The strange relationship between diabetes and abdominal aortic aneurysm.

In a 1997 report of a large abdominal aortic aneurysm (AAA) screening study, we observed a negative association between diabetes and AAA. Although this was not previously described and negative associations between diseases are rare, the credibility of the finding was supported by consistent results in several previous studies and by the absence of an obvious artifactual explanation. Since that time, a variety of studies of AAA diagnosis, both by screening and prospective clinical follow-up, have confirmed the finding. Other studies have reported slower aneurysm enlargement and fewer repairs for rupture in diabetics. The seeming protective effect of diabetes for AAA contrasts with its causal role in occlusive vascular disease and so provides a strong challenge to the traditional view of AAA as a manifestation of atherosclerosis. Research focused on a protective effect of diabetes has already increased our understanding of the etiology of AAA, and might eventually pave the way for new therapies to slow AAA progression.