue medication may be key elements involved in the link between PD, illness-specific panic-fear and healthrelated quality of life. Asthma-PD patients appear to feel subjectively more impaired and bothered by their asthma symptoms, despite no differences on markers of asthma severity. This finding is consistent with studies of chest pain (Bull Bringager, Arnesen, Friis, Husebye, & Dammen, 2007) and general somatic symptoms (Hoehn-Saric, McLeod, Funderburk, & Kowalski, 2004) among PD patients. Generalized panic-fear may affect self-management of asthma via decisions about use of rescue medication and avoidance of activities. Excessive trait anxiety might lead patients to treat their emotional distress with short-acting b2-agonists, particularly if they mistake respiratory symptoms of anxiety as asthma (Feldman, Siddique, et al., 2005). Conversely, excessive use of shortacting b2-agonists might also contribute to greater levels of anxiety via side effects, such as tachycardia and tremor (Cazzola, Matera, & Donner, 2005; Scalabrin, Sole, & Naspitz, 1996). The association between generalized panic-fear and avoidance of activities due to asthma may reflect agoraphobic avoidance and extend well beyond adaptive avoidance of asthma triggers (Yellowlees & Kalucy, 1990). The absence of associations between generalized panic-fear and pulmonary function or asthma medication severity class supports this notion. However, the very high rate of PD with agoraphobia (90%) in this sample prevents teasing apart the independent effects of generalized panic-fear from agoraphobia, although this may be difficult if this high rate of agoraphobia is replicated among asthma-PD patients. Although a significant association was found between generalized and illness-specific panic-fear, the size of the correlation (r = .37) was modest. The findings in this study suggest that both types of panic-fear may contribute to the finding that asthma-PD patients are at risk for greater asthma morbidity across time (Hasler et al., 2005). However, differential pathways may be involved and, thus it is important to examine both illness-specific and generalized panic-fear. The present study extends the large body of literature on panicfear to asthma-PD patients. The original studies at National Jewish Medical and Research Center were conducted primarily on inpatients with severe asthma and health care measures included length of hospitalizations and number of readmissions. A key difference in the present study was the milder disease severity of asthma among outpatients and thus, the use of primary care visits as the measure of health care use. The original panic-fear studies concluded that illness-specific panic-fear may be adaptive for asthma by focusing attention on asthma symptoms (Kinsman, Dirks, Jones, & Dahlem, 1980). However, the present data show that this heightened vigilance concerning asthma symptoms may also
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bear a cost for PD patients in terms of emotional distress. It is difficult to interpret whether the link between primary care office visits and illness-specific panic-fear represents appropriate or excessive use of health care resources. The present finding linking generalized panic-fear to PRN b2-agonist medication is consistent with the earlier research (Dirks et al., 1980; Kinsman, Dirks, & Dahlem, 1980). Our hypotheses concerning higher levels of illnessspecific and generalized panic-fear among asthma-PD patients versus asthma-only patients were supported. These findings are strengthened by the absence of between-group differences in asthma severity and the trend showing that asthma-PD patients had higher levels of %FEV1 (Feldman, Lehrer et al., 2005). AsthmaPD patients may use a common appraisal process that is applied to both narrower cues of asthma (illness-specific) and wider physiological cues in general. Therefore, the risk factors originally attributed to panic-fear from earlier studies also appear relevant to asthma-PD patients. There are limitations that should be considered in the context of these results. The use of a small, homogenous, and non-random sample is a major limitation of this study. The small sample size prevented examination of subgroups of panic-fear patients within asthma-PD patients. A question to address in future research is whether differences exist on asthma outcomes between asthmaPD patients with moderate versus high panic-fear. Despite the small sample, significant findings were present due to large effect sizes. Although the multiple comparisons conducted in the present study might increase the chance of a Type I error, a Bonferroni correction was employed and effect sizes were reported. Future research should examine associations between both panic-fear constructs and activity limitation due to asthma among PD patients without agoraphobia, which was not possible due to the high rate of agoraphobia in this sample. Additionally, self-report of short-acting b2-agonist use was a limitation in the present study. Daily, electronic measures of pulmonary function and short-acting b2-agonist use would provide information on whether rescue medication use and health care use are appropriate or excessive. In conclusion, there are several clinical implications for the assessment and treatment of panic-fear and PD among patients with asthma. Both the panic-fear subscale of the ASC and the MMPI panic-fear scale might be useful screening devices, particularly for asthma patients whose subjective report does not match objective measures of asthma control. Whereas treatments were not formally developed for panic-fear, empirically validated treatments are available for PD (Barlow, Gorman, Shear, & Woods, 2000). Furthermore, a psychological treatment has been specifically developed for patients with asthma and PD that combines cognitive behavioral therapy and asthma education (Feldman et al., 2000). A pilot study of this protocol showed that asthma-PD patients reported fewer asthma and panic symptoms, improvements in health-related quality of life, and decreased use of rescue medications at post-treatment (Lehrer et al., 2008). The cognitiveaffective dimensions of asthma are particularly important to target among patients with PD and illness-specific panic-fear. These patients may not only worry about when their next panic episode might occur, but they may also have excessive fear about the occurrence of their next asthma attack. Reducing illness-specific panic-fear and excessive restriction of activities among asthma-PD patients may be beneficial in improving health-related quality of life and reducing emotional distress. However, this goal must be balanced by maintaining potentially adaptive features of illnessspecific panic-fear, such as vigilance to asthma symptoms and medication regimens and avoidance of asthma triggers. An initial treatment goal should be to distinguish between anxiety that mobilizes appropriate asthma self-management versus panic that is mistaken as an asthma exacerbation.
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