We quantified the risk of myositis associated with statin and fibrate drug use with other covariates within a managed care organization (MCO) population.
The study spanned the years 1999-2003. Myositis cases had creatine kinase (CK) >or=10x upper limit of normal and a myopathy diagnosis. Exposures of statins, fibrates, and other drugs were assessed with age, gender, and indicators of suspected myopathy risk. Exposures were first analyzed within a cohort with CK monitoring and then within a more general secondary cohort. Adjusted relative risks (RRs) and incidence rates of myositis were generated by Poisson regression.
Myositis was significantly associated with statin monotherapy (RR 2.8 [95% confidence interval, CI=1.3-5.9]), statin-fibrate combination therapy (9.1 [95% CI=3.5-23]), comorbid liver disease (4.3 [95% CI=1.5-13], and/or renal disease (2.5 [95% CI=1.3-5.0]). Myositis rates per covariate pattern ranged from 33 to 6,400 per 100,000 person-years. The mean time to event was 1.7 years for statin-fibrate use, 2.0 years for statins alone, and 2.1 years for unexposed. Within the secondary cohort, RRs increased up to 10 times further away from the null.
Statins, with or without fibrates, and liver and renal disease were significantly associated with increased myositis risk in an MCO population.