Tracking National and Regional Spatial‐Temporal Mortality Risk Associated with NO2 Concentrations in Canada: A Bayesian Hierarchical Two‐Level Model
Tóm tắt
The association between daily variations in urban air quality and mortality has been well documented using time series statistical methods. This approach assumes a constant association over time. We develop a space‐time dynamic model that relaxes this assumption, thus more directly examining the hypothesis that improvements in air quality translate into improvements in public health. We postulate a Bayesian hierarchical two‐level model to estimate annual mortality risks at regional and national levels and to track both risk and heterogeneity of risk within and between regions over time. We illustrate our methods using daily nitrogen dioxide concentrations (NO2) and nonaccidental mortality data collected for 1984–2004 in 24 Canadian cities. Estimates of risk and heterogeneity are compared by cause of mortality (cardio‐pulmonary [CP] versus non‐CP) and season, respectively. Over the entire period, the NO2 risk for CP mortality was slightly lower but with a narrower credible interval than that for non‐CP mortality, mainly due to an unusually low risk for a single year (1998). Warm season NO2 risk was higher than cold season risk for both CP and non‐CP mortality. For 21 years overall there were no significant differences detected among the four regional NO2 risks. We found overall that there was no strong evidence for time trends in NO2 risk at national or regional levels. However, an increasing linear time trend in the annual between‐region heterogeneities was detected, which suggests the differences in risk among the four regions are getting larger, and further studies are necessary to understand the increasing heterogeneity.
Từ khóa
Tài liệu tham khảo
West BT, 2007, Linear Mixed Models
Statistics Canada.Appendix A Glossary Census division. Available at:http://geodepot.statcan.gc.ca/2006/180506051805140305/06180505162102/92‐‐149‐072305/2006001/01161605140409030519‐eng.htm#a1 Accessed on October 27 2010.
Statistics Canada.Vital Statistics—Deaths Database 2004. Available at:http://www.statcan.gc.ca/cgi‐bin/imdb/p2SV.pl?Function=getSurvey&SurvId=3233&SurvVer=0&InstaId=15306&InstaVer=7&SDDS=3233&lang=en&db=IMDB&adm=8&dis=2 Accessed on October 27 2010.
World Health Organization, 2003, International Statistical Classification of Diseases and Related Health Problems
Environment Canada.National Air Pollution Surveillance Network (NAPS). Available at:http://www.ec.gc.ca/natchem/default.asp?lang=en&n=EE0E2169‐‐1 Accessed on October 27 2010.
Environmental Technology Centre Analysis and Air Quality Division.National Air Pollution Surveillance Network: Quality Assurance and Quality Control Guidelines.2004. Available at:http://www.etc‐cte.ec.gc.ca/publications/naps/NAPSQAQC.pdf Accessed on October 27 2010.
Environment Canada.Nitrogen Measurements. Available at:http://www.ec.gc.ca/rs‐mn/default.asp?lang=en&n=72C88CD8‐‐1 Accessed on October 27 2010.
National Climate Data and Information Archive.Environment Canada.http://climate.weatheroffice.gc.ca/Welcome_e.html. Accessed on October 27 2010.
Hastie TJ, 1990, Generalized Additive Models
Johansen H, 2005, Diseases of the circulatory system—Hospitalization and mortality, Health Report, 17, 49
MillerBC ArmstrongB.Quantification of the impact of air pollution on chronic cause‐specific mortality. Edinburgh: Institute of Occupational Medicine Research Report TM/01/08 December 2001.
Public Health Agency of Canada (PHAC), 2007, Life and Breath: Respiratory Disease in Canada, 39
World Health Organization, 2005, Particulate Matter, Ozone, Nitrogen Dioxide and Sulphur Dioxide