Time course of temperature effects on cardiovascular mortality in Brisbane, Australia

Objective: To quantify the lagged effects of mean temperature on deaths from cardiovascular diseases in Brisbane, Australia. Design: Polynomial distributed lag models were used to assess the percentage increase in mortality up to 30 days associated with an increase (or decrease) of 1°C above (or below) the threshold temperature. Setting: Brisbane, Australia. Patients: 22 805 cardiovascular deaths registered between 1996 and 2004. Main outcome measures: Deaths from cardiovascular diseases. Results: The results show a longer lagged effect in cold days and a shorter lagged effect in hot days. For the hot effect, a statistically significant association was observed only for lag 0-1 days. The percentage increase in mortality was found to be 3.7% (95% CI 0.4% to 7.1%) for people aged ≥65 years and 3.5% (95% CI 0.4% to 6.7%) for all ages associated with an increase of 18C above the threshold temperature of 24°C. For the cold effect, a significant effect of temperature was found for 10-15 lag days. The percentage estimates for older people and all ages were 3.1% (95% CI 0.7% to 5.7%) and 2.8% (95% CI 0.5% to 5.1%), respectively, with a decrease of 18C below the threshold temperature of 24°C. Conclusions: The lagged effects lasted longer for cold temperatures but were apparently shorter for hot temperatures. There was no substantial difference in the lag effect of temperature on mortality between all ages and those aged ≥65 years in Brisbane, Australia.