Association of ambient particulate matter with heart failure incidence and all-cause readmissions in Tasmania: an observational study

OBJECTIVES: We sought to investigate the relationship between air quality and heart failure (HF) incidence and rehospitalisation to elucidate whether there is a threshold in this relationship and whether this relationship differs for HF incidence and rehospitalisation. METHODS: This retrospective observational study was performed in an Australian state-wide setting, where air pollution is mainly associated with wood-burning for winter heating. Data included all 1246 patients with a first-ever HF hospitalisation and their 3011 subsequent all-cause readmissions during 2009–2012. Daily particulate matter <2.5 µm (PM(2.5)), temperature, relative humidity and influenza infection were recorded. Poisson regression was used, with adjustment for time trend, public and school holiday and day of week. RESULTS: Tasmania has excellent air quality (median PM(2.5)=2.9 µg/m(3) (IQR: 1.8–6.0)). Greater HF incidences and readmissions occurred in winter than in other seasons (p<0.001). PM(2.5) was detrimentally associated with HF incidence (risk ratio (RR)=1.29 (1.15–1.42)) and weakly so with readmission (RR=1.07 (1.02–1.17)), with 1 day time lag. In multivariable analyses, PM(2.5) significantly predicted HF incidence (RR=1.12 (1.01–1.24)) but not readmission (RR=0.96 (0.89–1.04)). HF incidence was similarly low when PM <4 µg/m(3) and only started to rise when PM(2.5)≥4 µg/m(3). Stratified analyses showed that PM(2.5) was associated with readmissions among patients not taking beta-blockers but not among those taking beta-blockers (p(interaction)=0.011). CONCLUSIONS: PM(2.5) predicted HF incidence, independent of other environmental factors. A possible threshold of PM(2.5)=4 µg/m(3) is far below the daily Australian national standard of 25 µg/m(3). Our data suggest that beta-blockers might play a role in preventing adverse association between air pollution and patients with HF.