Carbon monoxide and stroke: A time series study of ambient air pollution and emergency hospitalizations

• Published in: International journal of cardiology 2015-12, Vol.201, p.4-9
• Main Authors: Tian, Linwei, Qiu, Hong, Pun, Vivian C, Ho, Kin-Fai, Chan, Chi Sing, Yu, Ignatius T.S
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Air Pollution - adverse effects; Carbon monoxide; Carbon Monoxide - adverse effects; Cardiovascular; Dose-Response Relationship, Drug; Emergency hospital admission; Emergency Medical Services - trends; Female; Hong Kong - epidemiology; Hospitalization - trends; Humans; Interrupted Time Series Analysis - trends; Longitudinal Studies; Male; Middle Aged; Particulate Matter - adverse effects; Stroke; Stroke - diagnosis; Stroke - epidemiology; Time series study
• ISSN: 0167-5273; 1874-1754
• DOI: 10.1016/j.ijcard.2015.07.099

Abstract Background Recent experimental and clinical studies suggested that exogenous carbon monoxide (CO) at low concentrations may have beneficial neuroprotective effects under certain circumstances. However, population-based epidemiological studies of environmentally relevant CO exposure generated mixed findings. The present study aimed to examine the short-term association of ambient CO with emergency stroke hospitalizations. Methods A time series study was conducted. Daily air pollution concentrations and emergency hospital admission data from January 2004 to December 2011 in Hong Kong were collected. Generalized additive Poisson models were used to estimate the associations between daily 24-hour mean concentrations of CO and emergency hospital admissions for stroke, while controlling for other traffic related co-pollutants: NO2 and PM2.5 . Sensitivity analyses were performed using daily 1-hour maximum concentration of CO as exposure indicator. Results Negative associations were observed between ambient CO concentrations and emergency hospital admissions for stroke. The previous 1–3 day cumulative exposure to CO was associated with a − 2.0% (95%CI, − 3.3% to − 0.7%) decrease in stroke admissions per interquartile range (IQR) increment in CO concentration (0.3 ppm). Similar results were obtained when using 1-hour maximum concentration of CO as exposure indicator. The negative association was robust to the co-pollutant adjustment for either NO2 or PM2.5 . Females and elders appeared to be more sensitive to ambient CO exposure. The negative association tended to be larger in cool season. Conclusion Short-term exposure to ambient CO was associated with decreased risk of emergency hospitalizations for stroke, suggesting some acute protective effects of CO exposure against stroke onsets.