Temporal trends of the association between ambient temperature and cardiovascular mortality: a 17-year case-crossover study

Aim. To examine the temporal variations of the association between ambient temperature and mortality for cardiovascular diseases in Queensland, Australia between 1997 and 2013. Methods. We obtained 147 238 cardiovascular deaths data from Queensland Health between 1 January 1997 and 31 December 2013. Time-stratified case-crossover design was fitted via the conditional quasi-Poisson regression with time-varying distributed lag non-linear model to estimate the associations between temperature and cardiovascular mortality. Stratified analyses were performed by age, sex, climate zone, and socioeconomic status. Results. We found a substantial decrease in the cold effect, while there was no significant change in the heat effect. Results of subgroup analyses showed an increasing trend for heat effects in men, people ⩽84 years old, those living in low and middle socioeconomic areas and those living in hot climate areas. There was a decreasing trend for the magnitude of associations between temperature (both cold and hot temperatures) and cardiovascular mortality in people ⩾85 years old and in areas of high socioeconomic status. Conclusions. The associations between cold temperature and cardiovascular mortality decreased in Queensland, Australia between 1997 and 2013, but no declines were observed for hot temperatures. Men, people ⩽84 years old, people living in low and middle socioeconomic score areas and people living in hot climate areas demonstrated increased susceptibility to hot temperatures. Our findings suggest a need for heat awareness health promotion campaigns to enhance adaptation to a warming climate among vulnerable population.