Effects of apparent temperature on daily mortality in Lisbon and Oporto, Portugal

Background: Evidence that elevated temperatures can lead to increased mortality is well documented, with population vulnerability being location specific. However, very few studies have been conducted that assess the effects of temperature on daily mortality in urban areas in Portugal. Methods: In this paper time-series analysis was used to model the relationship between mean apparent temperature and daily mortality during the warm season (April to September) in the two largest urban areas in Portugal: Lisbon and Oporto. We used generalized additive Poisson regression models, adjusted for day of week and season. Results: Our results show that in Lisbon, a 1 degrees C increase in mean apparent temperature is associated with a 2.1% (95% CI: 1.6, 2.5), 2.4% ( 95% CI: 1.7, 3.1) and 1.7% (95% CI: 0.1, 3.4) increase in all-causes, cardiovascular, and respiratory mortality, respectively. In Oporto the increase was 1.5% (95% CI: 1.0, 1.9), 2.1% (95% CI: 1.3, 2.9) and 2.7% (95% CI: 1.2, 4.3) respectively. In both cities, this increase was greater for the group >65 years. Conclusion: Even without extremes in apparent temperature, we observed an association between temperature and daily mortality in Portugal. Additional research is needed to allow for better assessment of vulnerability within populations in Portugal in order to develop more effective heat-related morbidity and mortality public health programs.