| Summary: | 博士 === 國立臺灣大學 === 流行病學與預防醫學研究所 === 100 === Background
Sudden cardiac death is the leading cause of death in developed countries. Circadian, weekly, and seasonal variations in the incidence of sudden cardiac death have been observed. Numerous animal and human studies provide biological evidence linking air pollution exposure and cardiovascular disease. Sudden cardiac death occurring outside hospital is usually referred to as out-of-hospital cardiac arrest (OHCA). This study was conducted to investigate the association between particulate matter (PM) and the incidence of OHCA.
Material and Methods
All adult OHCA patients that activated the emergency medical service system in Taipei city from September 2003 through December 2007 were included in the study. Patients with traumatic injuries, and patients for whom resuscitation was not attempted by emergency medical service personnel due to terminal illness or an existing do-not-attempt-resuscitate order were excluded. The data of climate and air pollution measurements, including carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxide (NO), nitrogen dioxide (NO2), ozone (O3), particulate matters (PM2.5 and PM10), and temperature were obtained from the Taiwan Environmental Protection Administration. Descriptive analyses of the study targets and air pollution data were performed. In the time-series analysis, Poisson regression models and generalized additive models were applied to analyze the association between daily-averaged air pollutant levels and daily OHCA patient numbers. The case-crossover design with matching by hour-of-day and day-of-week was used to explore the association between the incidence of OHCA and air pollution levels. Sensitivity analysis and investigations on effect modification were performed.
Results
There were 6341 cases of OHCA during the study period. The mean age was 71.7 years, and the study targets included more men than women. Circadian variation was observed, with a maximum occurrence rate between 6 and 10 AM and a secondary evening peak between 5 and 8 PM. There were significantly more OHCA patients during winter. Compared to other weekdays, there were significantly more OHCA patients on Monday, Friday, Saturday, and Sunday. There was high correlation between CO, NO, NO2 and NOx levels. PM2.5 was also highly correlated with PM10.
In the time-series analysis, positive trends indicated that increasing PM10 and PM2.5 levels were associated with increasing incidence of OHCA. However, in the case-crossover analysis, the 24-hour mean PM10 and PM2.5 levels with 24-hour lag were significantly associated with the incidence of OHCA. For an increase of one interquartile range (29.01 µg/m3 ) in PM10, the odds ratio estimate for OHCA was 1.054 (95% confidence interval: 1.017- 1.093). For an increase of one interquartile range (19.21 µg/m3) in PM2.5, the odds ratio estimate for OHCA was 1.060 (95% confidence interval: 1.022- 1.099). These associations were stronger in males and in the 40- 74-year group.
Limitations
There is no assurance that OHCA patients were indeed exposed to air pollution. Discrepancies between ambient and actual personal exposures may exist. Limited personal information in the database restricted the power of time-series analysis and the extent of exploring effect modification.
Conclusion
Particulate matter is positively associated with the incidence of OHCA. Controlling air pollution may be a preventable means to decrease cardiovascular mortality.
Key words: particulate matter, air pollution, sudden cardiac death, cardiac arrest, cardiovascular disease.
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