Academic journal article Iranian Journal of Public Health

Interaction of Depression and Nicotine Addiction on the Severity of Chronic Obstructive Pulmonary Disease: A Prospective Cohort Study

Academic journal article Iranian Journal of Public Health

Interaction of Depression and Nicotine Addiction on the Severity of Chronic Obstructive Pulmonary Disease: A Prospective Cohort Study

Article excerpt

Introduction

Chronic Obstructive Pulmonary Disease (COPD) is mainly caused by smoking and different air pollutants, and is a progressive disease defined by a limitation of airflow that is at least irreversible (1) .COPD can cause systematic manifestations, resulting in substantial co-morbidity (2). Depression is one of the most common co-morbidities of patients with COPD (3), and is thought to be associated with worse health status in patients with COPD such that two patients with the same degree of lung function impairment have different health outcomes (4).

Cigarette smoking is the principal environmental risk factor for developing COPD(1), despite the disease, COPD smokers smoke more cigarettes per day than the healthy smokers, determined by their greater nicotine dependence (5). Nicotine dependence is defined as addiction to nicotine and is considered a mental disorder by the Diagnostic and Statistical Manual of Mental Disorders (6). The pack-years is usually used to measure the extent of exposure to cigarette smoke for the smokers, however, it does not reflect other aspects of smoking behaviors such as depth of inhalation, number of puffs per cigarette, and age of onset of smoking(7). 39.7% of smokers with COPD showed high nicotine dependence, and smokers with high nicotine dependence had greater cumulative and current amounts of smoking (8). Therefore, nicotine dependence may increase the impact of smoking exposure due to altering the frequency or depth of smoke inhalation, even in COPD patients with the same pack-year history.

Cigarette smoking among individuals with COPD is not only known to worsen lung function (9), but also damage the quality of life (10). In addition, smoking confers a relative risk of mortality that is two times higher in COPD compared with the risk associated with smoking in other health conditions (11).

The severity of illness in patients with COPD is the result of interactions between many physiological, psychosocial factors and behavior risk factors (12). However, there is little understanding of these multivariate explanations of subjective health status in patients with COPD. There are no studies on the interaction of depression and smoking on severity in patients with COPD.

Therefore, our cohort study was a first research to explore the combined effects of smoking and depression on severity of patients with COPD. The primary aim of this cohort study was to examine the combined effects of depression and smoking on severity over a 4-year period in a Chinese primary care setting. A second aim was to examine the relationship between the BODE (body mass index, airflow obstruction, dyspnea, and exercise capacity) index (13), nicotine addiction, and depressive symptoms. The third aim was to compare the effect of depressive symptoms and smoking on impaired health status.

Methods

Study population

The selection of patients had been previously described (14), briefly, from May 2008 to May 2012, 4020 patients with COPD met the criteria in seven rural communities were enrolled in a prospective observational study. Patients selected had to meet the criteria of COPD diagnosed by the standards of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) at baseline (1). The following exclusion criteria were used by the County People's Hospital: presence of fever, active tuberculosis, changes in radiographic images or medication in the 4 wk immediately preceding recruitment, primary diagnosis of asthma or obvious bronchiectasis, cystic fibrosis, interstitial lung disease, previous lung volume reduction surgery, lung transplantation and pneumonectomy; Uncontrolled or serious conditions that could potentially affect the spirometry test, and refusal to fill out psychological questionnaires were also excluded.

Ethics approval

The study protocol was approved by the Ethics Committee of Xuzhou Center for Disease Control and Prevention. All participants provided written informed consents. …

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