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Risk of Depression and Anxiety in Employees With Chronic Bronchitis: The Modifying Effect of Cigarette Smoking

From the Department of General Practice, Care and Public Health Research Institute, Maastricht University, Maastricht, The Netherlands (E.J.W., C.P.v.S.); the Department of Epidemiology, Care and Public Health Research Institute, Maastricht University, Maastricht, The Netherlands (I.K., L.G.P.M.v.A., G.M.H.S.); and the Department of Respiratory Medicine, University Hospital Maastricht, Maastricht, The Netherlands (E.F.M.W.).

Address correspondence and reprint requests to E. J. Wagena, MA, Pulmonary Rehabilitation Centre Hornerheide, PO Box 4080, 6080 AB Haelen, The Netherlands. E-mail: edwinwageha{at}proteion.nl

	ABSTRACT

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OBJECTIVE: The present study evaluates whether smoking status modifies the association between chronic bronchitis and depression or anxiety in a population-based sample. Furthermore, we tested whether these associations are different in people without any respiratory complaints and those with asthma.

METHODS: For this study, we used cross-sectional data form the Maastricht Cohort Study, a population-based cohort study among Dutch employees.

RESULTS: In total, 7482 employees completed and returned the questionnaire (92.7%). In employees with chronic bronchitis, the prevalence of depression and anxiety was significantly higher compared with healthy employees and employees with asthma. Results indicate that the odds of having comorbid depression or anxiety for employees with chronic bronchitis compared with healthy employees is highest in current and past smokers, indicating that smoking status modifies this association.

CONCLUSION: Chronic bronchitis is strongly associated with depression and anxiety. Because depression and/or anxiety may not only interfere with an attempt to stop smoking but also contribute significantly to experiencing low quality of life, it is important to consider these disorders and chronic bronchitis as different disease entities. Prospective longitudinal studies are needed to elucidate the mechanisms underlying the association among chronic bronchitis, psychiatric disorders, and cigarette smoking.

Key Words: chronic bronchitis, • depression, • anxiety.

Abbreviations: COPD = chronic obstructive pulmonary disease;; HADS = Hospital Anxiety and Depression Scale;; OR = odds ratio;; CI = confidence interval.

	INTRODUCTION

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Respiratory disease such as chronic bronchitis is an important cause of temporary disability as expressed by sickness absence in both men and women (1). Approximately 10 years ago, almost 9% of all general practitioner consultations and approximately 13% of all absenteeism as a result of illness were caused by asthma and chronic bronchitis or emphysema (i.e., chronic obstructive pulmonary disease [COPD] (2)). Chronic bronchitis prevalence, morbidity, and mortality vary across countries and across different groups within countries but are in general directly related to the prevalence of tobacco smoking (3). In the developed world, smoking accounts for at least 75% of cases with chronic bronchitis (4,5). Because the main cause of the disease is exposure to cigarette smoke, chronic bronchitis is largely preventable. Furthermore, in the treatment of patients who already have been diagnosed with chronic bronchitis, the main preventive measure in reducing the decline in lung function is smoking cessation (as recommended by international guidelines for the management of chronic bronchitis; 3,6–8). Smoking cessation is the most effective way to reduce the risk of developing chronic bronchitis (9,10). Also, it can prevent or delay the development of airflow limitation or reduce its progression.

Smoking cessation has become a national priority in the United States and many other countries. However, the effectiveness of smoking cessation programs is influenced by the coexistence of psychiatric disorders such as depression and anxiety. Both depression and depressive symptoms are associated with failure to quit smoking and relapse. Smokers with a history of or current major depression have lower quit rates than smokers with either no current or past depression (11). A likely explanation is that smokers with a history of depression or current depression experience tobacco withdrawal symptoms more severely (12). Furthermore, because depression, depressed mood, or anxiety can occur during withdrawal from nicotine and because smoking cessation can contribute to the occurrence of depression during the postcessation period, depression-prone smokers are much less likely to remain abstinent from smoking (12).

Many different groups of chronically ill patients have high prevalence rates of depression or score higher on psychiatric disorder scales (13). Therefore, high prevalence of depression and anxiety might not be specific features of patients with chronic bronchitis (14,15). Although many clinicians and researchers remain uncertain about the exact status of psychiatric disorders in patients with a chronic disease, the physical illness itself is often considered to be reason enough for patients to be depressed (16). Comorbid psychiatric disorders are therefore often regarded as a complication of the physical complaints. As a result, comorbid psychiatric disorders complicating chronic bronchitis are regularly overlooked and often remain undiagnosed and under treated (16).

The objectives of this study are threefold. First, we wanted to evaluate whether people with chronic bronchitis can be characterized as a group of patients with a high prevalence of depression and anxiety compared with people without any respiratory complaints. Second, because patients with asthma also suffer from a chronic inflammatory disorder, but with a different nature of inflammation, (17,18) we wanted to evaluate whether the prevalence of depression and anxiety is different in this group of patients compared with patients with chronic bronchitis. Third, although a positive association among depression, anxiety, and cigarette smoking is well established (see Dierker et al. (19) for an overview; 11,20,21) it is still not clear how the presence of chronic bronchitis, smoking cigarettes, and psychiatric disorders are intertwined. Therefore, we examined whether smoking status modifies the association between chronic bronchitis and psychiatric comorbidity and tested whether these associations are different in people without any respiratory complaints and those with asthma.

	METHODS

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Sample
We used cross-sectional data from the Maastricht Cohort Study, a prospective population-based cohort study described in detail by Kant et al. (22) In January 2001, we sent a questionnaire on respiratory complaints, depression and anxiety, and smoking to 8070 employees. In total, 7482 employees completed and returned the questionnaire (92.7%). Data from 494 respondents (6.6%) were excluded from the analyses because they forgot to fill out part of the stem and leaf questions on smoking behavior. Furthermore, 93 respondents (1.2%) had missing values on any of the other variables used in this study (ie, dependent, independent, or demographic variables) and were therefore excluded. For this study, we also excluded a) employees who reported suffering simultaneously from chronic bronchitis and asthma (or asthmatic bronchitis), and b) employees who reported suffering from any of respiratory symptoms, but who did not fulfill the diagnostic criteria for chronic bronchitis or asthma. As a result, another 1267 respondents (16.9%) were excluded. For this article, we restricted the analyses to the data collected from 5628 employees.

Assessment of Chronic Bronchitis and Asthma
To determine the presence of chronic bronchitis and asthma, all participants were asked to complete a self-report questionnaire on respiratory complaints and diagnoses. This procedure has been used in several other epidemiological studies (4,15). The diagnoses were described in a way that was easy to understand for all respondents.

In clinical terms, chronic bronchitis is usually defined by the presence of chronic or recurrent increases in bronchial secretions sufficient to cause expectoration and cough (23). In this study, chronic bronchitis conforms to the definition and classification of chronic bronchitis for clinical and epidemiological purposes proposed by the Medical Research Council: "the presence of cough and sputum production on most days for a minimum of 3 months per year, in the previous 2 successive years, and cannot be attributed to other pulmonary or cardiac causes" (24,25). Furthermore, respondents were asked whether a clinician or family physician had ever diagnosed asthma.

Assessment of Depression and Anxiety
We used the validated Dutch version of the Hospital Anxiety and Depression Scale (HADS; 26). The HADS was developed by Zigmond and Snaith (27) originally to identify caseness (possible and probable) of anxiety and depression among patients in nonpsychiatric hospital clinics. Spinhoven et al. (26) found that the Dutch version of the HADS was stable across different age groups from the general population and in different clinical samples. It is divided into an anxiety subscale and a depression subscale, each containing seven items. Each question is rated 0 to 3, giving a possible maximum score for anxiety and depression of 21. Subjects scoring 11 or more on the depression subscale were classified as being depressed, and subjects scoring 11 or more on the anxiety subscale were classified as being anxious. To prevent bias from somatic disorders on the scores, symptoms of anxiety or depression also relating to a physical disorder, such as dizziness, headaches, insomnia, and fatigue, have never been included in the questionnaire (28).

Assessment of Smoking Status
Questions regarding the smoking habits of employees refer only to cigarette smoking. To assess the smoking status of respondents, we asked them whether they smoked cigarettes on a daily basis, and whether they used to smoke every day in the past. We defined respondents as never smokers if they answered no to both questions. Past smokers were defined as giving an affirmative response only to the second question, and current smokers if they gave an affirmative response to the question, "Do you smoke every day?" We also assessed how many cigarettes they smoked or used to smoke on average per day.

Statistical Procedures
We distinguished 3 subgroups: a) employees with chronic bronchitis, b) employees with asthma, and c) employees without any respiratory symptoms or diagnosis of lung disease. First, the Student t test and Pearson ² test were used to determine differences in demographic characteristics between the 3 groups. Next, multivariate logistic regression analyses were performed to calculate odds ratios (ORs; with 95% confidence intervals [CIs]) for the association between chronic bronchitis, asthma, smoking status, and (individual) potential confounders on the one hand and psychiatric morbidity (ie, depression and anxiety) on the other, adjusted for all other study variables. Third, logistic regression analyses were conducted to evaluate the association between the presence of respiratory complaints (i.e., the presence of chronic bronchitis or asthma) and depression or anxiety. Results were adjusted for sex, age, educational level, and the presence of one or more chronic disease (as assessed by a list of diseases that have a prevalence of more than 2% in the general population and are long-lasting by nature). Fourth, prevalence rates of depression and anxiety were calculated for the same groups, and for never-smokers, past smokers, and current smokers separately by using contingency tables. Finally, to determine whether these associations were similar in current smokers, past smokers, and never-smokers, we conducted stratified analysis.

The statistical analyses were performed using SAS release 8.02 (SAS Institute Inc., Cary, NC, USA).

	RESULTS

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Table 1 shows the demographic characteristics separately for employees with chronic bronchitis (N = 357), employees with asthma (N = 373), and employees without any respiratory complaints (N = 4898). All 3 groups consisted mainly of men (more than 70%). Compared with the group of employees with asthma and the group without respiratory complaints, the percentage of smokers in the group of employees with chronic bronchitis was significantly higher (² = 113.0; df = 2; p < .001; and ² = 75.9; df = 2; p < .001, respectively), in addition to the percentage of smokers who smoke on average more than 10 cigarettes per day (² = 30.2; df = 2; p < .001; and ² = 31.3; df = 2; p < .001, respectively).

	DISCUSSION

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To our knowledge, the present study is the first to examine the association among the presence of chronic bronchitis, psychiatric morbidity, and cigarette smoking. Although numerous studies have confirmed the finding that patients with a chronic disease are more likely to have depression or anxiety compared with the general population, the authors could not find a study in which the association between chronic bronchitis and psychiatric morbidity was assessed in a large population-based sample. Van Ede et al. conducted a systematic review to achieve a more definite answer to the question whether patients with COPD showed a higher than normal prevalence of depression. They concluded that the empirical evidence for a significant risk of depression in these patients remained inconclusive, mainly because of the poor methodological quality of most of the published studies, the absence of a control group, and the lack of studies with an adequate sample size. Recently, Van Manen et al. (29) showed that the risk of depression was significantly increased in patients with a chronic irreversible obstruction and in patients with COPD with severe impaired physical functioning. However, they did not study the role of cigarette smoking. Furthermore, it is expected that most of the patients with COPD did not work any more, because the average age of that group was a little greater than 65 years. Also, although in several studies the presence of anxiety was assessed in patients with COPD, most studies did not include a control group or presented average scores on an anxiety scale. In one study, it was found that patients with asthma or chronic bronchitis had higher mean ratings for anxiety compared with people without these disorders (30).

Several mechanisms may be responsible for the observed association between chronic bronchitis, depression and anxiety, and cigarette smoking. Although many clinicians and researchers remain uncertain about the exact status of depression and anxiety in patients with a chronic disease (31), the physical illness itself is often considered to be reason enough for patients to feel depressed or anxious. The presence of these psychiatric complaints is therefore often regarded as a complication of the physical complaints (16). The results found in this study could be explained by a difference in severity of somatic symptoms. Because the nature of the inflammation affects the response to pharmacological agents (17,18), which means that the treatment with inhaled corticosteroids is effective against the inflammation in asthma but not in COPD, patients with chronic bronchitis might feel more depressed or anxious when thinking of a future exacerbation. These feelings could even increase further if patients with chronic bronchitis experienced low self-efficacy of symptoms management. A number of studies have shown that the risk of depression and anxiety increases by increasing severity of respiratory complaints (30,32). Furthermore, McCathie et al. (33) showed that psychological factors like a low sense of personal mastery or efficacy regarding the management of symptoms is associated with higher levels of depression and anxiety. In smokers, the risk of psychiatric comorbidity might increase even further compared with nonsmokers because of a negative self-evaluation when they compared themselves with peers regarding sports and activities of daily living. This is being supported by the finding that during pulmonary rehabilitation, depression and anxiety decreased as the patients’ performance of daily living activities increased (34).

This study has several limitations. The first limitation pertains to the assessment of respiratory complaints and psychiatric morbidity. To determine the presence of chronic bronchitis and asthma, all participants were asked to complete a questionnaire on respiratory complaints and diagnoses. The assessment of (chronic) respiratory disease was thus self-reported. We could not evaluate the presence of chronic bronchitis or asthma by using diagnostic instruments. As a result, we may have systematically overrated or underrated the presence of chronic bronchitis or asthma. Misclassification of cases may therefore have occurred. However, if it occurred, it is expected to be nondifferential. Misclassification may also have occurred in the diagnosis of depressive disorders. Participants tend to underreport depressive symptoms, which will have resulted in an underestimation of the true point prevalence rates of depression and anxiety. However, because it is expected that the underreporting is not selective, it will not have introduced a major bias in our study.

Second, because the study population consisted of a relatively healthy population (i.e., employees), it is likely that relatively fewer patients with a severe chronic disease were included because they were still working. This might well have resulted in a lower prevalence of depression and anxiety in the group with chronic bronchitis compared with people with chronic bronchitis in the Dutch general population.

Third, given the cross-sectional design of the study, this study cannot show whether the observed association with depression and anxiety precipitates or results from chronic bronchitis.

In conclusion, in this population-based study, we found a strong association between the presence of chronic bronchitis and depression and anxiety. We also found that smoking cigarettes modifies this association, resulting in an increased risk for depression and anxiety in employees with chronic bronchitis who smoke or used to smoke. As depression and anxiety remain easily undiagnosed because of underpresentation and because the symptoms are not very specific, it is important to consider the presence of these disorders in employees with chronic bronchitis. Depression and/or anxiety might not only interfere with an attempt to stop smoking but also contribute significantly to experiencing low quality of life. The quality of life of patients with chronic bronchitis may be particularly complicated by a concurrent psychiatric disorder, which may bring the patient into a vicious circle (35): the presence of a psychiatric disorder lowers the force needed to cope with the chronic disease, the physical symptoms become less tolerable, and the psychosocially debilitating effect of the disease may be enforced by feeling depressed or anxious. To elucidate further the mechanisms underlying the association between chronic bronchitis, depression and anxiety, and cigarette smoking, prospective longitudinal studies are needed.

	ACKNOWLEDGMENTS

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The Maastricht Cohort Study is part of the Netherlands concerted research action on Fatigue at Work, granted by The Netherlands Organization for Scientific Research. The work presented in this paper was supported by the Dutch Asthma Foundation (NAF grant no. 3.2.00.21) and the Health Research and Development Council (ZorgOnderzoek Nederland grant no. 2200.0111), The Netherlands.

Received for publication October 17, 2003.

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