Secular pattern of aneurismal rupture with the lunar cycle and season.

Background The lunar cycle and seasons may be associated with rates of rupture of intracranial aneurysms, but the literature is mixed. Studies of the association between the lunar cycle and rates of aneurysm rupture used the eight qualitative moon phases. The purpose of this study was to assess any association of aneurysm rupture with the lunar cycle and with the season. Materials and methods We retrospectively reviewed all cases of subarachnoid haemorrhage secondary to ruptured intracranial aneurysm treated with endovascular coiling in our institution over a 10-year period. We included only cases with a known rupture date. We used the degree of illumination of the moon to quantitatively code the lunar cycle. Results A total of 212 cases were included in our analyses. The odds of aneurysm rupture were significantly greater ( p < 0.001) when the moon was least (new moon) and most (full moon) illuminated, as compared to the middle of the lunar cycle. The odds of rupture tended to be higher ( p = 0.059) in the summer, compared to autumn. Conclusions The odds of aneurysm rupture were greater when the moon was least illuminated (new moon) and most illuminated (full moon), compared to the middle of the lunar cycle.