Associations between ambient air pollution and daily mortality among persons with congestive heart failure

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Abstract

We conducted a mortality time series study to investigate the association between daily mortality for congestive heart failure (CHF), and daily concentrations of particles and gaseous pollutants in the ambient air of Montreal, Quebec, during the period 1984–1993. In addition, using data from the universal Quebec Health Insurance Plan, we identified individuals ⩾65 years of age who, one year before death, had a diagnosis of CHF. Fixed-site air pollution monitors in Montreal provided daily mean levels of pollutants. We regressed the logarithm of daily counts of mortality on the daily mean levels of each pollutant, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersion, weather variables, and other gaseous and particle pollutants. Using cause of death information, we did not find any associations between daily mortality for CHF and any air pollutants. The analyses of CHF defined from the medical record showed positive associations with coefficient of haze, the extinction coefficient, SO2, and NO2. For example, the mean percent increase in daily mortality for an increase in the coefficient of haze across the interquartile range was 4.32% (95% CI: 0.95–7.80%) and for NO2 it was 4.08% (95% CI: 0.59–7.68%). These effects were generally higher in the warm season.

Introduction

There is substantial and consistent evidence for an association between increases in levels of ambient air pollution and daily mortality (Dockery and Schwartz, 1995; Goldberg, 1996; Pope III, et al., 1995; Schwartz, 1992; Schwartz, 1994). It has been suggested that only persons in poor health are at high risk (Bates, 1992; Frank and Tankersley, 2002; Goldberg, 1996). A principal hypothesis is that exposure to air pollutants may cause acute pulmonary disease, such as bronchiolitis or pneumonia, thereby leading to congestive heart failure (CHF) in persons with myocardial damage or cardiac disease (Bates, 1992). Alternatively, exposure to ultrafine particles may invoke alveolar inflammation, release inflammatory mediators, exacerbate lung conditions, and increase coagulability of blood thereby leading to acute episodes of cardiovascular disease (Seaton et al., 1995). By extension, it can be hypothesized that persons with CHF may be particularly susceptible to the effects of air pollution (Bates, 1992; Kodavanti et al., 1998; Seaton et al., 1995). In the few studies in which CHF has been investigated, it was found generally that daily hospitalizations for CHF (Burnett et al., 1997; Morris et al., 1995; Morris and Naumova, 1998; Poloniecki et al., 1997; Schwartz, 1997) and daily mortality among persons with CHF (Kwon et al., 2001) increased when levels of ambient particles and gaseous pollutants increased. In the present paper, we present a time series investigation to determine whether persons with preexisting CHF are at higher risk of dying when levels of ambient air pollution increase.

Section snippets

The study population

The study took place in Montreal, Quebec, a large metropolitan area that experiences relatively low levels of air pollution (Goldberg et al (2000), Goldberg et al (2001), Goldberg et al (2001b)). Subjects were residents of Montreal who died in the metropolitan area during the period 1984–1993 and who were registered with the universal Quebec Health Insurance Plan (QHIP). They were first identified from the computerized provincial database of death certificates and each deceased subject was then

Results

There were a total of 133,904 non-accidental deaths during the study period 1984–1993. CHF accounted for 2.1% of these (2,740 deaths; Table 1), with the majority among persons age 65 years and over. All results presented subsequently are for this age group only. Using our definition of CHF from the morbidity data, we found 14,615 subjects 65 years of age and over who had CHF before death (Table 1). Of these subjects, 66% were coded as having a circulatory underlying cause of death, and only

Discussion

Among those persons whose underlying cause of death was CHF, we found no statistically significant associations with any of the pollutants. Among persons who were classified as having CHF within 1 year of death, we found that daily mortality increased in a linear fashion for COH, the extinction coefficient, SO2, and NO2, and that these associations were more pronounced in the warm season. We did not find any associations with specific measures of fine particles or sulfates.

There are no data

Acknowledgements

We thank the Montreal urban community and Environment Canada for providing the NAPS, CAPMoN, CAAMP, and meteorological data and we are grateful to the Ministère de la santé et des services sociaux de Québec for providing the health data. The authors gratefully acknowledge the assistance of Rose Dugandzic, Jacques Barry, Holly Lam, Marie-Claude Boivin, David Johnson, and Claude Gagnon. Mark S. Goldberg gratefully acknowledges receipt of an Investigator Award from the Canadian Institutes for

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    This study was supported financially through contracts with the Health Effects Institute, Cambridge, MA, the Toxic Substances Research Initiative, Health Canada, and the Canadian Institutes for Health Research. Ethics approval was obtained from the Institutional Review Board of McGill University and from the Commission de 1’accès à 1’information du Québec.

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