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We conducted the study described in this paper to investigate the impact of ambient temperature on mortality in the Netherlands during 1979-1997, the impact of heat waves and cold spells on mortality in particular, and the possibility of any heat wave- or cold spell-induced forward displacement of mortality. We found a V-like relationship between mortality and temperature, with an optimum temperature value (e.g., average temperature with lowest mortality rate) of 16.5 degrees C for total mortality, cardiovascular mortality, respiratory mortality, and mortality among those [Greater and equal to] 65 year of age. For mortality due to malignant neoplasms and mortality in the youngest age group, the optimum temperatures were 15.5 degrees C and 14.5 degrees C, respectively. For temperatures above the optimum, mortality increased by 0.47, 1.86, 12.82, and 2.72% for malignant neoplasms, cardiovascular 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, 1.69, 5.15, and 1.37%, respectively, for each degree Celsius decrease below the optimum in the preceding month. Mortality increased significantly during all of the heat waves studied, and the elderly were most effected by extreme heat. The heat waves led to increases in mortality due to all of the selected causes, especially respiratory mortality. Average total excess mortality during the heat waves studied was 12.1%, or 39.8 deaths/day. The average excess mortality during the cold spells was 12.8% or 46.6 deaths/day, which was mostly attributable 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 displacement of deaths.

Because the importance of established risk factors for coronary heart disease (CHD) is unclear in older people, the associations of white blood cell (WBC) count with the risk for CHD and all-cause mortality were investigated in an elderly cohort that was followed up for 5 years. In 1985, complete information on the risk factors of interest was available for 884 randomly selected men, aged 64 to 84 years, from the Dutch town of Zutphen (participation rate, 74%). Relative risks (RRs) for each 10(9)/L increase in WBC count were obtained for the 5-year incidence of and mortality from CHD and all causes. RRs were adjusted for age, body mass index, systolic blood pressure, total and high density lipoprotein cholesterol levels, and cigarette smoking habit. The WBC count was 6.7 +/- 1.8 X 10(9)/L (means +/- SD) at baseline. An increased WBC count was independently associated with mortality due to CHD, and the RR amounted to 1.32 (95% confidence interval [95% CI], 1.15 to 1.51). For the incidence of CHD the RR was 1.14 (95% CI, 0.98 to 1.32). These associations were observed regardless of cigarette smoking habit. Regarding all-cause mortality, the RR amounted to 1.25 (95% CI, 1.17 to 1.35). This association was especially noticeable among former smokers and those who had never smoked. In conclusion, during 5 years of follow-up WBC count predicted CHD and all-cause mortality in elderly men, independent of the conventional risk factors for CHD.