Health impacts and psychological risk factors of chronic obstructive pulmonary disease exacerbations: A one-year follow-up study in China

Chronic Obstructive Pulmonary Disease (COPD) exacerbations, characterized by acute worsening of respiratory symptoms, are the most important events in the progression of COPD. Despite significant health and economic consequences, COPD exacerbation remains a poorly understood and inadequately managed health problem worldwide. This thesis focused on two important research topics related to COPD exacerbations: (1) impacts of unreported COPD exacerbations on health-related quality of life (HRQL); and (2) impacts of psychological co-morbidities (anxiety and depression) on the risk of COPD exacerbations and hospitalizations. As the studies were conducted in China, which has one of the largest COPD populations in the world, this thesis also addressed measurement issues of translations, validations and clinical interpretations of two key measurement instruments used to assess HRQL and psychological symptoms in Chinese patients with COPD.;The first two studies included the translation, validation and interpretation of the St. George's Respiratory Questionnaire in Mandarin-Chinese (SGRQ-MC) and the Hospital Anxiety and Depression Scale in Mandarin-Chinese (HADS-MC). The SGRQ-MC was used to assess COPD-specific HRQL, which is the main outcome in the third study. The HADS-MC was used to assess anxiety and depression, which are the main exposures in the fourth study. Results suggested that the SGRQ-MC and the HADS-MC were reliable, valid and responsive instruments in Chinese patients with COPD. They have good levels of cultural and clinical equivalence to those in other populations and diseases.;The third study evaluated the impact of unreported exacerbations on patients' HRQL at one year. Unreported COPD exacerbations are common but their intermediate to long-term impacts on HRQL are unknown. Generalized Estimating Equations were used to estimate adjusted associations between unreported exacerbations and the change of HRQL at one year. Results showed that unreported exacerbations, despite being associated with fewer symptoms worsening as compared to reported exacerbations, had a moderate but clinically significant impact on HRQL at one year. Intervention trials appear to be warranted to evaluate the self-management strategies emphasizing the early recognition of symptom worsening and consequent action among patients with COPD. The frequency of unreported exacerbations should also be monitored and evaluated as an important outcome in future intervention trials (or a part of treatment benefits may be unrevealed).;The fourth study examined the independent effects of depression and anxiety on COPD exacerbations and hospitalizations. Depression and anxiety are significant co-morbid and potentially modifiable conditions in COPD, but their impacts on COPD exacerbations are unknown. Multivariate Poisson and linear regression analyses were used, respectively, to estimate the effects of anxiety and depression on incidence rates and durations of COPD exacerbations and hospitalizations. Results showed that depression identified in patients with stable COPD was significantly associated with increased risks of exacerbations and hospitalizations. Anxiety identified in patients with stable COPD was associated with a prolonged duration of COPD exacerbations in a sub-group of patients with at least one exacerbation. Intervention trials appear to be warranted to evaluate the effectiveness of antidepressants and psychotherapies on reducing COPD exacerbations and hospitalizations.;A prospective cohort of 491 patients with stable COPD in Beijing, China was monitored for 12 months. Patient characteristics and clinical profiles were assessed at the beginning and the end of the study. Patients were monitored monthly by telephone to record important clinical outcomes (exacerbation, hospitalization and death) and to collect health and clinical data during each exacerbation.;In conclusion, this thesis suggests that there are unmet healthcare needs in the management of exacerbations in patients with COPD. The future challenge lies in better understanding the causes of exacerbations, evaluating preventive strategies to reduce exacerbation frequency and severity, and improving early recognition and treatment to reduce the consequences on patients' health and the healthcare system.