Association of statin prescription with small abdominal aortic aneurysm progression

We thank Karrowni et al for their response to our recent article. They suggest that the finding that statin prescription was not associated with abdominal aortic aneurysm (AAA) growth in our recent article was a type II error evident because of the slow growth of AAAs in the cohort that we described.¹ We do not believe that this is a reasonable conclusion from the current data on statins and AAA growth for a large number of reasons. Firstly, as pointed out by Karrowni et al, a large number of patients were included in the cohort (n = 652) that we reported; and median followup was 5 years.¹ Thus, despite the slow average growth, the overall AAA growth was large enough to ensure that the study was powered to a much greater extent than previous small studies. Secondly, since the publication of our report, there have been a number of even larger studies, which have similarly failed to identify any association between statin prescription and AAA growth.²⁻³ One of the latter studies was the UK Small AAA study, which, as noted by Karrowni et al, included larger AAAs at entry and, thus, had greater average AAA growths than reported in our cohort.² The only scientifically sound way to assess the effect of statin prescription on AAA growth would be a large randomized controlled trial. The only trial of statins that included AAA outcomes that we are aware of is the UK Heart Protection Study.⁴ This randomized study of simvastatin included 6,748 patients with peripheral artery disease. Patients randomized to statins had a reduction in all major cardiovascular end points, but there was no reported reduction in the frequency of AAA repair required or AAA-related mortality. In conclusion, current evidence does not suggest that statins reduce AAA growth but does not exclude this possibility. A large prospective randomized controlled trial to assess this, although hard to recruit for, would be a very important study and should be undertaken in our opinion