Seasonal variation in the incidence of ruptured abdominal aortic aneurysm

This retrospective study was performed in order to correlate the season with the risk of rupture of an abdominal aortic aneurysm (AAA). From December 1968 to December 1990, 224 patients, 203 males (90.63%) and 21 females (9.37%), mean age 71 years, underwent surgery either urgently because of rupture or expansion (group A, 66 patients, 22.46%) or electively (group B, 158 patients, 70.53%) for AAA. Of the 66 patients in group A, 61 were male (92.4%) and five female (7.55%) with a mean age of 73 years. Of the 158 patients in group B, 142 were male (89.8%) and 16 female (10.1%). The frequency distribution of electively admitted and operated cases of AAA was shown to be similar during all seasons but the admissions of ruptured AAA were shown by non-parametric statistical analysis to increase during the autumn (p less than 0.05) with 43.9% of the cases being admitted during September, October and November. The male to female ratio and the ratio of the number of aneurysms ruptured to the total number of aneurysms did not change significantly. The explanation of this phenomenon is obscure and needs further epidemiological investigation to assess the seasonal variability or various parameters such as hypertension.