P U L M O N A RY R E H A B I L I TAT I O N
Comorbidity Associated With Referral to Pulmonary Rehabilitation in People Hospitalized With Chronic Obstructive Pulmonary Disease Lok Sze Katrina Li, B Physio; Gillian Caughey, BSc, PhD; Kylie Johnston, BAppSc(Physio), PhD
■ PURPOSE: Comorbid conditions are common in people with chronic obstructive pulmonary disease (COPD) and may affect therapeutic management. The aim of this study was to examine the association of comorbidity in people with COPD with referral to a pulmonary rehabilitation (PR) program.
K E Y
■ METHODS: An analysis of data was conducted from an observational study of 88 people admitted to hospital with a primary diagnosis of COPD. Demographic and admission-related data were extracted and comorbidity scores (Charlson and Rx-Risk-V) were calculated.
referral
■ RESULTS: Total comorbidity scores were not associated with referral to PR; however specific comorbid conditions were. The presence of anxiety (from medical records) was more frequent in those referred to PR (χ2 = 4.20; P = .04; OR, 7.0; 95% CI, 0.8–59.0). The presence of hypertension (as determined by Rx-Risk-V) was more likely to result in PR referral (χ2 = 6.69; P = .01; OR, 6.8; 95% CI, 1.6–29.1), and, in those with arrhythmia, PR referral was less likely (χ2 = 4.22; P = .04; OR, 0.28; 95% CI, 0.08–0.99). Patients who had been referred to PR had lower forced expiratory volume in 1 second (FEV1 percent predicted) (P < .001) and greater hospital bed days in previous 3 years (P = .051). In a multivariate analysis, FEV1 percent predicted, bed days in the last 3 years, and Rx-Risk-V categories of hypertension and arrhythmia accounted for 25% of variance in referral to PR. ■ CONCLUSIONS: In addition to COPD disease severity and hospital utilization, specific comorbidities identified with a comprehensive system (ie, the Rx-Risk score) were associated with referral to PR in this sample.
Chronic obstructive pulmonary disease (COPD) is currently the fifth leading cause of death in Australia1 and was ranked the third leading global cause of death in 2010.2 Comorbidity is common in people with COPD, with a reported average of 4 comorbid conditions.3 Common comorbidities in COPD include chronic heart failure,4 osteoporosis,5 diabetes,6 and mental illness.7 Indices such as the Charlson comorbidity index (which
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chronic obstructive pulmonary disease comorbidity
pulmonary rehabilitation
Author Affiliations: School of Health Sciences (Ms Li and Dr Johnston), and School of Pharmacy and Medical Sciences (Dr Caughey), University of South Australia, Adelaide, Australia. The authors declare no conflicts of interest. Correspondence: Kylie Johnston, BAppSc(Physio), PhD, School of Health Sciences, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia ([email protected]). DOI: 10.1097/HCR.0000000000000080
is based on hospitalization diagnosis of 17 specific conditions)8 and the Rx-Risk-V score (which is based on prescription medication dispensing)9 have been used to measure comorbidity status in administrative health databases. Although both indices are valid for predicting mortality, the ability to recognize particular diseases varies and therefore they may be used together to enhance the detection of the range of comorbidities.10
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The presence of comorbidities may negatively influence COPD management. For example, although corticosteroids are recommended in guidelines for the maintenance and treatment of acute exacerbations of COPD, approximately 20% of older patients with diabetes will also have COPD, thus corticosteroid use may interfere with blood glucose levels and result in poor diabetes control.11 Pulmonary rehabilitation (PR) is a key nonpharmacological intervention in the management of COPD.12 It involves exercise training, education, and psychosocial support and has been demonstrated to reduce symptoms, improve exercise tolerance, and enhance quality of life in people with COPD.13 Despite the high level of evidence regarding the effectiveness and cost-effectiveness of PR, referral to PR is low, with only 3% to 16% of suitable patients being referred.14 Although some comorbidities such as metabolic disease15 and osteoporosis16 have been associated with poorer outcomes from participation in a PR program, there is no current information on the influence of comorbidity status on PR referral in those with COPD. Therefore, the primary aim of this study was to understand the association of comorbidity status in patients with COPD who were and were not referred to PR. A secondary aim was to compare 3 methods for identifying comorbidities in this sample: documentation in the medical record, Charlson comorbidity index, and Rx-Risk-V score.
METHODS Study Population Data from a cross-sectional study of 88 patients admitted to a tertiary hospital in Adelaide, South Australia, with a primary diagnosis of COPD between March and November 2011 were analyzed in this study. 17 Patients with insufficient English language, insufficient cognitive status, who declined an interview, or were physically unable to participate (eg, palliation and deafness) were excluded. Ethics approval was obtained from the Royal Adelaide Hospital Human Research Ethics Committee and the University of South Australia Human Research Ethics Committee before data collection.
Data Collection Demographic, disease, and admission-related data were obtained from electronic and paper-based medical records of the index admission and previous contact with all public hospitals within the state. Data extracted from the medical record included ICD-10-AM (Australian version, International www.jcrpjournal.com
Classification of Diseases) codes for primary and secondary diagnoses. Medications prescribed during the admission for each patient were extracted from pharmacy records. Postal codes were used to determine the Index of Relative Socio-economic Advantage and Disadvantage. Documentation of referral to PR programs was identified from the same data sources. PR programs were defined according to the criteria of Lacasse et al13 including, “Any inpatient, outpatient, or homebased rehabilitation program of at least 4-weeks duration that included exercise therapy with or without any form of education and/or psychological support delivered to patients with exercise limitation attributable to COPD” (p. 3). The source of the referral to PR was documented when possible.
Measures of comorbidity status The frequency and classification of comorbid conditions documented in the medical record were calculated. All patients had the ICD-10-AM code for chronic pulmonary disease as their primary diagnosis; therefore, this comorbidity was excluded from the calculation of the Charlson index. The ICD-10-AM codes for patients’ comorbid diagnoses were organized into Charlson disease categories using the coding algorithm published by Quan et al.18 Each condition in the Charlson comorbidity index was assigned a weighting developed on the basis of relative risk estimates of mortality,8 which were then summed to calculate the weighted Charlson comorbidity index. The Rx-Risk-V score was calculated from pharmacy records of medications dispensed during the inpatient admission, using 42 indicators for general drug categories. Each prescribed medication was coded according to the World Health Organization Anatomical Therapeutic Chemical system,19 and subsequent categorization into Rx-Risk-V categories was conducted according to established methods.11
Statistical Analysis Data were analyzed using SPSS (PASW statistics 19, 2009). Demographic and disease characteristics between groups who were and were not referred to PR were compared with the independent sample t test or generalized linear model with binary outcomes for severely skewed data. The type and number of comorbidities documented in the medical records, Rx-Risk-V score, and Charlson comorbidity index were described and compared for those who were or were not referred for PR using the Shapiro-Wilk test or the MannWhitney test depending on data distribution. Univariate analysis (Pearson or Spearman correlation) was used to examine the influence of potential Comorbidity and Referral to PR / 431
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continuous data covariates on referral to PR. The chi-square test was used to analyze relationships of categorical data, including individual comorbidities as characterized by medical record documentation, Charlson and Rx-Risk-V indices with referral to PR. Partial least square path modeling was subsequently used to examine the effect of multiple associations on referral or not to PR.
medical record, and more than 20% of the patients had gastrointestinal tract conditions, osteoporosis, diabetes, or other pulmonary or airway conditions (Figure 1). Anxiety recorded in the medical record was associated with referral to PR (χ2 = 4.20; P = .04; OR, 7.0; 95% CI, 0.8–59.0) and documented depression trended toward an association with referral (χ2 = 3.96; P = .05; OR, 3.7; 95% CI, 1.0–14.2).
Charlson and Rx-Risk-V Indices
RESULTS Patient Demographic and Disease Characteristics Characteristics of the whole sample and groups of patients who were (n = 50) or were not referred to PR (n = 38) are described in Table 1. Patients who had been referred to PR had lower forced expiratory volume in 1 second expressed as a percentage of predicted (FEV1 percent predicted) than those who had not been referred (P < .001). Patients who had been referred also had a trend toward greater number of hospital bed days for respiratory conditions in the previous 3 years than those who had not been referred (P = .05). Participants had been referred to PR at the time of a hospital admission by the COPD program inpatient coordinator (26 of the 50; 52%), by a respiratory specialist in an outpatient setting (15 of the 50; 30%), by self-referral (2 of the 50; 4%), by a community exercise provider (1 of the 50; 2%), or an unknown source (6 of the 50; 12%).
The Charlson comorbidity score for patients referred and not referred to PR—mean (standard deviation)— was 0.4 (1.0) and 0.2 (0.5), respectively (P = .31). Similarly, the total Rx-Risk-V score was not significantly different between groups who had, 4.5 (2.2), and had not, 4.2 (2.0), been referred to PR (P = .54). The presence of the Rx-Risk-V category of hypertension was significantly associated with referral to PR (χ2 = 6.69; P = .01; Peto odds ratio estimate, 6.8; 95% CI, 1.6–29.1) and the Rx-Risk-V category of arrhythmia was associated with not being referred to PR (χ2 = 4.22; P = .04; OR, 0.28; 95%CI, 0.08–0.99).
Comparison of Comorbidity Identification Figure 1 compares common comorbidities identified by the medical record, Charlson comorbidity index, and Rx-Risk-V categories. Rx-Risk-V categories and medical record were more similar in identifying comorbidities whereas the Charlson comorbidity index (generated from ICD-10-AM codes) was only able to identify 2 of the common comorbidities.
Comorbid Conditions
Combined Influence of Variable on Referral or Not to PR
More than 40% of the patients had cardiovascular disease, hypertension, or hyperlipidemia according to the
Partial least square path modeling indicated that FEV1 percent predicted (β = −0.28; P < .001),
T a b l e 1 • Patient Characteristics by Referral Status to PR All Patients
Referred to PR
Not Referred to PR
n = 88
n = 50
n = 38
Male, n (%)
57 (65)
32 (56)
25 (44)
Age, mean ± SD, y
72 ± 12
72 ± 10
72 ± 14
IRSAD score, median (IQR)
992 (72)
1001 (76)
981 (67)
Number of hospital bed days for respiratory conditions in last 3 yrs, mean ± SD
7.5 ± 21
12.5 ± 24
1.5 ± 14
n = 64
n = 39
FEV1, percent predicted, mean ± SD
47 ± 19
41 ± 16
a
n = 25 b
56 ± 20
Abbreviations: FEV1, forced expiratory volume in 1 second; IQR, interquartile range; IRSAD, Index of Relative Socio-economic Advantage and Disadvantage; PR, pulmonary rehabilitation. Approaching significant difference for referred compared with not referred to PR (P = .051).
a
Referred compared with not referred to PR (P < .001).
b
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hospital bed days in last 3 years (β = 0.17; P = .01), Rx-Risk-V category of hypertension (β = 0.23; P = .002), and Rx-Risk-V category of arrhythmia (β = −0.23; P = .004)—all remained significantly associated with referral to PR in a multifactorial regression model (R2= 25%). Overall effect sizes (based on Cohen’s f2) were small and medium, with FEV1 percent predicted having the largest effect on referrals (effect sizes: FEV1 percent predicted, 0.96; hypertension, 0.64; arrhythmias, 0.05; hospital bed days in the last 3 years, 0.036).
DISCUSSION The findings of this study indicate that total Charlson or Rx-Risk-V comorbidity scores were not associated with referral to PR. However, specific comorbid conditions such as pharmacologically managed hypertension, absence of pharmacologically managed arrhythmia, and documented anxiety were related to referral to PR, along with worse lung function and greater hospital bed days within the previous 3 years. According to medical record documentation, patients with COPD in this study had an average of 4 comor-
bidities, which is consistent with previous reports involving similar populations.3 This study adds to the existing literature on factors influencing referral to PR, which have previously been only qualitative20,21 and examined primary care practitioners’ perceptions regarding barriers to and facilitators of referral, rather than intrinsic patient factors such as comorbidity. In contrast, this study sample was drawn from people hospitalized with COPD as their primary diagnosis, thus may present different associations of comorbidity with referral to PR from patients with COPD managed in primary care settings. Results of this study should therefore not be generalized to people with COPD who may be in earlier stages of the disease and have not required hospitalization. Most participants who were referred to PR in this study had been referred at the time of hospital admission by a COPD program clinician or by a respiratory specialist, and findings may reflect referral patterns specific to this regional area. The potential influence of comorbidities on the care and outcomes of people with COPD is increasingly recognized.22 However, the way in which comorbidities are recorded is highly variable. The Charlson comorbidity index was established to
Anxiety
RxRisk-V category
Comorbidity categories
Diabetes
Osteoporosis
Charlson comorbidity category
Hyperlipidaemia
Hypertension
Medical record comorbidity
Cardiovascular*
Depression
0%
10%
20%
30%
40%
50%
Frequency of occurence
Figure 1. Identification of comorbidities using the 3 resources. *Cardiovascular disease included in medical records: atrial fibrillation, ischemic heart disease, congestive cardiac failure, myocardial infarction, valve stenosis, angina, cardiomyopathy, heart failure, and pericarditis. Cardiovascular disease included in the Charlson comorbidity index: congestive heart failure and myocardial infarction. Cardiovascular disease included in Rx-Risk-V categories: arrhythmia, congestive heart failure, ischemic heart disease/angina, and ischemic heart disease/ hypertension. www.jcrpjournal.com
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examine the effect of various comorbid conditions on mortality8 and may not be as useful to reflect influence of comorbidity on other outcomes such as the process of care.23 In our study, the Rx-Risk-V score was selected for its potential ability to capture comorbid conditions common in patients with COPD that were not well described by the Charlson comorbidity index. Although neither total comorbidity score was associated with referral or not to PR, specific subcategories of the Rx-Risk-V score (hypertension and arrhythmia) were associated with referral. Pharmacologically managed hypertension (indicated by the Rx-Risk-V category) was present in nearly 50% of this study sample, slightly lower than other reports in patients with COPD (64%).23 Metabolic diseases including hypertension have been reported to have a negative association with achievement of clinically significant improvements in exercise capacity after a PR program,15 but our findings indicate that this does not seem to be acting as a barrier to referral. The association between presence of hypertension and referral to PR may indicate practitioners seeking to address the common goal of improved exercise tolerance for both pulmonary and cardiovascular conditions in their patients. Pharmacologically managed arrhythmia was associated with patients having never been referred to PR. Hanrahan et al24 reported a higher frequency of arrhythmia (atrial tachycardia identified in 41.8% of 1429 patients with moderate-to-severe COPD during 24-hour Holter monitoring) than in the current study (15%). Unstable cardiovascular disease (extreme and uncontrolled arrhythmia) would be a contraindication to the exercise component of PR.25 Concerns about arrhythmia limiting ability to participate in exercise may have negatively influenced referral to PR. The presence of anxiety (and possibly depression) documented in the medical records was associated with being referred to PR; however, being on antianxiety medication or antidepressants was not associated with referral. This may reflect a cohort of people with anxiety or depression who are not managed with a pharmacological intervention but are more likely to be referred to PR. Our study did not objectively identify anxiety or depression using a recognized scale (eg, the Hospital Anxiety and Depression Scale), but relied on reports in the medical record and prescribed medication use. A meta-analysis concluded that exercise training in patients with COPD significantly reduces symptoms of anxiety and depression.26 It seems that in our study, health professionals did not decline referral to PR for patients with COPD with documented or pharmacologically managed anxiety or depression.
Patients with worse lung function and greater health care utilization were more likely to have been referred to PR. This may indicate that clinicians delay referral to PR until patients have more severe disease or frequent presentations to the hospital. There is evidence that patients with COPD benefit from PR regardless of the disease severity27 and patients may benefit from early referral as current guidelines recommend referral to PR for any patients where shortness of breath is limiting function.12 Although qualitative studies have discussed barriers for referral to PR, the stage of lung disease in relation to referral has not been addressed.20,21
Limitations and Implications for Future Research The present study has several limitations. It was cross-sectional in design, so no inferences can be made regarding the direction or timing of influence of comorbidities and referral or not to PR. It is possible that the patients’ comorbid status changed since the time of their referral to PR. Prospective longitudinal studies would be required to address this limitation and to determine any causative effect of comorbidities on referral or not to PR. Study sample size was limited because pulmonary function data were available in only 64 of the 88 participants and a larger sample size would provide greater power for detecting effects. Neither of the comorbidity indexes included obesity, so the potential effect of obesity on referral or not to PR could not be explored in this study. Obesity has been associated with reduced exercise tolerance (distance walked in 6 minutes) in people with COPD.28,29 Given the high international prevalence of obesity,30,31 the relationship between referral to PR and obesity should be investigated in future studies. Arrhythmia can be a contraindication to exercise, and in this study was associated with not ever being referred to PR. Further research might investigate other options for exercise that are safe and within the patients’ capabilities so that they may benefit from PR. This study sample was composed of an older hospitalized COPD population with severe airflow obstruction. Associations of comorbidity with referral or not to PR should also be examined in populations with milder lung disease, as early referral to PR is encouraged to maximize the health benefits for the individual, reduce health care utilization, and hospitalization in the longer term.32 This study demonstrated differences in the frequency of reporting comorbid conditions depending on the method (ie, medical record review) or index (eg, Charlson comorbidity index and Rx-Risk-V score)
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used. Future studies investigating the role of comorbidity on outcomes in patients with COPD should examine a wide range of comorbidities using a consistent method of identification.
CONCLUSIONS This study found that a greater number of comorbid conditions were not associated with the likelihood of PR referral. However, specific comorbid conditions did influence PR referral; the presence of anxiety, depression in the medical records, and being on hypertensive medication increased PR referral whereas being on anti-arrhythmic medication decreased the likelihood of referral. Lower FEV1 percent predicted and greater number of hospital bed days, markers of more severe COPD, were associated with an increased likelihood of PR referral. Our findings suggest that identification of comorbidities with a comprehensive system such as the Rx-Risk score is valuable in studies that evaluate management of COPD care, as specific comorbidities may influence study outcomes, such as referrals along with demographic and COPD diseasespecific characteristics.
References 1. Erbas B, Ullah S, Hyndman RJ, Scollo M, Abramson M. Forecasts of COPD mortality in Australia: 2006–2025. BMC Med Res Methodol. 2012;12:17–26. 2. Lozano R, Naghavi M, Foreman K, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380:2095–2128. 3. Mapel DW, Hurley JS, Frost FJ, Petersen HV, Picchi MA, Coultas DB. Health care utilization in chronic obstructive pulmonary disease—a case-control study in a health maintenance organization. Arch Intern Med. 2000;160:2653–2658. 4. Tkácˇ J, Man SFP, Sin DD. Review: systemic consequences of COPD. Ther Adv Respir Dis. 2007;1:47–59. 5. O’Kelly S, Smith SM, Lane S, Teljeur C, O’Dowd T. Chronic respiratory disease and multimorbidity: prevalence and impact in a general practice setting. Respir Med. 2011;105:236–242. 6. Sharafkhaneh A, Petersen NJ, Yu H-J, Dalal AA, Johnson ML, Hanania NA. Burden of COPD in a government health care system: a retrospective observational study using data from the US Veterans Affairs population. Int J Chron Obstruct Pulmon Dis. 2010;5:125– 132. 7. Eisner MD, Blanc PD, Yelin EH, et al. Influence of anxiety on health outcomes in COPD. Thorax. 2010;65:229–234. 8. Charlson M, Pompei P, Ales K, MacKenzie C. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis. 1987;40:373–383. 9. Sloan KL, Sales AE, Liu C-F, et al. Construction and characteristics of the RxRisk-V: a VA-adapted pharmacy-based case-mix instrument. Med Care. 2003;41:761–774. 10. Lu CY, Barratt J, Vitry A, Roughead E. Charlson and Rx-Risk comorbidity indices were predictive of mortality in the Australian health care setting. J Clin Epidemiol. 2011;64:223–228.
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11. Caughey GE, Roughead EE, Vitry AI, McDermott RA, Shakib S, Gilbert AL. Comorbidity in the elderly with diabetes: identification of areas of potential treatment conflicts. Diabetes Res Clin Pract. 2010;87:385–393. 12. Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management and prevention of chronic obstructive pulmonary disease. http://www.goldcopd. org/uploads/users/files/GOLD_Report_2013_Feb20.pdf . Published 2013. Accessed June 4, 2013. 13. Lacasse Y, Goldstein R, Lasserson TJ, Martin S. Pulmonary rehabilitation for chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2006;(4):CD003793. 14. Johnston K, Grimmer-Somers K. Pulmonary rehabilitation: overwhelming evidence but lost in translation? Physiother Can. 2010;62:368–373. 15. Crisafulli E, Costi S, Luppi F, et al. Role of comorbidities in a cohort of patients with COPD undergoing pulmonary rehabilitation. Thorax. 2008;63:487–492. 16. Crisafulli E, Gorgone P, Vagaggini B, et al. Efficacy of standard rehabilitation in COPD outpatients with comorbidities. Eur Respir J. 2010;36:1042–1048. 17. Johnston K, Young M, Grimmer-Somers K, Antic R, Frith PA. Frequency of referral to and attendance at a pulmonary rehabilitation program amongst patients admitted to a tertiary hospital with chronic obstructive pulmonary disease. Respirology. 2013. doi:10.1111/resp.12128. [Epub ahead of print] 18. Quan H, Sundararajan V, Halfon P, et al. Coding algorithms for defining comorbidities in ICD-9-CM and ICD-10 administrative data. Med Care. 2005;43:1130–1139. 19. WHO Collaborating Centre for Drug Statistics Methodology. ATC/DDD Index 2012. http://www.whocc.no/atc_ddd_index./ Accessed March 16, 2012. 20. Harris D, Hayter M, Allender S. Factors affecting the offer of pulmonary rehabilitation to patients with chronic obstructive pulmonary disease by primary care professionals: a qualitative study. Prim Health Care Res Dev. 2008;9:280–290. 21. Johnston K, Young M, Grimmer-Somers KA, Antic R, Frith PA. Why are some evidence-based care recommendations in chronic obstructive pulmonary disease better implemented than others? Perspectives of medical practitioners. Int J Chron Obstruct Pulmon Dis. 2011;6:659–667. 22. Nussbaumer-Ochsner Y, Rabe KF. Systemic manifestations of COPD. Chest. 2011;139:165–173. 23. Terzano C, Conti V, Stefano FD, et al. Comorbidity, hospitalization, and mortality in COPD: results from a longitudinal study. Lung. 2010;188:321–329. 24. Hanrahan JP, Grogan DR , Baumgartner RA , et al. Arrhythmias in patients with chronic obstructive pulmonary disease (COPD): occurrence frequency and the effect of treatment with the inhaled long-acting beta2-agonists arformoterol and salmeterol . Medicine (Baltimore). 2008 ; 87 : 319 – 328 . 25. Jenkins S, Hill K, Cecins NM. State of the art: how to set up a pulmonary rehabilitation program . Respirology. 2010;15:1157–1173. 26. Coventry PA, Bower P, Keyworth C, et al. The effect of complex interventions on depression and anxiety in chronic obstructive pulmonary disease: systematic review and meta-analysis. PloS One. 2013;8:e60532. 27. Berry MJ, Rejeski WJ, Adair NE, Zaccaro D. Exercise rehabilitation and chronic obstructive pulmnonary disease stage. Am J Respir Crit Care Med. 1999;160:1248–1253. 28. Ramachandran K, McCusker C, Connors M, Zuwallack R, Lahiri B. The influence of obesity on pulmonary rehabilitation outcomes in patients with COPD. Chron Respir Dis. 2008;5:205–209.
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29. Sava F, Laviolette L, Bernard S, Breton M-J, Bourbeau J, Maltais F. The impact of obesity on walking and cycling performance and response to pulmonary rehabilitation in COPD. BMC Pulm Med. 2010;10:55. http://www.biomedcentral.com/1471-2466/10/55. 30. Flegal KM, Carroll MD, Kit BK, Ogden CL. Prevalence of obesity and trends in the distribution of body mass index among US adults, 1999–2010. JAMA. 2012;307:491–497.
31. Walls HL, Magliano DJ, Stevenson CE, et al. Projected progression of the prevalence of obesity in Australia. Obesity (Silver Spring). 2012;20:872–878. 32. Garcia-Aymerich J, Lange P, Benet M, Schnohr P, Anto JM. Regular physical activity reduces hospital admission and mortality in chronic obstructive pulmonary disease: a population based cohort study. Thorax. 2006;61:772–778.
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Comorbidity Associated With Referral to Pulmonary Rehabilitation in People Hospitalized With Chronic Obstructive Pulmonary Disease Lok Sze Katrina Li, B Physio; Gillian Caughey, BSc, PhD; Kylie Johnston, BAppSc(Physio), PhD
■ PURPOSE: Comorbid conditions are common in people with chronic obstructive pulmonary disease (COPD) and may affect therapeutic management. The aim of this study was to examine the association of comorbidity in people with COPD with referral to a pulmonary rehabilitation (PR) program.
K E Y
■ METHODS: An analysis of data was conducted from an observational study of 88 people admitted to hospital with a primary diagnosis of COPD. Demographic and admission-related data were extracted and comorbidity scores (Charlson and Rx-Risk-V) were calculated.
referral
■ RESULTS: Total comorbidity scores were not associated with referral to PR; however specific comorbid conditions were. The presence of anxiety (from medical records) was more frequent in those referred to PR (χ2 = 4.20; P = .04; OR, 7.0; 95% CI, 0.8–59.0). The presence of hypertension (as determined by Rx-Risk-V) was more likely to result in PR referral (χ2 = 6.69; P = .01; OR, 6.8; 95% CI, 1.6–29.1), and, in those with arrhythmia, PR referral was less likely (χ2 = 4.22; P = .04; OR, 0.28; 95% CI, 0.08–0.99). Patients who had been referred to PR had lower forced expiratory volume in 1 second (FEV1 percent predicted) (P < .001) and greater hospital bed days in previous 3 years (P = .051). In a multivariate analysis, FEV1 percent predicted, bed days in the last 3 years, and Rx-Risk-V categories of hypertension and arrhythmia accounted for 25% of variance in referral to PR. ■ CONCLUSIONS: In addition to COPD disease severity and hospital utilization, specific comorbidities identified with a comprehensive system (ie, the Rx-Risk score) were associated with referral to PR in this sample.
Chronic obstructive pulmonary disease (COPD) is currently the fifth leading cause of death in Australia1 and was ranked the third leading global cause of death in 2010.2 Comorbidity is common in people with COPD, with a reported average of 4 comorbid conditions.3 Common comorbidities in COPD include chronic heart failure,4 osteoporosis,5 diabetes,6 and mental illness.7 Indices such as the Charlson comorbidity index (which
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chronic obstructive pulmonary disease comorbidity
pulmonary rehabilitation
Author Affiliations: School of Health Sciences (Ms Li and Dr Johnston), and School of Pharmacy and Medical Sciences (Dr Caughey), University of South Australia, Adelaide, Australia. The authors declare no conflicts of interest. Correspondence: Kylie Johnston, BAppSc(Physio), PhD, School of Health Sciences, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia ([email protected]). DOI: 10.1097/HCR.0000000000000080
is based on hospitalization diagnosis of 17 specific conditions)8 and the Rx-Risk-V score (which is based on prescription medication dispensing)9 have been used to measure comorbidity status in administrative health databases. Although both indices are valid for predicting mortality, the ability to recognize particular diseases varies and therefore they may be used together to enhance the detection of the range of comorbidities.10
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The presence of comorbidities may negatively influence COPD management. For example, although corticosteroids are recommended in guidelines for the maintenance and treatment of acute exacerbations of COPD, approximately 20% of older patients with diabetes will also have COPD, thus corticosteroid use may interfere with blood glucose levels and result in poor diabetes control.11 Pulmonary rehabilitation (PR) is a key nonpharmacological intervention in the management of COPD.12 It involves exercise training, education, and psychosocial support and has been demonstrated to reduce symptoms, improve exercise tolerance, and enhance quality of life in people with COPD.13 Despite the high level of evidence regarding the effectiveness and cost-effectiveness of PR, referral to PR is low, with only 3% to 16% of suitable patients being referred.14 Although some comorbidities such as metabolic disease15 and osteoporosis16 have been associated with poorer outcomes from participation in a PR program, there is no current information on the influence of comorbidity status on PR referral in those with COPD. Therefore, the primary aim of this study was to understand the association of comorbidity status in patients with COPD who were and were not referred to PR. A secondary aim was to compare 3 methods for identifying comorbidities in this sample: documentation in the medical record, Charlson comorbidity index, and Rx-Risk-V score.
METHODS Study Population Data from a cross-sectional study of 88 patients admitted to a tertiary hospital in Adelaide, South Australia, with a primary diagnosis of COPD between March and November 2011 were analyzed in this study. 17 Patients with insufficient English language, insufficient cognitive status, who declined an interview, or were physically unable to participate (eg, palliation and deafness) were excluded. Ethics approval was obtained from the Royal Adelaide Hospital Human Research Ethics Committee and the University of South Australia Human Research Ethics Committee before data collection.
Data Collection Demographic, disease, and admission-related data were obtained from electronic and paper-based medical records of the index admission and previous contact with all public hospitals within the state. Data extracted from the medical record included ICD-10-AM (Australian version, International www.jcrpjournal.com
Classification of Diseases) codes for primary and secondary diagnoses. Medications prescribed during the admission for each patient were extracted from pharmacy records. Postal codes were used to determine the Index of Relative Socio-economic Advantage and Disadvantage. Documentation of referral to PR programs was identified from the same data sources. PR programs were defined according to the criteria of Lacasse et al13 including, “Any inpatient, outpatient, or homebased rehabilitation program of at least 4-weeks duration that included exercise therapy with or without any form of education and/or psychological support delivered to patients with exercise limitation attributable to COPD” (p. 3). The source of the referral to PR was documented when possible.
Measures of comorbidity status The frequency and classification of comorbid conditions documented in the medical record were calculated. All patients had the ICD-10-AM code for chronic pulmonary disease as their primary diagnosis; therefore, this comorbidity was excluded from the calculation of the Charlson index. The ICD-10-AM codes for patients’ comorbid diagnoses were organized into Charlson disease categories using the coding algorithm published by Quan et al.18 Each condition in the Charlson comorbidity index was assigned a weighting developed on the basis of relative risk estimates of mortality,8 which were then summed to calculate the weighted Charlson comorbidity index. The Rx-Risk-V score was calculated from pharmacy records of medications dispensed during the inpatient admission, using 42 indicators for general drug categories. Each prescribed medication was coded according to the World Health Organization Anatomical Therapeutic Chemical system,19 and subsequent categorization into Rx-Risk-V categories was conducted according to established methods.11
Statistical Analysis Data were analyzed using SPSS (PASW statistics 19, 2009). Demographic and disease characteristics between groups who were and were not referred to PR were compared with the independent sample t test or generalized linear model with binary outcomes for severely skewed data. The type and number of comorbidities documented in the medical records, Rx-Risk-V score, and Charlson comorbidity index were described and compared for those who were or were not referred for PR using the Shapiro-Wilk test or the MannWhitney test depending on data distribution. Univariate analysis (Pearson or Spearman correlation) was used to examine the influence of potential Comorbidity and Referral to PR / 431
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continuous data covariates on referral to PR. The chi-square test was used to analyze relationships of categorical data, including individual comorbidities as characterized by medical record documentation, Charlson and Rx-Risk-V indices with referral to PR. Partial least square path modeling was subsequently used to examine the effect of multiple associations on referral or not to PR.
medical record, and more than 20% of the patients had gastrointestinal tract conditions, osteoporosis, diabetes, or other pulmonary or airway conditions (Figure 1). Anxiety recorded in the medical record was associated with referral to PR (χ2 = 4.20; P = .04; OR, 7.0; 95% CI, 0.8–59.0) and documented depression trended toward an association with referral (χ2 = 3.96; P = .05; OR, 3.7; 95% CI, 1.0–14.2).
Charlson and Rx-Risk-V Indices
RESULTS Patient Demographic and Disease Characteristics Characteristics of the whole sample and groups of patients who were (n = 50) or were not referred to PR (n = 38) are described in Table 1. Patients who had been referred to PR had lower forced expiratory volume in 1 second expressed as a percentage of predicted (FEV1 percent predicted) than those who had not been referred (P < .001). Patients who had been referred also had a trend toward greater number of hospital bed days for respiratory conditions in the previous 3 years than those who had not been referred (P = .05). Participants had been referred to PR at the time of a hospital admission by the COPD program inpatient coordinator (26 of the 50; 52%), by a respiratory specialist in an outpatient setting (15 of the 50; 30%), by self-referral (2 of the 50; 4%), by a community exercise provider (1 of the 50; 2%), or an unknown source (6 of the 50; 12%).
The Charlson comorbidity score for patients referred and not referred to PR—mean (standard deviation)— was 0.4 (1.0) and 0.2 (0.5), respectively (P = .31). Similarly, the total Rx-Risk-V score was not significantly different between groups who had, 4.5 (2.2), and had not, 4.2 (2.0), been referred to PR (P = .54). The presence of the Rx-Risk-V category of hypertension was significantly associated with referral to PR (χ2 = 6.69; P = .01; Peto odds ratio estimate, 6.8; 95% CI, 1.6–29.1) and the Rx-Risk-V category of arrhythmia was associated with not being referred to PR (χ2 = 4.22; P = .04; OR, 0.28; 95%CI, 0.08–0.99).
Comparison of Comorbidity Identification Figure 1 compares common comorbidities identified by the medical record, Charlson comorbidity index, and Rx-Risk-V categories. Rx-Risk-V categories and medical record were more similar in identifying comorbidities whereas the Charlson comorbidity index (generated from ICD-10-AM codes) was only able to identify 2 of the common comorbidities.
Comorbid Conditions
Combined Influence of Variable on Referral or Not to PR
More than 40% of the patients had cardiovascular disease, hypertension, or hyperlipidemia according to the
Partial least square path modeling indicated that FEV1 percent predicted (β = −0.28; P < .001),
T a b l e 1 • Patient Characteristics by Referral Status to PR All Patients
Referred to PR
Not Referred to PR
n = 88
n = 50
n = 38
Male, n (%)
57 (65)
32 (56)
25 (44)
Age, mean ± SD, y
72 ± 12
72 ± 10
72 ± 14
IRSAD score, median (IQR)
992 (72)
1001 (76)
981 (67)
Number of hospital bed days for respiratory conditions in last 3 yrs, mean ± SD
7.5 ± 21
12.5 ± 24
1.5 ± 14
n = 64
n = 39
FEV1, percent predicted, mean ± SD
47 ± 19
41 ± 16
a
n = 25 b
56 ± 20
Abbreviations: FEV1, forced expiratory volume in 1 second; IQR, interquartile range; IRSAD, Index of Relative Socio-economic Advantage and Disadvantage; PR, pulmonary rehabilitation. Approaching significant difference for referred compared with not referred to PR (P = .051).
a
Referred compared with not referred to PR (P < .001).
b
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hospital bed days in last 3 years (β = 0.17; P = .01), Rx-Risk-V category of hypertension (β = 0.23; P = .002), and Rx-Risk-V category of arrhythmia (β = −0.23; P = .004)—all remained significantly associated with referral to PR in a multifactorial regression model (R2= 25%). Overall effect sizes (based on Cohen’s f2) were small and medium, with FEV1 percent predicted having the largest effect on referrals (effect sizes: FEV1 percent predicted, 0.96; hypertension, 0.64; arrhythmias, 0.05; hospital bed days in the last 3 years, 0.036).
DISCUSSION The findings of this study indicate that total Charlson or Rx-Risk-V comorbidity scores were not associated with referral to PR. However, specific comorbid conditions such as pharmacologically managed hypertension, absence of pharmacologically managed arrhythmia, and documented anxiety were related to referral to PR, along with worse lung function and greater hospital bed days within the previous 3 years. According to medical record documentation, patients with COPD in this study had an average of 4 comor-
bidities, which is consistent with previous reports involving similar populations.3 This study adds to the existing literature on factors influencing referral to PR, which have previously been only qualitative20,21 and examined primary care practitioners’ perceptions regarding barriers to and facilitators of referral, rather than intrinsic patient factors such as comorbidity. In contrast, this study sample was drawn from people hospitalized with COPD as their primary diagnosis, thus may present different associations of comorbidity with referral to PR from patients with COPD managed in primary care settings. Results of this study should therefore not be generalized to people with COPD who may be in earlier stages of the disease and have not required hospitalization. Most participants who were referred to PR in this study had been referred at the time of hospital admission by a COPD program clinician or by a respiratory specialist, and findings may reflect referral patterns specific to this regional area. The potential influence of comorbidities on the care and outcomes of people with COPD is increasingly recognized.22 However, the way in which comorbidities are recorded is highly variable. The Charlson comorbidity index was established to
Anxiety
RxRisk-V category
Comorbidity categories
Diabetes
Osteoporosis
Charlson comorbidity category
Hyperlipidaemia
Hypertension
Medical record comorbidity
Cardiovascular*
Depression
0%
10%
20%
30%
40%
50%
Frequency of occurence
Figure 1. Identification of comorbidities using the 3 resources. *Cardiovascular disease included in medical records: atrial fibrillation, ischemic heart disease, congestive cardiac failure, myocardial infarction, valve stenosis, angina, cardiomyopathy, heart failure, and pericarditis. Cardiovascular disease included in the Charlson comorbidity index: congestive heart failure and myocardial infarction. Cardiovascular disease included in Rx-Risk-V categories: arrhythmia, congestive heart failure, ischemic heart disease/angina, and ischemic heart disease/ hypertension. www.jcrpjournal.com
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examine the effect of various comorbid conditions on mortality8 and may not be as useful to reflect influence of comorbidity on other outcomes such as the process of care.23 In our study, the Rx-Risk-V score was selected for its potential ability to capture comorbid conditions common in patients with COPD that were not well described by the Charlson comorbidity index. Although neither total comorbidity score was associated with referral or not to PR, specific subcategories of the Rx-Risk-V score (hypertension and arrhythmia) were associated with referral. Pharmacologically managed hypertension (indicated by the Rx-Risk-V category) was present in nearly 50% of this study sample, slightly lower than other reports in patients with COPD (64%).23 Metabolic diseases including hypertension have been reported to have a negative association with achievement of clinically significant improvements in exercise capacity after a PR program,15 but our findings indicate that this does not seem to be acting as a barrier to referral. The association between presence of hypertension and referral to PR may indicate practitioners seeking to address the common goal of improved exercise tolerance for both pulmonary and cardiovascular conditions in their patients. Pharmacologically managed arrhythmia was associated with patients having never been referred to PR. Hanrahan et al24 reported a higher frequency of arrhythmia (atrial tachycardia identified in 41.8% of 1429 patients with moderate-to-severe COPD during 24-hour Holter monitoring) than in the current study (15%). Unstable cardiovascular disease (extreme and uncontrolled arrhythmia) would be a contraindication to the exercise component of PR.25 Concerns about arrhythmia limiting ability to participate in exercise may have negatively influenced referral to PR. The presence of anxiety (and possibly depression) documented in the medical records was associated with being referred to PR; however, being on antianxiety medication or antidepressants was not associated with referral. This may reflect a cohort of people with anxiety or depression who are not managed with a pharmacological intervention but are more likely to be referred to PR. Our study did not objectively identify anxiety or depression using a recognized scale (eg, the Hospital Anxiety and Depression Scale), but relied on reports in the medical record and prescribed medication use. A meta-analysis concluded that exercise training in patients with COPD significantly reduces symptoms of anxiety and depression.26 It seems that in our study, health professionals did not decline referral to PR for patients with COPD with documented or pharmacologically managed anxiety or depression.
Patients with worse lung function and greater health care utilization were more likely to have been referred to PR. This may indicate that clinicians delay referral to PR until patients have more severe disease or frequent presentations to the hospital. There is evidence that patients with COPD benefit from PR regardless of the disease severity27 and patients may benefit from early referral as current guidelines recommend referral to PR for any patients where shortness of breath is limiting function.12 Although qualitative studies have discussed barriers for referral to PR, the stage of lung disease in relation to referral has not been addressed.20,21
Limitations and Implications for Future Research The present study has several limitations. It was cross-sectional in design, so no inferences can be made regarding the direction or timing of influence of comorbidities and referral or not to PR. It is possible that the patients’ comorbid status changed since the time of their referral to PR. Prospective longitudinal studies would be required to address this limitation and to determine any causative effect of comorbidities on referral or not to PR. Study sample size was limited because pulmonary function data were available in only 64 of the 88 participants and a larger sample size would provide greater power for detecting effects. Neither of the comorbidity indexes included obesity, so the potential effect of obesity on referral or not to PR could not be explored in this study. Obesity has been associated with reduced exercise tolerance (distance walked in 6 minutes) in people with COPD.28,29 Given the high international prevalence of obesity,30,31 the relationship between referral to PR and obesity should be investigated in future studies. Arrhythmia can be a contraindication to exercise, and in this study was associated with not ever being referred to PR. Further research might investigate other options for exercise that are safe and within the patients’ capabilities so that they may benefit from PR. This study sample was composed of an older hospitalized COPD population with severe airflow obstruction. Associations of comorbidity with referral or not to PR should also be examined in populations with milder lung disease, as early referral to PR is encouraged to maximize the health benefits for the individual, reduce health care utilization, and hospitalization in the longer term.32 This study demonstrated differences in the frequency of reporting comorbid conditions depending on the method (ie, medical record review) or index (eg, Charlson comorbidity index and Rx-Risk-V score)
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used. Future studies investigating the role of comorbidity on outcomes in patients with COPD should examine a wide range of comorbidities using a consistent method of identification.
CONCLUSIONS This study found that a greater number of comorbid conditions were not associated with the likelihood of PR referral. However, specific comorbid conditions did influence PR referral; the presence of anxiety, depression in the medical records, and being on hypertensive medication increased PR referral whereas being on anti-arrhythmic medication decreased the likelihood of referral. Lower FEV1 percent predicted and greater number of hospital bed days, markers of more severe COPD, were associated with an increased likelihood of PR referral. Our findings suggest that identification of comorbidities with a comprehensive system such as the Rx-Risk score is valuable in studies that evaluate management of COPD care, as specific comorbidities may influence study outcomes, such as referrals along with demographic and COPD diseasespecific characteristics.
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