Size of Ruptured Intracranial Aneurysms Is Decreasing: Twenty-Year Long Consecutive Series of Hospitalized Patients

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Background and Purpose—

Decrease in the incidence of subarachnoid hemorrhage over the past decades has been related to decreased smoking rates, especially among <50-year-old people. We studied whether these epidemiological changes are reflected in changes in the size and location of ruptured intracranial aneurysms (RIAs).


We identified consecutive patients admitted to a nonprofit academic hospital with saccular RIAs between 1989 and 2008. We averaged and analyzed mean sizes of RIAs in 4-year admission groups. In statistical analysis, we used the χ2 test for categorical variables and the Kruskal–Wallis test to assess differences between continuous and categorical variables. For linear trend assessments, we used the linear-by-linear association and ANOVA tests.


Of 2660 consecutive patients (59% women) with RIAs, 1176 (44%) were <50 years on admission. In people <50 years, the averaged annual mean size of RIAs decreased 16% from 9.2 mm in 1989 to 1992 to 7.7 mm in 2005 to 2008 in women and 13% (from 9.3 to 8.1 mm) in men (decreasing linear trend; P=0.001). RIA sizes did not change in 50-year-old or older patients, whereas the proportion of posterior circulation RIAs almost tripled to 13%, also with a linear relationship (P<0.001).


The size of RIAs seems to be decreasing among younger generations of hospital-admitted subarachnoid hemorrhage patients, whereas 50-year-old and older subarachnoid hemorrhage patients have an increasing proportion of posterior circulation RIAs. These epidemiological changes are noteworthy, especially if they are universal and ongoing.

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