![]() ![]() We constructed daily time series of COPD hospitalization for male and female subjects separately. The codes for COPD were 491, 492, and 496. Patient data captured from the computerized medical record system included age, date of admission, source of admission, hospital, residential address, and principal diagnosis on discharge coded using the International Classification of Diseases, Ninth Revision. The hospitals that were included were publicly funded hospitals that provide 24-hour accident and emergency services and comprise 90% of hospital beds in Hong Kong ( 14). METHODS Hospitalization dataĭaily data on emergency hospital admissions in Hong Kong were collected from January 1, 2001, to December 31, 2007. Given the strong role of traffic as a source of carbon monoxide, we investigated whether associations between carbon monoxide and COPD hospitalizations were robust after adjustment for the traffic-related pollutants particulate matter with an aerodynamic diameter less than 2.5 μm (PM 2.5) and nitrogen dioxide. We conducted a time-series study to estimate the association between short-term exposure to ambient carbon monoxide and the risk of hospitalization for COPD in Hong Kong. The first human pilot study on the association of carbon monoxide with COPD indicated that inhalation of carbon monoxide at a concentration of 100–125 ppm by patients with COPD was feasible and led to reduction of sputum eosinophils and improvement of responsiveness to methacholine ( 13). On the other hand, beneficial antiinflammatory effects under certain circumstances have been suggested in recent experimental and clinical studies ( 11, 12). Moreover, the lack of copollutant models has contributed to the inability to disentangle the effects attributed to carbon monoxide from those of the larger complex air pollution mix (particularly motor vehicle emissions), and this creates uncertainty in interpreting the results observed in the epidemiologic studies ( 10). ![]() The few epidemiologic studies that did examine the association of ambient carbon monoxide with hospital admissions for COPD yielded mixed results ( 7–9). The specific effect of carbon monoxide on COPD, however, has seldom been reported. Many epidemiologic studies on the association have linked air pollution to increased rates of COPD exacerbations and emergency hospital admissions ( 4–6). In addition to bacterial and viral infections, air pollution is an environmental trigger that exacerbates COPD because of complex interactions between the host, respiratory viruses, airway bacteria, and environmental pollution and that leads to an increase in the inflammatory burden ( 2). Patients with moderate-to-severe airflow obstruction typically have 1–3 episodes per year ( 3). COPD currently has no cure, and one main objective of therapy for COPD is to reduce the rates of morbidity associated with exacerbations, namely episodes of increased dyspnea and cough and changes in the amount and character of sputum ( 2). In conclusion, short-term exposure to ambient carbon monoxide was associated with a decreased risk of hospitalization for COPD, which suggests that carbon monoxide exposure provides some acute protection of against exacerbation of COPD.Ĭarbon monoxide, chronic obstructive pulmonary disease, time series studyĬhronic obstructive pulmonary disease (COPD), which is a leading cause of morbidity and mortality worldwide ( 1), is characterized by airflow limitation that is not fully reversible. The risk estimates were similar for female and male subjects. After adjustment for levels nitrogen dioxide or particulate matter with an aerodynamic diameter less than 2.5 μm, the negative associations of carbon monoxide with COPD hospitalizations became stronger. Results showed that ambient carbon monoxide was negatively associated with the risk of hospitalizations for COPD. We used log-linear Poisson models to estimate the associations between daily hospital admissions for COPD and the average daily concentrations of carbon monoxide while controlling for the traffic-related copollutants nitrogen dioxide and particulate matter with an aerodynamic diameter less than 2.5 μm. ![]() We collected daily emergency hospital admission data and air pollution data from January 2001 to December 2007. We conducted a time-series study in Hong Kong to estimate the association of short-term exposure to ambient carbon monoxide with emergency hospitalizations for COPD. However, population-based epidemiologic studies of environmentally relevant carbon monoxide exposure have generated mixed findings. Inhaled carbon monoxide has the potential to be a therapeutic agent for chronic obstructive pulmonary diseases (COPD). Data from recent experimental and clinical studies have indicated that lower concentrations of inhaled carbon monoxide might have beneficial antiinflammatory effects. ![]()
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