Retrospective Australian data suggest association with rare but severe condition

by Nicole Lou, Contributing Writer, MedPage Today
July 30, 2018

Autoimmune muscle inflammation was more likely to turn up among patients using statins than those not on these medications, according to an Australian population-based study.

Statin use was seen in 30.8% of patients at the time of idiopathic inflammatory myositis (IIM) diagnosis, compared with 21.5% of matched controls who did not have the condition (P=0.005), researchers led by Gillian Caughey, PhD, of Adelaide Medical School in Australia, reported online in JAMA Internal Medicine.

After adjusting for the fact that IIM patients had more diabetes and cardiovascular disease at baseline, statin exposure was still more likely for this group (adjusted OR 1.79, 95% CI 1.23-2.60), even when patients with necrotizing myositis were excluded (adjusted OR 1.92, 95% CI 1.29-2.86).

“While the incidence of IIM is rare (0.1 per 100,000 persons per year to 1.0 per 100,000 persons per year) and statin-associated autoimmune myopathy even rarer (estimated 2 per 1,000,000 persons per year), increasing use of statins at the population level, the severity of this condition, and the need for immunosuppressive treatment highlights the importance of early recognition of this disease,” the authors noted.

“Recently, statin-associated autoimmune myopathy has been recognized as a distinct entity with the presence of specific autoantibodies against hydroxymethylglutaryl-coenzyme A [HMG-CoA] reductase, which results in a necrotizing myositis that does not resolve with cessation of statin therapy,” they added.

Their population-based study used the South Australian Myositis Database to find 221 histologically-confirmed cases of idiopathic inflammatory myositis from the region. Patients were diagnosed in 1990-2014, were 62.2 years old on average, and comprised a group with 59.7% women.

These cases were randomly matched by age and sex to controls from the North West Adelaide Health Study (n=662).

Caughey and colleagues couldn’t examine the association of individual types of IIM with statin exposure because the sample size was too small. “Further research focusing on the specific types of IIM is required to elucidate the potential association with disease development and previous statin exposure and the potential role of HMG-CoA reductase antibodies,” they said.

Another major limitation was that the investigators had no information on type, dosage, or duration of statin use.

How patients were determined to have been exposed to statins was an additional limitation, wrote JAMA Internal Medicine‘s editor on healthcare policy and law, Gregory Curfman, MD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, in an editor’s note.

“This study assessed statin exposure by different methods for cases (drug history in the medical record) and controls (prescription dispensing records), which may have resulted in misclassification bias. Thus, the association of IIM with statin therapy reported by Caughey et al cannot be considered definitive, although these are likely the best data currently available,” he said.

In any case, Curfman wrote, “[s]tatin-associated myopathy as well as muscular aches and pains will continue to be a concern to patients and a diagnosis elusive to physicians. This debilitating adverse effect underscores the importance of prescribing statins only to patients who will clearly have a net benefit.”

LAST UPDATED 08.02.2018Primary Source