Public Health Impacts of Climate Change in Portugal: Potential Effects on Chronic Diseases due to Extreme Temperatures

The connection between climate change and mortality is widely reported in numerous studies. Yet, only a few focus on the effects of extreme weather on mortality related to chronic diseases, particularly with regard to diabetes mellitus, cardiovascular and cerebro-vascular diseases, especially in Portugal. This study aimed to analyze the historical observed relationship between mortality and meteorological variables, and explore the extent to which this relationship can be used to generate future projections of mortality under climate change. A collection of meteorological data and the number of daily deaths related to chronic diseases (cardiovascular disease (ICD-10: I00-I99), cerebro-vascular disease (ICD-10: I60-I69), diabetes mellitus (ICD-10: E10-E14), ischaemic heart disease (ICD-10: I25), myocardial infarction (ICD-10: I21-I22), chronic obstructive pulmonary disease (ICD-10: J40-J42), and asthma (ICD-10: J45), according to age group (0-14, 15-24, 25-44, 45-64, 65-74, and >= 75 years) and gender, in mainland Portugal, were organized as daily time series for the period between 1986-2005. The indices developed by the ETCCDMI group (Expert Team and Climate Change Detection Monitoring & Clivar) were calculated in order to evaluate the frequency of extreme weather events (heat waves, cold spells); bioclimatic indices: apparent temperature (AT), and net effective temperature (NET); and, finally, mortality indices: excess winter mortality index (EWMI) and the coefficient of seasonal variation in mortality (CSVM). GEE Poisson models were used to estimate the relative risk (RR) for all-cause mortality, in the same period, under the previously considered climate conditions. The simulations obtained from the Weather Research and Forecasting (WRF) model were used to evaluate the future impact of extreme weather events on the number of deaths for the periods 2046-2065 and 2081-2100, under the climate change scenario RCP8.5. Last, we estimated the attributable fraction of daily deaths (AF), the total number of attributable deaths (AN) per year, the expected number of extreme weather-related excess deaths, and the projection of the previously considered indices, for current (1986-2005), medium term (2046-2065) and long term (2081-2100) climate, in a future scenario (RCP8.5). This research provides us with recommendations regarding the risks of, and the policies seeking to mitigate, the negative effects of climate change.