What is it with the weather and stroke?

An influence of climate upon cerebrovascular risk is both biologically plausible and supported by epidemiological evidence. These relationships are important as they could yield public health strategies to help protect the vulnerable from the increased death rates arising during extreme cold and heat waves. Change in temperature impacts on many cerebrovascular risk factors, including serum lipid and fibrinogen concentration and blood pressure. The relationship between stroke and meteorological variables is complex because of the number of potentially relevant meteorological variables, differences in study design and climate between geographical areas and potential for confounding. Behavioral factors are also influenced by the weather, which may in turn affect stroke risk. Some studies suggest that lower temperature increases stroke risk and others suggest the converse, while changes in atmospheric pressure may link with increased intracranial hemorrhage risk. To date, data are confusing and conflicting and well-conducted prospective studies are required to help clarify these potentially important relationships.