Transition in Incidence Rate of Hospitalised Stroke and Case Fatality Rate in the Hunter Region, Australia, 2001-2019: A Prospective Hospital-Based Study

Bushfire-smoke trigger hospital admissions with cerebrovascular diseases: Evidence from 2019-20 bushfire in Australia

INTRODUCTION

Exposure to ambient air pollution is strongly associated with increased cerebrovascular diseases. The 2019-20 bushfire season in Australia burnt 5.4 million hectares of land in New South Wales alone, with smoke so severe it affected cities in Argentina, 11,000 km away. The smoke emitted by bushfires consists of both gaseous and particle components. It is important to note that exposure to particulate matter has been shown to be linked to a heightened risk of stroke, which is the primary kind of cerebrovascular illness, as well as an increased likelihood of hospitalisations and mortality. However, the available data is inadequate in terms of documenting the response of patients diagnosed with a proven cerebrovascular illness to bushfire smoke. Additionally, there is a lack of information about the health effects associated with particulate matter throughout the bushfire season and on days when smoke was present in 2019 and 2020.Therefore, we aimed to determine the effects of (i) short-term air pollution triggered by bushfires and (ii) high smoke days in increasing the daily number of hospital admissions with cerebrovascular diseases.

MATERIALS AND METHODS

Hospitalisation data were accessed from the admitted patient dataset from seven local Government areas of Hunter New England Local Health District. The bushfire period was defined from 1 October 2019 to 10 February 2020, and a same period from 2018-19 as the control. High bushfire smoke days were days when the average daily concentration of particulate matter was higher than the 95th percentile of the control period. Poisson regression models and fixed effect meta-analysis were used to analyse the data.

RESULTS

In total, 275 patients with cerebrovascular admissions were identified, with 147 (53.5%) during the bushfire (2019-20) and 128 (46.5%) in the control period (2018-19). There was no significant increase in daily admissions for cerebrovascular disease (Incidence Rate Ratio, IRR: 1.04; 95% CI: 0.81-1.34; p-value: 0.73), acute stroke (IRR: 1.15; 95% CI: 0.88-1.50; p-value: 0.29) or acute ischaemic stroke (IRR: 1.18; 95% CI: 0.87-1.59; p-value: 0.28), over the entire bushfire period. However, the high bushfire smoke days were associated with increased acute ischaemic stroke-related hospital admissions across lead 0-3 and the highest cumulative effect was observed with lead 0 (IRR:1.52; 95% CI: 1.01-2.29; p-value: 0.04). In addition, during the bushfire period, particulate matter, both PM10 and PM2.5 (defined as particulates that have an effective aerodynamic diameter of 10, and 2.5 microns, respectively), were also associated with increased acute ischaemic stroke admissions with a lag of 0-3 days.

DISCUSSION AND CONCLUSION

The results suggested a possible association between particulate matter and high smoke days with increased hospital admissions due to acute ischaemic stroke during the recent Australian bushfire season.

Temporal and age-specific trends in incidence and 1-year case-fatality of hospitalized ischaemic stroke in Victoria, Australia

OBJECTIVES

Investigate temporal and age-specific trends in the incidence of ischaemic stroke and case-fatality risk in Victoria, Australia.

MATERIALS AND METHODS

Patients hospitalised with first ischaemic stroke between 2012 and 2018 were included. Trends in age-standardised incidence rates of ischaemic stroke were assessed using linear regression models. Cox proportional hazard regression models were used to examine the case-fatality risk.

RESULTS

Overall age-standardised incidence of ischaemic stroke was stable from 2012/13 to 2017/18 (87.6 to 84.8 events per 100,000 population; Annual percentage change [APC] -0.32; 95% Confidence interval [CI] -1.13 to 0.50). The incidence declined in females (APC -1.00; 95% CI -1.49 to -0.50), people aged 75-84 years (APC -1.60; 95% CI -2.83 to -0.36) and in metropolitan areas (APC -0.74; 95% CI -1.02 to -0.45). The risk of 1-year case-fatality (HR 0.85; 95% CI 0.78 to 0.93) significantly declined in 2016/17 compared to 2012/13.

CONCLUSIONS

Overall ischaemic stroke incidence remained stable while decreasing trends were observed in females, elderly and metropolitan areas. 1-year case-fatality declined from 2012 to 2017.