Heat mortality in Finland in the 2000s.

OBJECTIVES: To estimate the magnitude of heat-related mortality in Finland in the 2000s. STUDY
DESIGN: Daily numbers of deaths during the period 2000-2005 in Finland were classified according to the mean daily temperature.
METHODS: The temperature at which mortality was lowest was first determined from smoothed data based on the loess regression. Heat- and cold-related mortalities were estimated by subtracting deaths at this optimal temperature from actual deaths on both sides of this temperature.
RESULTS: In 2000-2005, the fewest deaths (126 per day) occurred at a mean daily temperature of 12 degrees C, and they increased to 138/day (by 10%) on the warmest days (+24 degrees C) and to 151/day (20%) on the coldest days (-31 degrees C). An estimated 160 deaths per year (0.3% of all deaths) were due to higher than optimal temperatures and 2,400 /year (5%) to low temperatures. In individual years, the fraction of deaths attributable to heat varied from 0-0.5%, with little consistency with mean summer temperatures. While the relative risk of an individual dying from heat increased consistently with rising temperatures, most heat-related deaths occurred at temperatures less than +20 degrees C. During the warm spell in summer 2000, deaths increased by an estimated 360 cases (0.7% of annual deaths), but this decreased to 250 (0.5%) once the Midsummer Festival was excluded.
CONCLUSIONS: As heat spells may occur in the future in an unpredictable way and because heat is not recognized as a health hazard in the North, more research should be devoted to clarifying the causal mechanisms underlying heat mortality, and pre-emptive measures should be planned.