The effect of changes in barometric pressure on the risk of rupture of intracranial aneurysms.

Several meteorological variables have been linked with an altered incidence of cerebrovascular disease. In particular, we had noticed that, following abrupt changes in weather, patients with aneurysmal subarachnoid haemorrhage (SAH) often presented in groups. This study was undertaken to determine whether changes in barometric pressure would be an important factor. A retrospective analysis of a two year period was carried out. Daily mean, peak and trough atmospheric pressures had been recorded independently by a weather bureau. Of the 157 patients with SAH due to a berry aneurysm, confirmed by CT and angiography, 60 were entered into the study. Patients residing outside the weather bureau region (n = 86), or where there was uncertainty of their day of ictus (n = 11), were excluded. Daily peak to trough pressure changes and mean monthly pressure fluctuations showed no association with an increased risk of SAH. However, a significant relationship between the incidence of onset of symptoms indicative of a rupture of the aneurysm and a change in barometric mean pressure (BMP) of > 10 hectapascals from the previous day was found (p = 0.0247). The calculated odds ratio of sustaining a SAH with this associated BMP change was therefore 2.7 times with a risk of 1-13 times at a 95% confidence level (p = 0.035).