Temperature, Air Pollution, and Hospitalization for Cardiovascular Diseases among Elderly People in Denver

Article excerpt

Daily measures of maximum temperature, particulate matter [less than or equal to] 10 pm in aerodynamic diameter (P[M.sub.10]), and gaseous pollution (ozone; nitrogen dioxide, sulfur dioxide, and carbon monoxide) were collected in Denver, Colorado, in July and August between 1993 and 1997. We then compared these exposures with concurrent data on the number of daily hospital admissions for cardiovascular diseases in men and women > 65 years of age. Generalized linear models, assuming a Poisson error structure for the selected cardiovascular disease hospital admissions, were constructed to evaluate the associations with air pollution and temperature. After adjusting the admission data for yearly trends, day-of-week effects, ambient maximum temperature, and dew point temperature, we studied the associations of the pollutants in single-pollutant models with lag times of 0-4 days. The results suggest that [O.sub.3] is associated with an increase in the risk of hospitalization for acute myocardial infarction, coronary atherosderosis, and pulmonary heart disease. S[O.sub.2] appears to be related to increased hospital stays for cardiac dysthythmias, and CO is significantly associated with congestive heart failure. No association was found between particulate matter or N[O.sub.2] and any of the health outcomes. Males tend to have higher numbers of hospital admissions than do females for all of the selected cardiovascular diseases, except for congestive heart failure. Higher temperatures appear to be an important factor in increasing the frequency of hospitalization for acute myocardial infarction and congestive heart failure, and are associated with a decrease in the frequency of visits for coronary atherosclerosis and pulmonary heart disease. Key words: acute myocardial infarction, air pollution, cardiac dysrhythmias, cardiovascular diseases, CO, congestive heart failure, coronary atherosderosis, generalized estimating equations, N[O.sub.2], [O.sub.3], P[M.sub.10], Poisson regression, pulmonary heart disease, S[O.sub.2], temperature.

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There is substantial epidemiologic literature indicating a link between air pollution and cardiovascular morbidity and mortality. This includes not only studies of episodic pollution such as occurred during 1930 in the Meuse Valley (Firket 1931), 1948 in Pennsylvania (Shrenk et al. 1949), and 1952 in London (Ministry of Health 1954) but also of the generally low concentrations found in urban areas. Studies have been carried out in North America (Burnett et al. 1997a, 1997b; Morris et al. 1995; Morris and Naumova 1998; Schwartz 1999; Schwartz and Morris 1995; Zanobetti et al. 2000), in Western Europe (Atkinson et al. 1999; Ballester et al. 2001; Diaz et al. 2001; Hoek et al. 2001; Prescott et al. 1998), in Tokyo, Japan (Piver et al. 1999), and in Hong Kong, China (Wong et al. 1999). Most of these studies showed a predominant effect of particulates and carbon monoxide on cardiovascular admissions (Ballester et al. 2001; Burnett et al. 1997b; Morris et al. 1995; Morris and Naumova 1998; Schwartz 1999; Schwartz and Morris 1995; Wong et al. 1999). However, the Tokyo study (Piver et al. 1999) suggests an independent effect of nitrogen dioxide. Furthermore, the studies in Canada (Burnett et al. 1997a) and Spain (Diaz et al. 2001) demonstrated consistent effects for sulfur dioxide and/or ozone on cardiovascular hospital admissions. Several reports have addressed the issue of weather and mortality; extreme temperatures have been associated with increased daily mortality in numerous regions of the world (Braga et al. 2001; Kunst et al. 1993). Mortality has also been observed to increase during periods of 3 or more days of unusual temperatures during summer or winter, showing that temperature variability is an important determinant of human health effects (Braga et al. 2001, 2002; Saez et al. 1995).

It has been suggested that weather and temperature may modify the effects of air pollution on health both at high temperatures (Katsouyanni et al. …