The seasonal variation in mortality from cerebrovascular disease.

The frequency distribution of deaths from cerebrovascular disease in England and Wales in 1975 by month of occurrence is described. The distribution is compared with that for related diseases, in particular ischaemic heart disease, hypertensive disease, pneumonia and bronchitis. The principal feature in all these diseases is high mortality in winter and spring and low mortality in late summer, but the range of variation is wider for pneumonia and bronchitis. The seasonal distribution of cerebrovascular disease death is similar in both sexes, all ages at death and for deaths at home and deaths in a hospital or institution. For both sexes the proportion of cerebrovascular disease deaths occurring at home increases significantly with age at death. Four hypotheses are examined to explain this characteristic seasonal mortality pattern, which is related inversely to ambient temperature, and similar to the seasonal pattern of the incidence and prevalence of cerebrovascular disease.