The impact of heat waves and cold spells on mortality rates in the Dutch population

We conducted the study described in this paper to investigate the impact of ambient temperature on mortality in the Netherlands during 1973-1997, the impact of heat waves and cold spells on mortality in particular, and the po ssibility of any heat wave- or cold spell-induced forward displacement of m ortality. We found a V-like relationship between mortality and temperature, with an optimum temperature value (e.g., average temperature with lowest m ortality rate) of 16.5 degreesC for total mortality, cardiovascular mortali ty, respiratory mortality, and mortality among those greater than or equal to 65 year of age. For mortality due to malignant neoplasms and mortality i n the youngest age group, the optimum temperatures were 15.5 degreesC and 1 4.5 degreesC, respectively For temperatures above the optimum, mortality in creased by 0.47, 1.86, 12.82, and 2.72% for malignant neoplasms, cardiovasc ular disease, respiratory diseases, and total mortality, respectively, for each degree Celsius increase above the optimum in the preceding month. For temperatures below the optimum, mortality increased 0.22, 1.63, 5.15, and 1 .37%, respectively, for each degree Celsius decrease below the optimum in t he preceding month. Mortality increased significantly during all of the hea t waves studied, and the elderly were most effected by extreme heat. The he at waves led to increases in mortality due to all of the selected causes, e specially respiratory mortality. Average total excess mortality during the heat waves studied was 12.1%, or 39.8 deaths/day. The average excess mortal ity during the cold spells was 12.8% or 46.6 deaths/day, which was mostly a ttributable to the increase in cardiovascular mortality and mortality among the elderly. The results concerning the forward displacement of deaths due to heat waves were not conclusive. We found no cold-induced forward displa cement of deaths.