The health impacts of heat waves in five regions of New South Wales, Australia: A case-only analysis

Objectives: To determine and characterise the health impacts of extreme heat events on the population in five regions of New South Wales (NSW). Such data provide evidence necessary for the development of policy and programme initiatives designed to reduce the burden of disease due to the impact of climate change. Methods: A case-only approach was used to analyse 1,497,655 emergency hospital admissions in Sydney East and West, Illawarra, Gosford-Wyong and Newcastle. The distribution of daily minimum and maximum temperatures in each region was used to define extreme heat (≥99th percentile). We investigated the susceptibility of the main causes of emergency hospital admission to extreme heat. We also examined the presence of underlying conditions as a risk modifier of emergency hospital admission on extreme heat. Logistic regression model was used to estimate the effect modifications. Results: Main causes: On days of extreme heat, the risk of emergency hospital admission due to heat-related injuries, dehydration and other disorders of fluid, electrolyte and acid-base balance increased more than the risk of admission from other causes. Underlying conditions: Those with underlying mental and behavioural disorders, diseases of nervous and circulatory system, especially cardiac, diseases of respiratory system, especially asthma and chronic obstructive pulmonary disease, neoplasms and renal disease, especially renal failure, were more susceptible to an extreme heat event. Conclusions: In this study, we identified several main diagnoses and underlying conditions for emergency hospital admission that are particularly susceptible to extreme heat events. This knowledge can contribute directly to establishing health programmes that would effectively target those with higher relative risk of emergency hospital admission due to extreme heat.