Excess winter mortality from ischaemic heart disease and stroke during colder and warmer years in Israel

Most data on winter excess mortality from cardiovascular disease have been reported from countries with large seasonal temperature variations. In this study, the contribution of environmental temperature to ischaemic heart disease (IHD) and stroke mortality was evaluated in a country with relatively small variations in seasonal temperature. The association between monthly temperature and cause-specific monthly proportion of annual mortality was studied in the population of Israel aged 45 years and over for the period 1976-85. Population size in this group averaged nearly 1 million people during the study period, and about 40% of all deaths were due to IHD or stroke. For men, IHD mortality was 51% higher and stroke mortality 48% higher in mid-winter than in mid-summer; for women the respective figures were 48% and 40%. In cosinor analysis for months above and below the median minimum temperature, it was shown that excess mortality in winter was greater in years below the median minimum temperature in almost all age-sex categories. In partial correlation analysis, most of the variation in IHD and stroke mortality was explained by variation in minimum monthly temperature. These findings strongly support the role of environmental temperature in excess winter mortality from cardiovascular disease over a wide age range, and efforts should be directed at identifying intervention measures which could significantly reduce the incidence of premature mortality.