The effects of air pollution on hospitalizations for cardiovascular disease in elderly people in Australian and New Zealand cities

Abstract

Objective: The goal of this study was to estimate the associations between outdoor air pollution and cardiovascular hospital admissions for the elderly.

Design: Associations were assessed using the case-crossover method for seven cities: Auckland and Christchurch, New Zealand; and Brisbane, Canberra, Melbourne, Perth, and Sydney Australia. Results were combined across cities using a random-effects meta-analysis and stratified for two adult age groups: 15-64 years and >/= 65 years of age (elderly). Pollutants considered were nitrogen dioxide, carbon monoxide, daily measures of particulate matter (PM) and ozone. Where multiple pollutant associations were found, a matched case-control analysis was used to identify the most consistent association.

Results: In the elderly, all pollutants except O3 were significantly associated with five categories of cardiovascular disease admissions. No associations were found for arrhythmia and stroke. For a 0.9-ppm increase in CO, there were significant increases in elderly hospital admissions for total cardiovascular disease (2.2%) , all cardiac disease (2.8%), cardiac failure (6.0%), ischemic heart disease (2.3%), and myocardial infarction (2.9%). There was some heterogeneity between cities, possibly due to differences in humidity and the percentage of elderly people. In matched analyses, CO had the most consistent association.

Conclusions: The results suggest that air pollution arising from common emission sources for CO, NO2, and PM (e.g., motor vehicle exhausts) has significant associations with adult cardiovascular hospital admissions, especially in the elderly, at air pollution concentrations below normal health guidelines. Relevance to clinical and professional practice: Elderly populations in Australia need to be protected from air pollution arising from outdoor sources to reduce cardiovascular disease.

Figure 1

Estimated increases (mean and 95% CI) for cardiac admissions in the elderly by city for four pollutants (average lag, 0–1; one IQR increase). (A) Maximum 8-hr CO. (B) Average 24-hr NO₂. (C) Average 24-hr PM_2.5. (D) Average 24-hr PM₁₀.