ORIGINAL ARTICLE Ambient Air Pollution and Daily Mortality Among Survivors of Myocardial Infarction Niklas Berglind, a,b Tom Bellander, a,b Francesco Forastiere, c Stephanie von Klot, d Pasi Aalto, e Roberto Elosua, f,g Markku Kulmala, e Timo Lanki, h Hannelore Lo ¨wel, d Annette Peters, d Sally Picciotto, c Veikko Salomaa, i Massimo Stafoggia, c Jordi Sunyer, g,j,k and Fredrik Nyberg a,l , for the HEAPSS study group Background: Certain subgroups in the general population, such as persons with existing cardiovascular or respiratory disease, may be more likely to experience adverse health effects from air pollution. Methods: In this European multicenter study, 25,006 myocardial infarction (MI) survivors in 5 cities were recruited from 1992 to 2002 via registers, and daily mortality was followed for 6 to 12 years in relation to ambient particulate and gaseous air pollution exposure. Daily air pollution levels were obtained from central monitor sites, and particle number concentrations were measured in 2001 and estimated retrospectively based on measured pollutants and meteo- rology. City-specific effect estimates from time-series analyses with Poisson regression were pooled over all 5 cities. Results: Particle number concentrations and PM 10 averaged over 2 days (lag 0 –1) were associated with increased total nontrauma mortality for patients of age 35 to 74 (5.6% 95% confidence interval, 2.8%– 8.5% per 10,000/cm 3 and 5.1% 1.6%–9.3% per 10 g/m 3 , respec- tively). For longer averaging times (5 and 15 days), carbon monoxide and nitrogen dioxide were also associated with mortality. There were no clear associations with ozone or sulfur dioxide. Conclusion: Exposure to traffic-related air pollution was associated with daily mortality in MI survivors. Point estimates suggest a stronger effect of air pollution in MI survivors than among the general population. (Epidemiology 2009;20: 110 –118) A mbient air pollution has been associated with increases in acute cardiorespiratory morbidity and mortality in many studies over the past 20 years. 1 Mortality effects have been confirmed in large multicenter studies at current ambient levels both in the United States 2 and in Europe. 3,4 Particulate matter seems to be the air pollutant most consistently asso- ciated with adverse health outcomes. In a recent meta-anal- ysis of 74 single-city studies and 2 large multicity studies, the estimated increase in all-cause mortality was 0.6% (95% confidence interval CI= 0.5– 0.7) per 10 g/m 3 increase in particulate matter with aerodynamic diameter of 10 m (PM 10 ). 5 Gaseous pollutants—in particular, nitrogen dioxide (NO 2 ) and carbon monoxide (CO)— have also repeatedly shown associations. 6–8 These may be indicators of vehicle emissions rather than single causative agents. 9 Cardiovascular disorders, especially coronary heart dis- ease, are the most prevalent chronic health conditions affecting both sexes in the western world and a leading cause of mortality. Patients hospitalized after a myocardial infarction (MI) are frail and at risk for subsequent death; an overall 30-day mortality rate of 14% to 15% and a 1-year mortality rate of 22% to 24% have been observed among these patients. 10 Cardiovascular mortality has repeatedly been linked to air pollution exposure. A recent meta-analysis of short-term studies estimated the increase in cardiovascular mortality as 0.5% (95% CI = 0.1–1.0) per 10 g/m 3 increase in PM 10 , 11 and a large case-control study showed a positive association between life-long air pollution exposure and fatal MI. 12 Submitted 7 October 2007; accepted 21 July 2008; posted 23 September 2008. From the a Institute of Environmental Medicine, Karolinska Institutet; b De- partment of Occupational and Environmental Health, Stockholm County Council, Stockholm, Sweden; c Department of Epidemiology, Rome E Health Authority, Rome, Italy; d Institute of Epidemiology, Helmholtz Zentrum M¨ unchen, Neuherberg, Germany; e Department of Physical Sci- ences, University of Helsinki, Finland; f Institut Municipal d’Investigacio ´ Me `dica (IMIM), Barcelona, Spain; g CIBER Epidemiologı ´a y Salud Pu ´blica (CIBERESP), Barcelona, Spain; h Unit of Environmental Epide- miology, KTL-National Public Health Institute, Kuopio, Finland; i De- partment of Epidemiology and Health Promotion, KTL-National Public Health Institute, Helsinki, Finland; j Environmental Epidemiology Re- search Centre (CREAL-IMIM), Barcelona, Spain; k Universitat Pompeu Fabra, Barcelona, Spain; and l AstraZeneca R&D Mo ¨lndal, Mo ¨lndal, Sweden. Funded by European Union (QLK4-2000-00708). In Finland, the study was also financially supported by the Centre of Excellence Programme 2002–2007 of the Academy of Finland (Contract 53307) and the National Technology Fund (TEKES, Contract 40715/01). Fredrik Nyberg, em- ployed by AstraZeneca, is also Lecturer in Epidemiology at Karolinska Institutet; AstraZeneca did not contribute any direct financing to this study. Annette Peters was partially supported by the US Environmental Protection Agency STAR center Grant R-827354. Supplemental material for this article is available with the online version of the journal at www.epidem.com; click on “Article Plus.” Correspondence: Niklas Berglind, Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden. E-mail: Niklas.Berglind@ki.se. Copyright © 2008 by Lippincott Williams & Wilkins ISSN: 1044-3983/09/2001-0110 DOI: 10.1097/EDE.0b013e3181878b50 Epidemiology • Volume 20, Number 1, January 2009 110