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/m³ (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/m³ and only started to rise when PM_2.5≥4 µg/m³. 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/m³ is far below the daily Australian national standard of 25 µg/m³. Our data suggest that beta-blockers might play a role in preventing adverse association between air pollution and patients with HF.