Biometeorological Assessment of Mortality Related to Extreme Temperatures in Helsinki Region, Finland, 1972–2014

Abstract

Climate change is expected to increase heat-related and decrease cold-related mortality. The extent of acclimatization of the population to gradually-changing thermal conditions is not well understood. We aimed to define the relationship between mortality and temperature extremes in different age groups in the Helsinki-Uusimaa hospital district in Southern Finland, and changes in sensitivity of the population to temperature extremes over the period of 1972–2014. Time series of mortality were made stationary with a method that utilizes 365-day Gaussian smoothing, removes trends and seasonality, and gives relative mortality as the result. We used generalized additive models to examine the association of relative mortality to physiologically equivalent temperature (PET) and to air temperature in the 43-year study period and in two 21-year long sub-periods (1972–1992 and 1994–2014). We calculated the mean values of relative mortality in percentile-based categories of thermal indices. Relative mortality increases more in the hot than in the cold tail of the thermal distribution. The increase is strongest among those aged 75 years and older, but is somewhat elevated even among those younger than 65 years. Above the 99th percentile of the PET distribution, the all-aged relative mortality decreased in time from 18.3 to 8.6%. Among those ≥75 years old, the decrease in relative mortality between the sub-periods were found to be above the 90th percentile. The dependence of relative mortality on cold extremes was negligible, except among those ≥75 years old, in the latter period. Thus, heat-related mortality is also remarkable in Finland, but the sensitivity to heat stress has decreased over the decades.

Impacts of the 2015 Heat Waves on Mortality in the Czech Republic—A Comparison with Previous Heat Waves

“…Daily air temperature was calculated as the mean from 12 high-quality meteorological stations operated by the Czech Hydrometeorological Institute, representing the spatial population distribution in the Czech Republic ( Figure 1 ), and used as a proxy variable of thermal conditions. While some studies have shown a theoretical advantage of indices combining multiple variables in order to assess human thermal comfort [ 69 ] as well as their better performance on mortality data [ 70 , 71 ], the differences between various temperature measures in evaluating heat’s impact on mortality are generally insignificant [ 36 , 72 , 73 , 74 ].…”

Temporal trends in human vulnerability to excessive heat

“…in Australia, with decreases in outdoor labor the male heat mortality rate has fallen faster than the female rate (Coates et al 2014), and in the greater decreases that are seen with children mortality rates, with other studies showing slower decreases in the elderly mortality rate (Åström et al 2013b) or even a noticeable uptick (Ekamper et al 2009) indicative of changes in overall age structure. In studies confined to more recent decades, decreases in vulnerability have been most substantial in the oldest age groups (Ruuhela et al 2017, Sheridan and Dixon 2017, Bobb et al 2014, de'Donato et al 2015, although in others there was no consistent age-related differentiation Hagihara 2015, Ha andKim 2013).…”

“…Rey et al (2007) Excess mortality was substantially lower than expected during 2006 heat wave in France, after the implementation of public health surveillance. Ruuhela et al (2017) In Finland, the sensitivity to heat stress has decreased from 1972-2014. Schifano et al (2012) A significant decrease in heat-related mortality in those 65 and older in Italy is observed in 2006-2010 following implementation of a national prevention plan.…”

Zoning and weighting in urban heat island vulnerability and risk mapping in Helsinki, Finland

“…The population density of the study area is 1490 per km 2 . Although the study area is located in temperate zone with reasonably cool climate, UHI and heat waves during summer months are one of the key climatic and weather hazards in the area (Ruuhela et al 2017), and they have been emphasized in climate change adaptation plans (Helsinki Region Environmental Services Authority 2016a).…”