Effects of Ambient Temperatures and Extreme Weather Events on Circulatory Mortality in a High Population Density Area : Exploring Mortality Data from Malta

BackgroundTemperature-related circulatory mortality has gained consistent public health importance worldwide due to the changes in inter-annual average temperatures and increased frequencies of extreme events over time. This study investigates the association between temperature and circulatory deaths in one of the highest population densities in the world (Malta) with a Mediterranean climate.MethodsDaily deaths relating to circulatory mortality (32,847 deaths) were obtained from January 1992 to December 2017. A distributed lag non-linear model (DLNM) with a Poisson distribution was utilized to estimate effects of ambient temperatures and heatwaves or cold spells (2-4 consecutive days). Effects were also explored for the specific cause of deaths, different age groups, gender and time periods.ResultsThe study observed a greater mortality risk due to cooler temperatures (8-15°C). At 8.9 °C (1st percentile), the daily mean temperature was significantly related to both ischemic heart disease (IHD) (95%CI, 1.24-2.77) and cerebrovascular disease (95% CI, 1.57-9.17). Cooler temperatures (8.99-12.6°C) were also significant for IHD mortality in males (95%CI, 1.05-3.59) and females (95%CI, 1.2-3.59), however, the effect on cerebrovascular deaths was only significant in females (95%CI, 2.58-26.80). Elderly females (over 65 years) had a higher risk of death relating to IHD (95% CI: 1.19-3.18) and cerebrovascular diseases (95%CI:2.64-29.61). Interestingly, colder temperatures (8.9°C) were significantly related to cerebrovascular deaths in the earliest time period (1992-2000) and IHD deaths in the most recent time period (2000-2017). The study didn’t find any heatwave effect across the time periods, however, there was some evidence for a cold-spell effect (at day 4) for cerebrovascular mortality (95%CI, 1.00-1.04).ConclusionThis is one of the first studies from a high population density area to explore the impact of ambient temperature and extreme events on circulatory deaths. The results of the study will help to improve preventive and adaptive strategies to mitigate climatic health impacts