When the heat is on: Threshold temperatures for AMI admissions to hospital in Melbourne Australia

Abstract

The main objective of this study was to identify threshold temperatures above which acute myocardial infarction (AMI) admissions to hospital increase in metropolitan Melbourne. This study used an ecological design which compared daily AMI admissions to hospital of persons aged 35 years and older in Melbourne with daily meteorological variables. Daily maximum, minimum, and average temperature measured at Melbourne Regional Office. The main outcome measures used were the median and inter-quartile ranges for daily AMI admissions to hospitals in Melbourne per 21–3 °C temperature band. The results indicated that threshold temperatures of 30 °C for daily average temperature, and 27 °C for 3-day average temperatures were identified. Days exceeding these thresholds resulted in a 10% and 37.7% increase in AMI admissions respectively. Males were more likely than females to be admitted during episodes of hot weather (1.9:1). Persons admitted on days exceeding the 30 °C threshold were younger than the AMI cohort overall. In conclusion we found that threshold temperatures above which AMI admissions to hospital increase are evident in Melbourne. This suggests that thermal stress occurs in persons with coronary disease when these thresholds are exceeded, and that the implementation of heat/health alert systems in Melbourne may reduce cardiac morbidity during hot weather.