BACKGROUND: The effect of ambient temperature on respiratory mortality has been consistently observed throughout the world under different climate change scenarios. Countries experiencing greater inter-annual variability in winter temperatures (and may not be lowest winter temperatures) have greater excess winter mortality compared to countries with colder winters. This study investigates the association between temperature and respiratory deaths in Malta which has one of the highest population densities in the world with a climate that is very hot in summer and mild in winter. METHODS: Daily number of respiratory deaths (7679 deaths) and meteorological data (daily average temperature, daily average humidity) were obtained from January 1992 to December 2017. The hot and cold effects were estimated at different temperatures using distributed lag non-linear models (DLNM) with a Poisson distribution, controlling for time trend, relative humidity and holidays. The reference temperature (MMT) for the minimum response-exposure relationship was estimated and the harvesting effects of daily temperature (0-27 lag days) were investigated for daily respiratory mortality. Effects were also explored for different age groups, gender and time periods. RESULTS: Cooler temperatures (8-15 °C) were significantly related to higher respiratory mortality. At 8.9 °C (1st percentile), the overall effect of daily mean temperature was related to respiratory deaths (RR 2.24, 95%CI 1.10-4.54). These effects were also found for males (95%CI 1.06-7.77) and males across different age groups (Males Over 65 years: RR 4.85, 95%CI 2.02-11.63 vs Males between 16 and 64 years: RR 5.00, 95%CI 2.08-12.03) but not for females. Interestingly, colder temperatures were related to respiratory deaths in the earliest time period (1992-2000), however, no strong cold effect was observed for later periods (2000-2017). In contrast, no heat effect was observed during the study period and across other groups. CONCLUSIONS: The higher risk for cold-related respiratory mortality observed in this study could be due to greater inter-annual variability in winter temperatures which needs further exploration after adjusting for potential physical and socio-demographic attributes. The study provides useful evidence for policymakers to improve local warning systems, adaptation, and intervention strategies to reduce the impact of cold temperatures.
Background: Temperature-related circulatory mortality has gained consistent public health importance worldwide due to changes in inter-annual average temperatures and the increased frequency of extreme events over time. This study investigates the association between temper-ature and circulatory deaths in one of the highest population densities in the world (Malta) with a Mediterranean climate. Methods: Daily 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 death, different age groups, gender and time periods. Results: The study observed a U-shaped cumulative exposure-response curve with a greater mortality risk due to cooler temperatures (8-15 degrees C) after adjusting for harvesting effects (0-27 days). Colder temperatures (<8.9
