Cool and dry weather enhances the effects of air pollution on emergency IHD hospital admissions.

BACKGROUND Associations between ambient pollution and cardiovascular morbidity including ischemic heart disease (IHD) have been confirmed. Weather factors such as temperature, season and relative humidity (RH) may modify the effects of pollution. We conducted this study to examine the effects of air pollution on emergency IHD hospital admissions varied across seasons and RH levels, and to explore the possible joint modification of weather factors on pollution effects. METHODS Daily time series of air pollution concentrations, mean temperature and RH were collected from IHD hospital admissions from 1998 to 2007 in Hong Kong. We used generalized additive Poisson models with interaction term to estimate the pollution effects varied across seasons and RH levels, after adjusting for time trends, weather conditions, and influenza outbreaks. RESULTS An increase in the detrimental effects of air pollution in cool season and on low humidity days was observed. In the cool and dry season, a 10 μg/m(3) increment of lag03 exposure was associated with an increase of emergency IHD admissions by 1.82% (95% CI: 1.24-2.40%), 3.89% (95% CI: 3.08-4.70%), and 2.19% (95% CI: 1.33-3.06%) for particles with an aerodynamic diameter less than 10 μm (PM10), nitrogen dioxide (NO2), and ozone (O3), respectively. The effects of pollutants decreased greatly and lost statistical significance in the warm and humid season. CONCLUSIONS We found season and RH jointly modified the associations between ambient pollution and IHD admissions, resulting in increased IHD admissions in the cool and dry season and reduced admissions in the warm and humid season.

[1]  A. Hedley,et al.  Does ozone have any effect on daily hospital admissions for circulatory diseases? , 1999, Journal of epidemiology and community health.

[2]  Kerrie Mengersen,et al.  Temperature Enhanced Effects of Ozone on Cardiovascular Mortality in 95 Large US Communities, 1987–2000: Assessment Using the NMMAPS Data , 2009, Archives of environmental & occupational health.

[3]  Haidong Kan,et al.  Public Health and Air Pollution in Asia (PAPA): A Multicity Study of Short-Term Effects of Air Pollution on Mortality , 2008, Environmental health perspectives.

[4]  B. Ostro,et al.  Air pollution and emergency room visits for asthma in Santa Clara County, California. , 1997, Environmental health perspectives.

[5]  Y. Béjot,et al.  Evidence of the role of short-term exposure to ozone on ischaemic cerebral and cardiac events: the Dijon Vascular Project (DIVA) , 2010, Heart.

[6]  D. Zmirou,et al.  Short-term effects of ambient particles on mortality in the elderly: results from 28 cities in the APHEA2 project , 2003, European Respiratory Journal.

[7]  A. Hedley,et al.  Effect of air pollution on daily mortality in Hong Kong. , 2001, Environmental health perspectives.

[8]  F. Dominici,et al.  Fine particulate air pollution and hospital admission for cardiovascular and respiratory diseases. , 2006, JAMA.

[9]  Stefan Ma,et al.  A tale of two cities: effects of air pollution on hospital admissions in Hong Kong and London compared. , 2001, Environmental health perspectives.

[10]  Gail M. Williams,et al.  Does Particulate Matter Modify the Association between Temperature and Cardiorespiratory Diseases? , 2006, Environmental health perspectives.

[11]  R. de Gaudemaris,et al.  Impact of urban atmospheric pollution on coronary disease. , 2006, European heart journal.

[12]  Shilu Tong,et al.  Temperature modifies the health effects of particulate matter in Brisbane, Australia , 2006, International journal of biometeorology.

[13]  V. Wagner,et al.  Short-term associations between fine and coarse particles and hospital admissions for cardiorespiratory diseases in six French cities , 2007, Occupational and Environmental Medicine.

[14]  J. Schwartz,et al.  Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions. , 1996, Journal of epidemiology and community health.

[15]  K. Bhaskaran,et al.  Effects of air pollution on the incidence of myocardial infarction , 2009, Heart.

[16]  A Haines,et al.  Effects of ambient temperature on the incidence of myocardial infarction , 2009, Heart.

[17]  T. Wong,et al.  Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong. , 1999, Occupational and environmental medicine.

[18]  R. Tibshirani,et al.  Generalized additive models for medical research , 1986, Statistical methods in medical research.

[19]  Kerrie Mengersen,et al.  Does temperature modify short-term effects of ozone on total mortality in 60 large eastern US communities? An assessment using the NMMAPS data. , 2008, Environment international.

[20]  Joel Schwartz,et al.  The association of daily sulfur dioxide air pollution levels with hospital admissions for cardiovascular diseases in Europe (The Aphea-II study). , 2003, European heart journal.

[21]  D. Christiani,et al.  Effects of air pollutants on acute stroke mortality. , 2002, Environmental Health Perspectives.

[22]  J. Peiris,et al.  Air pollutants and health outcomes: Assessment of confounding by influenza , 2010 .

[23]  Yuming Guo,et al.  The association between fine particulate air pollution and hospital emergency room visits for cardiovascular diseases in Beijing, China. , 2009, The Science of the total environment.

[24]  Francesca Dominici,et al.  Coarse particulate matter air pollution and hospital admissions for cardiovascular and respiratory diseases among Medicare patients. , 2008, JAMA.

[25]  J Schwartz,et al.  Confounding and Effect Modification in the Short-Term Effects of Ambient Particles on Total Mortality: Results from 29 European Cities within the APHEA2 Project , 2001, Epidemiology.

[26]  Howard Frumkin,et al.  Ambient Air Pollution and Cardiovascular Emergency Department Visits , 2004, Epidemiology.

[27]  F. Dominici,et al.  Seasonal and regional short-term effects of fine particles on hospital admissions in 202 US counties, 1999-2005. , 2008, American journal of epidemiology.

[28]  J. Townend,et al.  Effect of inhaled sulphur dioxide and carbon particles on heart rate variability and markers of inflammation and coagulation in human subjects , 2005, Heart.

[29]  R. D. Morris,et al.  Carbon monoxide and hospital admissions for congestive heart failure: evidence of an increased effect at low temperatures. , 1998, Environmental health perspectives.

[30]  J. Schwartz,et al.  Short term effects of air pollution on health: a European approach using epidemiologic time series data: the APHEA protocol. , 1996, Journal of epidemiology and community health.

[31]  L Morawska,et al.  Ozone modifies associations between temperature and cardiovascular mortality: analysis of the NMMAPS data , 2007, Occupational and Environmental Medicine.

[32]  J. Schwartz,et al.  Hospital Admissions for Heart Disease: The Effects of Temperature and Humidity , 2004, Epidemiology.

[33]  T. Louis,et al.  Model choice in time series studies of air pollution and mortality , 2006 .

[34]  A. Figueiras,et al.  Regression models: calculating the confidence interval of effects in the presence of interactions. , 1998, Statistics in medicine.