Questions under study: During June to August 2003, high temperatures were reported across Europe including Switzerland. In many European countries, particularly in France the heat wave was associated with an increase in mortality. This is the first analysis investigating whether the high temperatures during summer 2003 in Switzerland had a measurable impact on mortality.
Methods: Daily data on all-cause mortality for the period January 1990 to December 2003, and meteorological data from 20 different stations for the same period were analysed. Excess mortality for different age groups, gender and geographic regions was calculated. Daily mortality and temperature in 2003 was correlated with lags of temperature up to 7 days.
Results: An estimated 7% increase in all cause mortality occurred during June to August 2003. Excess mortality was limited to the region north of the Alps, to inhabitants of cities and suburban areas and was more pronounced among the elderly and the inhabitants of Basel, Geneva and Lausanne. North of the Alps, deviations in daily mortality were significantly correlated with deviations in maximum daily temperatures and night temperatures. The combination of day temperature above 35 degrees C and night temperatures above 20 degrees C predominantly occurred in Basel and Geneva and might in part explain the regional differences in excess mortality.
Conclusions: As the number of elderly people in Switzerland continues to rise and the occurrence of heat waves is predicted to increase as a consequence of global warming, preventive programmes targeting susceptible populations during heat waves are warranted.