ABSTRACT
Previous research has shown that personality traits are associated with self-reported health status in the general population. COPD Assessment Test (CAT) is increasingly used to assess health status such as the impact of chronic obstructive pulmonary disease (COPD) on patients' daily life, but knowledge about the influence of personality traits on CAT score is lacking. The aim of this study was to examine the influence of Big Five personality traits on CAT score and the relation between personality traits and mental symptoms with respect to their influence on CAT score. A sample of 168 patients diagnosed with COPD was consecutively recruited in a secondary care outpatient clinic. All participants completed CAT, NEO Five-Factor Inventory, and Hospital Depression and Anxiety Scale. Multiple linear regression analysis was used to explore the association between personality traits and CAT scores and how this association was influenced by mental symptoms. The personality traits neuroticism, agreeableness and conscientiousness; and the mental symptoms depression and anxiety showed significant influence on CAT score when analysed in separate regression models. Identical R-square (R = 0.24) was found for personality traits and mental symptoms, but combining personality traits and mental symptoms in one regression model showed substantially reduced effect estimates of neuroticism, conscientiousness and anxiety, reflecting the strong correlations between personality traits and mental symptoms. We found that the impact of COPD on daily life measured by CAT was related to personality and mental symptoms, which illustrates the necessity of taking individual differences in personality and mental status into account in the management of COPD.
Introduction
Chronic obstructive pulmonary disease (COPD) causes progressive airflow limitations, reduced physical capacity and decreased quality of life (Citation1, 2). An effective management of the disease should include aims to improve health status and survival, to reduce symptoms, and to minimise exacerbations and complications (Citation2, 3). CAT is a short, easy-to-complete health status tool that has been developed to help patients and clinicians to assess and quantify the impact of COPD on the patient's daily life and to enable better communication about the consequences of the disease Citation(4). The responsiveness of CAT is good, and it is used increasingly in clinical practice as well as clinical research in preference to more time-consuming and complex questionnaires such as the St. George's Respiratory Questionnaire (SGRQ) and the Chronic Respiratory disease Questionnaire (CRQ) (Citation4–10).
Previous research has shown that personality is associated with perception of health and self-reported health status measures in the general population (Citation11–14). Further, perception of health is a predictor of mortality and health outcome, and personality seems to be a predictor itself of all-cause mortality Citation(15). According to the five-factor model (FFM), personality can be described by the Big Five traits Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness which is the dominant trait approach to the conceptualisation of personality (Citation16, 17). So far, no previous research has explored the association between the Big Five personality traits and health status of patients with COPD.
It is very well documented that the Big Five personality traits correlate to mental symptoms such as depression and anxiety (Citation18, 19). The presence of mental symptoms has been shown to influence patients' pulmonary specific symptoms Citation(20) and reported CAT score (Citation21–24). Hence, when examining the relation between personality and CAT score it is important to take the relation between personality and mental symptoms into account.
Knowledge about the influence of personality on perceived impact on the daily life of patients is valuable in the interpretation of CAT score results and contributes with perspectives that are important in the increasing focus on patient-centred care in the management of COPD (Citation25, 26). Thus, the aim of this study was to examine the influence of the Big Five personality traits on the CAT score and the relation between personality traits and mental symptoms with respect to their influence on CAT score.
Materials and methods
Participants
The present study population were initially enrolled in a study of factors predicting adherence in the secondary outpatient clinic of the Section of Respiratory Medicine at Hvidovre Hospital, Denmark. From February 2011 to May 2013 we consecutively asked 335 out of 1919 patients diagnosed with COPD according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) to participate in the study, and 168 patients gave written consent to participate. The study was approved by Hvidovre Hospital, the Danish Data Protection Agency and the regional scientific ethics committees for the Copenhagen area (protocol number: H-3-2010-123).
Design
Participants in the adherence study were subject to a psychological characterisation where personality traits, CAT score, mental symptoms, intelligence, health beliefs, refill adherence, and demographic and disease-related factors were assessed via tests and self-reported questionnaires. The design of the present study was cross-sectional and it focused on describing the association of CAT scores with personality traits and mental symptoms. All assessments were analysed in another publication presenting analyses of psychological characteristics as predictors of adherence behaviour, and adherence data will therefore not be presented in this study.
Measures
NEO Five-Factor Inventory (NEO-FFI) is a shortened version of the Revised NEO Personality Inventory (NEO PI-R) for research purpose. The Big Five personality traits (Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness) are evaluated with 60 items answered on a five-point scale (zero to four) ranging from “strongly disagree” to “strongly agree.” Each trait score ranges from 0 (lowest degree of the trait) to 48 (highest degree of the trait) (Citation17, 27). In the Danish standardised NEO-FFI Cronbach's alpha was 0.84, 0.80, 0.77, 0.73 and 0.80 for Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness, respectively (Citation17, 27, 28).
Hospital Anxiety and Depression scale (HADS) aims to determine the level of anxiety and depression in two subscales comprising seven items. Each item is scored 0–3 leading to a sum score from 0 to 21 for each scale. Higher sum scores indicate higher anxiety/depression (Cut-off point = 8; 8–11: Mild; 11–14: Moderate; 15+: Severe). HADS is a validated and reliable measure widely used in clinical settings (Citation29–31). In the present study Cronbach's alpha was 0.81 and 0.77 for the anxiety and depression scales, respectively.
COPD Assessment Test (CAT) aims to determine the impact of COPD on the daily life of patients and is made up of eight items each scored from 0 (no impact) to 5 (very severe impact). All item scores are summed and high scores indicate more severe impact of COPD (<10: Low; 10–20: Medium; 21–30: High; >30: Very high). CAT provides a valid, reliable and standardised measure of COPD health status (Citation4, 7–10). In the present study Cronbach's alpha was 0.80.
Reynolds Intellectual Assessment Scale (RIAS) evaluates the participant's general intelligence and comprises two verbal sub-tests and two non-verbal sub-tests. A general intelligence (IQ) index was derived from the four subtests. RIAS is a reliable and valid individually administered test of intelligence. We used the Danish version of RIAS and Danish test norms Citation(32). Intelligence was included as confounder as some studies have found decreased cognitive functioning in patients with COPD Citation(33) and cognitive functioning can associate with personality traits Citation(34).
Forced expiratory Volume (FEV1) is the maximum forced expiratory volume in 1 second. FEV1 is an important measure in the management of COPD and was measured in the outpatient clinic before inclusion in the adherence study.
GOLD stages classify people with COPD based on their degree of airflow limitation. GOLD I: FEV1 < 80% of normal, GOLD II: FEV1 50–79% of normal, GOLD III: FEV1 30–49% of normal and GOLD IV: FEV1 < 30% of normal.
Statistics
We analysed the binary correlations between CAT score, personality traits and mental symptoms with Pearson's correlation (R) coefficient. In order to estimate the influence of personality traits and mental symptoms on CAT score we performed multiple linear regression models. We completed three linear regression models () each controlled for potential confounders: age, gender, IQ and FEV1 in % of predicted.
Table 1. Linear regression models of the association of personality traits and mental symptoms to CAT score.
All variables except gender were included as continuous scale variables. To be consistent, the four confounders were included in all three regression models irrespective of statistical significance. We conducted model check of the linear regression assumptions: linearity (by plot residuals vs. covariates), variance homogeneity (by plot residuals vs. predicted values) and normality (by histograms). To compare the estimates across the regression models the standardised parameters are presented in addition to the parameter estimates. R-square indicates the impact of the included variables in each regression model. A p value <0.05 was considered statistically significant. All statistics were performed using SAS 9.3.
Results
Descriptive
All 168 participants included in the adherence study completed the CAT questionnaire and were included in the present analyses. Nearly 75% of the participants were classified according to GOLD as severe or very severe and were comparable to patients with COPD in our outpatient clinic in general as indicated by similar variation in GOLD grade, Medical Research Council scale and so on. Citation(35). One-third of the participants reported a CAT score representing a high or very high impact of COPD, and the more severe disease the higher the CAT score. Twelve percent of the participants reported depression symptoms and 17% reported anxiety symptoms. Further details about characteristics of the participants and the scores for the included measurements are shown in and
Table 2. Participant's characteristics (n = 168).
Table 3. Scores of COPD assessment test, personality traits and mental symptoms (n = 168).
Correlations
In simple binary correlations we found statistically highly significant moderate relationships between CAT score and neuroticism, depression symptoms, and anxiety symptoms, respectively. Further, we found statistically significant relationship between CAT score and conscientiousness, and CAT and FEV1, . Depression and anxiety were shown to correlate significantly with several of the personality traits – especially neuroticism, but also extraversion and conscientiousness.
Table 4. Bivariate correlations of scores of COPD assessment test, personality traits, mental symptoms and relevant confounders (n = 168).
Linear regression
In linear regression models we found significant associations with both personality traits and mental symptoms. Model 1 showed significant effects of neuroticism, agreeableness, conscientiousness and FEV1 on CAT score, while Model 2 showed significant effects of depression, anxiety and FEV1 on CAT score (see ). When combining personality traits and mental symptoms in the same regression model (Model 3), the effect size was substantially reduced for neuroticism, conscientiousness and anxiety compared to the separate models. Furthermore, the effect estimates were not significant in the combined model. The remaining significant estimates were almost unaffected and remained statistically significant. The R-square for Model 1 and Model 2 was equal (R-square = 0.24), while Model 3 explained 6% more of the variance in CAT scores.
Table 5. Multivariate linear regression analysis with COPD assessment test score as dependent variable – three models each adjusted for IQ, FEV1, age and gender.
Discussion
In this study we examined the association between personality traits and CAT score and the relation between personality and mental symptoms in that association. Our findings suggest that the personality traits neuroticism, agreeableness and conscientiousness associate as strongly with CAT score as depression and anxiety symptoms when analysed in two separate models. When combining the two models only the effects of agreeableness and depression remained significant reflecting the strong correlations observed between personality traits and mental symptoms.
CAT is an important tool to assess patients' perceived impact of COPD on their daily life. Our findings show that personality traits (neuroticism, agreeableness, conscientiousness) and mental symptom impact to the same extent as FEV1 on CAT score. No previous research has explored the association between personality and any health status or symptoms measures in COPD, but association between personality and perception of health has been found in primary care (Citation11, 12) and in the general population Citation(13). Further, results from comparable research in chronic heart failure suggest that quality of life is not only determined by severity of the disease but also by the degree of neuroticism Citation(36).
We found that the R-square was identical for the association between CAT score and personality traits and between CAT score and mental symptoms, respectively. In the combined model the effect estimates were influenced by the highly significant bivariate correlations between personality traits and mental symptoms. This is consistent with previous psychological research where personality traits were found to be influenced by depression as well as anxiety disorders (Citation37, 38). Additionally, Schlecht et al. found that dyspnoea correlated more strongly with health-related quality of life, anxiety and depression than spirometric values Citation(19). Furthermore, they found that participants high on neuroticism or conscientiousness tended to report a higher degree of dyspnoea Citation(19).
Our findings reflects that personality traits are at least as important to consider as the mental symptoms when assessing the CAT score in clinical practice. This supports a person-centred approach in the management of COPD Citation(26) as differences in personality influence the perception of health status and the impact of the disease on daily life. However, we do not suggest that patients' personality traits should be assessed as a part of clinical practice, although our findings confirm the well-known experience from clinical practice that patients react differently despite the same degree of COPD symptoms and disease. In accordance with our findings, the diversity in patients' reactions and feelings of fear may reflect differences in neuroticism more than actual breathlessness or other symptoms. Further, our findings illustrate the ambiguity inherent in the overlap between neuroticism and depression and anxiety. Depression and anxiety may be a consequence of COPD and may lead to higher scores on neuroticism, but it is also likely that patients with high scores on neuroticism will react with depression and anxiety to the stress associated with COPD. The results of our regression analyses suggest that CAT scores are influenced by both the emotional state of the patient and enduring personality characteristics, but that the current emotional state (depression) has a stronger influence on CAT scores than the personality trait of neuroticism. High agreeableness has previously been shown to correlate with longer survival and better health care probably because of the capability of establishing social relations and networks Citation(15). Our findings of a positive association between agreeableness and CAT scores could theoretically be a contributing factor as higher perceived symptoms could lead to more intense care. It may seem a paradox that agreeableness are positively correlated with COPD assessment scores, but because depression and anxiety are included in Model 3 this correlation may reflect aspects of agreeableness that are related to social relations and social behaviour which may be negatively influenced by COPD and thus lead to higher CAT scores.
The negative association between conscientiousness and CAT score may reflect the self-discipline and control that characterise individuals scoring high on this trait.
In our study the mean CAT scores were slightly lower in GOLD stages III and IV compared to previous findings Citation(8), possibly caused by selection bias in the adherence study. The proportion of participants reporting depression and anxiety symptoms (12% and 17.5%) was similar to previous findings in COPD populations Citation(39), and our results are consistent with those of Hilmarsen et al. who found that participants with depression and/or anxiety symptoms reported higher CAT scores than people without these symptoms Citation(21). Additionally, our findings include mutual adjustment for personality traits and mental symptoms. Jones et al. found a weak correlation between CAT score and FEV1 (r = −0.23, p < 0.001) similar to our results. However, our regression model approach, which takes confounders into account, indicates that other parameters have at least as much influence on CAT scores as FEV1 Citation(10).
The results of our regression analyses were reasonable clear, but we recognise some primary limitations in this study. Firstly, due to the cross-sectional design we cannot conclude on the direction of causality between COPD and CAT scores on the one hand and NEO-FFI and HADS scores on the other hand. In particular, mutual bidirectional influence is likely for CAT scores and depression and anxiety scores. Secondly, participants were originally recruited for an adherence study and we had no information on the larger eligible population from which our sample was recruited. Thus, the representativeness is uncertain due to possible selection bias – the study population was comparable with COPD outpatients in general in our clinic Citation(40). Thirdly, the analyses are performed only in patients relevant for treatment in a secondary care outpatient clinic, and the generalisability of the results to COPD in general is therefore limited.
This study contributes important knowledge about the influence of personality on the perceived impact of COPD on patients' daily life and about the influence of symptoms of depression and anxiety on this association. Our findings illustrate the necessity of taking individual differences in personality and mental status into account in the management of COPD, but further research about personality in COPD patients is needed, including analyses of the possible prognostic value of personality Citation(41).
Declaration of interest
Dr. Vestbo receives personal fees from GlaxoSmithKline, personal fees from Chiesi Pharmaceuticals, personal fees from Boehringer-Ingelheim, personal fees from Novartis, personal fees from Almirall and personal fees from AstraZeneca, outside the submitted work.
Funding
The Danish Lung Association and the Danish Health Ministry funded this research.
References
- Effing T, Monninkhof EM, van der Valk PD, van der Palen J, van Herwaarden CL, Partidge MR, et al. Self-management education for patients with chronic obstructive pulmonary disease. Cochrane Database Syst Rev 2007; 4:CD002990.
- Global Strategy for the Diagnosis, Management and Prevention of COPD, Global Initiative for Chronic Obstructive Lung Disease (GOLD). 2015. Available from: http://www.goldcopd.org/uploads/users/files/GOLD_Report_2015.pdf (last accessed February 2015).
- Celli BR, MacNee W, Force AET. Standards for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper. Eur Respir J 2004; 23(6):932–946.
- Jones PW, Harding G, Berry P, Wiklund I, Chen WH, Kline Leidy N. Development and first validation of the COPD Assessment Test. Eur Respir J 2009; 34(3):648–654.
- Ringbaek T, Martinez G, Lange P. A comparison of the assessment of quality of life with CAT, CCQ, and SGRQ in COPD patients participating in pulmonary rehabilitation. Copd 2012; 9(1):12–25.
- Jones PW, Harding G, Wiklund I, Berry P, Tabberer M, Yu R, et al. Tests of the responsiveness of the COPD assessment test following acute exacerbation and pulmonary rehabilitation. Chest 2012; 142(1):134–140.
- Kon SS, Canavan JL, Jones SE, Nolan CM, Clark AL, Dickson MJ, et al. Minimum clinically important difference for the COPD Assessment Test: a prospective analysis. Lancet Respir Med 2014; 2(3):195–203.
- Gupta N, Pinto LM, Morogan A, Bourbeau J. The COPD assessment test: a systematic review. Eur Respir J 2014; 44(4):873–884.
- Jones PW, Nadeau G, Small M, Adamek L. COPD assessment test –rationale, development, validation and performance. Characteristics of a COPD population categorised using the GOLD framework by health status and exacerbations. Copd 2013; 10:269–271.
- Jones PW, Brusselle G, Dal Negro RW, Ferrer M, Kardos P, Levy ML, et al. Properties of the COPD assessment test in a cross-sectional European study. Eur Respir J 2011; 38(1):29–35.
- Chapman B, Duberstein P, Lyness JM. Personality traits, education, and health-related quality of life among older adult primary care patients. J Gerontol 2007; 62(6):P343–352.
- Duberstein PR, Sorensen S, Lyness JM, King DA, Conwell Y, Seidlitz L, et al. Personality is associated with perceived health and functional status in older primary care patients. Psychol Aging 2003; 18(1):25–37.
- Goodwin R, Engstrom G. Personality and the perception of health in the general population. Psychol Med 2002; 32(2):325–332.
- Costa PT, Jr., McCrae RR. Neuroticism, somatic complaints, and disease: is the bark worse than the bite? J Pers 1987; 55(2):299–316.
- Costa PT, Jr., Weiss A, Duberstein PR, Friedman B, Siegler IC. Personality facets and all-cause mortality among Medicare patients aged 66 to 102 years: a follow-on study of Weiss and Costa (2005). Psychosom Med 2014; 76(5):370–378.
- Hartmann P. The Five-Factor Model: Psychometric, biological and practical perspectives. Nordic Psychol 2006; 58(2):21.
- McCrae RR, Costa PT. A contemplated revision of the NEO Five-Factor Inventory. Pers Individ Dif 2004; 36(3):587–596.
- Kotov R, W G, F S, Watson D. Linking “big” personality traits to anxiety, depressive, and substance use disorders: a meta-analysis. Psychol Bull 2010; 136:768–821.
- Schlecht NF, K S, Bourbeau J. Dyspnea as clinical indicator in patients with chronic obstructive pulmonary disease. Chron Respir Dis 2005; 2:183–191.
- Doyle T, Palmer S, Johnson J, Babyak MA, Smith P, Mabe S, et al. Association of anxiety and depression with pulmonary-specific symptoms in chronic obstructive pulmonary disease. Int J Psychiatry Med 2013; 45(2):189–202.
- Hilmarsen CW, Wilke S, Engan H, Spruit MA, Rodenburg J, Janssen DJ, et al. Impact of symptoms of anxiety and depression on COPD Assessment Test scores. Eur Respir J 2014; 43(3):898–900.
- Di Marco F, Verga M, Reggente M, Maria Casanova F, Santus P, Blasi F, et al. Anxiety and depression in COPD patients: The roles of gender and disease severity. Respir Med 2006; 100(10):1767–1774.
- Miravitlles M, Molina J, Quintano JA, Campuzano A, Perez J, Roncero C, et al. Factors associated with depression and severe depression in patients with COPD. Respir Med 2014; 108(11):1615–1625.
- Cafarella PA, Effing TW, Usmani ZA, Frith PA. Treatments for anxiety and depression in patients with chronic obstructive pulmonary disease: a literature review. Respirology 2012; 17(4):627–638.
- Cloninger CR, Cloninger KM. Person-centered Therapeutics. Int J Pers Cent Med 2011; 1(1):43–52.
- NICE. 2010. Chronic Obstructive Pulmonary Disease. Management of chronic obstructive pulmonary disease in adults in primary and secondary care NICE National Institute for Health and Care Excellence.
- Costa PTJ, McCrae RR. Revised NEO Personality Inventory (NEO-PI-R) and NEO Five-Factor. Inventory (NEO-FFI) professional manual. Odessa, FL: Psychological Assessment Resources, 1992.
- Costa PTJ, McCrae RR. NEO PI-R Manual. Danish Psychological Publishers, 2010.
- Zigmond AS, Snaith RP. The hospital anxiety and depression scale. Acta Psychiatr Scand 1983; 67(6):361–370.
- Snaith RP, Zigmond AS. The hospital anxiety and depression scale. Br Med J (Clin Res Ed) 1986; 292(6516):344.
- GL A. The Hospital Anxiety and Depression Scale, Manual. London, UK: GL assessment Limited, 1994.
- Cecil R Reynolds RWK. Reynold Intellectual Assessment Scales, Reynolds Intellectual Screening test. Manual. Fredriksberg, Denmark: Hogrefe Psychological Publishers, 2011.
- Schou L, Ostergaard B, Rasmussen LS, Rydahl-Hansen S, Phanareth K. Cognitive dysfunction in patients with chronic obstructive pulmonary disease–a systematic review. Respir Med 2012; 106(8):1071–1081.
- Mortensen EL, Flensborg-Madsen T, Molbo D, Christensen U, Osler M, Avlund K, et al. Personality in late midlife: associations with demographic factors and cognitive ability. J Aging Health 2014; 26(1):21–36.
- DrKOL. Danish COPD register. Copenhagen: National Board of Health, 2012.
- Samartzis L, Dimopoulos S, Manetos C, Agapitou V, Tasoulis A, Tseliou E, et al. Neuroticism personality trait is associated with Quality of Life in patients with Chronic Heart Failure. World J Cardiol 2014; 6(10):1113–1121.
- Klein DN, Kotov R, Bufferd SJ. Personality and depression: explanatory models and review of the evidence. Annu Rev Clin Psychol 2011; 7:269–295.
- Karsten J, Penninx BW, Riese H, Ormel J, Nolen WA, Hartman CA. The state effect of depressive and anxiety disorders on big five personality traits. J Psychiatr Res 2012; 46(5):644–650.
- Maurer J, Rebbapragada V, Borson S, Goldstein R, Kunik ME, Yohannes AM, Hanania NA, et al. Anxiety and depression in COPD: current understanding, unanswered questions, and research needs. Chest 2008; 134:43S–56S.
- DrKOL. Danish COPD register. Copenhagen: National Board of Health, 2013.
- Denollet J, Vaes J, Brutsaert DL. Inadequate response to treatment in coronary heart disease : adverse effects of type D personality and younger age on 5-year prognosis and quality of life. Circulation. 2000; 102(6):630–635.